didehydrostemofoline and stemofoline

Multidrug resistance (MDR) is a major reason for the failure of chemotherapy in the treatment of cancer patients. P-gp over-expression in MDR cancer cells is a multifactorial phenomenon with biochemical resistance mechanisms. Stemofoline (STF), isolated from Stemona bukillii, has been reported to be an MDR reversing compound.. This study investigated whether other Stemona alkaloids that had been purified from Stemonaceae plants exerted MDR modulation activity.. MTT assay was performed to determine the MDR reversing property of the alkaloids. Modulation of P-gp function by these compounds was investigated using cell cycle analysis and P-gp fluorescent substrate accumulation assays. P-gp expression was determined by Western blot analysis. We preliminarily examined the safety of these compounds in normal human fibroblasts and human peripheral blood mononuclear cells (PBMCs) using the MTT assay, and in red blood cells (human and rat) through in vitro hemolysis assays.. Three of the eight alkaloids tested, isostemofoline (ISTF), 11Z -didehydrostemofoline (11Z-DSTF) and 11E-didehydrostemofoline (11E-DSTF), enhanced the chemotherapeutic sensitivity of MDR leukemic K562/Adr cells, which overexpressed P-gp. The P-gp functional studies showed that these three alkaloids increased the accumulation of P-gp substrates, calcein-AM (C-AM) and rhodamine123 (Rho 123) in K562/Adr cells, while this effect was not seen in drug sensitive parental K562 cells. Whereas, the alkaloids did not alter P-gp expression as was determined by Western blotting analysis.. The alkaloids reversed MDR via the inhibition of P-gp function. For pharmaceutical safety testing, the alkaloids were found to be not toxic to normal human fibroblasts and PBMCs. Moreover, the effective compounds did not induce hemolysis in either human or rat erythrocytes. These compounds may be introduced as potential candidate molecules for treating cancers exhibiting P-gp-mediated MDR.

Topics: Alkaloids; Animals; Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily B; Cells, Cultured; Doxorubicin; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Heterocyclic Compounds, 4 or More Rings; Humans; K562 Cells; Leukocytes, Mononuclear; Rats; Stemonaceae

A concise and highly diastereoselective synthesis of the polyfused tetracyclic cores of the Stemona alkaloids asparagamine A and stemofoline that relies on a 2-propylidine-1,3-(bis)silane bicyclization onto a enantiodefined pyrrolidine 2,5-di(cation) equivalent derived from l-malic acid is reported. A crucial feature of this divergent synthetic approach involves the solvolysis of a transient and highly labile tertiary-propargylic hydroxylactam trifluoroacetate in the strongly ionizing medium 5 M LiClO4/Et2O. The acyliminium ion generated in this manner undergoes stereospecific interception by the aforementioned (bis)silane nucleophile.

Topics: Crystallography, X-Ray; Cyclization; Heterocyclic Compounds, 4 or More Rings; Models, Molecular; Molecular Structure; Stereoisomerism; Trimethylsilyl Compounds

Resistance to chemotherapy in cancer patients has been correlated to the overexpression of the ATP-binding cassette (ABC) drug transporters including P-glycoprotein (P-gp) that actively efflux chemotherapeutic drugs from cancer cells. We examined the multidrug resistance reversing property of stemofoline derivatives in drug-resistance human cervical carcinoma (KB-V1) and human leukemic (K562/Adr) cell lines that overexpress P-gp. Didehydrostemofoline and eleven of its derivatives were synthesized and the cytotoxicity and their effect on doxorubicin, vinblastine and paclitaxel sensitivity in drug resistant (KB-V1 and K562/Adr) and drug sensitive (KB-3-1 and K562) cell lines by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were determined. We found that three out of the twelve stemofoline derivatives including OH-A1, NH-B6 and NH-D6 showed commitment efficiency to increase sensitivity to doxorubicin, vinblastine and paclitaxel in KB-V1 cells and increase sensitivity to doxorubicin, and paclitaxel in K562/Adr cells whereas the effects have not been seen in their parental sensitive cancer cell lines (KB-3-1 and K562). These results indicate that stemofoline derivatives reversed P-gp-mediated multidrug resistance in vitro, and thus could be developed as effective chemosensitizers to treat multidrug-resistant cancers. The molecular mechanism of modulation of P-gp would be further determined.

Topics: Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cell Line, Tumor; Cell Survival; Doxorubicin; Drug Resistance, Neoplasm; Heterocyclic Compounds, 4 or More Rings; Humans; K562 Cells; Paclitaxel; Vinblastine

A new stemofoline alkaloid, (2'S)-hydroxy-(11S,12R)-dihydrostemofoline (3), new stemofurans M-R (8-13), and known compounds stemofoline (1), (2'S)-hydroxystemofoline (2), stemofuran E (4), stemofuran F (5), stemofuran J (6), and stilbostemin F (7) have been isolated from the root extracts of Stemona aphylla. The structures and relative configurations of these new compounds have been determined by spectroscopic data interpretation and from semisynthetic studies. These natural and semisynthetic alkaloids were tested for acetylcholinesterase inhibitory activities and were found to be 10-20 times less active than 1',2'-didehydrostemofoline itself. Stemofurans 4, 6, 8, 11, and 13 were tested for their antibacterial and antifungal activities. Three of these showed antibacterial activities against MRSA with MIC values of 15.6 μg/mL.

Topics: Alkaloids; Anti-Infective Agents; Candida albicans; Cryptococcus neoformans; Escherichia coli; Heterocyclic Compounds, 4 or More Rings; Klebsiella pneumoniae; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Plant Roots; Staphylococcus aureus; Stemonaceae; Streptococcus pyogenes; Thailand

The semisynthesis of the Stemona alkaloids (3'R)-stemofolenol (1), (3'S)-stemofolenol (2), methylstemofoline (3), and (3'S)-hydroxystemofoline (5) and the unnatural analogues (11E)-methylstemofoline (15) and 3'R-hydroxystemofoline (11) has been achieved starting from (11Z)-1',2'-didehydrostemofoline (4). This synthesis allowed, for the first time, access to diastereomerically enriched samples of 1 and 2 and the assignment of their absolute configurations at C-3'. These compounds were obtained in sufficient quantities to allow for their biological testing. In a quantitative assay as AChE inhibitors, (11Z)-1',2'-didehydrostemofoline (4) and (3'S)-hydroxystemofoline (5) were found to be the most active.

Topics: Alkaloids; Candida albicans; Cholinesterase Inhibitors; Escherichia coli; Heterocyclic Compounds, 4 or More Rings; Microbial Sensitivity Tests; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Pseudomonas aeruginosa; Staphylococcus aureus; Stemonaceae; Stereoisomerism