Abstract
Flavonoids and phenolics are abundant in loquat flowers. Methanol had the highest extraction efficiency among five solvents, followed by ethanol. Considering the safety and residue, ethanol is better as extraction solvent. The average content of flavonoids and phenolics of loquat flower of five cultivars were 1.59 ± 0.24 and 7.86 ± 0.87 mg/g DW, respectively, when using ethanol as extraction solvent. The contents of both bioactive components in flowers at different developmental stages and in the various flower tissues clearly differed, with the highest flavonoids and phenolics content in flowers of stage 3 (flower fully open) and petal, respectively. The antioxidant capacity was measured using FRAP, DPPH, and ABTS methods. The values of ABTS method was highest, followed by DPPH, the lowest was FRAP, when using vitamin C equivalent antioxidant capacity (VCEAC) as unit. Correlation analysis showed that the ABTS method showed the highest correlation coefficients with flavonoids and phenolics, i.e., 0.886 and 0.973, respectively.
Highlights
Free radical is an intermediate of aerobic metabolism, and the balance between its generation and removal determines whether the human body would be subject to oxidative destruction
Thaipong et al [23] measured the antioxidant capacity in methanol and dichloromethane extracts of guava fruit by the above three methods, and found that the value determined by ABTS+ assay was highest, but those determined by DPPH and FRAP assay were similar to each other, though the results using DPPH was slightly higher than that of FRAP
Loquat flowers are rich in flavonoids and phenolics, and the methanol and ethanol extracts of loquat flowers showed high antioxidant capacities obtained by FRAP, DPPH and ABTS+ assays
Summary
Free radical (or reactive oxygen species) is an intermediate of aerobic metabolism, and the balance between its generation and removal determines whether the human body would be subject to oxidative destruction. Examination of the antioxidant capacity of flowers was mainly focused on annuals flowers [7,8,9,10], while few studies were conducted on the flowers of woody fruit trees [11,12]. Reports of identification and analysis of bioactive components in loquat flowers are mainly focused on triterpenoids and amygdalin [21,22], but there is no research on flavonoids, phenolics and antioxidant capacity of loquat flowers. Different methods of antioxidant capacity determination were employed to evaluate the efficiency of scavenging free radicals; simultaneously, the relationship between antioxidant capacity and the contents of flavonoids and phenolics were discussed with the aim to provide scientific basis for the research and exploitation of loquat flower resources
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