Effects of methanolic extract of <i>Pausinystalia yohimbe</i>bark on blood glucose level in normal fasting rats

Background: Pausinystalia yohimbe (L.) is a member of the family Rubiaceae. It is a valuable medicinal tree, distributed in evergreen closed-canopy forests in West Africa. It is traditionally used for treatment of erectile dysfunction and diabetes. Objective: This was an attempt to evaluate the effects of methanolic extract of P. yohimbe bark on blood glucose level in normal fasting rats. Methods: Different doses of methanolic extract of P. yohimbe bark (5, 10, 20, 40 and 80 mg/kg/mL) were orally administered to normal fasting rats to assess their effects on blood glucose levels. Results: The methanolic extract of P. yohimbe bark in different concentrations (5, 10, 20, 40 and 80 mg/kg/mL) when administered to normal fasting rats, only a considerable reduction (26.57 mg/dL) was produced by the dose of 20 mg/kg/mL. Conclusion and Recommendation: Although P. yohimbe has long been reported to regulate blood glucose levels;such effect is unclear and remains requiring further studies.

Effects of methanolic extract of yohimbe bark (<i>Pausinystalia yohimbe</i>) on isolated rabbit aortic strip and rat uterus

Background: Medicinal plants contain physiologically active principles that over the years have been exploited in traditional medicine for the treatment of various ailments. Objectives and Methods: This study aimed to investigate the effects of the methanolic extract of Pausinystalia yohimbe bark (5 mg/ml) on isolated rabbit aortic strip and rat uterus. Results: methanolic extract of P. yohimbe bark (5 mg/ml) produced relaxation of the phenylephrine precontracted-rabbit aortic strip. This relaxation may be resulted through nitric oxide (NO), since the pretreatment of the isolated rabbit aortic strip with methylene blue inhibited the NO-mediated relaxation. Moreover, the extract exhibited relaxation of rat uterine muscles, which appeared to be not mediated by activation of β2-adrenoceptors and/or H2 receptors, since the relaxant effect continued even after the pretreatment of the tissue with propranolol and ranitidine respectively. Conclusion: The obtained results revealed that methanolic extract of P. yohimbe bark caused relaxation of both isolated rat uterus and rabbit aortic strip through facilitating the role of endogenous compounds such as NO.

The relaxant effect of methanolic extract of yohimbe bark (<i>Pausinystalia yohimbe</i>) on rabbit corpus cavernosum smooth muscles

Background: Development and maintenance of penile erection requires the relaxation of corpus cavernosum smooth muscle (CCSM) cells and it is essentially mediated by nitric oxide (NO). Pausinystalia yohimbe bark is traditionally used for the treatment of erectile dysfunction (ED). Objectives and Methods: This study aimed to evaluate the effects of the methanolic extract of P. yohimbe bark (10 mg/ml) on isolated rabbit corpus cavernosum smooth muscle (CCSM). Results: Methanolic extract of P. yohimbe bark blocked contractions in CCSM induced by adrenergic agonists, through facilitating NO release from the endothelial cells. Conclusion: The obtained results revealed that, methanolic extract of P. yohimbe bark caused relaxation of CCSM that validates its traditional aphrodisiac property, thus it could be used to initiate and maintain erection in cases of erectile dysfunction.

Reproductive,cytological and biochemical toxicity of Yohimbe in male swiss albino mice

Aim:To study the effect of Corynanthe Yohimbe(Yohimbe)on germ cells in Swiss albino mice.Methods:Adult male mice were orally(gavage)treated with different doses(188,375 and 750 mg/[kg.day])of aqueous suspension of Yohimbe for 90 days.The following parameters were evaluated:(i)reproductive organ weight,(ii)motility and count of sperm,(iii)study on rate of pregnancy and mean implants,(iv)spermatozoa morphology,(v)cytology of the testes chromosomes,and(vi)biochemical study on estimation of proteins,RNA,DNA,malondialdehyde,nonprotein sulfhydryl(NP-SH)and hormones.Results:The treatment caused significant increase in the weight of seminal vesicles,motility and count of spermatozoa,pre-and post-implants.Male fertility was decreased.These results are confirmed by our data on spermatozoa abnormalities and chromosomal aberrations.The data on biochemical param- eters showed increase of malondialdehyde and depletion of NP-SH,proteins,RNA and DNA in the testicular cells. Conclusion:Our results elucidated the role of free radical species in cytological and reproductive changes,possibly, under the influence of yohimbine(principal constituent of Yohimbe)on neurotransmitters,including norephinephrine. These data warrant careful use of Yohimbe.(Asian J Androl 2006 Jul;8:469-476)