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 Table of Contents 
ORIGINAL ARTICLE
Year : 2019  |  Volume : 11  |  Issue : 1  |  Page : 78-85  

Euphorbia hirta methanolic extract displays potential antioxidant activity for the development of local natural products


1 Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
2 Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, 16150 Kubang Kerian; Faculty of Veterinary Medicine, Universiti Malaysia Kelantan, Locked Bag 36, Pengkalan Chepa 16100 Kota Bharu, Kelantan, Malaysia
3 Fukang Herbs Sdn Bhd, 31350 Ipoh, Perak, Malaysia
4 Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, 11800 Penang, Malaysia

Date of Web Publication20-Feb-2019

Correspondence Address:
Dr. Khoo Boon Yin
Institute for Research in Molecular Medicine, Universiti Sains Malaysia, 11800 Penang
Malaysia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/pr.pr_113_18

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   Abstract 


Background: The level of free radicals, which counteract the capability of the antioxidant system in plant products, is often measured in advance for further promising antidisease effect. Objective: In this study, we sought to evaluate the antioxidant activity of local medicinal plants (Angelica keiskei, Annona muricata, Chromolaena odorata, Clinacanthus nutans, Euphorbia hirta, and Leea indica) for their potential of use as distinctive local natural nutraceutical products. Materials and Methods: To recover active compounds, including yield and composition of the plants, the solvent extraction method, the Folin–Ciocalteu method, the aluminum chloride approach, and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay were first performed to evaluate the antioxidant level and capacity of the plant extracts. Results: The aqueous extracts presented the highest yield for all plants, with the highest yield observed in C. nutans. However, the highest total phenolic and flavonoid contents were observed in the methanolic extract of E. hirta rather than in the aqueous extract. The methanolic extract of E. hirta also exhibited the most promising antioxidant activity, with the 50% inhibition concentration (IC50) value of DPPH inhibition at 0.013 mg/mL. Conclusion: High total phenolic and flavonoid contents, as well as low IC50value, suggested that E. hirta methanolic extract is a potential antioxidant agent for the development of local natural products for disease treatment.
Abbreviations Used: DPPH: 2,2-diphenyl-1-picrylhydrazyl; DMSO: Dimethyl sulfoxide; RPMI: Roswell Park Memorial Institute; DMEM: Dulbecco's Modified Eagle Medium; GAE: Gallic acid equivalents; QE: quercetin equivalent; SEM: Standard error of the mean; IC50: 50% inhibition concentration; MTT: 3-(4,5-Dimethylthial-2-yl)-2, 5-diphenyltetrazalium bromide.

Keywords: Antioxidant activity, free radical scavenging activity, natural product, total flavonoid content, total phenolic content


How to cite this article:
Ismail A, Mohamed M, Kwei YF, Yin KB. Euphorbia hirta methanolic extract displays potential antioxidant activity for the development of local natural products. Phcog Res 2019;11:78-85

How to cite this URL:
Ismail A, Mohamed M, Kwei YF, Yin KB. Euphorbia hirta methanolic extract displays potential antioxidant activity for the development of local natural products. Phcog Res [serial online] 2019 [cited 2019 May 24];11:78-85. Available from: http://www.phcogres.com/text.asp?2019/11/1/78/252559





SUMMARY

  • The methanolic extract of Euphorbia hirta contained the highest total phenolic and flavonoid contents
  • The extract also exhibited the most promising antioxidant activity with the 50% inhibition concentration value of 2,2-diphenyl-1-picrylhydrazyl inhibition in E. hirta at 0.013 mg/mL
  • This phenomenon suggests that E. hirta methanolic extract is a potential antioxidant agent.



   Introduction Top


From as early as 3000 B.C., humans have used plants as herbal medicines to treat ailments.[1] The use of herbal medicine is extensively quoted throughout history in numerous sacred texts, including the Quran and the Bible. The Bible tells us that herbs are placed on earth for the healing of humans. For example, Punica granatum or pomegranate has long been used in herbal medicine to treat a variety of diseases, including inflammation and rheumatism.[2] In Ayurvedic medicine, pomegranate is considered “a pharmacy unto itself,” where the whole plant can be used to cure diseases.[3] Despite a plethora of claims about the therapeutic capabilities in plants, only recently have researchers seen the importance of plants as pharmaceuticals agents, leading to the isolation of active compounds and ingredients from plants. For example, isolation of morphine from Papaver somniferum (the opium poppy) in the early 19th century indicates the importance of identifying active compounds and ingredients from natural products for pharmaceutical purposes and industries. The contributions of natural products toward the development of novel pharmaceutical drugs have led many pharmaceutical companies to put forth effort to screen more plants to be used locally in treating diseases. Nearly 60% of anticancer products are derived from natural products, including vinblastine and vincristine, which are vinca alkaloids derived from Catharanthus roseus; etoposide, which is a semisynthetic derivative of mandrake plant substance podophyllotoxin; paclitaxel, which is derived from the bark of Pacific yew tree (Taxus brevifolia); docetaxel, which is derived from the needles of yew plants; topotecan, which is semisynthetically manufactured from the plant-derived alkaloid camptothecin; and irinotecan, which is a plant alkaloid.[4],[5],[6] These plant products have been identified as having the antioxidant effect and contain high levels of polyphenols and flavonoids, and their synthetic analogs dominate the list of promising anticancer agents in the treatment of various human cancers, including ovarian, breast, pancreatic, and lung cancers.[7],[8],[9],[10] For screening purposes, the level of free radicals, which counteract the defense capability of the antioxidant system in a plant product, should be investigated before that plant product is subjected to the next steps for showing promise as an antidisease agent.

A free radical is an atom or molecule with unpaired electrons that cause oxidative damage by stealing electrons from a nearby compound or molecule. The body generates free radicals as by-products of cells using oxygen to generate energy.[11] Elevated free radical production may lead to oxidative stress, damaging cells, leading to the development of chronic and degenerative diseases, including cardiovascular diseases, neurodegenerative diseases, and cancers.[12] Antioxidants, a group of defenders against free radicals, act by donating electrons to free radicals without turning into electron-scavenging molecules themselves. Antioxidants act as free radical scavengers, thus preventing free radical damage to cells and minimizing the risk of contracting diseases. Antioxidants, including phenols and flavonoids, are found abundantly in plants. The body can produce antioxidants (endogenous antioxidants), while antioxidants from the diet (exogenous antioxidants) are important helpers in neutralizing oxidative stress. Plants are commonly a good source of natural antioxidants. Epidemiological studies have shown that consumption of plants rich in antioxidants is beneficial to health because it lowers the risk of chronic diseases, especially cancers.[13] Hence, we sought to evaluate the antioxidant activity in local medicinal plants (Angelica keiskei, Annona muricata, Chromolaena odorata, Clinacanthus nutans, Euphorbia hirta, and Leea indica) in this study for their potential to be used as distinctive natural nutraceutical products for cancer prevention and treatment. This evaluation will help in the development of local industries for natural products. To obtain active compounds from plants, an extraction procedure is required to separate medicinally active portions of plants from the inactive or inert components using specific solvents. There are many techniques available to recover active compounds from plants, including Soxhlet extraction, maceration, and ultrasound-assisted extraction. The solvent used for the extraction also influences extraction yield and composition of active compounds. In the current study, the solvent extraction method, the Folin–Ciocalteu method, with an aluminum chloride approach, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay were performed to evaluate the antioxidant level and capacity of the plant extracts. The DPPH assay is widely used to evaluate the antioxidant capacity of the plant crude extracts. The DPPH assay provides information on the capacity of the active compounds in the extracts to reduce the stable free radical DPPH. The study provides appropriate assays that are simple, specific, and rapid to screen for the presence of active compounds in plants, which is valuable for the development of natural products for local industries.


   Materials and Methods Top


Plant materials

A total of six plants were included in this study. C. odorata and E. hirta were collected from the state of Kelantan, Malaysia, whereas the additional plants namely A. keiskei, A. muricata, C. nutans, and L. indica were generously contributed by Fukang Herbs Sdn. Bhd. All study plants were identified by the Herbarium of the School of Biological Sciences, Universiti Sains Malaysia.

Preparation of plant extracts

The collected plants were subjected to extraction. Briefly, the plant materials were washed and placed in a drying oven at 42°C overnight. The dried plant materials were then ground to small particles using a domestic blender. Then, the solvent (water or methanol) was added in the proportion of 10 g in 100 mL solvent to the flasks. The mixture was left on a shaker set at 100 rpm and ran for 16 h at 30°C to macerate. The mixture was decanted through Whatman filter paper, and the filtrate was collected and concentrated by a vacuum rotary evaporator (Heidolph Rotavac, Germany). The stock solution of plant extracts (50 mg/mL) and cisplatin (100 mg/mL; Sigma-Aldrich, USA) was prepared by dissolving the dried substances in dimethyl sulfoxide (DMSO, ≥99.9% pure solution; Sigma-Aldrich, USA). The solution was filtered through a 0.22-μm polyethersulfone filter membrane (Millipore, USA) and serially diluted into several working solution concentrations in culture medium. Both stock and working solutions of plant crude extracts and cisplatin were stored at −20°C until further use. The percentage (%) yield of each plant crude extract prepared using different solvents was calculated.

Total phenolic content determination

The total phenolic content of the plant extracts was determined using the Folin–Ciocalteu method described by a previous study.[14] Briefly, the Folin–Ciocalteu reagent (Merck, USA) was diluted 10 times with distilled water. Then, 50 μL of 1.0 mg/mL extract or standard solution of gallic acid at various concentrations was added to 50 μL of distilled water. In a 96-well plate, 50 μL of diluted Folin–Ciocalteu reagent and 50 μL of 1.0 M sodium carbonate (Sigma-Aldrich, USA) were added to each well. The reactions were incubated for 1 h at room temperature in the dark. The absorbance was then measured at 750 nm with a SpectraMax M5 microplate reader (Molecular Devices, USA). A standard curve was prepared with gallic acid (r2 = 0.999). The results were expressed as mg gallic acid equivalents (GAEs) per gram of dried plant material.

Total flavonoid content determination

The total flavonoid content was determined using a method described by the previous study.[14] In a 96-well plate, 50 μL of 1.0 mg/mL extract or a standard solution of quercetin in 80% ethanol was added to 10 μL of 10% aluminum chloride solution. Then, 150 μL of 95% ethanol and 10 μL of 1.0 M sodium acetate (Sigma-Aldrich, USA) were added to the mixture. The reaction was incubated for 40 min at room temperature in the dark, and then, the absorbance was measured at 415 nm. A standard curve of the quercetin was prepared (r2 = 0.993). The total flavonoid content in the plant extract was expressed as quercetin equivalent (QE) per gram of dried plant material.

Free radical scavenging activity determination

The DPPH free radical scavenging activity determination was performed to determine the scavenging activity of the plant extracts. Briefly, 10 μL of crude extract at various concentrations (0.125–1.000 mg/mL) was added to a 96-well plate. Then, 20 μL of 0.5 mM DPPH was added to each well in the plate. The reaction was incubated for 30 min at room temperature in the dark, and then, the absorbance was measured at 517 nm. The reduction in absorbance is reflective of the radical scavenging capacity of the extract. The degree of color change is proportional to the concentration and potency of the antioxidant capacity in scavenging free radicals. The percentage (%) of DPPH free radical scavenging activity in the plant extracts was calculated by comparing with the % of DPPH free radical scavenging activity of gallic acid as below. The Pearson correlation analysis was also performed between DPPH scavenging activity with total phenolic and flavonoid contents.



Antiproliferative effect determination

The antiproliferative effect of the selected extract on thyroid cells was determined using 3-(4,5-dimethylthial-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. For the process, Nthy-ori 3-1, FTC-133, and Hth-74 cells were seeded at a density of 5 × 104 cells per/mL in 100 μL culture medium: Roswell Park Memorial Institute-1640 (Nacalai Tesque, Japan), Dulbecco's Modified Eagle Medium (DMEM, Nacalai Tesque, Japan), or DMEM/Ham's F12 (Nacalai Tesque, Japan) based on the needs of the respective cell line in 96-well culture plates overnight in a humidified CO2 incubator at 37°C. The culture medium was supplemented with 10% fetal bovine serum (Gibco, USA), penicillin (100 units/mL; Nacalai Tesque, Japan), and streptomycin (100 μg/mL; Nacalai Tesque, Japan). The extract was then added at various concentrations (0–250 μg/mL) to all cell lines, and the cells were incubated in the incubator at 37°C for 72 h. Ten microliters of freshly prepared MTT solution (Amresco, USA) was added to all wells 3 h before the end of incubation time. The media were aspirated from the wells without disturbing the formazan crystals formation and 100 μL of DMSO was added to the wells. The color intensity of the formazan solution, which reflects the number of cells under the specific growth conditions, was measured at 570 nm using the microplate reader SpectraMax M5 (Molecular Devices, USA). The proliferation curve of the extract in respective cells was plotted using nonlinear regression by GraphPad Prism 7 is GraphPad Software Inc., USA. The % of surviving cells in treated cells relative to untreated cells (control) and 50% inhibition of cells (IC50 value) were calculated from the curves.

Statistical analysis

All experiments were performed in triplicate. Data were expressed as the standard error of the mean of triplicates in three independent experiments. Statistically significant differences were determined with one-way analysis of variance, and differences were considered significant at P < 0.05.


   Results Top


Percentage yield of plant crude extracts

The % yield of A. keiskei, A. muricata, C. odorata, C. nutans, E. hirta, and L. indica crude extracts as prepared using different solvents (water and methanol) is shown in [Table 1]. Among the solvents used in the study, the extraction method using water possesses a higher recovery yield over the extraction with methanol. In general, the aqueous extracts presented the highest yield for all plants, with the highest yield observed for C. nutans at 11.45%. The % yield of the extracts from water extraction was found to be in the order of C. odorata (1.69%) < L. indica (6.29%) < E. hirta (6.85%) < A. keiskei (8.10%) < A. muricata (10.47%) < C. nutans (11.45%). For methanolic extracts, C. odorata provided the least % yield (0.80%), while C. nutans produced the highest yield (7.49%). The % yield of the extracts for methanol extraction was found to be in the order of C. odorata (0.80%) < L. indica (4.44%) < E. hirta (4.59%) < A. keiskei (4.86%) < A. muricata (5.35%) < C. nutans (7.49%).
Table 1: The percentage yield of plant crude extracts prepared using different solvents

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Total phenolic content in plant crude extracts

The total phenolic content of the plant aqueous and methanolic crude extracts was calculated from the calibration curve of gallic acid [Supplementary Figure 1 [Additional file 1]]. The highest total phenolic content among aqueous extracts was obtained in L. indica (235.56 ± 1.37 mg GAE/g dw), followed by A. muricata (74.35 ± 1.14 mg GAE/g dw), C. odorata (66.61 ± 1.22 mg GAE/g dw), E. hirta (60.84 ± 1.19 mg GAE/g dw), A. keiskei (46.67 ± 0.66 mg GAE/g dw), and C. nutans (31.21 ± 0.70 mg GAE/g dw), as shown in [Figure 1]a. L. indica aqueous extract is significantly higher compared to the aqueous extracts of A. keiskei (P < 0.05), C. nutans (P < 0.01), C. odorata (P < 0.05), and E. hirta (P < 0.05). In general, the total phenolic content of aqueous extracts is lower when compared to methanolic extracts despite the high % yield that was obtained during the extraction. As shown in [Figure 1]b, among the methanolic extracts, E. hirta showed the highest total phenolic content at 307.59 ± 3.57 mg GAE/g dw, followed by L. indica (243.67 ± 1.68 mg GAE/g dw), A. muricata (145.36 ± 0.68 mg GAE/g dw), C. odorata (134.26 ± 0.26 mg GAE/g dw), and C. nutans (98.24 ± 0.30 mg GAE/g dw), while A. keiskei exhibited the lowest total phenolic content at 70.49 ± 0.34 mg GAE/g dw. The total phenolic content of the E. hirta methanolic extract is significantly higher than the methanolic extracts of A. keiskei (P < 0.001), C. nutans (P < 0.01), and C. odorata (P < 0.05).
Figure 1: The total phenolic content of (a) aqueous and (b) methanolic extracts of medicinal plants (mg GAE/g dw). Data are presented as the mean (standard error of the mean) of triplicates in three independent experiments; GAE: Gallic acid equivalent; dw: Dry weight; *P < 0.05, **P < 0.01, and ***P < 0.001. A. keiskei: Angelica keiskei; A. muricata: Annona muricata; C. odorata: Chromolaena odorata; C. nutans: Clinacanthus nutans; E. hirta: Euphorbia hirta; L. indica: Leea indica

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Total flavonoid content in plant crude extracts

The total flavonoid content for all the plant crude extracts was determined by the aluminum chloride approach using a standard curve of quercetin [Supplementary Figure 2 [Additional file 2]]. A similar trend was observed in the total flavonoid content, where the aqueous extract of L. indica and methanolic extract of E. hirta exhibited the highest amount of total flavonoid content. The methanolic extracts also showed higher flavonoid content when compared to aqueous extracts, except for L. indica, where the methanolic extract (26.12 ± 4.21 mg QE/g dw) was lower than the aqueous extract (40.22 ± 5.76 mg QE/g dw). Among the aqueous extracts, L. indica exhibited the highest flavonoid content, followed by A. muricata (20.14 ± 4.12 mg QE/g dw), A. keiskei (12.49 ± 3.45 mg QE/g dw), E. hirta (9.26 ± 3.50 mg QE/g dw), C. nutans (8.76 ± 2.58 mg QE/g dw), and C. odorata (8.16 ± 2.59 mg QE/g dw), as shown in [Figure 2]a. L. indica aqueous extract is significantly higher than the aqueous extracts of A. keiskei (P < 0.01), C. odorata (P < 0.001), C. nutans (P < 0.001), and E. hirta (P < 0.01). However, the E. hirta methanolic extract was observed at 76.43 ± 4.34 mg QE/g dw, followed by C. nutans (64.59 ± 3.54 mg QE/g dw), A. muricata (57.75 ± 7.04 mg QE/g dw), C. odorata (46.54 ± 3.37 mg QE/g dw), L. indica (26.16 ± 4.21 mg QE/g dw) and A. keiskei (22.82 ± 0.89 mg QE/g dw), as shown in [Figure 2]b. E. hirta methanolic extract is significantly higher than the methanolic extracts of A. keiskei (P < 0.001), C. odorata (P < 0.01), and L. indica (P < 0.001).
Figure 2: Total flavonoid content of (a) aqueous and (b) methanolic extracts of medicinal plants (mg QE/g dw). Data are presented as the mean (standard error of the mean) of triplicates in three independent experiments; QE: Quercetin equivalent; dw: Dry weight; **P < 0.01 and ***P < 0.001. A. keiskei: Angelica keiskei; A. muricata: Annona muricata; C. odorata: Chromolaena odorata; C. nutans: Clinacanthus nutans; E. hirta: Euphorbia hirta; L. indica: Leea indica

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Free radical scavenging activity of plant crude extracts

The antioxidant activity of plant crude extracts was determined using the DPPH free radical scavenging assay and gallic acid as the control for the assay. All extracts inhibited DPPH, indicating the presence of antioxidant activity of the extracts. In general, the % inhibition ranged from 16.08% to 99.77% within the concentrations used for all the tested plant extracts, whereby the methanolic extract of E. hirta exhibited the most promising antioxidant activity compared to gallic acid [Table 2]. At the concentration of 1.0 mg/mL, the methanolic extract of E. hirta showed 99.77% ± 0.16% (P < 0.05) of DPPH inhibition, which was significantly higher than the corresponding values of gallic acid. It is worth mentioning that at 0.5 mg/mL, the methanolic extract of E. hirta, which exhibited 87.21% ± 0.12% of DPPH inhibition, was not statistically significant in comparison to the scavenging activity shown by the standard antioxidant. This may be due to the experimental error. A better reduction of scavenging activity was observed when 0.25 mg/mL of methanolic extract of E. hirta was used, whereby the inhibition of DPPH was 89.17% ± 0.35% (P < 0.01).
Table 2: Percentage inhibition of DPPH plant aqueous and methanolic crude extracts. All values were acquired from Supplementary Figure 3

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[Additional file 3]

On the other hand, the % inhibition of DPPH shown by C. nutans extracts was significantly lower than the corresponding values for gallic acid. At the concentration of 1.0 mg/mL, the methanolic extract of C. nutans showed 31.71% ± 1.88% (P < 0.01) of DPPH inhibition. At 0.5 mg/mL, the methanolic extract of C. nutans exhibited 26.01% ± 0.16% (P < 0.01) of DPPH inhibition. The inhibition of DPPH at both concentrations of methanol is significantly lower in comparison to the scavenging activity shown by the standard antioxidant. The lowest % inhibition of DPPH at 0.25 mg/mL C. nutans was not observed in the methanolic extract but in the aqueous extract. The inhibition of DPPH was 16.08% ± 1.12% (P < 0.01) in the aqueous extract. Almost all extracts showed concentration-dependent free radical inhibition in the range of the tested concentrations except for aqueous extracts of A. muricata, C. odorata, and E. hirta and methanolic extracts of A. keiskei and C. nutans, where the % of DPPH inhibition remains similar despite the differences in the extract concentrations.

The IC50 of the extracts is also shown in [Table 2], whereby the lower IC50 value indicated higher antioxidant activity. Based on the data collected, the IC50 values of DPPH inhibition could be determined for several crude extracts, including aqueous extracts of A. keiskei (0.76 mg/mL), A. muricata (0.15 mg/mL), C. odorata (1.00 mg/mL), and L. indica (0.27 mg/mL) and methanolic extracts of A. muricata (0.34 mg/mL), C. odorata (0.35 mg/mL), E. hirta (0.013 mg/mL), and L. indica (0.28 mg/mL). The IC50 value of DPPH inhibition showed that methanolic extract of E. hirta possesses the highest antioxidant activity.

Correlations of antioxidant activity and total phenolic and flavonoid contents among plant crude extracts

Correlation coefficient analysis was performed by comparing the DPPH IC50 values, total phenolic content, and total flavonoid content of the plant crude extracts. The Pearson correlation coefficients between the variables are presented in [Table 3]. The current data suggest an inverse correlation (r = − 0.690, P > 0.05) between the amount of phenolics and the value of IC50 in the DPPH assay [Figure 3]a. However, there was a strong negative significant correlation between DPPH radical scavenging and total flavonoid content (r = −0.708, P < 0.05), as shown in [Figure 3]b. High flavonoid content and low IC50 suggest that a small amount of flavonoid is required to scavenge DPPH, as observed in E. hirta methanolic extract. Therefore, the methanolic extract of E. hirta is selected for the subsequent study.
Table 3: Pearson correlation coefficients between the variables of the plant crude extracts

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Figure 3: Linear correlation for DPPH radical scavenging versus (a) total phenolic content (Pearson correlation coefficient, r = −0.690; P > 0.05; n = 8) and (b) total flavonoid content of the extracts (Pearson correlation coefficient, r = −0.708; P < 0.05; n = 8). DPPH: 2,2-diphenyl-1-picrylhydrazyl

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Anti-proliferative effect of methanolic plant extract on thyroid cells

In vitro MTT assay for methanolic extract of E. hirta in thyroid cells showed that the extract was not entirely cytotoxic to the cells, whereby the cells treated with the extract showed significant growth inhibition (P < 0.05) only after 72 h of treatment. [Figure 4] shows the dose- and time-dependent growth inhibition of Nthy-ori 3-1 and FTC-133 cells treated with E. hirta methanolic extract for 72 h. At 72 h of treatment, the IC50 values for methanolic extract of E. hirta and cisplatin on Nthy-ori 3-1 cells were 62.7 and 145.5 μg/mL, respectively, whereas the IC50 values for the extract and cisplatin on FTC-133 cells were 119.3 and 145.8 μg/mL, respectively. The analysis of the E. hirta methanolic extract demonstrated that the extract could suppress cancerous cells from multiplying at a high concentration after 72 h of treatment. On the other hand, the cells treated with the extract (62.0 μg/mL) and cisplatin (123.6 μg/mL) showed dose-dependent growth inhibition of Hth-74 cells at 72 h of treatment. However, the IC50 value of E. hirta methanolic extract was determined as >50 μg/mL in Hth-74 cells at this treatment time point, indicating that the E. hirta methanolic extract is not a selective cytotoxic agent.
Figure 4: The viability of thyroid cells treated with methanolic crude Euphorbia hirta extracts and cisplatin for 72 h. The 50% inhibition concentration graphs correspond to the treatments at 72 hours in (a) Nthy-ori 3-1, (b) FTC-133, and (c) Hth-74 cells. Data are shown as percentage of viable cells calculated by comparing with untreated control group. All results are expressed in mean (standard error of the mean); n = 3

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   Discussion Top


Many medicinal plants contain large amounts of antioxidant agents, including polyphenols. The presence of active phytochemicals with antioxidant activity contributes to the medicinal properties of plants. Polyphenols, including flavonoids, play an important role in reducing the risk of disease in humans, including cardiovascular diseases, inflammation, and cancers.[15],[16],[17],[18],[19] Increased evidence shows that free radicals give rise to oxidative stress, which leads to disease development.[20],[21] Polyphenols are well-recognized antioxidant agents that can act as free radical terminators. The redox properties of polyphenols allow these compounds to act as potential antioxidant agents. Phenolic compounds are able to neutralize free radicals due to their redox properties, which allow the phenolic compounds to act as reducing agents or free radical inhibitors.[22] Quercetin is naturally found in plants and serves important roles in numerous biological activities, including antioxidant activity and antitumorigenesis.[23],[24] Phytochemicals present in plants protect against oxidative stress and help maintain the balance between free radicals and antioxidants. Nonetheless, biologically active phytochemicals that contribute to the medicinal properties usually occur in low concentration in plants.[25] Therefore, the extraction procedure of the antioxidants is a crucial process in studying the medicinal properties of the plants.

In the present study, six local medicinal plants: A. keiskei, A. muricata, C. odorata, C. nutans, E. hirta, and L. indica were selected for extraction using water and methanol as solvents. There are many methods to obtain phytochemicals from the plant, including extraction, homogenization, and grinding. Extraction is the most common method for recovering phytochemicals from plant materials. In addition, the type of extraction solvent also has a significant impact on the antioxidant activity of the extracts and the % yield of the plant materials.[26] The results obtained with the extracts demonstrate that the solvent of choice could influence the composition of the extracts and their antioxidant activity, due to the presence of compounds of varied chemical properties and polarities.[27] Polar solvents, such as water and methanol, are frequently used for recovering polyphenols from plants; therefore, water and methanol were used in the extraction process. Water has a polarity index of 10.2 while methanol has a polarity index of 5.1. In our current study, the % yield for water was higher than the % yield for methanol, showing that extraction yield increases when the polarity of the solvent increases. Water is commonly used for extraction because it is safe to use and is frequently used for the preparation of infusions and decoctions by herbal medicine practitioners, whereas methanol is commonly used because it is relatively inexpensive, able to dissolve various compounds, and easily evaporates, which is especially useful when the bioactive compounds need to be concentrated using a rotary evaporator. To further evaluate the efficiency of the extraction, total phenolic contents and flavonoid contents were determined using the Folin–Ciocalteu method and aluminum chloride method, respectively.

In general, the total phenolic content in the aqueous crude extracts was lower when compared to the methanolic extracts, possibly attributable to the content, where more nonphenol compounds, such as carbohydrates and terpenes, are accumulated in the aqueous extracts.[28] Furthermore, methanol is found to be more efficient in the extraction of lower molecular weight polyphenols,[29] causing more phenolic compounds to accumulate in the methanolic extracts. In addition, the increased temperature during the concentration step using rotary evaporation possibly could affect the total phenolic activity in the extracts. Plant phenolics are easily degraded when exposed to high temperature as heat may accelerate their oxidation. The effect of solvents on total flavonoid content in the crude extracts is similar to the effect on total phenolic content.

In accordance with the current study, other studies have found high phenolic content in methanolic extract of E. hirta. A study of Basma et al. showed total phenolic content in methanolic extract of E. hirta leaves at 206.17 ± 1.95 mg GAE/g dw, when compared to other parts of the plant.[30] Unlike the current study, Asha et al.'s study found the presence of high phenolic content in the methanolic extract (285.41 ± 3.00 GAE/g dw) and in the aqueous extract (275.64 ± 2.45 mg GAE/g dw) of E. hirta leaves.[31] The variation in the content of the extracts could be a consequence of several factors, including the differences in the plant matrix and the method, as well as the conditions of extraction, such as temperature and duration of extraction.[32],[33] Several studies have reported the presence of polyphenols and antioxidant activity in the extracts of L. indica,[34],[35],[36],[37],[38],[39] C. nutans,[40],[41],[42],[43] C. odorata,[44],[45],[46],[47],[48] and A. muricata.[49],[50],[51],[52],[53] A study found variation in the polyphenol content in the extracts of A. keiskei, when the plant was extracted with different compositions of water/ethanol and stored at different temperatures.[54]

The DPPH scavenging activity of the E. hirta methanolic extract is higher than the scavenging activity of the standard drug showing proton-donating ability and thus could serve as the free radical inhibitor. The potent antioxidant activity of the E. hirta methanolic extract was also reported by Rajeh et al.'s study,[55] showing the highest content in the leaf extract. The observed free radical scavenging activity may be attributed to the presence of polyphenols in the extracts.[56]

The correlation analysis was performed on total phenolic content, total flavonoid content, and DPPH IC50 of the E. hirta crude extracts in this study. The significant negative correlation between DPPH IC50 and total flavonoid content compared to total phenolic content, indicating a pronounced influence of flavonoids on the antioxidant activity of the crude extracts in terms of DPPH radical scavenging. Kiselova et al.'s study found a strong linear correlation between the polyphenol content of the aqueous extracts from Bulgarian herbs and the in vitro antioxidant activities.[57] Our data are in agreement with those reported by Borkataky et al.'s study [58] in Eclipta alba and the study by Rebaya et al.[59] in Halimium halimifolium, where the polyphenols in the medicinal plants exhibited strong linear relationships with the antioxidant activities. However, a study reported that the strong linear relationship could not be established between total polyphenols and antioxidant activity against β-carotene and linoleic acid of several medicinal plant extracts.[60] Ghasemi et al.'s study did not find a good correlation between the radical scavenging activity and phenolic content in 13 citrus species peels and tissue,[61] possibly due to the differences in structural features of polyphenols that determine their antioxidant properties, where the number of radicals that are reduced seems to be correlated with the number of the available hydroxyl groups.[62]


   Conclusion Top


E. hirta methanolic extract is a potential antioxidant agent for the development of local industries for natural products as the E. hirta methanolic extract displays high total phenolic and flavonoid contents, as well as a low IC50 value. The study also provides appropriate assays that are simple, specific, and rapid to screen for the presence of active compounds in plants for the development of local industries for natural products.

Acknowledgements

We thank Dr. Nils-Erik Heldin for providing the cells lines. We also thank the Fukang Herbs Sdn Bhd for providing the plant materials.

Financial support and sponsorship

The study was supported by the University-Industry Engagement Project Grant Scheme from Malaysian Anti-Cancer Association (MACA; account no: 304/CIPPM/650717/M146). The first author is funded by Universiti Sains Malaysia Fellowship Scheme.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Petrovska BB. Historical review of medicinal plants' usage. Pharmacogn Rev 2012;6:1-5.  Back to cited text no. 1
    
2.
Zarfeshany A, Asgary S, Javanmard SH. Potent health effects of pomegranate. Adv Biomed Res 2014;3:100.  Back to cited text no. 2
[PUBMED]  [Full text]  
3.
Jurenka JS. Therapeutic applications of pomegranate (Punica granatum L.): A review. Altern Med Rev 2008;13:128-44.  Back to cited text no. 3
    
4.
Cragg GM, Newman DJ. Plants as a source of anti-cancer agents. J Ethnopharmacol 2005;100:72-9.  Back to cited text no. 4
    
5.
Newman DJ, Cragg GM. Natural products as sources of new drugs over the 30 years from 1981 to 2010. J Nat Prod 2012;75:311-35.  Back to cited text no. 5
    
6.
Cragg GM, Pezzuto JM. Natural products as a vital source for the discovery of cancer chemotherapeutic and chemopreventive agents. Med Princ Pract 2016;25 Suppl 2:41-59.  Back to cited text no. 6
    
7.
Squires MS, Hudson EA, Howells L, Sale S, Houghton CE, Jones JL, et al. Relevance of mitogen activated protein kinase (MAPK) and phosphotidylinositol-3-kinase/protein kinase B (PI3K/PKB) pathways to induction of apoptosis by curcumin in breast cells. Biochem Pharmacol 2003;65:361-76.  Back to cited text no. 7
    
8.
Chan MM, Soprano KJ, Weinstein K, Fong D. Epigallocatechin-3-gallate delivers hydrogen peroxide to induce death of ovarian cancer cells and enhances their cisplatin susceptibility. J Cell Physiol 2006;207:389-96.  Back to cited text no. 8
    
9.
Lev-Ari S, Starr A, Vexler A, Karaush V, Loew V, Greif J, et al. Inhibition of pancreatic and lung adenocarcinoma cell survival by curcumin is associated with increased apoptosis, down-regulation of COX-2 and EGFR and inhibition of erk1/2 activity. Anticancer Res 2006;26:4423-30.  Back to cited text no. 9
    
10.
Tang SN, Fu J, Shankar S, Srivastava RK. EGCG enhances the therapeutic potential of gemcitabine and CP690550 by inhibiting STAT3 signaling pathway in human pancreatic cancer. PLoS One 2012;7:e31067.  Back to cited text no. 10
    
11.
Pham-Huy LA, He H, Pham-Huy C. Free radicals, antioxidants in disease and health. Int J Biomed Sci 2008;4:89-96.  Back to cited text no. 11
    
12.
Halliwell B. Free radicals and antioxidants: Updating a personal view. Nutr Rev 2012;70:257-65.  Back to cited text no. 12
    
13.
Batra P, Sharma AK. Anti-cancer potential of flavonoids: Recent trends and future perspectives 3 Biotech 2013;3:439-59.  Back to cited text no. 13
    
14.
Chatatikun M, Chiabchalard A. Phytochemical screening and free radical scavenging activities of orange baby carrot and carrot (Daucus carota linn.) root crude extracts. J Chem Pharm Res 2013;5:97-102.  Back to cited text no. 14
    
15.
Hertog MG, Kromhout D, Aravanis C, Blackburn H, Buzina R, Fidanza F, et al. Flavonoid intake and long-term risk of coronary heart disease and cancer in the seven countries study. Arch Intern Med 1995;155:381-6.  Back to cited text no. 15
    
16.
Fotsis T, Pepper MS, Aktas E, Breit S, Rasku S, Adlercreutz H, et al. Flavonoids, dietary-derived inhibitors of cell proliferation and in vitro angiogenesis. Cancer Res 1997;57:2916-21.  Back to cited text no. 16
    
17.
Hollman PC, Katan MB. Absorption, metabolism and health effects of dietary flavonoids in man. Biomed Pharmacother 1997;51:305-10.  Back to cited text no. 17
    
18.
Agrawal AD. Pharmacological activities of flavonoids: A review. Int J Pharm Sci Nanotechnol 2011;4:1394-8.  Back to cited text no. 18
    
19.
Kumar S, Pandey S, Pandey AK. In vitro antibacterial, antioxidant, and cytotoxic activities of Parthenium hysterophorus and characterization of extracts by LC-MS analysis. Biomed Res Int 2014;2014:495154.  Back to cited text no. 19
    
20.
Machlin LJ, Bendich A. Free radical tissue damage: Protective role of antioxidant nutrients. FASEB J 1987;1:441-5.  Back to cited text no. 20
    
21.
Uddin S, Ahmad S. Dietary antioxidants protection against oxidative stress. Biochem Educ 1995;23:2-7.  Back to cited text no. 21
    
22.
Soobrattee MA, Neergheen VS, Luximon-Ramma A, Aruoma OI, Bahorun T. Phenolics as potential antioxidant therapeutic agents: Mechanism and actions. Mutat Res 2005;579:200-13.  Back to cited text no. 22
    
23.
Suolinna EM, Buchsbaum RN, Racker E. The effect of flavonoids on aerobic glycolysis and growth of tumor cells. Cancer Res 1975;35:1865-72.  Back to cited text no. 23
    
24.
Nakayama T. Suppression of hydroperoxide-induced cytotoxicity by polyphenols. Cancer Res 1994;54:1991s-3s.  Back to cited text no. 24
    
25.
Dhanani T, Shah S, Gajbhiye NA, Kumar S. Effect of extraction methods on yield, phytochemical constituents and antioxidant activity of Withania somnifera. Arabia J Chem 2017;10:S1193-9.  Back to cited text no. 25
    
26.
Gong Y, Liu X, He WH, Xu HG, Yuan F, Gao YX, et al. Investigation into the antioxidant activity and chemical composition of alcoholic extracts from defatted marigold (Tagetes erecta L.) residue. Fitoterapia 2012;83:481-9.  Back to cited text no. 26
    
27.
Sultana B, Anwar F, Ashraf M. Effect of extraction solvent/technique on the antioxidant activity of selected medicinal plant extracts. Molecules 2009;14:2167-80.  Back to cited text no. 27
    
28.
Do QD, Angkawijaya AE, Tran-Nguyen PL, Huynh LH, Soetaredjo FE, Ismadji S, et al. Effect of extraction solvent on total phenol content, total flavonoid content, and antioxidant activity of Limnophila aromatica. J Food Drug Anal 2014;22:296-302.  Back to cited text no. 28
    
29.
Dai J, Mumper RJ. Plant phenolics: Extraction, analysis and their antioxidant and anticancer properties. Molecules 2010;15:7313-52.  Back to cited text no. 29
    
30.
Basma AA, Zakaria Z, Latha LY, Sasidharan S. Antioxidant activity and phytochemical screening of the methanol extracts of Euphorbia hirta L. Asian Pac J Trop Med 2011;4:386-90.  Back to cited text no. 30
    
31.
Asha S, Thirunavukkarasu P, Mani VM, Sadiq AM. Antioxidant activity of Euphorbia hirta linn leaves extracts. Eur J Med Plants 2016;14:1-14.  Back to cited text no. 31
    
32.
Robards K. Strategies for the determination of bioactive phenols in plants, fruit and vegetables. J Chromatogr A 2003;1000:657-91.  Back to cited text no. 32
    
33.
Pinelo M, Manzocco L, Nuñez MJ, Nicoli MC. Interaction among phenols in food fortification: Negative synergism on antioxidant capacity. J Agric Food Chem 2004;52:1177-80.  Back to cited text no. 33
    
34.
Srinivasan GV, Ranjith C, Vijayan KK. Identification of chemical compounds from the leaves of Leea indica. Acta Pharm 2008;58:207-14.  Back to cited text no. 34
    
35.
Kirillov NF, Makhmudov RR, Gavrilov AG, Mardanova LG. Analgesic activity of 4-aryl-8(arylmethylene)-5,6,7,8-tetrahydrospiro[chromen-3,1'-cycloalkan]-2 (4H)-ones. Pharm Chem J 2012;46:269-70.  Back to cited text no. 35
    
36.
Reddy NS, Navanesan S, Sinniah SK, Wahab NA, Sim KS. Phenolic content, antioxidant effect and cytotoxic activity of Leea indica leaves. BMC Complement Altern Med 2012;12:128.  Back to cited text no. 36
    
37.
Wong YH, Abdul Kadir H. Induction of mitochondria-mediated apoptosis in Ca Ski human cervical cancer cells triggered by mollic acid arabinoside isolated from Leea indica. Evid Based Complement Alternat Med 2012;2012:684740.  Back to cited text no. 37
    
38.
Rahman MA, Imran TB, Islam S. Antioxidative, antimicrobial and cytotoxic effects of the phenolics of Leea indica leaf extract. Saudi J Biol Sci 2013;20:213-25.  Back to cited text no. 38
    
39.
Ramesh D, Ramesh DY, Kekuda TR, Onkarappa R, Vinayaka KS, Raghavendra HL. Antifungal and radical scavenging activity of leaf and bark of Leea indica (Burm. f.) Merr. J Chem Pharm Res 2015;7:105-10.  Back to cited text no. 39
    
40.
Ghasemzadeh A, Nasiri A, Jaafar HZ, Baghdadi A, Ahmad I. Changes in phytochemical synthesis, chalcone synthase activity and pharmaceutical qualities of Sabah snake grass (Clinacanthus nutans L.) in relation to plant age. Molecules 2014;19:17632-48.  Back to cited text no. 40
    
41.
Barek ML, Hasmadi M, Zaleha AZ, Fadzelly AB. Effect of different drying methods on phytochemicals and antioxidant properties of unfermented and fermented teas from Sabah snake grass (Clinacanthus nutans lind.) leaves. Int Food Res J 2015;22:661-70.  Back to cited text no. 41
    
42.
Raya KB, Ahmad SH, Farhana SF, Mohammad M, Tajidin NE, Parvez A. Changes in phytochemical contents in different parts of Clinacanthus nutans (Burm. f.) Lindau due to storage duration. Bragantia 2015;74:445-2.  Back to cited text no. 42
    
43.
Sarega N, Imam MU, Ooi DJ, Chan KW, Md Esa N, Zawawi N, et al. Phenolic rich extract from Clinacanthus nutans attenuates hyperlipidemia-associated oxidative stress in rats. Oxid Med Cell Longev 2016;2016:4137908.  Back to cited text no. 43
    
44.
Srinivasa Rao K, Chaudhury PK, Pradhan A. Evaluation of anti-oxidant activities and total phenolic content of Chromolaena odorata. Food Chem Toxicol 2010;48:729-32.  Back to cited text no. 44
    
45.
Balakrishna A, Josthna P, Naidu CV. Evaluation of in vitro antioxidant activity of root bark of Chromolaena odorata – An important antidiabetic medicinal plant. Pharmacophore 2014;5:49-57.  Back to cited text no. 45
    
46.
Omoregie ES, Oriakhi K, Oikeh EI, Okugbo OT, Akpobire D. Comparative study of phenolic content and antioxidant activity of leaf extracts of Alstonia boonei and Eupatorium odoratum. Nig J Basic Appl Sci 2014;22:91-7.  Back to cited text no. 46
    
47.
Madhavan M. Quantitative estimation of total phenols and antibacterial studies of leaves extracts of Chromolaena odorata (L.) King and HE Robins. Int J Herb Med 2015;3:20-3.  Back to cited text no. 47
    
48.
Hanphanphoom S, Krajangsang S. Antimicrobial activity of Chromolaena odorata extracts against bacterial human skin infections. Mod Appl Sci 2016;10:159.  Back to cited text no. 48
    
49.
Adefegha SA, Oyeleye SI, Oboh G. Distribution of phenolic contents, antidiabetic potentials, antihypertensive properties, and antioxidative effects of soursop (Annona muricata L.) fruit parts in vitro. Biochem Res Int 2015;2015:347673.  Back to cited text no. 49
    
50.
Hardoko H, Putri TS, Eveline E. In vitro anti-gout activity and phenolic content of “black tea” soursop Annona muricata L. leaves brew. J Chem Pharm Res 2015;7:735-43.  Back to cited text no. 50
    
51.
Ibrahim NS, Abdullahi M. Cytotoxicity, total phenolic contents and antioxidant activity of the leaves extract of Annona muricata. ChemSearch J 2015;6:46-51.  Back to cited text no. 51
    
52.
Padmini SM, Samarasekera R, Pushpakumara DK. Antioxidant capacity and total phenol content of Sri Lankan Annona muricata L. Trop Agric Res 2015;25:252-60.  Back to cited text no. 52
    
53.
Siqueira AD, Moreira AC, Melo ED, Stamford TC, Stamford TL. Dietary fibre content, phenolic compounds and antioxidant activity in soursops (Annona muricata L.). Rev Bras Frutic 2015;37:1020-6.  Back to cited text no. 53
    
54.
Li L, Aldini G, Carini M, Chen CY, Chun HK, Cho SM, et al. Characterisation, extraction efficiency, stability and antioxidant activity of phytonutrients in Angelica keiskei. Food Chem 2009;115:227-32.  Back to cited text no. 54
    
55.
Rajeh MA, Zuraini Z, Sasidharan S, Latha LY, Amutha S. Assessment of Euphorbia hirta L. leaf, flower, stem and root extracts for their antibacterial and antifungal activity and brine shrimp lethality. Molecules 2010;15:6008-18.  Back to cited text no. 55
    
56.
Firuzi O, Lacanna A, Petrucci R, Marrosu G, Saso L. Evaluation of the antioxidant activity of flavonoids by “ferric reducing antioxidant power” assay and cyclic voltammetry. Biochim Biophys Acta 2005;1721:174-84.  Back to cited text no. 56
    
57.
Kiselova Y, Ivanova D, Chervenkov T, Gerova D, Galunska B, Yankova T. Correlation between the in vitro antioxidant activity and polyphenol content of aqueous extracts from Bulgarian herbs. Phytother Res 2006;20:961-5.  Back to cited text no. 57
    
58.
Borkataky M, Kakoty BB, Saikia LR. Influence of total phenolic content and total flavonoid content on the DPPH radical scavenging activity of Eclipta alba (L.) Hassk. Int J Pharm Pharm Sci 2013;5:324-7.  Back to cited text no. 58
    
59.
Rebaya A, Belghith SI, Baghdikian B, Leddet VM, Mabrouki F, Olivier E, et al. Total phenolic, total flavonoid, tannin content, and antioxidant capacity of Halimium halimifolium (Cistaceae ). J Appl Pharm Sci 2015;5:52-7.  Back to cited text no. 59
    
60.
Bajpai M, Pande A, Tewari SK, Prakash D. Phenolic contents and antioxidant activity of some food and medicinal plants. Int J Food Sci Nutr 2005;56:287-91.  Back to cited text no. 60
    
61.
Ghasemi K, Ghasemi Y, Ebrahimzadeh MA. Antioxidant activity, phenol and flavonoid contents of 13 Citrus species peels and tissues. Pak J Pharm Sci 2009;22:277-81.  Back to cited text no. 61
    
62.
Mensor LL, Menezes FS, Leitão GG, Reis AS, dos Santos TC, Coube CS, et al. Screening of Brazilian plant extracts for antioxidant activity by the use of DPPH free radical method. Phytother Res 2001;15:127-30.  Back to cited text no. 62
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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