The term “oxidative stress” refers to the imbalance between oxidants and antioxidants in favor of oxidants that could potentially lead to damage. While it is well accepted that a low level of production of free radicals (ROS) is necessary to maintain the physiological function, on the other hand it is believed that an excessive formation of ROS causes damage in the biomolecules. ROS defense systems include endogenous / exogenous antioxidants, scavenger enzymes and chelating proteins for pro-oxidant metals. The damage of lipids, proteins and nucleic acids, at the cellular and tissue level, as a consequence of oxidative stress, has been linked not only to a number of serious diseases, including tumors and heart disease, but also accelerates the aging process. Diet is believed to play an important role in the regulation of oxidative stress. Many epidemiological studies have reported an inverse association between consumption of vegetables, fruits, foods rich in antioxidant compounds and the risk of chronic diseases, especially cancer and cardiovascular diseases. Many natural products, especially herbs, have been studied for their antioxidant activity.
Aloe barbadensis or commonly known as Aloe vera has a long tradition in herbal medicine. The processing of the aloe vera leaf pulp has become a major global industry and has been used as an ingredient in the production of functional food and healthy drinks containing gel. So far in the Aloe vera gel have been found over 75 different active constituents and the main ones include minerals, amino acids, polyphenols and polysaccharides. The antioxidant effect of Aloe vera has been reported both in vitro and in vivo in animals. In detail, vitamins A, C, E, B1, B3, B2 and components such as choline, folic acid, phenolic compounds and polysaccharides act directly as scavengers of free radicals against the DPPH radical, superoxide anion, and hydrogen peroxide. Furthermore, it has been reported that Aloe vera reduces lipid peroxidation and inhibits the production of prostaglandin E2 from arachidonic acid, probably through the scavenging mechanism of ROS / RNS. Furthermore, Aloe vera seems to increase some of the antioxidant enzymes such as SOD, catalase and glutathione-S-transferase.
But there are no clinical studies on the effects of Aloe vera in oxidative stress, nor data if Aloe improves the bioavailability of antioxidant vitamins. This is why a team from the Department of Nutrition and Dietetics of Harokopio University, Athens, Greece, conducted a clinical study on the effects of a supplement based on Aloe vera, with vitamins, resveratrol and tea extract (Camellia sinensis) as an additional complement to antioxidants. This was an eight-week, double-blind, randomized, parallel-arm, placebo-controlled study. 62 volunteers were enrolled in the study and assigned to the MM group (n = 32) or to the placebo group (n = 30) using a stratified randomization of age, sex and distribution of body mass index (BMI) between the two groups. No difference was observed in glucose, total cholesterol, HDL cholesterol, LDL cholesterol, TAG and uric acid levels in any group during surgery. Among the oxidative stress markers analyzed (oxLDL, TBARS, carbonyls, catabolites, etc.) a significant difference was seen only in the case of isoprostanes eliminated in the urine.
These reflect the presence of internal inflammation and as individuals have had a 10% reduction in isoprostane, whereas those who took placebo have registered a 3% increase, indicating that the supplement has anti-inflammatory effect. This is consistent with a previous study that revealed that an Aloe vera extract had a significant reduction in F2 isoprostanes, compared to placebo after 8 weeks of food supplementation. But a much greater effect was recorded for protection against nucleic acids. At the end of the 8 weeks of treatment, the subjects with placebo had greater urinary elimination of oxidized nitrogenous bases (8-OHG, 8-OHdG and 8-OHGr) derived from DNA or RNA (2.8%), against a reduced elimination of 27.7 % in those who regularly took the supplement. This is in line with a previous report in which the fraction of polysaccharide obtained from Aloe vera decreased the oxidative damage of DNA in vitro. The same can be said for the protein carbonyls at four weeks (16.7%) and even more at 8 weeks (18.7%), among those who drank the supplement based on Aloe.
There are no reports on the effect of Aloe vera on protein oxidation; therefore, this could represent the first amount of data related to this problem. Overall, the data of the present study support the idea that the integration with a combination of natural extracts and vitamins significantly reduces the oxidative damage in vivo of the water-soluble systems and to a lesser extent the fat-soluble ones.
- edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
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