Chang-Qiang Ke

Antidiabetic Activities of Triterpenoids Isolated from Bitter Melon Associated with Activation of the AMPK Pathway

Four cucurbitane glycosides, momordicosides Q, R, S, and T, and stereochemistry-established karaviloside XI, were isolated from the vegetable bitter melon (Momordica charantia). These compounds and their aglycones exhibited a number of biologic effects beneficial to diabetes and obesity. In both L6 myotubes and 3T3-L1 adipocytes, they stimulated GLUT4 translocation to the cell membrane--an essential step for inducible glucose entry into cells. This was associated with increased activity of AMP-activated protein kinase (AMPK), a key pathway mediating glucose uptake and fatty acid oxidation. Furthermore, momordicoside(s) enhanced fatty acid oxidation and glucose disposal during glucose tolerance tests in both insulin-sensitive and insulin-resistant mice. These findings indicate that cucurbitane triterpenoids, the characteristic constituents of M. charantia, may provide leads as a class of therapeutics for diabetes and obesity.

Naturally occurring homoisoflavonoids function as potent protein tyrosine kinase inhibitors by c-Src-based high-throughput screening

Protein tyrosine kinase (PTK) inhibitors represent emerging therapeutics for cancer chemoprevention. In our study, hematoxylin (26) was identified as one of the most remarkable c-Src inhibitors in an orthogonal compound-mixing library (32200 compounds) by using an ELISA-based automated high-throughput screening (HTS) strategy. Interestingly, hematoxylin was found to be an ATP competitive broad-spectrum PTK inhibitor in vitro, with IC50 values ranging from nanomolar to micromolar level. Further studies showed that such inhibition was associated with the PTK phosphorylation and subsequent downstream signaling pathways. The structure-activity relationship assessment of the PTK inhibitory potency of hematoxylin analogues isolated from Heamatoxylon campechianum was in good agreement with the result of concurrent molecular docking simulation: the catechol moiety in ring A and the hematoxylin-like three-dimensional structure were essential for c-Src-targeted activities. Hematoxylin and its natural analogues were substantially validated to function as a new class of PTK inhibitors.

Limonoids and Triterpenoids from the Stem Bark of Melia toosendan

Four new limonoids (1, 3, 4, 6), named meliatoosenins A-D, eight new euphane- and tirucallane-type triterpenoids (8-15), named meliasenins A-H, and 13 known compounds have been isolated from the stem bark of Melia toosendan. The structures of new compounds were established on the basis of 1D and 2D NMR experiments ((1)H-(1)H COSY, HSQC, HMBC, and ROESY).

Constituents of Trigonostemon chinensis.

Phytochemical investigation on the stem bark and wood of Trigonostemon chinensis led to the isolation of four new dinorditerpenoids, trigonostemons A-D (1, 3, 5, 6), a new phenanthrenone, trigonostemon E (7), and a new bisindole alkaloid, trigonostemon F (8). The structures were established by extensive spectroscopic methods. The absolute configurations of 1-6 were determined by X-ray crystallography, circular dichroism, quantum chemical TDDFT calculations, and chemical transformations. The relative configuration of 8 was confirmed by X-ray diffraction analysis.

Bicunningines A and B, Two New Dimeric Diterpenes from Cunninghamia lanceolata

Two unprecedented dimeric diterpenoids, with a 2,3-dihydrofuran ring fusing an abietane and a 4,5-seco-abietane diterpene, were isolated from Cunninghamia lanceolata. Their structures were elucidated by spectroscopic measurements, and their absolute configurations were determined by quantum chemical TDDFT ECD calculations, chemical transformations, and Moshers method. The Mosher method carried out with MPA and MTPA esters of the sterically hindered sec-hydroxyl group gave contradictory results, while MPA afforded the correct absolute configuration.

Sesquiterpenoids and phenylpropanoids from pericarps of Illicium oligandrum.

Four new merrillianin-type sesquiterpenes, oligandrumins A-D (1-4), two new seco-prezizaane-type sesquiterpenes, veranisatins D and E (5 and 6), and a new phenylpropane glycoside, oligandrumin E (7), were isolated from the ethanol extract of pericarps of Illicium oligandrum, together with six known sesquiterpenoids and two phenylpropanoids. Their structures were established on the basis of extensive spectroscopic analyses. The structures of 1 and 2 were further confirmed by single-crystal X-ray diffraction experiments. Anislactone B (13) and the erythro form of anethole glycol (14) were shown to attenuate the damage induced by H(2)O(2) in SH-SY5Y cells.

Alkaloids from Roots of Stemona sessilifolia and Their Antitussive Activities

Protostemonamide ( 1), a new protostemonine-type alkaloid, and 12 known compounds were isolated from the roots of Stemona sessilifolia. Their structures were elucidated by 1 D and 2 D NMR spectral and other spectroscopic studies. The main alkaloidal constituents, protostemonine ( 2), stemospironine ( 4), and maistemonine ( 7), showed significant antitussive activity in a citric acid-induced guinea pig cough model following peripheral administration; stemonamine ( 11) had antitussive activity following i. c. v. administration.

Antitussive Indole Alkaloids from Kopsia hainanensis

Three new indole alkaloids, named kopsihainins A-C (1-3), and two known compounds, kopsinine (4) and methyl demethoxycarbonylchanofruticosinate (5), were isolated from the stems of Kopsia hainanensis. Their structures were determined using extensive spectroscopic methods. The two main constituents 4 and 5 exhibited significant antitussive activity in a citric acid induced guinea pig cough model. The antitussive effect of 4 was demonstrated to interact with the δ-opioid receptor. This is the first report of antitussive effects of aspidofractinine type and chanofruticosinate type alkaloids.

Limonoids from the fruits of Melia toosendan

Fifteen limonoids, meliatoosenins E-S (1-15), and 10 known compounds were isolated from the fruits of Melia toosendan. Their structures were elucidated on the basis of extensive spectroscopic methods including DEPT, HSQC, HMBC, (1)H-(1)H COSY, and ROESY experiments. All the compounds were evaluated for antiproliferative activity using A-549 and HL-60 cell lines.

Antidiabetic effects of flavonoids from Sophora flavescens EtOAc extract in type 2 diabetic KK-ay mice

ETHNOPHARMACOLOGICAL RELEVANCE Bitter and cold Chinese medicines have been long used for the treatment for diabetes mellitus (DM) for thousands of years in China. The roots of Sophora flavescens Ait., one of bitter and cold Chinese medicines commonly used to remove lung heat have been used to counteract DM and exerted good clinical effects for diabetic patients in some folk hospitals in Fujian province, PR China. However, the corresponding active principles and antidiabetic mechanism of this Traditional Chinese Medicine remain unclear. Therefore, in this study, we aim at chemical profiling of the active principles, validating the potential antidiabetic effects of the active EtOAc extract (SF-EtOAc) in vitro and in vivo, and elucidating its probable antidiabetic mechanism as well as evaluating its acute oral toxicity. MATERIALS AND METHODS An off-line semi-preparative LC-NMR and LC-UV-ESI MS protocol was developed to determine the chemical principles of the active EtOAc extract rapidly and unambiguously. The effect of SF-EtOAc on the glucose transporter type 4 (GLUT4) translocation in L6 myotubes was examined. T2DM KK-Ay mice were induced by high-fat diet. SF-EtOAc was orally administration at the dose of 30, 60 and 120 mg/kg/d, for 21 days. Metformin was used as positive control. Body weight, plasma glucose, oral glucose tolerance test, serum insulin and blood-lipid indexes were measured. Phosphorylation of the AMP-activated protein kinase (AMPK) expression in liver was measured. RESULTS We found that SF-EtOAc significantly improved oral glucose tolerance, increased serum high density lipoprotein cholesterol (HDL-C) and reduced body weight, blood glucose levels and other related blood-lipid indexes. Mechanistically, SF-EtOAc elevated phosphorylation of AMP-activated protein kinase (AMPK) and stimulated membrane translocation of GLUT4. Moreover, it was unveiled that oral median lethal dose (LD50) of SF-EtOAc was more than 7500 mg/kg, suggesting that SF-EtOAc was practically non-toxic for mice. CONCLUSIONS SF-EtOAc improves glucose tolerance, reduces hyperglycemia and resumes insulin levels, at least in part, by activating GLUT4 translocation which may be modulated by AMPK pathway. According to the results of the present study, SF-EtOAc possesses a potent antidiabetic activity and could be used as a safe remedy for the treatment of diabetes.