Bioactive phenolics of fresh and freeze-dried sweet and semi-spicy pepper fruits (Capsicum annuum L.)

Abstract

Changes in contents of eight phenolic compounds in extracts from fresh and freeze-dried placentas and pericarps of four cultivars of pepper fruit (Capsicum annuum) were investigated. These compounds comprised two phenolic acid derivatives, four flavonoid O-glycosides, and two flavonoid C-glycosides. Quantitative HPLC–DAD analysis was performed on the basis of the peak area of standards isolated from pepper and identified by MS/MS2 analysis. The main compounds in the pericarp were quercetin O-glycosides, while trans-p-feruloyl-β-d-glucopyranoside predominated in the placenta, at a concentration almost 10 times higher than that in the pericarp. In general, lower levels of phenolic acid derivatives were found in extracts from lyophilised fruits, but different directions of changes in the concentrations of flavonoid O- and C-glycosides from fresh and freeze-dried fruits were noted. The antioxidant activity measured by the DPPH method was higher for samples of fresh fruits than for freeze-dried samples. Additionally, the antioxidant activities of extracts from placentas correlated well with the changes in flavonoid C-glycosides (R2=0.63), while the antioxidant activities from the pericarp correlated with changes in phenolic acid derivatives (R2=0.78).