Cytotoxicity of Triterpene Seco -Acids from Betula pubescens Buds.

The present study investigated the magnitude and mechanism of the cytotoxic effect on selected cancer cell lines of 3,4- seco -urs-4(23),20(30)-dien-3-oic acid ( 1 ), 3,4- seco -olean-4(24)-en-19-oxo-3-oic acid ( 2 ), and 3,4- seco -urs-4(23),20(30)-dien-19-ol-3-oic acid ( 3 ) isolated from downy birch ( Betula pubescens ) buds by carbon dioxide supercritical fluid extraction and gradient column chromatography. Cell viability in six human cancer lines exposed to these compounds was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was quantified by annexin V/propidium iodide staining of gastric cancer AGS and colorectal cancer DLD-1 cells. To evaluate the mechanism of apoptosis, the expression of apoptosis-related proteins was analyzed by Western blot. Compound 1 exhibited non-specific toxicity, while compounds 2 and 3 were specifically toxic to colon and stomach cancer cells. The toxicity of compounds 2 and 3 against these two cell lines was greater than for compound 1 . Cleavage of caspase-8, -9, and -3 was found in AGS and DLD-1 cells treated with all three seco -acids, indicating the induction of apoptosis via extrinsic and intrinsic pathways. Therefore, triterpene seco -acids ( 1 - 3 ) decreased cell viability by apoptosis induction. AGS and DLD-1 cells were more susceptible to seco -acids with an oxidized C19 than normal fibroblasts. Hence, it made them a new group of triterpenes with potential anticancer activity.