(200-40) Comparative phytochemical evaluation and determination of the antioxidant potential of five congeneric species of genus Rheum from the North-West Indian Himalayas: Identification of elite chemotype(s)
DST INSPIRE Faculty Fellow University of Kashmir, Srinagar, India Srinagar, Jammu and Kashmir, India
Body of Abstract: The genus Rheum has been recognized as a rich source of significant phytoconstituents with high therapeutic repute in different traditional systems of medicine. The present study aimed to identify and quantify important specialized metabolites, the effect of altitude and environmental stress on their abundance, and the evaluation of total antioxidant (scavenging) potential in five congeneric species of Rheum thriving in different ecological niches across the NW Himalayas. Among seven different extraction solvents used, HPLC-ESI-MS/MS revealed that ethyl acetate extract provides a better yield and was taken forward for all subsequent extractions. Following LC-QTOF-MS, R. spiciforme was found to contain the highest proportion of all studied metabolites among all species. The intra-specific variation in metabolite content presented AL3, TL1, WL4, ML1, and SL3 populations as the elite chemotypes for R. australe, R. tibeticum, R. webbianum, R. moorcroftianum, and R. spiciforme, respectively. Further, metabolite accumulation patterns in these species showed a positive correlation with altitude advocating its role in defining the chemistry of the host. In addition, the altitude was also found to influence plant antioxidant components including anthocyanins, phyto-pigments, total flavonoids, and total phenolics proportionally in all five species. Oxidative stress at higher altitudes was perceived to be responsible for higher phytoconstituents accumulation as observed from higher levels of superoxide dismutase (SOD), catalase (CAT), and proline. Five different assays (conclusive) including [DPPH (1,1-diphenyl-2-picrylhydrazyl), ABTS (2,2-azino-bis ethylbenzthiazoline-6-sulphonic acid), FRAP (Ferric ion reducing antioxidant power), CUPRAC (Cupric ion reducing capacity), and PM (Phosphomolybdenum)] revealed a similar trend of the scavenging potential wherein R. tibeticum and R. spiciforme exhibited the highest antioxidant potential. Overall, this study has the potential to act as a resource base for prospective endeavors targeting elite chemotypes from the studied species for examining their potential applications in the manufacturing and marketing of health-promoting and therapeutic natural products.