Phytochemical Insights and Bioactive Potentials of Alstonia scholaris, a Variety from Mizoram, India: Studies of the Antioxidant and Anti-Infective Properties

Background: A distinct variety of Alstonia scholaris in Mizoram, Northeast India, is a medicinal plant applied in the remedy of various ailments, including diarrhoea, dysentery, gastrointestinal infections, malaria and wounds. Objectives: To evaluate A. scholaris bark for its secondary metabolite components, antioxidant, antibacterial, antifungal and anthelmintic properties. Materials and Methods: The chloroform extract of A. scholaris was chemically assessed for its phytocompounds. Antioxidant content was evaluated using phenol, flavonoid and total antioxidant estimations. Antioxidant reaction was determined using DPPH (2,2-diphenyl-1-picrylhydrazyl)- scavenging and ferric-reducing activities. Antimicrobial susceptibility assays were performed against bacteria and fungi. Anthelmintic activity was examined on a parasitic tapeworm of chicken. Results: Carbohydrates, reducing sugars, phytosterols and saponins were detected as the main bioactive secondary metabolites. The plant extract possesses appreciable amounts of antioxidants, with the total phenolic content of 11.42±0.08 mg GAE/g (gallic acid equivalent), the total flavonoid content of 57.87±3.53 mg QCE/g (quercetin equivalent) and the total antioxidant capacity of 7.22±0.01 mg AAE/g (ascorbic acid equivalent). Free radical-scavenging estimation against DPPH (2,2-diphenyl-1-picrylhydrazyl) indicated a half-maximal Inhibitory Concentration (IC₅₀) value of 28.96 μg/mL. The Ferric-Reducing Antioxidant Power (FRAP) assay showed a linear concentration-dependent antioxidation reaction similar to the standard ascorbic acid. It effectively inhibited Gram-positive bacteria (Bacillus cereus, Enterococcus faecalis and two strains of Staphylococcus aureus), as well as Gram-negative species (Escherichia coli and Salmonella typhi). A notable observation was its effectiveness against an antibiotic-resistant S. aureus. The antifungal efficacy against three pathogenic species was in the order Fusarium keratoplasticum keratoplasticum<Aspergillus fumigatus<Candida albicans. It was highly effective against an intestinal tapeworm, causing structural damages in all vital parts of the parasite body as revealed by histology and scanning electron microscopy. Conclusion: The findings indicate that A. scholaris bark contains important bioactive compounds that are health benefit, antimicrobial and anthelmintic in nature. This is the first report on the broad-spectrum anti-infective potential of A. scholaris and provides an evident-based therapeutic value of the plant.