Intra-specific genetic diversity, phytochemical analysis and antioxidant activities of a potential Himalayan Swertia (Swertia bimaculata Hook. F. & Thomas.)

Swertia bimaculata Hook. F. & Thomas. is an unexplored, less bitter species which is frequently mixed with Swertia chirayita as a substitute and adulterants. Continuous indiscriminate harvesting has enormously reduced its population strength in the natural habitat of Eastern Himalayas. The aim of the present work was to evaluate the level of genetic diversity, phytochemical constituents and antioxidant potential of different parts of S. bimaculata. Nineteen accessions of S. bimaculata collected from different locations of the Sikkim Himalayan region were analysed for genetic variation using 20 ISSR primers which generated 56 (93.3%) polymorphic amplicons. A high level of genetic diversity (h = 0.22 and I = 0.32) was detected among accessions. There was a moderate genetic differentiation (Gst = 0.44) observed among populations. Different parts of the species were evaluated in terms of total polyphenol, flavonoid, alkaloid, saponin and tannin contents. The study revealed that the level of polyphenols, flavonoids and alkaloids in the methanol extracts of the leaf and stem of S. bimaculata was considerable. However, leaf extracts showed significantly higher content of phytochemicals than the other parts. Antioxidant potential of different parts was tested by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) model system. Methanolic extracts of leaf exhibited stronger radical scavenging ability and its percentage of inhibition reached to 93.14% with the lowest IC50 value of 4.80 μg/ml, which indicates its good antioxidant potential. Leaf of S. bimaculata can be used as a source of important phytochemicals like xanthones and as a substitute of commonly used S. chirayita.