Antioxidant, anti-acetylcholinesterase and anti-glycosidase properties of three species of Swertia, their xanthones and amarogentin: A comparative study

Aim: The aim of the study was to analyze the antioxidant, anti-amylase, anti-glucosidase and antiacetylcholinesterase (anti-AChE) properties of the leafy shoots of three Indian species of Swertia e.g. Swertia chirata and its substitutes Swertia bimaculata, and Swertia decussata, their xanthones and amarogentin. Methods: Antioxidant activity of the methanolic extracts of leafy shoots was measured in terms of DPPH, superoxide and nitric oxide radical scavenging activities as well as metal chelating properties. Enzyme inhibitory properties were measured using AChE, α-amylase and α-glucosidase respectively. Five xanthones bellidifolin (1), swerchirin (2), decussatin (3), mangiferin (4) and 1-hydroxy-3,5,8-trimethoxy xanthone (6) and one iridoid, amarogentin (5) were isolated from Swertia chirata. The activities of the isolated components were compared. Results: Swertia chirata exhibited best antioxidant and anti-AChE properties than the other two species. The plants also possessed α-glucosidase inhibitory properties but weak α-amylase inhibitory activity. Highest activities were observed in Swertia chirata. We report here, for the first time, the antioxidant, anti-AChE and anti-glycosidase activity of 1-hydroxy-3,5,8-trimethoxy xanthone. This xanthone had strongest DPPH radical scavenging activity and anti-AChE property. Conclusion: The results suggest the beneficial effects of the xanthones of Swertia chirata. But further study should be carried out to prove the efficacy in vivo