Evaluation of the acute toxicity of ellagic acid and gallic acid incorporated in Poloxamer407® gel, in Zophobas morio larvae

Gallic acid (GA) has antioxidant, anti-inflammatory and antimicrobial properties, while ellagic acid (EA) demonstrates anticancer, antiviral and photoprotective activity. In this study, the combination of these substances incorporated into a poloxamer gel was tested to verify the individual effect of the substances, in addition to taking advantage of a probable complementary effect, aiming to provide additional therapeutic benefits. As a result of the incorporation, formulations containing GA, EA and GA + EA were obtained, which were evaluated for the effects of the Freeze-thaw cycle on pH, which revealed a significant decrease (p < 0.05) in most samples, including the vehicle (without drug) and the gel containing both drugs. No sample showed variation outside the normal pH range for the skin, with values ranging from 4.8 to 6.0. Regarding conductivity, the GA, EA and GA + EA formulations showed a reduction (p < 0.05) after the freeze-thaw cycle. The drug content in the formulations ranged from 95.86% to 101.35% initially to 91.30% to 101.51% after the freeze-thaw cycle. Regarding the drug release, the results revealed the following cumulative percentages: GA-3% - 92.58% after 1.5 h; AE-3% - 51.60% after 6 h; GA + EA (1.5% = 1.5%) - 99.91% after 2 h; GA + EA- (1.5% = 1.5%) released 57.06%, after 6 h. Regarding toxicity, it was observed that the group treated with GA showed a lower survival rate of the larvae (40%) at the dose 3000 mg/Kg in the formulation. Following the same trend, in the acute lethal concentration (ALC50) test performed using Zophobas morio larvae, an ALC50 of 2191.51 mg/Kg was observed for GA at 48 h. Melanin analysis showed a decrease in concentrations of 30 mg/Kg in the GA group, 3 mg/Kg of EA and 3, 300, 3000 mg/Kg of GA + EA, of the pure drugs. In the groups with the drugs incorporated into the gel, there was a significant decrease (P < 0.05) in melanin in the vehicle (gel), at concentrations of 300 and 3000 mg/Kg of GA and EA. On the other hand, in the combination of GA + EA, a reduction was observed at concentrations of 3 and 30 mg/Kg when compared to the control group. Thus, the gel showed good quality as a pharmaceutical formulation for topical use and low toxicity, making it promising for use in skin therapies.