Polyhydroxy-2,3-diarylxanthones as antioxidants

Abstract

Xanthones are a class of oxygenated heterocyclic compounds widely occurring in nature.[1] The biological properties of these compounds have been extensively reported in the literature and one of the most promising is their potential application as antioxidant agents.[2] This fact led us to start a programme on the synthesis of 2,3-diarylxanthones bearing hydroxyl groups in certain positions of their skeleton for further structure- antioxidant activity studies. In this communication we will describe the synthesis of 2,3-diarylxanthones starting with 2’-hydroxyacetophenone and cinnamic acid derivatives (Scheme 1). The Heck reaction of 3-bromo-2-styrylchromones 3 with styrenes give the methoxyxanthones 4 which, after cleavage of the protecting groups, give the desired polyhydroxy-2,3-diarylxanthones 5.[3] We will also report the inhibitory effect of the synthesized xanthones 5 on Cu2+-induced oxidation of isolated human serum low-density lipoproteins (LDLs). The formation of conjugated dienes and the consumption of carotenoids were chosen as markers of LDL lipid peroxidation.[4] The induction of oxidative stress studies in NCTC 2544 cells will also be presented.