In vitro Antioxidant Activities and Polyphenol Contents of Seven Commercially Available Fruits

Background: Fruits are considered one of the richest sources of natural antioxidants. Their consumption has been linked to the prevention of oxidative stress‑induced diseases. Objective: In this study, in vitro antioxidant activities of blueberry, jackfruit, blackberry, black raspberry, red raspberry, strawberry, and California table grape extracts were evaluated. Materials and Methods: Antioxidant activities were determined by 2,2‑diphenyl‑1‑picrylhydrazyl (DPPH), ferric reducing antioxidant potential (FRAP), 2,2′‑azino‑bis (3‑ethylbenzothiazoline‑6‑sulfonic acid) diammonium salt (ABTS), nitric oxide (NO), superoxide anion (O2 −) scavenging assays, and ferric reducing power. Results: Black raspberry extract had the highest phenolic (965.6 ± 2.9 mg gallic acid equivalents [GAE]/g), flavonoid (186.4 ± 1.7 mg quercetin equivalents/g), and proanthocyanidin (2677 ± 71.1 mg GAE/g) contents. All fruit extracts exhibited increasing radical scavenging activities with increased concentrations. At 100 μg/ml, red raspberry extract showed the highest ferric reducing power (A700 = 0.3 ± 0.0052) and FRAP activity (A593 = 11.43 mM Fe2+/g). Black raspberry extract (100 μg/ml) exhibited the highest DPPH activity (A517 = 89.03 ± 0.0471). Jackfruit extract (100 μg/ml) had the highest ABTS (A734 = 35.6 ± 0.613), NO (A540 = 81.7 ± 0.2), and O2 − radical scavenging (A230 = 55.5 ± 0.2) activities. Positive correlations were observed between IC₅₀ values for different radical scavenging activities and different polyphenolics. Red raspberry extract had the highest Pearson’s coefficient values (0.952–1) between total phenolics, flavonoids, and proanthocyanidins and DPPH and superoxide radical scavenging activities. Conclusions: The antioxidant rich fruits in this study are good source of functional food and nutraceuticals that have the potential to improve human health.