Antioxidant activity of xanthone derivatives

Certain xanthone derivatives, such as these present in mangosteen fruits, show strong antioxidant activity. On the other hand, evidences accumulated that oxidative stress is involved in epileptogenesis. Therefore, the aim of the present study was to estimate total antioxidant capacity (expressed as a ferric reducing antioxidant power - FRAP) and evaluate ability to scavenge free radicals (DPPH methods) by xanthone derivatives showing antiepileptic activity. Selected 2-(aminomethyl)-9H-xanthen-9-one derivatives shared structural features, such as chlorine substituent in xanthone ring and different chiral (or not) alkanol groups at the nitrogen atom. The results of antioxidant activities among racemates revealed the highest activity for compound (R/S)-3 (31.7% in diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and (0.184 ± 0.003 mM Fe2+/L) in FRAP assay. Among tested pair of enantiomers we observed that (R)-1 and (R)-2 showed higher reduction capacity ((R)ñ1: 0.096 ± 0.007 mM Fe2+/L; (R)-2: 0.048 ± 0.005 mM Fe2+/L, respectively) and strongerDPPH scavenging activity ((R)-1: 31 ± 3.0%; (R)-2: 29 ± 2.5%, respectively) comparing to their (S)-enantiomers and racemates.