Toxicity Studies on Anti-fungal Essential Oils Extracted from Selected Aromatic Plants from Mabira and Kakamega Forests, East Africa

Aim: In a bid to explore for grain bio-preservatives, essential oils extracted from Cymbopogon citratus, Rosmarinus officinalis, Monanthataxis littoralis and Aframomum angustifolium, that were earlier established to have anti-mold activity, were evaluated for their biosafety by determining the oral LD50.

Methods: The essential oils were extracted by hydro-distillation from aromatic plants collected from Kakamega and Mabira forests in Kenya and Uganda, respectively. Acute oral toxicity was established using mice by determining the LD50; after which sub-acute toxicity studies were performed. The animals were observed for behavioural changes; and the gross and histopathological effects, if any, on the intestinal mucosa, spleen, lungs, liver, kidney and heart were noted.

Results: The oral LD50 for Cymbopogon citratus, Rosmarinus officinalis, Monanthataxis littoralis and Aframomum angustifolium essential oils were established as 7,046.90; 4,723.33; 13,335.82; and 17,539.82 (mg/kg body weight), respectively. In all cases, increased breathing rates were observed, however Rosemary also caused lethargy and convulsions. Grossly, no changes were seen in the liver, kidney, lungs, heart and spleen from both the control and the treated mice except for Monanthataxis littoralis where the lungs and liver seemed changed; and the urinary bladder distended. However, the latter effects were noted at higher doses than the established oral LD50. Histopathologically, thickened intestinal mucosa lining; tubular degeneration and proteinuria in the kidneys; vascular congestion, focal necrosis and hydropic degeneration of hepatocytes in the liver, were encountered.

Conclusion: Basing on the oral LD50 in mice, all oils were safe and can be explored further as anti-mold grain preservatives. However, Rosmarinus officinalis was marginally safe as per the OECD guidelines. The histopathological effects of Monanthataxis littoralis essential oil need to be investigated further.