Assessment of azadirachtin-A, a neem tetranortritarpinoid, on rat spermatozoa during in vitro capacitation.

Background: The exploration of the biological assessment of technical azadirachtin, a tetranortritarpinoid from the neem seed kernel, was reviewed. The present study was, therefore, designed to evaluate the dose-dependent in vitro effects of azadirachtin-A, particularly on the functional studies and determination of molecular events, which are critical in the process of sperm capacitation.

Methods: To assess the effects of the azadirachtin-A on the functional studies, sperm capacitation, the total sperm adenosine triphosphate levels, acrosome reaction (AR), the sperm-egg interaction and the determination of molecular events like cyclic adenosine-3',5'-monophosphate and calcium levels, the appropriate volumes of the sperm suspension were added to the medium to a final concentration of 1×106 sperm/mL and incubated in a humidified atmosphere of 5% CO2 in air at 37°C. The increasing quantities 0.5-2.0 mM/mL and the equivalent volumes of 50% dimethyl sulfoxide were added to the control dishes prior to the addition of spermatozoa and then observed at various time-points for motility and other analyses.

Results: Results revealed the dose- and time-dependent decrease in the functional consequence of capacitation, i.e. the percentage of motile spermatozoa, motility score and sperm motility index, levels of molecular events in spermatozoa, followed by declined spontaneous AR leading to lesser binding of the cauda epididymal sperm to the Zona pellucida.

Conclusions: The findings confirm the inhibition of rat sperm motility by blocking some biochemical pathways like energy utilization. They also demonstrate that sperm capacitation is associated with the decrease in AR and that the levels of molecular events in spermatozoa can guide us towards the development of a new male contraceptive constituent.