Eco-friendly one pot synthesis is developed for 1,8-dioxo-octahydroxanthenes from aldehydes and dimedone using non-toxic, easily prepared and recyclable catalyst (Sm2O3/SiO2) as a silica supported rare earth element under solvent –free conditions. four of the synthesized compounds showed promising ABTS (3i, 68.7; 3b, 59.2; 3h, 50.2 inhibition%) compared with ascorbic acid.