in vitro antioxidant activities and phenolic profiles of different solvent extracts of a wild kiwifruit (Actinidia macrosperma)
Sujeewa Krishanthi Hettihewa, Yasine Hemar, HP Vasantha Rupasinghe
The aim of this study was to study the effect of different solvents on extraction of polyphenols and characterization of antioxidant capacity in vitro of a wild kiwi (Actinidia macrosperma) fruit. The total phenolic, flavonoid, flavonol contents were determined by Folin-Ciocalteu, aluminiumchloride colorimetric, and ρ-dimethylaminocinnamaldehyde (DMACA) methods, respectively. The radical scavenging activity was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, and antioxidant activity was determined by ferric reducing power activity (FRAP) assay. Polyphenols of the extracts were quantified using high performance liquid chromatography coupled to diode array detector (HPLC-DAD) and identification of the compounds was validated by HPLC-electrospray ionization coupled with mass spectrometry (HPLC-ESI-MS/MS). Among the extraction solvents tested, 70% aqueous acetone showed the highest values of total phenolic (823±14 mg GAE/100 g DW), total flavonoid (171±2 mg CAE/100 g DW), total flavanol (83±0.6 mg CAE/100 g DW) contents and the radical scavenging activity (5.1±0.1 mmolTrolox equivalent/100 g DW) and antioxidant capacity (8.3±0.1 mmol Fe (II) equivalent/100 g DW) by DPPH and FRAP assays, respectively. Analysis of each extract on LC-DAD and LC-ESI-MS/MS revealed the presence of many flavonoids such as quercetin-3-O-galactoside (most abundant), quercetin-3-O-glucoside, and quercetin-3-O-arabinoglucoside in 70% aqueous acetone extract obtained. Therefore, 70% aqueous acetone can be suggested as the best extraction solvent to extract polyphenols of A. macrosperma fruit.