Single and 90-day repeated oral dose toxicity studies of fermented Rhus verniciflua stem bark extract in Sprague-Dawley rats.

Fermented Rhus verniciflua stem bark (FRVSB) extract, an urushiol-free extract of Rhus verniciflua Stokes (RVS) fermented with Fomitella fraxinea, has various biological activities. The present study was carried out to investigate the potential toxicity of the FRVSB extract following single and repeated oral administration to Sprague-Dawley rats. In the single dose toxicity study, the FRVSB extract was administered orally to male and female rats at single doses of 0, 2500, 5000, and 10,000mg/kg. No animals died and no toxic changes were observed in clinical signs, body weight, and necropsy findings during the 15-day period following administration. In the repeated dose toxicity study, the FRVSB extract was administered orally to male and female rats for 90days at doses of 0, 556, 1667, and 5000mg/kg/day. There were no treatment-related adverse effects in clinical signs, body weight, food and water consumption, ophthalmic examination, urinalysis, hematology, serum biochemistry, necropsy findings, organ weight, and histopathology at any dose tested. The approximate lethal dose of the FRVSB extract was >10,000mg/kg in both genders, the oral no-observed-adverse-effect level of the FRVSB extract was >5000mg/kg/day in both genders, and no target organs were identified.

Monoterpenes from thyme (Thymus vulgaris) as potential mosquito repellents.

Five monoterpenes (carvacrol, p-cymene, linalool, alpha-terpinene, and thymol) derived from the essential oil of thyme (Thymus vulgaris) were examined for their repellency against the mosquito Culex pipiens pallens. All 5 monoterpenes effectively repelled mosquitoes based on a human forearm bioassay. Alpha-terpinene and carvacrol showed significantly greater repellency than a commercial formulation, N,N-diethyl-m-methylbenzamide (deet), whereas thymol showed similar repellency to that of deet. The duration of repellency after application for all these monoterpenes was equal to or higher than that of deet. These findings indicate that a spray-type solution containing 2% alpha-terpinene may serve as an alternative mosquito repellent.