The invention concerns novel silicon compounds derived from ascorbic acid consisting of a silicon-containing chain or of silanes, comprising at least a radical A of formula (I) wherein: at least one of the radicals L is a divalent radical for fixing A on the silicon chain. The invention further concerns methods for preparing said compounds, compositions, in particular cosmetic or pharmaceutical, containing them, and their use as antioxidant and/or anti-free radical agent, particularly for treating oxidant stress, for treating the effects of exposure to the sun and for preventing ageing.