Inhibition of lipoprotein oxidation by prenylated xanthones derived from mangostin

Oxidative damage is thought to play a critical role in cardiovascular and o ther chronic diseases. This has led to considerable interest in the antioxi dant activity of dietary compounds. Flavonoids have received the most atten tion and much is known about the structural requirements for antioxidant ac tivity. However, little is known about the antioxidant activity of other pl ant derived phenolic compounds such as the xanthones. We have previously sh own that the prenylated xanthone, mangostin, can inhibit the oxidation of l ow density lipoprotein. In order to examine the effects of structure modifi cation on antioxidant activity of this class of compound we have prepared a number of derivatives of mangostin and tested antioxidant activity in an i solated LDL and plasma assay. The results of this study show that structura l modification of mangostin can have a profound effect on antioxidant activ ity. Derivatisation of the C-3 and C-6 hydroxyl groups with either methyl, acetate, propane diol or nitrile substantially reduces antioxidant activity . In contrast, derivatisation of C-3 and C-6 with aminoethyl derivatives en hanced antioxidant activity, which may be related to changes in solubility. Cyclisation of the prenyl chains had little influence on antioxidant activ ity.