The Tiger Milk Medicinal Mushroom TM02®, Lignosus rhinocerus (Agaricomycetes), Water-Soluble Sclerotial Extract (xLr®) Induces Vasorelaxation in Rat Isolated Aortae

Lignosus rhinocerus (Cooke) Ryvarden, a traditional medicinal mushroom in Southeast Asia, is utilized for various health conditions. Although there is evidence that L. rhinocerus sclerotia supplementation had decreased systolic blood pressure and improved acetylcholine-induced vasorelaxation, the underlying mechanism remains poorly understood. Therefore, this study investigated the vasorelaxant effect and possible mechanism of action of L. rhinocerus TM02® sclerotial cold water extract (xLr®) on rat-isolated aortae using an organ bath technique. Aortic rings removed from Sprague Dawley rats were pre-contracted with phenylephrine (PE) prior to the construction of the cumulative concentration-response curve to xLr®. Exposure to increasing concentrations of xLr® significantly relaxed the pre-contracted aorta [maximum tissue contraction or relaxation response (Emax): 97.70 ± 5.21%; P = 0.0005]. Furthermore, our findings revealed that the xLr®-induced vasorelaxation is independent of endothelium and muscarinic receptor-mediated pathways. The attenuation of PE-induced contractions by SKF96365 and nifedipine suggests the possible effect of xLr®-induced vasorelaxation on the inhibition of external calcium influx through membrane calcium channels. This is the first study detailing the endothelium-independent vasorelaxant effects of xLr® in isolated blood vessels. These findings have enhanced our understanding of the pharmacological effects of xLr® on vasculature.