Vasorelaxant property of Plectranthus vettiveroides root essential oil and its possible mechanism

Ethnopharmacological relevance: Plectranthus vettiveroides (Jacob) N.P. Singh & B.D. Sharma is a traditional medicinal plant used in Siddha System of Medicine and its aromatic root is used to reduce the elevated blood pressure. Aim: The aim of the present study was to study vasorelaxant property of the root essential oil nanoemulsion (EON) of P. vettiveroides. Methods: The EON was formulated to enhance the solubility and bioavailability and characterized. The preliminary screening was performed by treating the EON with aortic rings pre-contracted with phenylephrine (1 mu M) and potassium chloride (80 mM). The role of K+ channels in EON induced vasorelaxation was investigated by pre-incubating the aortic rings with different K+ channel inhibitors namely, glibenclamide (a non-specific ATP sensitive K+ channel blocker, 10 mu M), TEA (a Ca2+ activated non-selective K+ channel blocker, 10(-2) M), 4-AP (a voltage-activated K+ channel blocker, 10 3 M) and barium chloride (inward rectifier K+ channel blocker, 1 mM). The involvement of extracellular Ca2+ was performed by adding cumulative dose of extracellular calcium in the presence and absence of EON and the concentration-response curve (CRC) obtained is compared. Similarly, the role of nitric oxide synthase, muscarinic and prostacyclin receptors on EON induced vasorelaxation were evaluated by pre-incubating the aortic rings with their inhibitors and the CRC obtained in the presence and absence of inhibitor were compared. Results: The GC-MS and GC-FID analyses of the root essential oil revealed the presence of 62 volatile compounds. The EON exhibited significant vasorelaxant effect through nitric oxide-mediated pathway, G-protein coupled muscarinic (M3) receptor pathway, involvement of K+ channels (KATP, KIR, KCa), and blocking of the calcium influx by receptor-operated calcium channel. Conclusion: It is concluded that the root essential oil of P. vettiveroides is possessing marked vasorelaxant property. The multiple mechanisms of action of the essential oil of P. vettiveroides make it a potential source of antihypertensive drug.

Automated summary

The root essential oil nanoemulsion of P. vettiveroides exhibited significant vasorelaxant effect through multiple mechanisms, including nitric oxide-mediated pathway, G-protein coupled muscarinic (M3) receptor pathway, involvement of K+ channels (KATP, KIR, KCa), and blocking of the calcium influx by receptor-operated calcium channel.