Abstract
Natural products like eugenol and curcumin have been reported to control hypertension. The purpose of our study was to examine the role of iNOS in eugenol/curcumin/nanocurcumin–induced vasorelaxation in the middle uterine artery (MUA) obtained from non-pregnant (NP) and pregnant (P) Capra hircus (Ch). The MUA rings were mounted in an automatic organ bath attached to a powerlab data acquisition system. Vasorelaxation was induced by eugenol/curcumin/nanocurcumin in either the absence or presence of aminoguanidine in phenylephrine precontracted MUA rings. The vasorelaxation response was recorded isometrically by a highly sensitive isometric force transducer automatic organ bath connected to powerlab and analysed using Labchart 7.1.3 software. The maximal vasorelaxation (Rmax) obtained from eugenol, curcumin and nanocurcumin -induced concentration related contractile response elicited in PE- precontracted ED+ MUA rings was 49.5%, 42.6%, and 40.4% in NP, and 79.5%, 55.5%, and 44.1% in P Ch. Aminoguanidine attenuated the Rmax of eugenol, curcumin and nanocurcumin to 28.2%, 28.5%, and 16.4% in MUA of NP, and 57.2%, 57.4%, and 38.0% in MUA of P Ch, respectively. The results demonstrated that vasorelaxation to (i) Eugenol is partly mediated by partial activation of aminoguanidine-sensitive iNOS in the uterine artery and this pathway is augmented in pregnancy, (ii) Nanocurcumin is mediated by activation of aminoguanidine-sensitive iNOS in the uterine artery of NP, but not in P Ch and (iii) Curcumin is mediated by minimal activation of aminoguanidine sensitive iNOS only in the uterine artery of NP, but not in P Ch. In conclusion, eugenol and nanocurcumin possess a greater potential than curcumin in the control of hypertension due to partial activation of iNOS. These nutraceuticals could be useful to improve blood flow to the uterus to maintain oestrus cycle, maternal and fetal health.