Calcium Ascorbate Best Antioxidant Anti-Ageing Calcium Ascorbate description Form of vitamin C; other forms include ascorbic acid, L-ascorbic acid, ascorbyl palmitate and magnesium ascorbyl phosphate. Calcium ascorbate, often referred to as Ester-C, is considered a stable form of vitamin C and an antioxidant. Related ingredients: Ascorbic Acid Vitamin C Ascorbyl Palmitate Magnesium Ascorbyl Phosphate