Abstract
Background: The evaluation of medicinal plants’ toxicity is a prerequisite prior their usage. The vertebrate models used for this purpose are often the object of ethical consideration. Though invertebrate models including Galleria mellonella (GM) have shown their ability to be used to assess various products’ toxicity. To our knowledge, GM has never been exploited to determine the toxicity of medicinal plants.

Aim: The aim of this study was to demonstrate the potential of GM larvae as a simple, inexpensive and rapid model for the evaluation of the toxicity of herbal medicines.
Method: In this study, the toxicity of aqueous and ethanolic (80%, v/v) extracts of seven (7) well known plants from Cameroon namely leaves of Cymbopogon citratus (DC.) Stapf, Moringa oleifera Lam and Vernonia amygdalina Delile; barks of Cinchona officinalis and Enantia chlorantha Oliv; barks and seeds of Garcinia lucida Vesque and leaves and seeds of Azadirachta indica (Neem) was evaluated using the larval form of GM. The median lethal doses (LD50), 90% lethal doses (LD90) and 100% lethal doses were determined using the spline cubic survival curves and equations from the data obtained on the survival rate of G. mellonella 24h after the injection with the extracts.

Results: We found that distilled water extracted a more important mass of phytochemical compounds (7.4-21.2%) compared to ethanolic solution (5.8-12.4%). Lethal doses varied depending on the plant materials and ethanolic extracts (HAE) were more toxic to GM than aqueous ones. The LD50 (mg/ml) of the extracts tested varied from 4.87 (3.90 g/kg bw (body weight)) to >200 (> 166.67 g/kg bw), the LD90 (mg/ml) from 25.00 (18.52 g/kg bw) to >200 (> 181.82 g/kg bw) and LD100 (mg/ml) from 45.00 (40.91 g/kg bw) to > 200 (>181.82 g/kg bw). The HAE of A. indica seed and C. officinalis bark exhibited the highest toxicity with respective LD50 (g/kg bw) of 3.90 and 4.81.

Conclusion: The results obtained in this study suggest that G. mellonella can be used as a sensitive, reliable, and robust eco-friendly model to gauge the toxicity of medicinal plants. Thus, avoid the sacrifice of vertebrate models often used for this purpose to limit ethical concerns.

Key words: Medicinal plants, Greater Wax Moth, Galleria mellonella, Insect model, Toxicity