RESUMEN
Infusions of Orthosiphon stamineus Benth., Lamiaceae, leaves are widely used in Southeastern Asia to treat different illnesses. Nonetheless, no data is available on the safety of O. stamineus for pregnant women and their babies. This study was undertaken to evaluate the developmental toxicity of O. stamineus standardized aqueous extract in female Sprague Dawley rats (n=21) at 0, 250, 500, 1000 and 2000 mg/kg/day, by gavage on gestation days 6-20. Clinical signs of maternal toxicity, body weight gain, and food and water consumption were recorded. Caesarean sections were performed on gestation day 21; resorptions and living and dead fetuses were counted. Fetuses were weighed and examined for external abnormalities. Half of the fetuses from each litter were cleared and stained with Alizarin red S for skeleton evaluation. O. stamineus standardized aqueous extract did not alter pregnancy body weight gain and food and water consumption and caused no other sign of maternal toxicity. Embryolethality and prenatal growth retardation were not observed either. O. stamineus standardized aqueous extract increased a few skeleton variations and a skull bone malformation (hyoid bone absent) in a non-dose dependent manner. Anogenital distance was increased in male and female fetuses exposed to the highest O. stamineus standardized aqueous extract dose, an indication that the extract could possibly contain androgenic compounds.