Antioxidant activity of polyphenolic compounds isolated from ethyl-acetate fraction of Acacia hydaspica R. Parker.

Background: Acacia hydaspica belongs to family leguminosae possess antioxidant, anti-inflammatory and anticancer activities. During our search for antioxidant compounds from A. hydaspica, we carried out bioassay guided fractionation and obtained antioxidant compounds with free radical scavenging activity.

Materials and methods: The polyphenol compounds in the plant extract of A. hydaspica were isolated by combination of different chromatographic techniques involving vacuum liquid chromatography and medium pressure liquid chromatography. The structural heterogeneity of isolated compounds was characterized by high pressure liquid chromatography, MS-ESI and NMR spectroscopic analyses. The antioxidant potential of isolated compounds has been investigated by 1,1-diphenyl-2-picrylhydrazyl (DPPH), nitric oxide scavenging potential, hydroxyl radical scavenging potential, ferric reducing/antioxidant power (FRAP) model systems and total antioxidant capacity measurement.

Results: The isolated compounds show the predominance of signals representative of 7-O-galloyl catechins, catechins and methyl gallate. Flash chromatographic separation gives 750 mg of 7-O galloyl catechin, 400 mg of catechin and 150 mg of methyl gallate from 4 g loaded fraction on ISCO. Results revealed that C1 was the most potent compound against DPPH (EC₅₀ 1.60 ± 0.035 µM), nitric oxide radical (EC₅₀ 6 ± 0.346 µM), showed highest antioxidant index (1.710 ± 0.04) and FRAP [649.5 ± 1.5 µM Fe(II)/g] potency at 12.5 µM dose compared to C2, C3 and standard reference, whereas C3 showed lower EC₅₀ values (4.33 ± 0.618 µM) in OH radical scavenging assay.

Conclusion: Present research reports for the first time the antioxidant activity of polyphenolic compounds of A. hydaspica. Result showed good resolution and separation from other constituents of extract and method was found to be simple and precise. The isolation of catechin from this new species could provide a varied opportunity to obtain large quantities of catechin and catechin isomers beside from green tea. Free radical scavenging properties of isolated catechin isomers from A. hydaspica merit further investigations for consumption of this plant in oxidative stress related disorders.