L-Ascorbic acid (vitamin C) and its derivatives perform important physiological functions in the human organism. Except dietary supplements, numerous topical formulations containing L-ascorbic acid and its derivatives are available on the market. These formulations induce collagen synthesis, strengthening of skin tissue, reduction in hyperpigmentation spots and improvement of overall skin health. L-ascorbic acid has also been used as antioxidant, pH adjuster and photoprotecting agent in cosmetic products. Due to it's sensitivity to external factors such as temperature, presence of oxygen, light an pH, L-ascorbic acid is combined with stabilizing agents such as vitamin E and ferulic acid. Along chemical stabilization, strict control of production conditions is required (oxygen level, pH, etc.). Except controlling of production conditions and adding stabilizing agents, chemical modifications of this molecule have led to stable derivatives development. Well known L-ascorbic acid derivatives, such as magnesium ascorbyl phosphate and sodium ascorbyl phosphate are more stable than L-ascorbic acid but they lack the pharmacological activity of L-ascorbic acid. In this thesis, the antioxidant activity and stability of 6-amino-6-deoxy-L-ascorbic acid and N-methyl-6-amino-6-deoxy-L-ascorbic acid have been examined using ABTS and DPPH assays. In addition, optimal storing conditions, as well as the pH at which new synthesised derivatives maintain the stability, were determined using mass sepctrometry. Results have shown the similarity in antioxidative activity between the new synthesised derivatives and L-ascorbic acid. In addition, these derivatives showed good stability in acidic medium during 30 days. By proving the antioxidative activity and antioxidative stability of synthesised L-ascorbic acid derivatives, we made a base for a further biological tests.