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

R. Suri, A. Crozier, H. Zaharinah and A.R. Zuraida

Abstract

Citrus hystrix, Citrus microcarpa and Citrus suhuiensis fruits were analysed by high-performance liquid chromatography (HPLC) with photo-diode array and MS 2 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 othofagin, the potent antioxidant compounds in rooibos tea.

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