Effects of capsaicin analogs on adrenal catecholamine secretion in rats

To assess the relationship among the structure, pungency and thermogenic action, a series of capsaicin analogs with saturated acyl moieties (heptanoyl to eicosanoyl vanillylamide) were synthesized. Pungency of the compounds and the thermogenic action, which was examined by the potential of the compounds (655 nmol/kg, i.v.) to enhance adrenal catecholamine secretion for 15 min in anesthetized rats, were compared. On the chain length of the acyl moieties of the analogs, nonanoyl to octadecanoyl vanillylamide caused strong adrenal catecholamine secretion, but heptanoyl vanillylamide and eicosanoyl vanillylamide caused weak or no response. Pungent analogs except heptanoyl vanillylamide and non-pungent analogs except eicosanoyl vanillylamide had strong potency to secrete adrenal catecholamine.