Ganoderma lucidum triterpenoid extract induces apoptosis in human colon carcinoma cells (Caco-2)

An ethanolic extraction of Ganoderma lucidum, a medicinal mushroom, was fractioned into four extracts by flash chromatography. Only fraction 2 and 3 contained triterpenoids. Fraction 2 was less polar and contained ganoderic acids ζ, A, B, C2, C6, D, G, H, I, K and ganoderenic acids D and K, all with presence of oxyl or hydroxyl groups at position C23. Fraction 3 contained ganoderic acid DM, ganoderic aldehyde TR and an unknown compound. None of identified compounds has functional groups at C23. Both fractions 2 and 3 inhibited Caco-2 cells in a dose dependent manner. The LC50 of fraction 2 and 3 were 0.528 ± 0.078 and 0.348 ± 0.032 mg/mL. A significant accumulation of sub-G1 cells (18.77 ± 4.37%) were found with fraction 3 but not with fraction 2. TUNEL assay resulted in 29.97 ± 3.03% apoptotic cells and caspase apoptotic assay showed 11.73 ± 2.05% mid-apoptotic cells and 16.03 ± 2.45% late apoptotic cells. The caspase apoptotic assay indicated an involvement of caspase enzyme family mediation. Two fractions were cytotoxic. Fraction 2 caused a G2/M arrest while fraction 3 induced apoptosis. These differences are likely a result of the polarity of the triterpenoids.