Comparative evaluation of the antioxidant activity of some ortho -substituted mono- and dialkylphenols with the para -po
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Comparative evaluation of the antioxidant activity of some ortho-substituted mono- and dialkylphenols with the para-positioned hydroxymethyl group* E. V. Buravlev,a I. V. Fedorova,a O. G. Shevchenko,b and A. V. Kutchina aInstitute
of Chemistry, Komi Science Center, Ural Branch of the Russian Academy of Sciences, 48 ul. Pervomayskaya, 167000 Syktyvkar, Russian Federation. Fax: +7 (821 2) 21 9916. E-mail: [email protected] bInstitute of Biology, Komi Science Center, Ural Branch of the Russian Academy of Sciences, 28 ul. Kommunisticheskaya, 167982 Syktyvkar, Russian Federation. Fax: +7 (821 2) 24 0163 The para-hydroxymethyl derivatives of 2,6-di-tert-butylphenol, 2,6-diisobornylphenol, 2-isobornyl-6-tert-butylphenol, 2-isobornyl-6-methylphenol, and 2-isobornylphenol were synthesized. A comparative evaluation of the antioxidant properties of the synthesized compounds was carried out in in vitro models. The activity of derivatives is predetermined by the number and bulkiness of the substituents at the ortho positions relative to the phenolic OH group and is consistent with the relationships previously identified by us for other phenolic antioxidants. Keywords: phenols, alkylphenols, terpenephenols, hydroxymethyl derivatives, antioxidant activity, membrane-protective activities, red blood cells, oxidative hemolysis.
It is known that the most common antioxidants are the phenolic derivatives with the sterically hindered OH group (sterically hindered phenols).1 Similarly to alkylphenols, terpenephenols2 and their derivatives, viz. phenolic compounds bearing the terpene substituents,3 are capable of inhibiting oxidative processes.4—8 For example, it was demonstrated that some para-alkoxymethyl terpenephenol derivatives have in vitro antioxidant activity,5 p-hydroxymethylphenol derivative bearing two isobornyl substituents is efficient in vivo against benign prostatic hyperplasia in male rats,9 and its parent compound, 2,6-diisobornyl-4-methylphenol, is very active in the model of experimental pathospermia in rats increasing the antioxidant potential of spermatozoa and reducing the percentage of degenerative forms of spermatozoa.10 Nevertheless, it is still challenging to study the effects of the alkyl and/or terpene substituents positioned ortho to the phenolic OH group on biological activity of the para-hydroxymethyl derivatives. Such research requires increasing the range of the compounds by including new analogs based on available alkyl- and terpenephenols and an in vitro comparative evaluation of the new compounds as inhibitors of the oxidative processes, which was the aim of this work.
* Dedicated to Academician of the Russian Academy of Sciences A. M. Muzafarov on the occasion of his 70th birthday.
Results and Discussion The known aldehydes 1—5 were subjected to the sodium borohydride reduction to give hydroxymethyl derivatives 6—10 (Scheme 1). The 1H and 13C NMR spectral data, IR spectral data, and elemental analysis data of products 6, 8, and 10 confirm expectations on their structure. The spectral prope
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