Synonyma, popis, zařazení, historie
Popis
- vitamin E je nutriční název pro
- Four tocopherols and four tocotrienols
Stavba
- Constituted by a trimethylated chromanol ring and a saturated phytyl side chain
- Molecular mass is 430.71 Da
- Similar chromanol structures
- Trimethyl (alpha-),
- Dimethyl (beta- or gamma-),
- Monomethyl (delta-) tocopherol, and the corresponding tocotrienols [5]
- Alpha-Tocopherol is the most abundant form of vitamin E in humans [5]
Tokoferoly (TOH) (beta, gamma, delta)
- Different methylation levels and positions on the chromanol ring
- Containing a saturated phytyl side chain
- Having 3, 2, and 1 methyl group on the chromanol ring [9]
Tocotrienoly (T3) (alpha, beta, gamma, delta)
- Three double bonds present in the phytyl side chain characteristic [9]
Alpha-TEs - alpha-tocopherol equivalents
- Factors have been used to convert food contents of tocopherols and tocotrienols to alpha-tocopherol equivalents [2]
- vitamin E as alpha-tocopherol only (dle autorů EFSA ) [2]
- RRR-alpha-tocopherol - jako jediná uznaná součást směsi syntetického vitamínu A jako vit. E (EFSA)
Alpha-Tocopherol
- Three stereogenic centres
- At position 2 on the ring
- At positions 4' and 8' in the side chain
- = potentially eight stereoisomers
- Configuration R or S of the three stereogenic centres
Commercially available forms of alpha-tocopherol
- Natural RRR-alpha-tocopherol (formerly d-alpha-tocopherol)
- By chemical methylation of by-products of soy oil production
- Contains in equal proportions the eight stereoisomers of alpha-tocopherol
- RRR-, RRS-, RSR-, RSS- and their enantiomers SSS-, SSR-, SRS-, SRR-
- Is called all-rac-alpha-tocopherol (formerly dl-alpha-tocopherol)
- Esterified forms (e.g. RRR-alpha-tocopheryl acetate, all-rac-alpha-tocopheryl acetate)
- Bioactivity of each stereoisomer of alpha-tocopheryl acetate has been determined using the resorption–gestation test in the rat (Weiser and Vecchi, 1982)
- Ranges from 21 % for the SSR isomer
- To 90 % for the RRS isomer
- Compared with RRR-alpha-tocopheryl acetate [2]
Tokoferol
Alfa, beta, gamma, delta
- Deriváty 2-metyl-6-chromanolu s pytylovým postranním řetězcem z pozice C2
- Alfa až delta se liší množstvím a pozicí metylových skupin na aromatickém kruhu
- Biologicky nejaktivnější je alfa-tokoferol, poté beta, gamma a pak delta
Tokotrienol
Alfa, beta, gamma, delta
- Isproenoidový řtězec odlišný od tokoferolů
- Nesaturovaný na C3´, C7´ a C11´
- Homologní vrianty vykazující aktivitu vit. E
Biochemické vlastnosti vit. E
- Lipofilní
- V plazmě transp. vaz. na lipoproteiny
- All stereoisomers have equal in vitro antioxidant activity [10]
Historie
- 1922 - Evans and Bishop, discovery of the vitamin E
- Fed lard-containing diets is at the origin [2]