β-Sitosterol Mediates Gastrointestinal Smooth Muscle Relaxation Induced by Coccoloba uvifera via Muscarinic Acetylcholine Receptor Subtype 3

Coccoloba uvifera is a Mayan medicinal plant, and these leaves are used as antidiarrheal and diuretic agents. In the present work, we develop in-vitro, ex-vivo, in-vivo, and in-silico strategies to evaluate several aqueous extracts of C. uvifera leaves. In vitro tests showed that decoction extract (CuDe) presented the best yield and chlorophyll, phenol, and flavonoid content; however, CuDe showed low antioxidant activity (DPPH model). All aqueous extracts exert spasmolytic and vasorelaxant activity in a concentration-dependent manner (ex vivo), and in vivo tests showed that CuDe exerts the best antiperistaltic and diuretic effects. The in-silico analysis suggests that C. uvifera triterpenes act as a ligand of GPCR, and β-sitosterol could act as an antagonist of muscarinic acetylcholine receptor subtype 3 (m3AChR). In the context of aqueous extracts of C. uvifera, β-sitosterol and their heterosides were identified by FTIR and 1H-NMR spectroscopy. The concerted binding of β-sitosterol and other triterpenes within the m3AChR binding site may be relevant for the induction of relaxant effects at the gastrointestinal smooth muscle level. In this context, C. uvifera is a high-value plant species that requires analytical and pharmacological studies to confirm traditional medicinal use.