Studies of the Toxicological Potential of Capsinoids, XIII: Inhibitory Effects of Capsaicin and Capsinoids on Cytochrome P450 3A4 in Human Liver Microsomes

This study evaluated potential effects of a number of capsinoids (ie, capsiate, dihydrocapsiate, nordihydrocapsiate) and a single capsaicinoid (ie, capsaicin) on liver microsomal cytochrome P450 3A4-mediated midazolam 1'-hydroxylase activity. Where possible, an inhibition curve was prepared; the concentration at which enzyme activity dropped to 50% was calculated. Capsaicin clearly inhibited cytochrome P450 3A4 activity, losing 50% of the activity at 21.5 μmol/L. No enzyme inhibition was observed in the presence of capsiate, dihydrocapsiate, or nordihydrocapsiate (