Purification and structure determination of glucosides of capsaicin and dihydrocapsaicin from various Capsicum fruits

Two new glucosides, capsaicin-beta-D-glucopyranoside (1) and dihydrocapsaicin-beta-D-glucopyranoside (2), were discovered in the fruit of the Capsicum annuum cultivar 'High Heat'. They were sequentially purified by acetone extraction, n-hexane extraction, and acetonitrile extraction, followed by medium-pressure liquid chromatography and high-performance liquid chromatography performed on an octadecylsilane column. Their chemical structures were elucidated by proton nuclear magnetic resonance, carbon nuclear magnetic resonance, and hydrolysis with alpha- and beta-glucosidases. The glucosides were also detected in various pungent cultivars of C. annuum, Capsicum frutescens, and Capsicum chinense by liquid chromatography-mass spectrometry. However, they were not detected in nonpungent cultivars of C. annuum. Furthermore, a positive correlation was observed between the quantity of the capsaicinoids, capsaicin, and dihydrocapsaicin and their glucosides.