Formation of long-chain N-vanillyl-acylamides from plant oils.

Long-chain N-vanillyl-acylamides (LCNVAs) were generated from plant oils and vanillylamine (VA) by nucleophilic amidation without any catalytic reagents. The resulting LCNVAs varied according to the fatty acid composition of the plant oil used. Therefore, the LCNVAs contained in Capsicum oleoresins were products that were spontaneously generated from the oleoresin during storage.

Long-chain N-vanillyl-acylamides from Capsicum oleoresin.

N-Vanillyl-acylamides (NVAs) naturally occur as capsaicinoids in Capsicum plants. NVAs with a longer chain acyl moiety (LCNVAs) have been developed as attractive tools for medicinal usage because of their capsaicin-like bioactive and physiological properties, without harmful irritancy. In this study, we isolated four LCNVAs from Capsicum oleoresin. Their structures were determined to be N-vanillyl-hexadecanamide (palvanil, 2), N-vanillyl-octadecanamide (stevanil, 3), N-vanillyl-9E-octadecenamide (olvanil, 4), and N-vanillyl-9E,12E-octadecadienamide (livanil, 5) by spectroscopic analysis and gas chromatography-mass spectrometry analysis of their methanolysis products. Furthermore, the existence of two LCNVAs in oleoresin, N-vanillyl-tetradecanamide (myrvanil, 1) and N-vanillyl-9E,12E,15E-octadecatrienamide (linvanil, 6), was suggested. The contents of these LCNVAs and the major capsaicinoids-capsaicin and dihydrocapsaicin-in three Capsicum oleoresins and the fresh fruits of two hot peppers were measured by a liquid chromatography-tandem mass spectrometry system. The content ratios of the total LCNVAs, except for myrvanil, versus the capsaicin in the oleoresins (0.1-41%) was significantly larger than that in fresh fruits (<0.01%). The composition of these LCNVAs in each oleoresin was similar to that of fatty acids in the oil fraction of each oleoresin. We observed no relationship between the composition of these LCNVAs in the fresh fruits.