Theoretical Study of the Reaction of Vitamin B₆ with ¹O₂

Abstract

Singlet oxygen is known to cause oxidative stress in cells, leading to severe damage (e.g., lipid peroxidation, membrane degradation, mutagenic alterations to DNA, protein misfunctionality). Recently, pyridoxine has been discovered to be capable of quenching singlet oxygen, however, the mechanism of this reaction remains essentially unknown. In this work, we have investigated four sets of reactions: 1) 1,3-addition to a double bond connected to a hydrogen-carrying group, resulting in the formation of allylic hydroperoxides; 2) [pi2+pi2] 1,2-cycloaddition to an isolated double bond, resulting in the formation of 1,2-peroxides; 3) 1,4-cycloaddition to a system containing at least two conjugated double bonds, resulting in the formation of the so-called 1,4-peroxides; 4) 1,4-addition to phenols and naphthols with the formation of hydroperoxide ketones. Thermodynamically, reaction 4 and the 6(9), 3(8), and 5(8) cases of reaction 1 are the most exergonic ones, with energies ranging from -16 to -18 kcal mol(-1). Furthermore, reaction 4 shows the lowest barrier through the reaction path, and is predicted to be the preferred mechanism for the pyridoxine + singlet-oxygen reaction, which is in agreement with previous experimental results.

Oral exposure to the anti-pyridoxine compound 1-amino d-proline further perturbs homocysteine metabolism through the transsulfuration pathway in moderately vitamin B6 deficient rats

“…Apart from the role of PLP as a coenzyme, vitamin B 6 has putative anti-oxidative [8] and anti-inflammatory properties [9,10]. Additionally, it functions as a proton donor or acceptor through the 5-phosphate group of PLP to activate glycogen phosphorylase [11].…”

The antioxidative effect of de novo generated vitamin B6 in Plasmodium falciparum validated by protein interference

“…Vitamin B 6 has been shown to possess a high antioxidative potential in detoxifying 1 O 2 [39]. The human ) were exposed to 80 nM cercosporin before adding 1 % DMSO and 20 μM APF to visualize 1 O 2 in the parasites.…”

A Combination of Zinc and Pyridoxine Supplementation to the Diet of Laying Hens Improves Performance and Egg Quality

“…Vitamin B-6 mainly as pyridoxal phosphate and sometimes as pyridoximine phosphate is involved in protein metabolism (transamination, decarboxylation, diamination, transsulfuration, tryptophan conversion to nicotinic acid, hemoglobin formation, and absorption of amino acids), carbohydrate and fat metabolism (conversion of glycogen to glucose-1 phosphate and conversion of linoleic acid to arachidonic acid) [1,3]. Vitamin B-6 and its derivatives are also involved in stress tolerance in living organisms, especially in alleviating oxidative stress [23]. In eukaryotes, it has been implied that stress resistance involves pyridoxine-dependent singlet-oxygen quenching [24] whereby the pyridoxine itself would act as an antioxidant [23][24][25].…”

“…Vitamin B-6 and its derivatives are also involved in stress tolerance in living organisms, especially in alleviating oxidative stress [23]. In eukaryotes, it has been implied that stress resistance involves pyridoxine-dependent singlet-oxygen quenching [24] whereby the pyridoxine itself would act as an antioxidant [23][24][25]. Singlet oxygen is a reactive form of dioxygen that can cause damage to lipids, amino acids, DNA, and other biologically important molecules [26].…”