Antioxidant compounds from a South Asian beverage and medicinal plant, Cassia auriculata

Cassia auriculata (Caesalpiniaceae) is a common South Asian beverage and medicinal plant widely used in tradition medicine for treating diabetes and various other disease conditions. The alcoholic extract of the aerial part of C. auriculata displayed potent antioxidant activity when assessed by DPPH radical scavenging, lipid peroxidation and reducing power analysis. Fractionation of the crude extract using solvents of ascending polarity showed that the ethyl acetate fraction is the most active followed by the chloroform fraction while the petroleum ether, n-butanol and water fractions were less active than the crude extract. Further activity-guided fractionation studies on the active fractions resulted in the isolation of the major antioxidant constituent kaempferol-3-O-rutinoside together with kaempferol, quercetin and luteolin. The identity of the compounds was established based on extensive spectroscopic studies including 2D NMR.