In vitro antioxidant activity evaluation of selected xanthene derivatives

Xanthendiones (1,8-dioxooctahydroxanthenes) are a special class of oxygenincorporating tricyclic compounds bearing as a basic feature a pyran nucleus fused on either side with cyclohex-2-enone rings. They are often found as a structural motif in natural products with a wide range of biological activities, such as: antioxidant, antimicrobial, trypanocidal, antiinflammatory, antiproliferative and anticancer. A convenient and efficient approach toward the synthesis of seven aromatically substituted xanthendiones 1‒7 and one structurally-related xanthenone 8 through condensation of dimedone and the appropriate aromatic aldehyde is reported. The relationship between the chemical structure and pharmacological activity was determined empirically using appropriate software packages and in vitro using the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) method. The results of the ABTS assay indicate that five compounds possess the ability to scavenge the ABTS•+ radical cation. Based on the comparison of the IC50 values, the activity of the compounds was found to be as follows: 6 > 1 > 7 > 2 > 8.