Natural deuterium distribution in branched-chain medium-length fatty acids is nonstatistical: a site-specific study by quantitative 2H NMR spectroscopy of the fatty acids of capsaicinoids.

Quantitative 2H NMR spectroscopy has been used to determine the natural abundance site-specific 2H isotopic content of 6,7-dihydrocapsaicin (1) and capsaicin (2). Prior to analysis, the fatty acyl moieties were released as methyl 8-methylnonanoate (3) and methyl E-8-methylnon-6-enoate (4), respectively. A marked and similar nonstatistical isotopic distribution of (2)H is observed for both fatty acids.