Characterization and quantification of unusual capsaicinoid derivatives from Chinese pepper cultivars and their antioxidant activity

Capsaicinoids are the main bioactive compounds in hot chili peppers. In the present work, Ultra-performance liquid chromatography coupled with a photodiode detector-quadrupole and tandem time-of-flight mass spectrometry detector (UPLC-ESI-Q-TOF-MS/PDA) was established to characterize, identify and quantify 7 capsaicinoid derivatives based on their MS spectra, and comparisons with standards when available, as well as with literature data. According to the systematic analysis of the collected MS spectra and the observed fragmentation, the detected compounds were glycosylated and acylated capsaicinoids. Namely, capsaicin-glucoside, dihydrocapsaicin-glucoside, nordihydrocapsaicin-glucoside, homocapsaicin-glucoside and homodihydrocapsaicin-glucoside, beside capsaicin-ferulate and dihydrocapsaicin-ferulate, were isolated for the first time from pepper cultivars. Capsaicinoid-glucoside were detected in Xingshuzaohui and Shuailiang cultivars (cultivated in a greenhouse), while capsaicinoid-ferulate were detected in Hangzhou and Xiaomila cultivars. The capsaicinoid-glucoside content ranged from 6.93 to 9.85 mg/kg of fresh weight, while total capsaicinoid-ferulate content ranged from 1.79 to 3.78 mg/kg. The changes in the content of the detected capsaicinoid derivatives depended on the pepper-cultivated method and maturity stages. The scatterplot demonstrated a strong correlation between pepper extracts’ anti-oxidant activity (DPPH and ABTS) and their capsaicinoid content, particularly capsaicin-glucoside.