Synthesis and Pharmacological Properties of Novel Esters Based on Monoterpenoids and Glycine

Esters based on mono- and bicyclic terpenoids with glycine have been synthesized via Steglich esterification and characterized by (1)H-NMR, IR, and mass spectral studies. Their analgesic and anti-inflammatory activities were investigated after transdermal delivery on models of formalin, capsaicin, and AITC-induced pain, respectively. Glycine esters of menthol and borneol exhibited higher antinociceptive action, whereas eugenol derivative significantly suppressed the development of the inflammatory process. The mechanism of competitive binding between terpenoid esters and TRPA1/TRPV1 agonists was proposed explaining significant analgesic effect of synthesized derivatives. For an explanation of high anti-inflammatory activity, competitive inhibition between terpenoid esters and AITC for binding sites of the TRPA1 ion channel has been suggested.