Antioxidant analysis and antioxidant composition of water dropwort (Oenanthe javanica)

Water dropwort (Oenanthe javanica) is a plant endemic in China, Japan, and other Asian Countries, including the Philippines. Locally called Seri in Japan and ongsoy in the Philippines, it has recently been shown to possess high antioxidant capacity, and therefore a potential functional food resource. This study was conducted to identify and characterize the major antioxidants in water dropwort. Twenty-two water dropwort samples cultivated in three regions in Japan from October 2012 to December 2013 were subjected to lyophilization, and the lipophilic and hydrophilic components were sequentially extracted with n-hexane : dichloromethane and methanol : water : acetic acid, respectively, using an accelerated solvent extraction system. Their antioxidant capacities were evaluated by the oxygen radical absorbance capacity (ORAC) method, and the major antioxidants were identified and quantified by high performance liquid chromatography-mass spectrometry. ORAC values of the hydrophilic fractions (H-ORAC) ranged 1,338-1,052 umol Trolox equivalents (TE)/100 g fresh weight (FW), while lipophilic ORAC (L-ORAC) were 280-954 umol TE/100 g FW. Chlorogenic acid (CGA) and quercetin glycosides, namely, rutin (quercetin-3-O-rutinoside), quercetin-3-O-glucoside, hyperoside (quercetin-3-O-galactoside), and quercetin-3-O-rhamnosyl-galactoside, were identified as major contributors to the H-ORAC. Contribution of CGA was the highest among these antioxidants, while quercetin glycosides positively influenced antioxidant capacity at a lower extent. Y-tocopherol showed very low contribution to the L-ORAC values, suggesting the presence of other lipophilic antioxidants. Production location affected H-ORAC values and CGA content, while no significant differences in total quecetin glycoside levels were observed. These results provide information on bioactive compounds in water dropwort and the conditions favorable for the cultivation of water dropwort possessing higher antioxidant capacity.