Phenolic Contents and Antioxidant Activities of Solvent Extracts from Four Edible Flowers

In order to identify new sources of natural antioxidants, the antioxidant activities of various solvent extracts from four edible flower samples [Wisteria sinensis (Sims) DC., Benincasa hispida (Thunb.) Cogn, Luffa cylindrica (L.) Roem, and Cucurbita pepo L.) were systemically investigated. The total phenolic content (TPC) and total flavonoid content (TFC), and individual phenolic profile of each extract were investigated, and antioxidant activities were measured by the DPPH radical scavenging activity, superoxide radical scavenging activity, total reduction capability, and ferrous ions chelating activity. Results revealed that all flower extracts exhibited antioxidant activities, and contained certain amounts of phenolic compounds. Specifically, different solvents exhibited different efficiencies in the extraction of phenolics, flavonoids, and compounds with antioxidant activities. The 70% ethanolic extract from B. hispida yielded the highest TPC (49.92 mg GAE/g DW), superoxide radical scavenging activity (IC50, 0.073 mg/mL), and FRAP value (18.05 mg of GAE/g DW). The highest TFC was obtained with the ethanolic extract of W. sinensis (30.39 mg QE/g DW), and the contents of apigenin, luteolin, and myricetin in the ethanolic extract of W. sinensis were significantly higher than those in the other extracts. The 40% ethanolic extract of L. cylindrica yielded the highest DPPH scavenging capacity (IC50, 0.340 mg/mL), and water extract of B. hispida yielded the highest chelating activity (0.027 mg/mL). Correlation analysis indicated that total phenolics and flavonoids in the extracts were the major contributors to the DPPH scavenging activities and FRAP activities. Overall, results demonstrated that these edible flowers could serve as useful source of natural antioxidants, and be used as functional food ingredients.