Studies have found that several compounds present in aloe gel protect tissues against oxidative damage caused by free radicals ('t Hart et al 1990, Singh et al 2000, Wu et al 2006, Yagi et al 2002, Zhang et al 2006). This is achieved by direct antioxidant activity and indirect activity through stimulation of endogenous antioxidant systems.
Treatment with aloe gel extract decreased lipid peroxidation and hydroperoxides in diabetic rats to near normal levels (Rajasekaran et al 2005). The extract also significantly increased superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase in the liver and kidney. In another study, data obtained 3, 7 and 10 days after exposure to radiation showed that aloe gel significantly reduced oxidative damage in the liver, lungs, and kidney tissues of irradiated rats (Saada et al 2003).
Three-year-old aloe plants appear to have the highest amounts of flavonoids and polysaccharides and hence the best free radical scavenging capacity, as compared to 2- and 4-year-old plants (Hu et al 2003). Interestingly, the 3-year-old plant demonstrated antioxidant activity of 72.19%, compared to alpha-tocopherol at 65.20%.
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