Comparative Toxicological Assessment of Dioscorea hispida,Dioscorea bulbifera, and Dioscorea esculenta in Wistar Rats:Acute Oral and 28-Day Repeated Dose Studies

Abstract

The toxicological profiles of three yam species (Dioscorea hispida, Dioscorea bulbifera, Dioscorea esculenta) were evaluated in Wistar rats via OECD-compliant acute oral (Test No. 423) and 28-day repeated-dose oral (Test No. 407) studies. Acute administration of D. hispida extract at 2000 mg/kg caused 100% mortality, whereas 300 mg/kg was non-lethal, yielding an LD₅₀ cut-off value 500 mg/kg (300< ATE ≤ 2000 mg/kg body, GHS Category 4). In contrast, D. bulbifera and D. esculenta extracts induced no mortality up to 2000 mg/kg (LD₅₀ >2000 mg/kg, GHS category 5 or
unclassified). No clinical signs were seen in surviving acute animals except lethargy and tremor, and in gross observation, lung congestion in D. hispida at the highest dose. In the 28-day study, rats received daily doses up to 600 mg/kg for D. bulbifera/D. esculenta and up to 100 mg/kg for D. hispida. No treatment-related mortality, clinical signs, detailed clinical, functional observation or ophthalmic lesions occurred in any group. Based on the results, body weight gain, feed consumption, hematology, clinical chemistry, urine analysis, organ weights, and histopathology did not reveal any treatment-related adverse effects at any tested dose except in clinical chemistry effect observed at 100 mg/kg in D. hispida and at 600 mg/kg in D. bulbifera. Consequently, the No Observed-Adverse-Effect Level (NOAEL) for the 28-day oral toxicity study was determined to be 50 mg/kg/day for Dioscorea hispida, 300 mg/kg/day for D. bulbifera and 600 mg/kg/day for D. esculenta. These findings confirm a distinct toxicity profile: D. hispida exhibits moderate acute oral toxicity (LD₅₀ between 300–2000 mg/kg), likely attributable to constituents such as dioscorine and cyanogenic compounds. In contrast, D. bulbifera and D. esculenta demonstrated significantly lower acute hazards, with no mortality observed at the limit dose of 2000 mg/kg. The comprehensive dataset from both acute and repeated-dose studies provides a robust foundation for hazard characterization and risk assessment of these botanical extracts in accordance with OECD and GHS criteria.