The antioxidative effects of 30 xanthone derivatives (XDs) (XD-n, n = 1-30) in HepG2 cells were evaluated by the cellular antioxidant activity assay. Results showed that all XDs were antioxidants and 1,3,5,8-tetrahydroxy-9H-xanthen-9-one (XD-2) was the most active antioxidant. The all-oxygenated substituted xanthones extended the lifespan of wild-type N2 nematodes under normal culture conditions and XD-2 was the best one. XD-2 eliminated excessive intracellular reactive oxygen species and enhanced the expression levels and activities of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase. XD-2 inhibited the H2 O2 -increased phosphorylation levels of c-JUN N-terminal kinase, extracellular signal-regulated kinase, and p38 in HepG2 cells. In vivo, XD-2 also extended the lifespan of wild-type N2 nematodes under oxidative stress induced by paraquat, but failed in extending the lifespan of CF1038 (daf-16 deletion) and AY102 (pmk-1 deletion) mutant nematodes. It was revealed by real-time polymerase chain reaction that the genes daf-16, sir-2.1, akt-1, and age-1 were all inhibited by paraquat stimuli, while XD-2 reversed these inhibitions; in contrast, paraquat stimuli upregulated both the skn-1 and pmk-1 genes. However, treatment by XD-2 further increased the levels of both genes. These pieces of evidence implied that XD-2 promotes longevity through endogenous signaling pathways rather than through the antioxidative activity alone. Taken all together, it may be concluded that XD-2 is a promising antiageing agent.
Keywords: MAPKs; antiageing; antioxidant; stress-response genes; xanthones.
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