Chapter I 

 VITAMINS A AND CAROTENES 



Page 



I. Nomenclature and Formulas 3 



II. Chcmistr}^ and Industrial Preparation 4 



A. The Antixerophthalmic Provitamins 4 



1. Introduction 4 



2. Isolation of Provitamin A Carotenoids 5 



3. Chemical Constitution of Provitamin A Carotenoids 8 



4. Biologically Active Derivatives of Provitamins A 17 



5. Total Sj-nthesis of Provitamin A Carotenoids 21 



6. Conversion of Provitamin A Carotenoids to Vitamin A . . . . 24 



B. The Antixerophthalmic Vitamin or Vitamins A 25 



1. Introduction 25 



2. Vitamin Ai (Axerophthol) 26 



3. Stereoisomers of Vitamin A 43 



4. Vitamin A Aldehyde (Retinene) 46 



5. Vitamin A Acid 47 



6. Anhydrovitamin Ai 48 



7. Vitamin A2 50 



8. Reh\'drovitamin A 54 



9. Synthetic Homologs and Analogs of Vitamin A and Related Prod- 

 ucts 55 



10. Chemical Constitution and Biological Activity 55 



III. Biochemical Systems 59 



A. Rhodopsin, Porphyropsin, and lodopsin 59 



B. Vitamin A and Retinene 62 



C. Vitamin Ao and Rctinene2 64 



D. The Alcohol Dehydrogenase System 66 



E. The Synthesis of Rhodopsin 71 



F. cis-trans Isomers of Vitamin A and Retinene 75 



G. The General Metabolism of Vitamin A 82 



IV. Determination 87 



A. Physical and Chemical Methods 87 



1. General Considerations 87 



2. Determination of Vitamins A 90 



3. Determination of Provitamins A 92 



4. Determination of Vitamin A and Provitamins A Concurrently. . 95 



B. Biological Methods for the Determination of V^itaniiii A .Activity . 97 

 V. Standardization of .\ctivity 99 



V^I. Occurrence 100 



VII. Effects of Vitamin A Deficiency and Ilypervitaminosis A in .\nimals . 106 



A. General Considerations 106 



B. Vitamin A Deficienc}', Postnatal 107 



1. Epithelial Tissues and Organs 107 



1 



