The in vitro cytotoxicities of the ethanol extract of Andrographis paniculata (APE) and its main diterpenoid components were evaluated in various cancer cells. APE was found to be significantly growth inhibitory to human acute myeloid leukemic HL-60 cells with an IC₅₀ value of 14.01 μg/mL after 24 h of treatment. Among the three main diterpenoids in A. paniculata, andrographolide exhibited the highest degree of cytotoxicity followed by deoxyandrographolide while neoandrographolide was the least effective. Laser confocal microscopy and gel electrophoresis studies revealed chromosomal DNA fragmentations suggesting the occurrence of apoptosis. An increase of G₀/G₁ phase cells from 51.88 % to 78.69 % was noted after andrographolide treatment for 36 h. The G₀/G₁ phase arrest and apoptosis were associated with disappearance of mitochondrial cytochrome c and increased expression of Bax but decreased expression of Bcl-2 proteins in the inhibited cells. Although the order of all these events has not been determined, it is concluded that APE and andrographolide induce cell cycle arrest and affect an intrinsic mitochondria-dependent pathway of apoptosis by regulating the expression of some pro-apoptotic markers in HL-60 cells. APE:extract of Andrographis paniculata DSAM:deoxyandrographolide succinic acid monoester HIV:human immunodeficiency virus MTT:3-[4,5-dimethylthiazol-2-yl]-3,5-diphenyl-tetrazolium bromide AO/EB:acridine orange/ethidium bromide PBS:phosphate buffer saline FACS:fluorescence-activated Cell Sorting system PI:propidium iodide SDS-PAGE:sodium dodecyl polyacrylamide gel electrophoresis ECL:enhance dchemiluminescence

Chlorhexidine is a chlorinated phenolic disinfectant used commonly in mouthwash for its action against bacteria. However, a comparative study of the action of chlorhexidine on the cell morphology of Gram-positive and Gram-negative bacteria is lacking. In this study, the actions of chlorhexidine on the cell morphology were identified with the aids of electron microscopy. After exposure to chlorhexidine, numerous spots of indentation on the cell wall were found in both Bacillus subtilis and Escherichia coli. The number of indentation spots increased with time of incubation and increasing chlorhexidine concentration. Interestingly, the dented spots found in B. subtilis appeared mainly at the hemispherical caps of the cells, while in E. coli the dented spots were found all over the cells. After being exposed to chlorhexidine for a prolonged period, leakage of cellular contents and subsequent ghost cells were observed, especially from B subtilis. By using 2-D gel/MS-MS analysis, five proteins related to purine nucleoside interconversion and metabolism were preferentially induced in the cell wall of E. coli, while three proteins related to stress response and four others in amino acid biosynthesis were up-regulated in the cell wall materials of B. subtilis. The localized morphological damages together with the biochemical and protein analysis of the chlorhexidine-treated cells suggest that chlorhexidine may act on the differentially distributed lipids in the cell membranes/wall of B. subtilis and E. coli.