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. Nω-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.
OBJECTIVE: This study was designed to prepare caffeoylquinic acids rich and poor fractions of the ethanolic extract using resin column technology and compare their antihyperlipidemic and antioxidant potentials.
RESULTS: Among the treatment groups, caffeoylquinic acids rich fraction (F2) and chlorogenic acid (CA, one of the major caffeoylquinic acids) showed potent antihyperlipidemic effects, with significant reductions in total cholesterol (TC), triglycerides (TG), low-density lipoprotein-cholesterol (LDL-C), very low-density lipoprotein-cholesterol (VLDL-C), atherogenic index (AI) and coronary risk index (CRI) (p<0.01 or better) compared to the hyperlipidemic control at the 58 h. The effect was better than that of ethanolic extract. In addition, only F2 significantly increased the high-density lipoproteincholesterol (HDL-C) level (p<0.05). F2 showed better effect than CA alone (60 mg) despite the fact that it only contained 9.81 mg CA/1000 mg dose. The findings suggest that the di-caffeoylquinic acids (86.61 mg/g dose) may also in part be responsible for the potent antihyperlipidemic effect shown by the F2. Likewise, F2 showed the highest antioxidant activity. Thus, simple fractionation of ethanolic extract using the Amberlite XAD-2 resin technique had successfully enriched the caffeoylquinic acids into F2 with improved antihyperlipidemic and antioxidant capacities than that of the ethanolic extract.
CONCLUSION: The resin separation technology may find application in caffeoylquinic acids enrichment of plant extracts for pre-clinical studies. The F2 has potential for development into phytopharmaceuticals as adjunct therapy for management of hyperlipidemia.
METHODS: Extracts of ZOVR were subjected to in-vivo antihypertensive screening using noninvasive blood pressures in SHRs. The most potent extract, ZOVR petroleum ether extract (ZOP) was then fractionated using n-hexane, chloroform and water. Isolated thoracic aortic rings were harvested and subjected to vascular relaxation studies of n-hexane fraction of ZOP (HFZOP) with incubation of different antagonists such as Nω-nitro-l-arginine methyl ester (L-NAME, 10 µmol/L), indomethacin (10 µmol/L), methylene blue (10 µmol/L), atropine (1 µmol/L), glibenclamide (10 µmol/L), prazosin (0.01 µmol/L), and propranolol (1 µmol/L).
RESULTS: During the screening of various ZOVR extracts, ZOP produced the most reduction in blood pressures of SHRs and so did HFZOP. HFZOP significantly decreased phenylephrine-induced contraction and enhanced acetylcholine-induced relaxation. L-NAME, indomethacin, methylene blue, atropine, and glibenclamide significantly potentiated the vasorelaxant effects of HFZOP. Propranolol and prazosin did not alter the vasorelaxant effects of HFZOP. HFZOP significantly suppressed the Ca2+-dependent contraction and influenced the ratio of the responses to phenylephrine in Ca2+-free medium.
CONCLUSION: This study demonstrates that ZOP may exert an antihypertensive effect in the SHR model. Its possible vascular relaxation mechanisms involve nitric oxide and prostacyclin release, activation of cGMP-KATP channels, stimulation of muscarinic receptors, and transmembrane calcium channel or Ca2+ release from intracellular stores. Possible active compounds that contribute to the vasorelaxant effects are 6-gingerol, 8-gingerol and 6-shogaol.