Abstract

The aim of this study was to assess the antioxidant capacities, phytochemical constituents, total phenolic and flavonoid contents of methanol and aqueous extracts of Hippophae rhamnoides L. leaves form trans-Himalayan cold desert of Ladakh. The 1,1-diphenyl-2-picrylhydrazyl radical (DPPH^∙) scavenging capacity of the methanol and aqueous extracts increased in a dose dependent manner (up to 0.1 mg/ ml) and plant leaves extract concentrations required for 50% inhibition of DPPH radical scavenging effect (IC₅₀) were recorded as 0.014 and 0.015 mg/ml for methanol and aqueous extracts, respectively. The leaf extracts also scavenged the ABTS^.+ radical generated by 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS)/2.4 mM potassium persulfate (PPS) system and the IC₅₀ values were found to be 0.017 and 0.018 mg/ml for methanol and aqueous extracts, respectively. The total antioxidant power of the extract was determined by ferric reducing antioxidant power (FRAP) assay. Qualitative  analysis  of  the  phytochemicals  of  aqueous  extract  revealed  the  presence  of alkaloids, carbohydrates, saponins, proteins, phenols and  flavonoids. The methanol extract was found to contain phenols and flavonoids as major phyto-components. Total polyphenol and phenolic acidcontents in the methanol extract were found to be 269.85 ± 15.25 and 410.72 ± 9.48 mg gallic acid equivalent (GAE)/g dry weight, respectively. Total flavonoid and flavonol contents were estimated to be 82.28 ± 3.21 and 151.25 ± 8.75 mg quercetin equivalent (QE)/g dry weight, respectively. Total polyphenol and phenolic acid contents in the aqueous extract were found to be 157.05 ± 11.21 and 490.50 ± 10.20 mg GAE/g dry weight, respectively. Total  flavonoid  and  flavonol contents  in the aqueous  extract were  estimated  to be 95.80  ±  3.12 and  162.72  ± 9.18  mg  QE/g  dry  weight,  respectively. The methanol and aqueous leaf extracts indicated presence of vital phytoconstituents of polyphenols, flavonoids, flavonols that contributed significantly to its antioxidant capacity. Results obtained from the present study signify that the methanol and aqueous leaf extracts of H. rhamnoides possess antioxidant properties and could possibly act as primary antioxidants by scavenging free radicals in disease conditions.

Key words: Hippophae rhamnoides L., leaf extract, antioxidant capacities, phyto-components, phenolics, flavonoids.