Evaluation of chemical constituents and in vitro antimicrobial, antioxidant and cytotoxicity potential of rhizome of Astilbe rivularis (Bodho-okhati), an indigenous medicinal plant from Eastern Himalayan region of India.

Astilbe rivularis L. is an indigenous medicinal plant growing in high altitude of Darjeeling Himalayan region of India and Nepal. The plant rhizome has been used traditionally as medicine by local tribes to treat various ailments including infectious and other diseases. The present study aims to evaluate the plant rhizome for chemical composition and in vitro antioxidant, antibacterial and cytotoxic bioactivities.The methanolic extract of rhizome was analyzed for phytochemical constituents by biochemical and GC-MS methods. The antibacterial property of the extract was monitored by agar well diffusion assay. Antioxidant potential was assessed by in vitro DPPH and ABTS scavenging assays and scavenging of induced ROS in normal cell line using fluorescent probe 2', 7'- dichlorofluorescin diacetate. Cytotoxic effect of the extract in cancer and normal cell lines was determined by MTT assay.

Rhizome methanolic extract contained terpenoids, flavonoids, tannins, phenols, alkaloids, saponins and reducing sugars. Further analysis of extract by GC-MS showed the presence of nine major constituents belonging to terpenoids and fatty acid groups. The extract had marked in vitro ROS scavenging activity and moderate antibacterial activity against gram positive and gram negative bacteria. It showed cytotoxicity to neuroblastoma (SHSY5Y) cell line with IC₅₀ value < 100 μg ml^{- 1} but had least damaging effect on normal cells, like human embryonic kidney (HEK-293) and liver (WRL-68) cell lines.

The study suggests that Astilbe rivularis has potential as source of new potent antibacterial, antioxidant and anticancer agents. Further studies on purification and characterization of active compounds from Astilbe rivularis and their biological evaluation are highly recommended.