A large group of water soluble vitamins that function as co-enzymes, including thiamine (B₁); riboflavin or vitamin G (B₂); niacin or nicotinic acid (B₃); pantothenic acid (B₅); pyridoxine (B₆); cyanocobalamin (B₁₂); biotin or vitamin H; folic acid or vitamin M (Bc); inositol; choline; and others.