Effects of plants with presumed cardiotonic properties on the decreased contractility of isolated guinea pig atria caused by acetylcholine: Implications for their clinical usefulness

Heart failure (HF) has been related to a chronic imbalance between autonomic sympathetic and parasympathetic activation. In the Republic of Suriname (South America), this condition is regularly treated with plant-derived preparations with presumed cardiotonic properties, mostly by traditional healers. In this study, aqueous extracts from Annona muricata (leaf), Mansoa alliacea (leaf), Momordica charantia (leaf and stem), Gossypium barbadensis (leaf), Artocarpus altilis (leaf), Chrysophyllum cainito (leaf), Solanum melongena (unripe fruit), and Stachytarpheta jamaicensis (leaf and stem) were evaluated at serial dilutions for their capability to reverse the decreased contractility and for their effects on the decreased beating frequency of isolated guinea pig atria caused by EC₅₀ acetylcholine (10^-7 M). The effects of the plant extracts alone were also investigated. Experiments were for 3 min with 2 x 2-min intervals in Ringer-Locke buffer, 100% O₂, and 30 °C. Results (g/sec and beats/min, means ± SDs; n ≥ 3) were expressed relative to those found with acetylcholine alone or buffer alone, and compared for statistically significant differences using one-way ANOVA (p < 0.05). None of the extracts reversed the decreased contractility and beating frequency of the atria caused by acetylcholine, but those from M. alliacea (0.001 mg/mL) and S. melongena (0.001 and 0.01 mg/mL) lowered these activities by more than 50%. The latter extracts exerted similar effects on their own. Thus, the preparations did not display useful cardiotonic properties against parasympathetic abnormalities in HF, and those from M. alliacea and S. melongena might even be cardiotoxic, warranting care when they are medicinally used.