Applications of argentation solid phase extraction to the capsaicinoids: Purification of commercial standards and isolation of homodihydrocapsaicin (8-methyl) from ‘Bhut Jolokia’

Argentation solid phase extraction was employed to purify commercial standards of capsaicin (6-ene-8-methyl) and dihydrocapsaicin (8-methyl). The purity was improved from 96.7% to 99.6% and from 89% to 96%, respectively, with 75% and 60% yield, respectively. Reversed phase solid phase extraction, argentation solid phase extraction, and preparative liquid chromatography with a C30 phase were used to isolate capsaicinoids from the fruits of ‘Bhut Jolokia’ peppers. The compounds capsaicin (6-ene-8-methyl) and dihydrocapsaicin (8-methyl) comprised 74% and 21% of the total mass of capsaicinoids, respectively. The remaining 5% of the capsaicinoids mass included the compounds: nordihydrocapsaicin (7-methyl), N-vanillylnonanamide, two homocapsaicin isomers, N-vanillyldecanamide, and two homodihydrocapsaicin isomers. All but one of these compounds were identified by comparison to known standards. The presence of homodihydrocapsaicin (8-methyl) was confirmed by its absorbance at 280 nm, electrospray ions at m/z 322 and m/z 137, elution just prior to homodihydrocapsaicin (9-methyl), and a carbon-13 NMR spectrum that matched predicted chemical shifts.