Inorganic Ions in Leonotis Leonurus Extract Do Not Explain Changes in Isolated Wistar Rat Heart Function

Leonotis leonurus (L. leonurus) R. Br. (Lamiaceae) is used by healers in South Africa. The present study was conducted to determine if the L. leonurus effect on isolated rat heart is due to ionic changes in the perfusion fluid. Isolated rat hearts were perfused after Langendorff at 74 mmHg with modified Krebs–Henseleit buffer (K-H) and three test solutions: Ll (2 mg/ml dried crude aqueous leaf extract in K-H), HighK (K-H with [K] = [K] in Ll), and HighMgK (K-H with both [K] and [Mg] = that in Ll). [Na], [Cl], [Ca] and [PO4 ] did not change significantly in Ll but the [K] and [Mg] were increased significantly. Ll stopped some hearts completely and reduced all parameters excluding left ventricular end diastolic pressure (LVEDP) while other hearts became erratic showing increased LVEDP and coronary flow (Q), with decreased heart rate (HR), left ventricular developed pressure (LVDP) and cardiac work (CW). HighK had no significant effect on any parameters. HighMgK reduced LVESP, LVEDP, LVDP, HR, CW and Q vs. control but less so than Ll. Neither the HighK, nor the HighMgK mimicked the changes observed with Ll. The effects of Ll are thus not due to changes in ionic composition of the perfusion fluid.