Antioxidant activity of resveratrol, piceatannol and 3,3',4,4',5,5'-hexahydroxy-trans-stilbene in three leukemia cell lines.

trans-Resveratrol (t-RES) is one of the most relevant and extensively investigated stilbenes with a broad spectrum of biological activities. In contrast to the detailed knowledge of t-RES activities in biological systems, much less is known about the effects of higher hydroxylated stilbenes. Therefore, the aim of this study was to evaluate the protective effects (antioxidant activities) of t-RES and two analogues: the natural metabolite piceatannol (PCA) and the synthesized 3,3',4,4',5,5'-hexahydroxy-trans-stilbene (HHS) against H2O2-induced DNA damage in leukemic L1210, K562 and HL-60 cells using single-cell gel electrophoresis (SCGE). After 24 h pre-treatment of cells all compounds investigated significantly inhibited the incidence of DNA single strand breaks induced by H2O2. The protective effects of PCA and HHS in L1210 cells and of HHS in HL-60 cells were significantly higher compared to the activity of t-RES (+P < 0.05). In K562 cells the differences of the antioxidant activities of PCA and HHS, and of PCA in HL-60 cells were of much higher significance when compared to t-RES (++P < 0.01). In conclusion, we can prove that all stilbenes investigated, t-RES, PCA, and HHS, manifested potent antioxidant effects on three leukemic cell lines and the presence of ortho-dihydroxy structures enhanced the protective effect against DNA damage caused by .OH radicals.

Protective effects of ursolic acid and oleanolic acid in leukemic cells.

Ursolic acid (UA) and oleanolic acid (OA) have similar chemical structures but differ in the position of one methyl group on the ring E. We investigated protective effects of these two triterpenoic acids against H(2)O(2)-induced DNA damage in leukemic L1210, K562 and HL-60 cells using single-cell gel electrophoresis (SCGE). We compared their protective effects (antioxidant activities) with respect to the different position of the methyl group in their chemical structures. After 24h pre-treatment of cells both compounds investigated inhibited significantly the incidence of DNA single strand breaks induced by H(2)O(2). The concentration range of UA and OA was in all experiments 2.5-10 micromol/l. The antioxidant activity of OA determined by SCGE was significantly higher compared to UA in L1210 ((+)P<0.05) and K562 cells ((+++)P<0.001). Significant difference of the antioxidant activities of the two compounds was evidently connected with the different position of the methyl group. The protective effect of OA was in HL-60 cells slightly lower compared to the activity of UA, but the difference between the protective effects of UA and OA was not significant. In conclusion we can say that both natural pentacyclic triterpenoic acids investigated, UA and OA, manifested potent antioxidant effects. The different position of one methyl group in their chemical structures caused moderately different biological activities of these compounds on three leukemic cell lines. To explore their mechanisms of action further investigation seems to be therefore worthwhile.