Ganoderma lucidum is a medicinal mushroom that has been used as a Chinese traditional folk remedy for centuries. Triterpenoids extracted or isolated from Ganoderma lucidum have been reported to be responsible for many of the pharmaceutical activities of Ganoderma lucidum [1]. So far, hundreds of triterpenoids have been found in Ganoderma lucidum and many more continued to be discovered [2–4]. Two major types of triterpenoids in Ganoderma lucidum are ganoderic acids (C30) and lucidenic acids (C27) and the total triterpenoid content in Ganoderma lucidum varies from 0.6 to 11 mg/g dry powder [5,6]. These triterpenoids were reported to influence metabolic states including exhibiting antidiabetic
properties and regulating inflammatory pathways in cell culture [7–9]. Triterpenoids from Ganoderma lucidum also possess significant chemo-preventative potential. Ganoderiol F (30 _M) was found to induce senescence in Hep-G2 human hepatic cells [10]. Ganoderic acid Mf and S (0–97.7 _M) were reported to suppress cell growth of human cervical carcinoma HeLa cells through apoptotic cell death [11]. Ganoderic acid T (24.20 _M) was shown to possess anti-metastasis effect on 95-D human highly metastatic lung tumor cells [12]. Multiple regulating mechanisms mediated by triterpenoid from Ganoderma lucidum on different colon carcinoma cells were also reported. Ganoderic acid Me was shown to induce apoptosis in HCT-116 cells with a LC50 of 36.9 _M [13]. While ganodermanontriol (0–80 _M) inhibited cell growth in HT-29 cells through down regulation of _-catenin signaling which binds to lymphoid enhancing factor/T-cell factor and increases transcriptional activation of cyclin D1, c-myc and proliferator-activated
reporter _ [14]. Triterpenoid extracts of Ganoderma lucidum also exhibited cytotoxic effects on colon carcinoma cells by distinct molecular mechanisms. A Ganoderma lucidum extract containing a mixture of lanostanoid triterpenes (0.25 mg/mL) was found to induce autophagic cell death in HT-29 cells, while another triterpenoid enriched extract induced apoptosis in SW620 cells at a concentration of 50 _M [15,16]. However, content and composition of triterpenoids in these extracts were not reported. The objective of this study is to use a bioassay-guided approach to identify Ganoderma lucidum fractions that are cytotoxic and induce apoptosis in cultured human colon carcinoma cells (Caco-2).