RESUMO
OBJECTIVES: The quassinoids eurycomanone (EN) and 13α,21-dihydroeurycomanone (DHY) of Eurycoma longifolia Jack are reported to enhance spermatogenesis. This study aims to profile the pharmacokinetics of DHY, a minor and hitherto unstudied constituent, evaluate its spermatogenesis enhancement property and compare these attributes with that of the predominant EN. METHODS: Crude Eurycoma longifolia extract was chromatographed into a DHY-enriched extract (DHY-F) and an EN-enriched extract (EN-F). Male Sprague-Dawley rats were administered intravenously and orally with both extracts and their plasma levels of both quassinoids were determined. The extracts were then tested for their spermatogenesis augmentation ability in normal rats and an andrographolide-induced oligospermia model. KEY FINDINGS: Chromatographic enrichment resulted in a 28-fold increase of DHY in DHY-F and a 5-fold increase of EN in EN-F compared with non-chromatographed crude extracts. DHY showed better oral bioavailability (1.04 ± 0.58%) than EN (0.31 ± 0.19%). At 5 mg/kg, EN exhibited higher efficacy in spermatogenesis enhancement in normal rats and restoration of oligospermia to normal sperm profile versus DHY. CONCLUSIONS: Despite the better pharmacokinetic profile of DHY, EN remains the main chemical contributor to plant bioactivity. DHY-F and EN-F represent improvements in developing Eurycoma longifolia as a potential phytomedicine for male infertility particularly oligospermia.