Elementary plant Biochemistry and Biotechnology (2+1)

Introduction

• Vitamins are low molecular weight organic compounds required in small amounts in the diet.
  
• Most of the vitamins are not synthesized in the human body but are synthesized by the plants. Hence these essential nutrients are mainly obtained through the food.
  
• Though most of them are present in the diet as such, some are present as precursors known as provitamins.
  
• Vitamins are divided into two major categories.
• They are fat-soluble (A, D, E and K) and water-soluble vitamins (B-complex and vitamin C).
  
• B complex vitamins include thiamine (B1), riboflavin (B2), niacin, pyridoxine (B6) biotin, folic acid, pantothenic acid and cobalamin (B12).
• Inositol, choline and para-aminobenzoic acid are vitamin-like substances sometimes classified as part of the B complex, but no convincing evidence has been shown so far to be included as vitamins.
  
• All the fat-soluble vitamins and some B vitamins exist in multiple forms.
• The active forms of vitamin A are retinol, retinal and retinoic acid and vitamin D is available as ergocalciferol (D¬2¬) and cholecalciferol (D3).
  
• The vitamin E family includes four tocopherols and four tocotrienols but α-tocopherol being the most abundant and active form.
  
• The multiple forms of vitamins are interconvertible and some are interchangeable.