Bo-Gang Li

Synthesis and biological activities of novel nonpeptide angiotensin II receptor antagonists based on benzimidazole derivatives bearing a heterocyclic ring

A series of benzimidazole derivatives bearing a heterocyclic ring imidazole (1), 5-chloroimidazole (2), 1,2,4-triazol (3), and imidazoline (4) were synthesized and evaluated for angiotensin II antagonistic activities. The synthetic compounds 1-4 were biologically evaluated in vitro using an AT(1) receptor binding assay, where compounds 1 and 3 provided weak binding affinity, compound 2 showed moderate binding affinity, and compound 4 showed good binding affinity. Moreover, compound 4 was found to be almost equipotent with telmisartan in vivo biological evaluation study.

Novel ceramides and a new glucoceramide from the roots of Incarvillea arguta

Novel ceramides, rel-(3S,4S,5S)-3-[(2R)-2-hydroxycosanoyl-hexacosanoylamino]-4-hydroxy-5-[(4Z)-tetradecane-4-ene]-2,3,4,5-tetrahydrofuran (1a-g), and a new glucoceramide, 1-O-β-d-glucopyranosyl-(2S,3S,4R,8E)-2-[(2R)-2-hydroxytetracosanoylamino]-1,3,4-octodecanetriol-8-ene (2) were isolated from the aqueous ethanolic extract of the roots of Incarvillea arguta, together with eight known compounds: β-sitosterol (3), oleanolic acid (4), ursolic acid (5), piperin (6), maslinic acid (7), β-sitosterol 6′-O-acyl-β-d-glucopyranoside (8), 8-epideoxyloganic acid (9), and plantarenaloside (10). Their structures were elucidated on the basis of spectral data including IR, MS, NMR [1H NMR, 13C NMR (distortionless enhancement by polarization transfer), 1H−1H COSY, heteronuclear multiplequantum coherence, and heteronuclear multiple-bond coherence correlations]. The relative configurations were established by nuclear Overhauser effect spectroscopy experiments and by comparison of the NMR spectral data and coupling constants with those already reported in the literature.

Novel synthesis of 12,13-seco norditerpenoid alkaloids via semipinacol rearrangement and reaction with Br2–HOAc

Treatment of 14-methylsulfonyl pseudaconine 3 with DMF-NaOH at 150 degreesC for 10 h afforded the desired C-nor and 12,13-seco norditerpenoid alkaloids 16 alpha -methoxyl ketone 7 (70%) and 16 beta -methoxyl ketone 8 (15%) as a pair of epimers. Reaction of 7 with Br-2-HOAc at room temperature for 1.5-2 h produced the phenols 9 (40%), 10 (10%) and 13 (29%). Whereas, treatment of 8 with Br-2-HOAc under same conditions as the case for 7 gave phenolic compound 9 (38%) besides the by-product alpha -bromoketone 14 (25%)

Chemical study on Cyathula officinalis Kuan.

Four new compounds, 4-[(1-ethoxy-2-hydroxy)ethyl]phenol (1), 2,3-isopropylidene cyasterone (2), 24-hydroxycyasterone (3) and 2,3-isopropylidene isocyasterone (4), together with fourteen known compounds, have been isolated from the roots of Cyathula officinalis Kuan. Their structures have been elucidated predominantly by spectroscopic methods.

In vitro synergistic antibacterial activities of helvolic acid on multi-drug resistant Staphylococcus aureus

An agar plate method was established to screen synergistic antibacterial agents other than β-lactamase inhibitors. By using this method, a strain Aspergillus sp136 was selected for further studies. From the metabolites of this strain, a synergistic antibacterial compound was isolated by bioautographic TLC assay-guided fractionation and identified as helvolic acid. The synergistic effect of helvolic acid to penicillin was about 3 times that of clavulanic acid to penicillin in agar diffusion assay on Bacillus cereus. In checkerboard studies, helvolic acid exhibited synergistic effects with erythromycin on all tested multi-drug resistant Staphylococcus aureus and with penicillin and tetracycline on some multi-drug resistant S. aureus. A pattern of enhanced killing was also found in time-kill studies on multi-drug resistant S. aureus.

A new triterpene and an antiarrhythmic liriodendrin from Pittosporum brevicalyx.

A new triterpene, 21-O-senecioyl-R1-barrigenol (1) and 13 known compounds were isolated from the ethanol extracts of the leaves and bark of Pittosporum brevicalyx (Oliv.) Gagnep. Their structures were elucidated based on spectral data. The antiarrhythmic action of one furofuran lignan, liriodendrin (2), was tested on a model of CaCl2-induced arrhythmia and compared with the effect of verapamil. The prophylactic administration of liriodendrin (2) was effective in prolonging latency of arrhythmia and reducing the occurrence of ventricular fibrillation from 75% to 25%. The overall mortality rate was significantly reduced by the prophylactic administration of liriodendrin from 87.5% to 25%. The antiarrhythmic effect of liriodendrin (5.0 mg/kg) was similar to that of verapamil (1.05 mg/kg). Thus, liriodendrin may be a potent suppressor of CaCl2-induced arrhythmias.

A novel alkaloid from Mitrephora maingayi

A novel alkaloid, maingayinine, together with dicentrinone, dicentrinene, L-2-O-methyl-chiro-inositol, allantoin, glaucine, N-phenyl-2-naphthylamine, terephthalic acid and ayanin, was isolated from the twigs of Mitrephora maingayi Hook (Annonaceae). Their structures were established predominantly by IR, MS and NMR spectral data.

Phytoecdysteroids and glycoceramides from Eriophyton wallchii

Two new compounds, 28-epi-cyasterone and eriophytonoide, along with 11 known compounds, cyasterone, ajuforrestins A and B, 20-hydroxyecdysone, polypodin B, ajugalactone, 8-O-acetylharpagid, apigenin, N-[2hydroxy-(nonadecanoyl-tricosanoyl)]-4-hydroxy-trans-8-sphingenine, beta-sitosterol, and daucosterol, were isolated from the aqueous ethanolic extract of the whole herb of Eriophyton wallchii Benth. The structures of 28-epi-cyasterone and eriophytonoide were elucidated as (22R,24S,25S,28S)-5beta-stigmast-7-en-26-oic acid, 2beta,3beta,14,20,22,28-hexa hydroxy-6-oxo-gamma-lactone, and 1-O-beta-d-glucopyranosyl-(2S,3S,4R,8E)-2-[(2R)-2-hydroxyhexadecanoylamino]-1,3,4-octadecanetriol-8-ene, respectively, on the basis of spectral and chemical evidence.

A new anthraquinone from Gladiolus gandavensis.

A new anthraquinone, 1,6,7-trihydroxy-3-methoxyanthraquinone, along with three known compounds methyl trans-p-hydroxycinnamate, eugenin and 1,3,6-trihydroxy-8-methylanthraquinone, were isolated from the subterranean rhizomes of Gladiolus gandavensis Van Houtt. Their structures were established on the basis of spectroscopic data including 2D NMR techniques and chemical methods.

Anthraquinones from Gladiolus gandavensis

Five new anthraquinones have been obtained from the ethanolic extracts of the subterranean corms of Gladiolus gandavensis Van Houtt. Their structures were elucidated as 3,8-dihydroxy-6-methoxy-1-methyl-anthraquinone (gandavensin D, 1), methyl 3,8-dihydroxy-6,7-methylenedioxy-1-methyl-anthraquinone- 2-carboxylate (gandavensin E, 2), 2,3,8-trihydroxy-6-methoxy-1-methoxymethyl-anthraquinone (gandavensin F, 3), 8-hydroxy-3,6-dimethoxy-1-methyl-anthraquinone-2-carboxylic acid (gandavensin G, 4) and 1,7-dihydroxy-3,6-dimethoxy-anthraquinone (gandavensin H, 5) on the basis of spectral data. The known compounds isolated for the first time from this plant have been determined to be methyl 3,6,8-trihydroxy-7-methoxy-1-methyl-anthraquinone-2-carboxylate (6), methyl 3,6,8-trihydroxy-1-methyl-anthraquinone-2-carboxylate (7), 3,8-dihydroxy-6-methoxy-1-methyl-anthraquinone-2-carboxylic acid (8), 3,6,8-trihydroxy-1-methyl-anthraquinone-2-carboxylic acid (9), 6,8-dihydroxy-3-methoxy-1-methyl-anthraquinone-2-carboxylic acid (10), methyl 3,8-dihydroxy-6-methoxy-1-methyl-anthraquinone-2-carboxylate (11) and methyl 3,7,8-trihydroxy-1-methyl-anthraquinone-2-carboxylate (12).