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Turning pyridoxine into a catalytic chain-breaking and hydroperoxide-decomposing antioxidant.

The Journal of organic chemistry (2013-01-16)
Vijay P Singh, Jia-fei Poon, Lars Engman
ABSTRACT

Vitamin B6 is involved in a variety of enzymatic transformations. Some recent findings also indicate an antioxidant role of the vitamin in biological systems. We set out to turn pyridoxine (1a) into a catalytic chain-breaking and hydroperoxide-decomposing antioxidant by replacing the 2-methyl substituent with an alkyltelluro group. Target molecules 12 and derivatives 14, 17, 18, and 20 thereof were accessed by subjecting suitably substituted 2-halopyridin-3-ols to aromatic substitution using sodium alkanetellurolates as nucleophiles and then LAH-reduction of ester groups. The novel pyridoxine compounds were found to inhibit azo-initiated peroxidation of linoleic acid an order of magnitude more efficiently than α-tocopherol in a water/chlorobenzene two-phase system containing N-acetylcysteine as a reducing agent in the aqueous phase. The most lipid-soluble pyridoxine derivative 20c was regenerable and could inhibit peroxidation for substantially longer time (>410 min) than α-tocopherol (87 min). The chalcogen-containing pyridoxines could also mimic the action of the glutathione peroxidase enzymes. Thus, compound 20a catalyzed reduction of hydrogen peroxide three times more efficiently than Ebselen in the presence of glutathione as a stoichiometric reducing agent.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Pyridoxine, ≥98%
Supelco
Pyridoxine hydrochloride, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
Pyridoxine Hydrochloride (B6), analytical standard
Sigma-Aldrich
Pyridoxine hydrochloride, meets USP testing specifications
Sigma-Aldrich
Pyridoxine hydrochloride, BioReagent, suitable for cell culture, suitable for insect cell culture, suitable for plant cell culture
Sigma-Aldrich
Pyridoxine hydrochloride, ≥98% (HPLC)
Pyridoxine hydrochloride, European Pharmacopoeia (EP) Reference Standard