Synthesis of 3-azabicyclo[3.2.2]nonanes and their antiprotozoal activities.

Several bicyclic compounds, 3-azabicyclo[3.2.2]nonanes, have been prepared. The new compounds were tested for their activities against one strain of the causative organism of Malaria tropica, Plasmodium falciparum K1, which is resistant against chloroquine and pyrimethamine. In addition, their cytotoxicity and their activity against the pathogen of the East African form of sleeping sickness, Trypanosoma brucei rhodesiense, were investigated. Structure-activity relationships are discussed considering data of readily prepared compounds. For the first time, a distinct in vivo activity was observed against Plasmodium berghei in a mouse model. The active compound was further investigated.

Compounds of Alpinia katsumadai as potential efflux inhibitors in Mycobacterium smegmatis.

Efflux pumps are one of the well established mechanisms that contribute to antibiotic resistance in bacteria, such as mycobacteria. As a result, the identification of efflux pump inhibitors is an attractive target in antimicrobial therapy. The isolated compounds, three diarylheptanoids, trans,trans-1,7-diphenylhepta-4,6-dien-3-one (1), (5R)-trans-1,7-diphenyl-5-hydroxyhept-6-en-3-one (2), (3S,5S)-trans-1,7-diphenylhept-1-ene-3,5-diol (3) and the flavonoid pinocembrin (4), from Alpinia katsumadai, Zingiberaceae, were examined for their antimycobacterial activity and their synergistic effects with different antibiotics against M. smegmatis mc(2) 155. Furthermore, these compounds were evaluated as potential EtBr efflux inhibitors. Although they showed weak antimycobacterial activities (MIC ≥ 64 mg/L), especially compound 1 revealed a significant activity on the EtBr accumulation and efflux as well as a synergistic effect in combination with rifampicin.

Putative mycobacterial efflux inhibitors from the seeds of Aframomum melegueta.

In order to identify new putative efflux pump inhibitors that represent an appropriate target in antimycobacterial chemotherapy, nine paradol- and gingerol-related compounds (1-9) isolated from the seeds of Aframomum melegueta were assessed for their potential to inhibit ethidium bromide (EtBr) efflux in a Mycobacterium smegmatis model. Five of the compounds from A. melegueta and NMR spectroscopic data of the diketone 6-gingerdione (2) and its enolic tautomers, methyl-6-gingerol (5) and rac-6-dihydroparadol (7), are presented herein for the first time. After determination of their antimycobacterial activities and modulatory effects on the MIC of antibiotics as well as their synergistic effects in combination with antibiotics against M. smegmatis mc(2) 155, their impact on EtBr accumulation and efflux was evaluated using a microtiter plate-based fluorometric assay. The compounds exhibited moderate to weak antimycobacterial activities, and the best modulators induced a 4- to 16-fold decrease of the MICs of EtBr and rifampicin as well as a reduction of the MIC of isoniazid with fractional inhibitory concentration index values indicating synergistic activities in some cases. 6-Paradol (3), 8-gingerol (6), and rac-6-dihydroparadol (7) were the most potent EtBr efflux inhibitors in M. smegmatis mc(2) 155, displaying EtBr efflux inhibiting activities comparable to reference inhibitors.

Identification and characterization of [6]-shogaol from ginger as inhibitor of vascular smooth muscle cell proliferation.

SCOPE: Vascular smooth muscle cell (VSMC) proliferation is involved in the pathogenesis of cardiovascular disease, making the identification of new counteracting agents and their mechanisms of action relevant. Ginger and its constituents have been reported to improve cardiovascular health, but no studies exist addressing a potential interference with VSMC proliferation. METHODS AND RESULTS: The dichloromethane extract of ginger inhibited VSMC proliferation when monitored by resazurin metabolic conversion (IC50 = 2.5 µg/mL). The examination of major constituents from ginger yielded [6]-shogaol as the most active compound (IC50 = 2.7 µM). In the tested concentration range [6]-shogaol did not exhibit cytotoxicity toward VSMC and did not interfere with endothelial cell proliferation. [6]-shogaol inhibited DNA synthesis and induced accumulation of the VSMC in the G0 /G1 cell-cycle phase accompanied with activation of the nuclear factor-erythroid 2-related factor 2 (Nrf2)/HO-1 pathway. Since [6]-shogaol lost its antiproliferative activity in the presence of the heme oxygenase-1 (HO-1) inhibitor tin protoporphyrin IX, HO-1 induction appears to contribute to the antiproliferative effect. CONCLUSION: This study demonstrates for the first time inhibitory potential of ginger constituents on VSMC proliferation. The presented data suggest that [6]-shogaol exerts its antiproliferative effect through accumulation of cells in the G0 /G1 cell-cycle phase associated with activation of the Nrf2/HO-1 pathway.

Dibenzocyclooctadiene lignans from Magnolia and Talauma (Magnoliaceae): their absolute configuration ascertained by circular dichroism and X-ray crystallography and re-evaluation of previously published pyramidatin structures.

Twelve pyramidatins, i.e., dibenzocyclooctadiene-type lignans, together with Machilin G, were isolated from the dichloromethane extracts of aerial material of Talauma gloriensis, Magnolia fraseri, and Magnolia pyramidata (Magnoliaceae). These lignans contain a highly oxidized 7,9'-epoxy-2,2'-cyclolignane skeleton. Their structures were established using NMR spectroscopy (1D and 2D experiments) and mass spectrometry. The absolute configurations of five pairs of atropisomers (S(a)/R(a)-pyramidatins) and two single atropisomers (S(a)-pyramidatins) were determined by experimental and calculated circular dichroism (CD). In addition, the absolute configuration of (S(a))-3,3',4,4',5,5'-hexamethoxypyramidatin was confirmed using X-ray crystallography. Five pyramidatins, (R(a))-3,3',4,4',5,5'-hexamethoxypyramidatin, (R(a))-3,3'-dimethoxy-4,5:4',5'-bis(methylenedioxy)pyramidatin, (S(a))-3,3',4,5'-tetramethoxy-4,5-methylenedioxypyramidatin, (R(a))-3,3',4,5'-tetramethoxy-4,5-methylenedioxypyramidatin, and (R(a))-3,3',4,5-tetramethoxy-4',5'-methylenedioxypyramidatin are reported herein for the first time. In the current dataset, NMR values are in accordance with the observed and calculated CD values. These values are herein reported with particular reference to previously described data of pyramidatins, which have to be revised.