Anti-oxidant activities of curcumin and related enones

The natural product curcumin (diferuloylmethane, 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione), obtained from the spice turmeric, exhibits numerous biological activities including anti-cancer, anti-inflammatory, and anti-angiogenesis activities. Some of these biological activities may derive from its anti-oxidant properties. There are conflicting reports concerning the structural/electronic basis of the anti-oxidant activity of curcumin. Curcumin is a symmetrical diphenolic dienone.

A series of enone analogues of curcumin were synthesized that included:

1) curcumin analogues that retained the 7-carbon spacer between the aryl rings;
2) curcumin analogues with a 5-carbon spacer; and
3) curcumin analogues with a 3-carbon spacer (chalcones).

These series included members that retained or were devoid of phenolic groups. Anti-oxidant activities were determined by the TRAP assay and the FRAP assay. Most of the analogues with anti-oxidant activity retained the phenolic ring substituents similar to curcumin. However, a number of analogues devoid of phenolic substituents were also active; these non-phenolic analogues are capable of forming stable tertiary carbon-centered radicals. .

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