Antioxidant studies on monosubstituted chalcone derivatives - understanding substituent effects

An over production of reactive oxygen species beyond basal levels generated continuously in the body as part of natural metabolic processes often results in serious and diverse disease conditions including cancer. Chalcones are known to possess good antioxidant properties, and structure activity relationship studies have been effective in designing molecules with better antioxidant profiles. The present study constitutes a preliminary investigation in seeking safer anti-inflammatory agents with good antioxidant properties. A ten-membered chalcone library - comprising nine monosubstituted derivatives and the unsubstituted parent chalcone - characterized by varying stereoelectronic properties was screened for antioxidant activity using four well established in vitro assays including the hydrogen peroxide, nitric oxide and super oxide radical scavenging assays along with reducing power assay. The trends observed were then correlated with their anti-inflammatory profiles. All the derivatives except 4'-phenylchalcone (4i) showed improved antioxidant profiles compared to the unsubstituted parent compound. The three bromo derivatives (4d, 4g and 4j) clearly portrayed the effect that bulky substituents may have on antioxidant activity; with the paraderivative 4j exhibiting the highest activity amongst these regioisomers. The 2'-hydroxy analog 4b is an optimized lead with the best antioxidant as well as anti-inflammatory properties. There exists a significant correlation between the antioxidant and anti-inflammatory activity.