Eurycoma longifolia Jack (Simaroubaceae family), known locally as 'Tongkat Ali' by the ethnic population, is popularly taken as a traditional remedy to improve the male libido, sexual prowess and fertility. Presently, many tea, coffee and carbonated beverages, pre-mixed with the root extract are available commercially for the improvement of general health and labido. Eurycomanone, the highest concentrated quassinoid in the root extract of E. longifolia improved fertility by increasing testosterone and spermatogenesis of rats through the hypothalamus-pituitary-gonadal axis, but the mechanisms underlying the effects are not totally clear.