Feng-Peng Wang

H1, a derivative of Tetrandrine, exerts anti-MDR activity by initiating intrinsic apoptosis pathway and inhibiting the activation of Erk1/2 and Akt1/2.

Currently, multi-drug resistance (MDR) to anticancer drugs is a major obstacle to successful treatment of cancer. Looking for novel compounds with anti-MDR activity is an effectively way to overcome cancer drug resistance. Here, we found that H1, a novel derivate of Tetrandrine, displayed anti-MDR activity in vitro and in vivo. Average resistant factor of H1 is only 1.6. In KB and KBv200 cancer cells xenograft mice, H1 also displayed favorable anti-MDR activity. It could induce typical apoptosis as indicated by morphologic changes, DNA fragmentation in sensitive and resistant cancer cells. Further studies showed that H1 treatment resulted in the increase of ROS generation, elevation of the Bax/Bcl-2 ratio, loss of mitochondrial transmembrane potential (ΔΨ(m)), release of cytochrome c and AIF from mitochondria into cytosol, and activation of caspase-9 and caspase-3, but had no effect on activation of caspase-8 and the expression of Fas/FasL. On the other hand, H1 also inhibited survival pathways such as the activation of Erk1/2 and Akt1/2. In conclusion, H1 exerts good anti-MDR activity in vitro and in vivo, its mechanisms may be associated with initiating intrinsic apoptosis pathway and inhibiting the activation of Erk1/2 and Akt1/2. These findings further support the potential of H1 to be used in clinical trial of MDR cancer treatment.

H1, a novel derivative of tetrandrine reverse P-glycoprotein-mediated multidrug resistance by inhibiting transport function and expression of P-glycoprotein

PurposeH1 is a novel derivative of tetrandrine (Tet). Here we investigate the ability of H1 to reverse P-glycoprotein (Pgp)-mediated multidrug resistance (MDR) and its mechanisms.MethodsKBv200, MCF-7/adr and their parental sensitive cell lines KB, MCF-7 were used for reversal study. The intracellular accumulation and efflux studies with Pgp substrates of doxorubicin and rhodamine 123 were determined by flow cytometry. The expression of Pgp was investigated by Western blot and RT-PCR analysis. ATPase activity of Pgp was performed by Pgp-Glo™ assay systems. The ubiquitination level of Pgp was determined by immunoprecipitation analysis. The effect of ERK1/2 on Pgp expression in KBv200 cells were investigated by RNA interference.ResultsH1 significantly potentiated the sensitivity of Pgp substrates in KBv200 and MCF-7/adr cells, but not in parental cells KB and MCF-7. H1 inhibited Pgp expression in KBv200 cells in a dose-dependent manner, but had no effect on MDR1 expression. Further studies showed that H1 prompted the degradation of Pgp and decreased Pgp protein half-life by enhancing the ubiquitination of Pgp, which may be related to downregulated MEK-ERK signal pathway. We also found H1 inhibited ATPase activity of Pgp in a dose-dependent manner.ConclusionsH1 is an effectively and potential agent in reversing Pgp-mediated MDR by inhibiting the transport function and expression of Pgp.

A novel conversion of norditerpenoid alkaloids into aconane-type diterpenes

Two methods for the synthesis of N,19-seco norditerpenoid alkaloids were developed. One method prepared new N,19-seco norditerpenoid alkaloids possessing an oxaziridine group from yunaconitine in five steps involving acetylation, imination, quaternization, formation of N,O-mixed ketal, and oxidation in 50% overall yield. Another method provided a series of novel N,19-seco norditerpenoid alkaloids bearing the oximino or nitro groups through oxidation of the imine N-oxides with HIO4 in moderate yields. Two novel aconane- type diterpenes were synthesized from an N,19-seco nitro compound and an imine N-oxide through Nef reaction and HIO4 oxidation, respectively, in moderate yields. q 2002 Elsevier Science Ltd. All rights reserved.

Expedient Construction of the ABEF Azatetracyclic Ring Systems of Lycoctonine-Type and 7,17-seco-Type C19-Diterpenoid Alkaloids

A synthetic strategy for the modeling construction of the highly bridged azatetracyclic ABEF ring system of numerous lycoctonine-type C19-diterpenoid alkaloids bearing a characteristic oxygenated quaternary center at C-7 has been successfully developed. The tetracyclic core was constructed rapidly from a readily prepared 6,7-bicyclic AB ring precursor through a 13-step sequence via an advanced tetracyclic N,O-acetal intermediate, which belong to another core structure of natural 7,17-seco-type alkaloids. The key step involves an SmI2-promoted intramolecular radical coupling reaction of an N,O-acetal with a carbonyl group, mimicking a plausible biogenetic transformation.

Diterpenoid Alkaloids from Delphinium majus.

From the whole herbs of Delphinium majus, three new C(19)-diterpenoid alkaloids, majusines A-C (1-3), and six new C(20)-diterpenoid alkaloids, majusimines A-D (4-7) and majusidine A and B (8 and 9), have been isolated, together with 15 known compounds. The structures of compounds 1-9 were elucidated by spectroscopic data interpretation.

An effective O-demethylation of some C19-diterpenoid alkaloids with HBr-glacial acetic acid.

The aconitine-type alkaloids talatisamine (1), 8,14-diacetyltalatisamine (11), and compound 3, the lycoctonine-type alkaloid deltaline (5), and the 7,17-seco C19-diterpenoid alkaloids 7 and 9 were treated with HBr–glacial acetic acid to give useful O-demethylated derivatives 2, 2, 4, 6, 8, and 10 respectively in good to high yields (49–90%).

Five new norditerpenoid alkaloids from Aconitum sinomontanum.

Abstract From the roots of Aconitum sinomontanum, five new norditerpenoid alkaloids, sinomontanitines A (1) and B (2), sinomontanines A (3), B (4) and C (5), were isolated together with the known alkaloids lappaconitine (6) and ranaconitine (7), The structures of the new alkaloids were determined by spectral analysis.

Reversal of P-glycoprotein-mediated multidrug resistance by the novel tetrandrine derivative W6.

Overexpression of ATP-dependent efflux pump P-glycoprotein (P-gp) is the main cause of multidrug resistance (MDR) and chemotherapy failure in cancer treatment. Inhibition of P-gp-mediated drug efflux is an effective way to overcome cancer drug resistance. The present study investigated the reversal effect of the novel tetrandrine derivative W6 on P-gp-mediated MDR. KBv200, MCF-7/adr and their parental sensitive cell lines KB, MCF-7 were used for reversal study. The intracellular accumulation with P-gp substrates of doxorubicin was determined by flow cytometry. The expression of P-gp and ERK1/2 was investigated by western blot and real-time-PCR (RT-PCR) analysis. ATPase activity of P-gp was performed by P-gp-GloTM assay systems. In comparison with P-gp-negative parental cells, W6 produced a favorable reversal effect in the MDR cells, as determined using the MTT assay. W6 significantly and dose-dependently increased intracellular accumulation of P-gp substrate doxorubicin (DOX) in P-gp overexpressing KBv200 cells, and also inhibited the ATPase activity of P-gp. W6 inhibited P-gp expression in KBv200 cells in a time-dependent manner, but it had no effect on MDR1 expression. In addition, W6 significantly decreased the ERK1/2 activation in KBv200 cells. Our results showed that W6 effectively reversed P-gp-mediated MDR by inhibiting the transport function and expression of P-gp, demonstrating the potential clinical utility of W6.

Partial synthesis and biological evaluation of bisbenzylisoquinoline alkaloids derivatives: potential modulators of multidrug resistance in cancer

A series of new bisbenzylisoquinoline alkaloids was partially synthesized from tetrandrine and fangchinoline and evaluated for their ability to reverse P-glycoprotein-mediated multidrug resistance (MDR) in cancer cells. All the test compounds increased the intracellular accumulation rate of rhodamine 123 in MDR cells (Bel7402 and HCT8), and most exhibited more potent MDR-reversing activity relative to the reference compound verapamil. Compounds 8, 10, 13, and 14 enhanced intracellular accumulation of doxorubicin in Bel7402 and HCT8 cells.

Synthesis of the 10-Azatricyclo[3.3.2.04,8]decane Core of C20-Diterpenoid Alkaloid Racemulsonine via Iodine(III) Promoted Transannular Aziridination Reaction

The functionalized A/E/F ring system of C20-diterpenoid alkaloid racemulsonine has been efficiently synthesized. The Key steps involved a diastereoselective Au(I)-catalyzed annulation to form cis-fused cyclopentene and a PIDA promoted transannular aziridination of primary amine followed by regio- and stereoselective ring cleavage of bridged aziridine.