Cholestane glycosides from Ornithogalum saundersiae bulbs and the induction of apoptosis in HL-60 cells by OSW-1 through a mitochondrial-independent signaling pathway.

A search for cytotoxic cholestane glycosides from Ornithogalum saundersiae bulbs resulted in the isolation of three new OSW-1 analogues (1-3), a new cholestane bisdesmoside (4), a 5ß-cholestane diglycoside (5), and four new 24(23 → 22)-abeo-cholestane glycosides (6-9), together with 11 known cholestane glycosides (10-20), including OSW-1 (11). The structures of 1-9 were determined based on conventional spectroscopic analysis and chemical evidence. As expected, based on previous data, 1-3 exhibited potent cytotoxic activity against HL-60 human promyelocytic leukemia cells and A549 human lung adenocarcinoma cells. Furthermore, the ability of OSW-1 to induce apoptosis in HL-60 cells was examined. Aggregation of nuclear chromatin, accumulation of the sub-G1 cells, DNA fragmentation, and caspase-3 activation were assessed in HL-60 cells treated with OSW-1, providing evidence for OSW-1-induced apoptosis in HL-60 cells. No mitochondrial membrane potential or release of cytochrome c into the cytoplasm were observed in the OSW-1-treated apoptotic HL-60 cells, indicating that a mitochondria-independent signaling pathway is involved in apoptotic cell death.

Structural Characterization of Cholestane Rhamnosides from Ornithogalum saundersiae Bulbs and Their Cytotoxic Activity against Cultured Tumor Cells.

Previous phytochemical studies of the bulbs of Ornithogalum saundersiae, an ornamental perennial plant native to South Africa, resulted in the isolation of 29 new cholestane glycosides, some of which were structurally unique and showed potent cytotoxic activity against cultured tumor cell lines. Therefore, we aimed to perform further phytochemical examinations of methanolic extracts obtained from Ornithogalum saundersiae bulbs, isolating 12 new cholestane rhamnosides (1-12) and seven known compounds (13-19). The structures of the new compounds (1-12) were identified via NMR-based structural characterization methods, and through a sequence of chemical transformations followed by spectroscopic and chromatographic analysis. The cytotoxic activity of the isolated compounds (1-19) and the derivatives (1a and 6a) against HL-60 human promyelocytic leukemia cells and A549 human lung adenocarcinoma cells was evaluated. Compounds 10-12, 16, and 17 showed cytotoxicity against both HL-60 and A549 cells. Compound 11 showed potent cytotoxicity with an IC50 value of 0.16 µM against HL-60 cells and induced apoptotic cell death via a mitochondrion-independent pathway.

Effect of high dietary fat on insulin secretion in genetically diabetic Goto-Kakizaki rats.

INTRODUCTION AND AIM: To clarify the effects of a high fat-diet on insulin secretion from genetically diabetic beta cells, Goto-Kakizaki rats and Wistar rats were subjected to oral glucose tolerance test (OGTT) after 12-week high-fat feeding. METHODOLOGY: We compared Wistar and Goto-Kakizaki (GK) rats fed a high-fat diet (45% fat content) for 12 weeks, measuring insulin secretion and insulin release. RESULTS: Insulin secretion during oral glucose tolerance test (OGTT) was enhanced in high-fat diet-fed Wistar rats (WF) with normal glucose tolerance. Insulin secretion in high-fat diet-fed GK rats (GF) during OGTT also was enhanced together with deteriorated glucose tolerance. Basal insulin release from the isolated perfused pancreas at 3.3 m glucose in WF was comparable to that in normal chow-fed Wistar rats (WN), but basal insulin release in GF was remarkably higher than in normal chow-fed GK rats (GN). Stimulated insulin release induced by 16.7 m glucose was remarkably increased in WF compared with WN. Total insulin release at 16.7 m glucose in both GK rat groups was similar and minimal. CONCLUSION: These results indicate that normal pancreatic beta-cells have the ability to secrete sufficient insulin to compensate for the insulin resistance induced by a high-fat diet. In contrast, glucose metabolism in diabetic rats after high-fat diet deteriorated partly because of insufficient insulin secretion caused by genetic defects and lipotoxicity due to chronically high FFA levels.