Abstract
Objective: Mentha (M.) longifolia (L.) is traditionally used for various ailments. The current study was intended to explore the underlying vasorelaxation mechanisms of M. longifolia.
Material and methods: Aqueous-methanol extract from the aerial parts of M. longifolia was prepared and subjected to activity-guided fractionation. The vasorelaxant activity was performed using porcine coronary arteries with intact and denuded endothelium. In-vitro PDE inhibitory activity of the active fraction was carried out using the radio-enzymatic assay. The active fraction was also subjected to GCMS. Docking and molecular dynamic simulation studies were also performed
Result: We had observed that aqueous-methanolic extract induced relaxation in the coronary artery in a dose-dependent manner when the endothelium was intact and denuded. n-butanol fraction (MLB) has produced a maximum effect, and it was selected for mechanistic studies. MLB has significantly enhanced the relaxation produced by cAMP and cGMP, elevating atrial natriuretic peptide, sodium nitroprusside, isoproterenol, and forskolin. The pre-treatment with MLB inhibited the contractile response produced by KCl, U46619, and CaCl2 in without endothelium rings. MLB has non-selectively inhibited the PDE isoforms. GCMS analysis of MLB has revealed the presence of menthol, thymol, and carvacrol in the active fraction. Docking and molecular dynamic simulation studies have indicated that thymol can be a competitive inhibitor for PDE1.
Conclusion: It is postulated that an n-butanol fraction of Mentha longifolia produced endothelium-independent relaxation due to increased levels of cAMP and cGMP caused by the inhibition of various PDEs.