The present invention is directed to a process for stabilizing antioxidant compounds comprising the step of adding to said compound, in an aqueous mean, at least an oxygen-removing compound, at least a metallic ion sequestering compound and at least an oxidation reaction reversing compound. The invention is particularly useful to stabilize antioxidant compounds such as levogyrous ascorbic acid (LAA), popularly known as "Vitamin C", and the LAA associated with proantocianidines (OPC) for the preparation of pharmaceutical and cosmetic compositions.