... vitamins arerepresented by vitamins A, D, E, and K; also included are the 50 or socarotenoids that possess varying degrees of vitamin A activity. Thewater-soluble vitamins comprise vitamin C and ... vitamin C and the members of thevitamin B group, namely thiamin (vitamin B1), riboflavin (vitamin B2),niacin, vitamin B6, pantothenic acid, folate, and vitamin B12. Thissimple classification ... 36Chapter 3. Vitamin A: Retinoids and the ProvitaminA Carotenoids3.1 Background . . 393.2 Chemical Structure, Biopotency, and PhysicochemicalProperties. . . . 403.2.1 Structure and Biopotency ....