Vasorelaxant effect of water fraction of Labisia Pumila and its mechanisms in spontaneously hypertensive rats aortic ring preparation

Nurul Maizan Manshor; Nadiah Razali; Rusdiah Ruzanna Jusoh; Mohd Zaini Asmawi; Nornisah Mohamed; Syafinaz Zainol; Rabia Altaf; Aidiahmad Dewa

doi:10.1016/j.ijchy.2020.100024

Vasorelaxant effect of water fraction of Labisia Pumila and its mechanisms in spontaneously hypertensive rats aortic ring preparation

Int J Cardiol Hypertens. 2020 Jan 11:4:100024. doi: 10.1016/j.ijchy.2020.100024. eCollection 2020 Mar.

Authors

Nurul Maizan Manshor¹, Nadiah Razali¹, Rusdiah Ruzanna Jusoh¹, Mohd Zaini Asmawi¹, Nornisah Mohamed², Syafinaz Zainol², Rabia Altaf³, Aidiahmad Dewa¹

Affiliations

¹ Department of Physiology and Pharmacology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800, Minden, Penang, Malaysia.
² Department of Chemistry, School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800, Minden, Penang, Malaysia.
³ Basic Medical Sciences Department, Lahore Pharmacy College, LMDC Tulspura North Canal Bank Road, 53400, Lahore, Pakistan.

Abstract

Introduction: Labisia pumila has been reported to possess activities including antioxidant, anti-aging and anti-cancer but there is no report on its vasorelaxant effects.

Objective: This study aims to fractionate water extract of Labisia pumila, identify the compound(s) involved and elucidate the possible mechanism(s) of its vasorelaxant effects.

Methods: Water extract of Labisia pumila was subjected to liquid-liquid extraction to obtain ethyl acetate, n-butanol and water fractions. In SHR aortic ring preparations, water fraction (WF-LPWE) was established as the most potent fraction for vasorelaxation. The pharmacological mechanisms of the vasorelaxant effect of WF-LPWE were investigated with and without the presence of various inhibitors. The cumulative dose-response curves of potassium chloride (KCl)-induced contractions were conducted to study the possible mechanisms of WF-LPWE in reducing vasoconstriction.

Results: WF-LPWE produced dose-dependent vasorelaxant effect in endothelium-denuded aortic ring and showed non-competitive inhibition of dose-response curves of PE-induced contraction, and at its higher concentrations reduced KCl-induced contraction. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) significantly inhibited vasorelaxant effect of WF-LPWE. WF-LPWE significantly reduced the release of intracellular calcium ion (Ca²⁺) from the intracellular stores and suppressed the calcium chloride (CaCal₂)-induced contraction. N^ω-nitro-L-arginine methyl ester (L-NAME), methylene blue, indomethacin and atropine did not influence the vasorelaxant effects of WF-LPWE.

Conclusion: WF-LPWE exerts its vasorelaxant effect independently of endothelium and possibly by inhibiting the release of calcium from intracellular calcium stores, receptor-operated calcium channels and formation of inositol 1,4,5- triphosphate. WF-LPWE vasorelaxant effect may also mediated via nitric oxide-independent direct involvement of soluble guanylate cyclase (sGC)/ cyclic guanosine monophosphate (cGMP) pathways.

Keywords: Labisia pumila; Spontaneously hypertensive rat; Vasorelaxation.