I have written before about the existential danger to plants from potentially lethal interactions between chlorophyll, light and oxygen. The chlorophyll molecule has a light-absorbing head group and a long, hydrophobic #phytol chain that anchors it in the photosynthetic membrane. Oxygen gas is also hydrophobic and dissolves quite well in themembrane.
Plants make #Tocopherol as protection. Like chlorophyll, it has a phytol membrane anchor, but its head group is a strong bifunctional antioxidant. As a “quencher” tocopherol deactivates dangerous“ singlet oxygen”. As a sacrificial “scavenger”, it gets oxidised in the membrane, but then at the membrane surface is re-reduced by hydrophilic antioxidantssuch as ascorbic acid. Thus, tocopherol extends antioxidative protection to themembrane interior.
Tocopherol is an essential antioxidant in animals too. Known as Vitamin E, it is obtained from nuts, grains, fruits and vegetables. Avocado is a particularly rich source, hence the title for this week’s leaf.
Tocopherol is widely used as an antioxidativepreservative, particularly in foods and other products containingoxidation-prone fats and oils. #E306-8 are all different tocopherol forms or mixtures. #E307 is alpha-tocopherol, the most important physiologicalform.
Tocopherol is a common cosmetic ingredient. It is an effective preservative, but once applied the antioxidant activity on the skin surface is short-lived as only molecules that penetrate into living cells get re-re-reduced by cellular metabolism.
A Vitamin E derivative without the phytoltail, Trolox is used as a standard to calibrate the antioxidative power of bodyfluids and materials such as plant extracts and fruit juices. Trolox is moreamenable for use in laboratory tests. We use this method at @ Green Mountain Biotech to test the antioxidative activity of our botanical extracts.
Reading list
Traber MG, Atkinson J. Vitamin E, antioxidant and nothing more. Free Radic Biol Med. 2007;43(1):4-15. https://doi.org/10.1016/j.freeradbiomed.2007.03.024
Niki E, Traber M, G: A History of Vitamin E. Ann Nutr Metab 2012;61:207-212. https://doi.org/10.1159/000343106
The 10 best foods high in vitamin E -Medical News Today https://www.medicalnewstoday.com/articles/324308
Miller, N J et al. “A novel method formeasuring antioxidant capacity and its application to monitoring theantioxidant status in premature neonates.” Clin Sci (London) vol.84,4 (1993): 407-12. https://doi.org/10.1042/cs0840407
