Thymol analogues with antioxidant and L-type calcium current inhibitory activity

Thymol is a natural product, which has antioxidant activity. 4‐Morpholinomethyl‐2‐isopropyl‐5‐methylphenol (THMO), and 4‐Pyrrolidinomethyl‐2‐isopropyl‐ 5‐methylphenol (THPY) were synthesized by reacting thymol with formaldehyde and, respectively, morpholine or pyrrolidine. Since there is a relationship between the antioxidative status and incidence of human disease, anti‐superoxidation, free radical scavenger activity, and anti‐lipid peroxidation of the thymol analogues were determined by xanthine oxidase inhibition, cytochrome C system with superoxide anion releasing with formyl‐Met‐Leu‐Phe (fMLP)/cytochalasin (CB) or phorbol myristate acetate (PMA) activating pathway in human neutrophils. All compounds studied had antioxidant activity. Mannich bases derived from thymol were generally found to be more potent compounds than thymol. THMO demonstrated the greatest antioxidant activity with IC50 values for xanthine oxidase inhibition and anti‐lipid peroxidation being 21±2.78 and 61.29±5.83 µM, respectively. Moreover, since oxidative stress by free radical regulates the activity of L‐type Ca2+ channel, the whole‐cell configuration of the patch‐clamp technique was used to investigate the effect of THMO upon ionic currents within NG108‐15 cells. THMO (10 µM) suppressed the peak amplitude of L‐type Ca2+ inward current (ICa,L), indicating that the antioxidative potential of the thymol analogues might be related to calcium current inhibition. The present studies suggest that THMO‐dependent antioxidant and calcium ion current inhibition activity may be useful in treating free radical‐related disorders. Drug Dev Res 64:195–202, 2005. © 2005 Wiley‐Liss, Inc.