Extraction efficiency and validation of an HPLC method for flavonoid analysis in peppers

Efficient extraction procedures including solvent selection, sample to solvent ratio, extraction time, and hydrolysis condition were developed for the analysis of flavonoids in peppers. Maximum flavonoids were extracted in ethanol, while N-N-dimethylformamide was able to extract myricetin, which was rarely reported in peppers. Flavonoids were obtained at the 1:8 ratio of sample to solvent after 3 h of extraction time. The effective hydrolysis of glycosides to aglycones was observed in 3 M HCl at 60 min at 95 °C. The validated HPLC method was applied to quantify five flavonoids from peppers. The ethanol extract exhibited maximum total phenolics (1.39 mg of catechin equivalent/g), and the DPPH assay showed a similar free radical scavenging activity in MeOH, EtOH, and EtOH:water (80:20). Reducing property of the MeOH extract was higher than the EtOH extract. This study demonstrated that the developed methods for the extraction of pepper flavonoids could be useful for analysing large numbers of samples.