The Cytotoxic Constituents of Betula platyphylla and their Effects on Human Lung A549 Cancer Cells

During the screening for cytotoxic compounds from plants grown in Korea, Betula platyphylla (BP) showed potent activity against the adenocarcinomic human alveolar basal epithelial A549 cell line. To identify the cytotoxic components from BP, the CH₂Cl₂ fraction with the most significant cytotoxic effect was applied to the column chromatographies. Seven compounds were isolated: lupeol (1), betulinic acid (2), (−)-rhododendrol (3), platyphyllenone (4), platyphyllone (5), (−)-centrolobol (6), and oleanolic acid (7). Among them, three diarylheptanoids (4 – 6) exhibited cytotoxicity toward A549 cells. Especially, 50 µM of 4 reduced A549 cell viability to 18.93 ± 0.82% compared to control (100.00 ± 21.48%). Lactate dehydrogenase (LDH) leakage and intracellular reactive oxygen species (ROS) production were also induced by 50 µM 4. This is the first report on the cytotoxic effect of BP-derived diarylheptanoids 4–6 against A549 cells. The compound 4 may be useful for the development of early hit compounds for non-small cell lung carcinoma, but the consideration about selectivity of 4 is required since 4 also showed the cytotoxicity in the human normal lung epithelial BEAS-2B cell line.

Korean Mistletoe (Viscum album var. coloratum) Inhibits Amyloid beta Protein (25-35)-induced Cultured Neuronal Cell Damage and Memory Impairment

The present study aims to investigate the effect of methanol extract of Korean mistletoe (KM; Viscum album var. coloratum), on amyloid beta protein (Abeta) (25-35), a synthetic 25-35 amyloid peptide, -induced neurotoxicity in cultured rat cerebral cortical neurons and memory impairment in mice. Exposure of cultured neurons to 10 microM Abeta (25-35) for 24 h induced a neuronal cell death, which was measured by a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay and Hoechst 33342 staining. KM (10, 30 and 50 microg/ml) significantly inhibited the Abeta (25-35)-induced apoptotic neuronal death. KM (50 microg/ml) inhibited 10 microM Abeta (25-35)-induced elevation of intracellular calcium concentration ([Ca2+]i), which was measured by a fluorescent dye, Fluo-4 AM. Glutamate release into medium and generation of reactive oxygen species (ROS) induced by 10 microM Abeta (25-35) were also inhibited by KM (10, 30 and 50 microg/ml). These results suggest that KM may mitigate the Abeta (25-35)-induced neurotoxicity by interfering with the increase of [Ca2+]i and then inhibiting glutamate release and generation of ROS in cultured neurons. In addition, orally administered KM (25 and 50 mg/kg, 7 days) significantly prevented memory impairment induced by intracerebroventricular injection of Abeta (25-35) (8 nmol). Taken together, it is suggested that anti-dementia effect of KM is due to its neuroprotective effect against Abeta (25-35)-induced neurotoxicity and that KM may have therapeutic role in prevention of the progression of Alzheimer's disease.

A Comparison of the In Vitro Inhibitory Effects of Thelephoric Acid and SKF-525A on Human Cytochrome P450 Activity

Thelephoric acid is an antioxidant produced by the hydrolysis of polyozellin, which is isolated from Polyozellus multiplex. In the present study, the inhibitory effects of polyozellin and thelephoric acid on 9 cytochrome P450 (CYP) family members (CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4) were examined in pooled human liver microsomes (HLMs) using a cocktail probe assay. Polyozellin exhibited weak inhibitory effects on the activities of all 9 CYPs examined, whereas thelephoric acid exhibited dose- and time-dependent inhibition of all 9 CYP isoforms (IC50 values, 3.2-33.7 muM). Dixon plots of CYP inhibition indicated that thelephoric acid was a competitive inhibitor of CYP1A2 and CYP3A4. In contrast, thelephoric acid was a noncompetitive inhibitor of CYP2D6. Our findings indicate that thelephoric acid may be a novel, non-specific CYP inhibitor, suggesting that it could replace SKF-525A in inhibitory studies designed to investigate the effects of CYP enzymes on the metabolism of given compounds.