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 IC 50 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 G 0 /G 1 phase cells from 51.88 % to 78.69 % was noted after andrographolide treatment for 36 h. The G 0 /G 1 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. Abbreviations 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
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Cheung et al. (2005) studied this question.