This study was carried out to investigate the effect of the methanolic crude extract of Euphorbia tirucalli Linn (Aveloz) stems on sperm head morphology in male balb/c albino mice. A total of 55 male mice were divided into 5 groups. Each of the Control- (D.W.) and Control+ (MMC) groups consisted of 5 animals, while each of the three treatment groups which injected intraperitoneally with (0.07, 0.14, 0.28) mg/kg doses consisted of 15 animals, and the results were investigated after (7, 21, 35) days of daily injection using 5 animals per each period. The results revealed that the effect of methanolic crude extract of Euphorbia tirucalli stems was dose and time dependent and had significant (P<0.01) toxic effects on sperms of male mice that increased with the increasing of dose and time. The sperm head morphological changes that investigated were: the sperms with (swelling head, twisty hook, no hook, abnormal terminal body and irregular head shape). From these results, it can be concluded that in spite of the Euphorbia tirucalli medical effects and uses in traditional medicine, the caution and the choice of the appropriate dose and period of treatment must be taken into account. Also, the Gas chromatography-Mass spectrometry (GC-MS) analysis was carried out to detect the chemical content of the extract; the results revealed that it contains 15 chemical compounds which are hydrocarbons, fatty acids and steroids, alcohols and one terpenoid compound.
Keywords: Euphorbia tirucalli, sperm head morphology, mice, GC-MS