Effect of Cleistanthins A and B on the Isolated Aorta of Guinea Pig

Abstract

Objectives: Cleistanthins A and B are the active compounds isolated from Cleistanthus collinus leaves. The hypotensive activity of both cleistanthins A and B and the leaf extract has been previously demonstrated, but the exact mechanism of action is not clear. So, this study was designed to test the vasorelaxant property of cleistanthins A and B and delineate its mechanism of action. Methods: Variable force transducers were used to record the force of contraction from the aortic rings of 24 male guinea pigs. The effect of cleistanthin A, cleistanthin B, prazosin and vehicle on the phenylephrine-induced contractions and potassium chloride-induced contractions was demonstrated and compared. Results: Cleistanthin B inhibited the phenylephrine-induced contractions in a dose-dependent manner and demonstrated potency (pIC 50 = 6.8 ± 1.06) comparable to prazosin (pIC 50 = 5.7 ± 0.7). Cleistanthin A potency could not be calculated. Both cleistanthin A (4 µg) and cleistanthin B (40 µg) caused a reduction of the maximal response of phenylephrine demonstrating irreversible blockade. They did not affect the potassium chloride-induced contractions. This illustrates that cleistanthins A and B are noncompetitive α 1 adrenergic blockers and the potency of cleistanthin B is comparable to prazosin. Conclusion: Both cleistanthins A and B have vasodilatory action on guinea pig aorta. The action is through non-competitive α 1 adrenergic receptor inhibition and calcium channel blockade does not contribute to the inhibition.

Cleistanthins A and B Ameliorate Testosterone-Induced Benign Prostatic Hyperplasia in Castrated Rats by Regulating Apoptosis and Cell Differentiation

“…Cleistanthin B exerts in vivo anti-tumor effect in Ehrlich's ascites carcinoma and Dalton's ascites lymphoma cell line tumor-bearing animals by significantly increasing overall survival [16]. [11,17,18]. Cytotoxic and anti-proliferative herbal-based formulations and plant-derived compounds have been investigated for the treatment of BPH, and preclinical studies on these drugs were found to be effective [19].…”

“…Parasuraman et al, Priyadharsini et al, and Sahoo et al have shown that cleistanthins A and B have prominent α-adrenergic antagonistic action on the peripheral vascular system [ 11 , 17 , 18 ]. Cytotoxic and anti-proliferative herbal-based formulations and plant-derived compounds have been investigated for the treatment of BPH, and preclinical studies on these drugs were found to be effective [ 19 ].…”