Background: ALA Alpha lipoic acid (ALA) is a cofactor of sev- eral enzyme complexes in the mitochondria and has antioxidant properties. The effect of ALA on motility, acrosome reaction and membrane integrity of human sperm was evaluated in vitro. Materials and Methods: Semen samples of 30 fertile men were divided into: fresh, control and ALA (0.02mM ALA for one hour). Sperm motility was evaluated with light microscope, sperm membrane integrity with hypo-osmotic swelling (HOS) test and acrosome reaction with Fluorescein isothiocyanate- labelled pisum sativum agglutinin (FITC-PSA) staining. Data were analyzed using Repeated Measure analysis. Results: A significant increase (P<0.001) in the total motility and the progressive sperm motility was observed in the ALA group compared to the fresh and control groups (P<0.001). While, a significant decrease (P<0.05) in the mean non-pro- gressive motility was reported in the ALA group compared to the fresh and control groups. The mean integrity of the sperm membrane in the ALA group showed a significant increase compared to the control group (P<0.001). A significant de- crease in the mean percentage of premature acrosomal reaction was observed in the ALA group compared to the control group (P<0.001). Conclusion: ALA prevents membrane destruction and prema- ture acrosomal reaction due to its antioxidant properties and also increases sperm motility.
