On-line high-performance liquid chromatography analysis of the antioxidant activity of phenolic compounds in selected tropical citrus

Citrus hystrix, citrus microcarpa and citrus suhuiensis fruits were analysed by high-performance liquid chromatography (hplc) with photo-diode array and ms2 detector (hplc-pda-ms2) to identify flavone, flavanone and dihydrochalcone. the antioxidant potential on each tropical citrus flavonoid was performed using hplc with post-column on-line antioxidant detection based on 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (abts) radical scavenging assay. phloretin-3′,5′-di-c-glucopyranoside present in c. microcarpa fruit peel and flesh possess high trolox equivalent antioxidant ratio (tear) values by 3.4 and 3.1 respectively. quercetin-3-o-rutinoside, hesperetin-7-oneohesperidoside and hesperetin-7-o-rutinoside also showed high tear values in c. hystrix and c. suhuiensis fruit, but have lower than phloretin-3′,5′-di-c-glucopyranoside. levels of tear values of flavonoids in c. microcarpa, c. suhuiensis and c. hystrix fruits were as follows; phloretin-3′,5′-di-cglucopyranoside > quercetin-3-o-rutinoside > hesperetin-7-o-neohesperidoside > hesperetin-7-o-rutinoside = luteolin-7-o-rutinoside = naringenin-7-orutinoside. citrus microcarpa has been widely used in asian food and beverages or as a preserved snack, is consider to be a good source of phloretin-33′,5′-di-cglucopyranoside. this compound is structurally almost similar to aspalathin and nothofagin, the potent antioxidant compounds in rooibos tea.