In vitro antioxidant potential of eleven medicinal herbs in Sri Lanka: Correlation with phenols and flavonoids

Antioxidants play a crucial role in preventing and treating non-communicable diseases (NCDs) by scavenging free radicals. Medicinal herbs, used for centuries in traditional healthcare systems, have been gaining attention recently due to the negative effects of synthetic medicines. This study assessed the total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity of aqueous extracts from eleven commonly used Sri Lankan Ayurvedic plants and determined the relationship between their phenolic and flavonoid content with antioxidant activities. TPC and TFC were measured using the Folin-Ciocalteu and Aluminum chloride methods, respectively. Antioxidant activity was evaluated using ABTS, FRAP, and DPPH assays. Pearson correlation analysis assessed the relationship between TPC and TFC with antioxidant activity. Phyllanthus emblica (PE) showed the highest TPC, TFC, and antioxidant activity (p≤0.05) significantly. TPC and TFC exhibited significantly positive correlations with FRAP and ABTS assays while the DPPH assay showed a negative correlation. Phenols and flavonoids in the selected extracts may significantly contribute to the antioxidant activity measured by ABTS and FRAP assays, while other secondary metabolites and their synergism effect may influence the DPPH assay. The significant antioxidant properties of PE, highlight its potential to treat various NCDs. Further studies are essential to determine their bioactivities, effective doses, and toxicity levels.