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.