Structure-Activity Relationships of Capsaicinoids

Various studies have evidenced strict structure-activity relationships within capsaicinoids, and the existence of these relationships provided a hint for the existence of a specific receptor [72]. On the other hand, different end-points have been used in the literature, and it is difficult to draw a consistent picture. In vivo assays such as pungency and ocular irritancy, functional assays such as the measurement of calcium currents in dorsal root ganglion neurons, and receptor assays such as the displacement of labeled RTX have been used. The relationship between the results of these assays is, at best, approximate [75]. 

The acyl moiety of capsaicin contains only one functional group, a double bond that is redundant for activity. On the contrary, the presence of the double bond is critical for the activity of olvanil, and interesting structure-activity relationships were discovered for this compound. Thus, an analog hydroxylated on the homoallylic carbon is easily available from the amidation of commercial and cheap ricinoleic 

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