The toxicity of Aloe barbadensis Miller juice is due to the induction of oxidative stress

Abstract

Exposure of Artemia nauplii to Aloe vera juice resulted in acute toxicity at dilutions as low as approximately 4 % (24 h LC50 4.6 % ± 0.3). All antioxidants examined were also toxic when tested in high doses with 24 h LC50's in the following order of toxicity: vitamin C (203.1 µg/ml ± 11.3) > Trolox™ (283.3 µg/ml ± 25.8) > vitamin E (only low toxicity was observed at 24 h). At lower doses, vitamin E and Trolox™ were non-toxic and could block the toxicity induced by Aloe vera juice. Vitamin E was more effective than Trolox™. Treatment of A. franciscana with antioxidants prior to exposure to juice was more effective than the simultaneous treatment of antioxidant and the toxin, suggesting that Aloe vera juice induced lethality is due to oxidative stress which can be blocked by antioxidant addition. The mechanism of Aloe vera juice toxicity was examined by measuring its effect on various biomarker enzymes. Exposure of Artemia nauplii to sub-lethal levels of Aloe vera juice resulted in a decreased activity of thioredoxin reductase, glutathione reductase and glutathione peroxidase by 34%, 79% and 90% respectively. Vitamin E co-exposure resulted in enzyme activities closer to the control value (78%, 56% and 32% of control enzymatic activities for thioredoxin reductase, glutathione reductase and glutathione peroxidase activity respectively). These results indicate that exposure to sub-lethal doses of Aloe vera juice induces alterations in the cellular redox status of Artemia franciscana and that vitamin E addition helps the Artemia franciscana nauplii to overcome/block the juice induced oxidative stress.