Sclareol, a plant diterpene, exhibits potent antiproliferative effects via the induction of apoptosis and mitochondrial membrane potential loss in osteosarcoma cancer cells.

The objective of the current study was to evaluate the antiproliferative activity of sclareol against MG63 osteosarcoma cells. A 3­(4,5­dimethylthiazol­2­yl)­2,5­diphenyltetrazolium bromide assay was used to evaluate the cell viability of cells following treatment with sclareol. The extent of cell death induced by sclareol was evaluated using a lactate dehydrogenase (LDH) assay. The effect of sclareol on cell cycle progression and mitochondrial membrane potential (ΛΨm) was evaluated with flow cytometry using the DNA­binding fluorescent dyes propidium iodide and rhodamine­123, respectively. Fluorescence microscopy was used to detect the morphological changes in the MG63 osteosarcoma cancer cells and the appearance of apoptotic bodies following sclareol treatment. The results revealed that sclareol induced dose­ and time­dependent growth inhibition of MG63 cancer cells with an IC50 value of 65.2 µM following a 12­h incubation. Furthermore, sclareol induced a significant increase in the release of LDH from MG63 cell cultures, which was much more pronounced at higher doses. Fluorescence microscopy revealed that sclareol induced characteristic morphological features of apoptosis and the appearance of apoptotic bodies. Flow cytometry revealed that sclareol induced G1­phase cell cycle arrest, which showed significant dose­dependence. Additionally, sclareol induced a progressive and dose­dependent reduction in the ΛΨm. In summary, sclareol inhibits the growth of osteosarcoma cancer cells via the induction of apoptosis, which is accompanied by G1­phase cell cycle arrest and loss of ΛΨm.

[Characterization of enzymatic degradation of microcystins by a new isolated bacterium].

A strain of bacterium capable of biodegrading microcystin (MC) RR and MC-LR was isolated from the sediments of Dianchi Lake. It was demonstrated that the enzymes in cell-free extract of this bacterium were responsible for the degradation of MC-RR and MC-LR, and the dead-end products of MC-RR and MC-LR catalyzed by these enzymes were observed on HPLC chromatograms. Results show that the optimum pH for the activities of these enzymes was in the range from 6.0 to 8.0, however the metal ions of Cu2+, Mn2+ and Zn2+ had no apparent effects on the enzymatic degradation of MC-RR and MC-LR.