Two new alkaloids from the bark of Sarcomelicope megistophylla

Two new alkaloids, megistophylline I (1) and megistophylline II (2), were isolated from the bark of Sarcomelicope megistophylla. Their structures have been elucidated on the basis of MS and NMR data.     

Flavonoids as cycline-dependent kinase inhibitors: inhibition of cdc 25 phosphatase activity by flavonoids belonging to the quercetin and kaempferol series

In an effort to detect potential inhibitors of cdc25 phosphatase, nineteen flavonoids belonging to the quercetin and kaempferol series have been evaluated, using a colorimetric assay of recombinant human cdc25A tyrosine phosphatase as a cell cycle-specific target. Compounds bearing two benzyl or methyl groups in positions 7 and 4' and acetyl on the hydroxy groups of the sugar moiety showed the maximal activity.     

Plants from New Caledonia. Alkaloids from Sarcomelicope dogniensis Hartley stem bark

Two new pyranofuroquinoline alkaloids, cis-1,2-dihydroxy-1,2 dihydroacronydine 2 and trans-1,2-dihydroxy-1,2-dihydroacronydine 3 have been isolated from Sarcomelicope dogniensis stem bark. Their structures have been elucidated by spectral analysis and chemical correlations. In addition, 11 other alkaloids have been isolated from the stem bark of this species.     

Composition of the essential oil of two Nepeta species and in vitro evaluation of their activity against Helicobacter pylori.

The chemical composition of the essential oils obtained from the aerial parts of Nepeta camphorata and Nepeta argolica ssp. dirphya were analysed by GC-MS. A total of 52 components were identified and significant differences (qualitative and quantitative) were observed between the two samples. 1,8-Cineol and two nepetalactones were found to be the major components of the oil of N. camphorata and N. argolica ssp. dirphya respectively. The in vitro activity, of the two oils and the three above mentioned isolated compounds, against 25 clinically isolated and commercial strains of Helicobacter pylori was investigated and some activity was found.     

Cytotoxic activity of kaempferol glycosides against human leukaemic cell lines in vitro.

Two kaempferol coumaroyl glycosides (i.e. platanoside and tiliroside) isolated from the methanolic extract of Platanus orientalis L. buds, were examined for their in vitro cytotoxic activity against a panel of human leukaemic cell lines. Platanoside (1) exhibited cytotoxic activity against most of the cell lines tested, while tiliroside (2) was active against two of the nine tested cell lines. Compound 1, was examined for its effect on the uptake of [(3)H]thymidine as a marker of DNA synthesis. Kaempferol was used as a control.     

Antiviral In vitro activity of Hypericum perforatum l. extract on the human cytomegalovirus (HCMV)

The total methanol extract and chromatographic fractions of the extract of the aerial parts of Hypericum perforatum L. were investigated for their antiviral activity against human cytomegalovirus (HCMV) AD-169 laboratory strain by modification of the widely used diagnostic method ‘shell-vial’ culture. The plant selection was based on its traditional use against viruses of the Herpes family in Greece. The results showed extract fraction III had the most potent antiviral activity against HCMV which was also superior to that of ganciclovir. Copyright © 1998 John Wiley & Sons, Ltd.     

Effects of plant phenolics and grape extracts from Greek varieties of Vitis vinifera on Mitomycin C and topoisomerase I-induced nicking of DNA

In recent years, a number of reports have shown the anticancer activity of grape extracts and wine against various types of cancer such as breast, lung and gastric cancer. This property is mainly attributed to the plant polyphenols identified in grapes. The aim of the present study was to investigate the mechanisms by which grape extracts and plant polyphenols found in them exert their chemopreventive and antitumour activities. Thus, aqueous and methanolic extracts from two Greek varieties of Vitis vinifera, fractions enriched in polyphenols of these extracts and polyphenolics (caffeic acid, ferulic acid, gallic acid, protocatechuic acid and rutin) found in grapes were screened using two in vitro assays: i) the topoisomerase I relaxation assay and ii) the mitomycin C-induced DNA strand breakage. The grape extracts, the polyphenol-rich fractions and some of the polyphenolics (caffeic acid and protocatechuic acid) were potent inhibitors of topoisomerase I, indicating that the inhibition of this enzyme may be one of the mechanisms accounting for the anticancer activity of these compounds. Moreover, the grape extracts inhibited the mitomycin C-induced DNA strand breakage suggesting that they could prevent ROS-mediated DNA damage. On the other hand, the polyphenol-rich fractions and the plant polyphenols enhanced the mitomycin C-induced DNA strand breakage indicating prooxidant activity. Thus, it is of interest that whole grape extracts act as chemopreventive agents by inhibiting topo I and mitomycin C-induced DNA damage, while polyphenol enriched fractions and plant polyphenolics exert prooxidant activity leading to enhancement of DNA damage which may account for the cytotoxic and apoptosis-inducing properties of plant polyphenols against cancer cells.     

Synthesis and Anti-proliferative Activity of 2-Hydroxy-l,2-dihydroacronycine Glycosides

Purpose. Combination of the acronycine pharmacophore with various sugar units appeared of interest, since numerous anticancer agents possess a sugar moiety, which strongly influence both their bioavailability and their selective toxicity towards tumor cells. Methods. A series of 2-hydroxy-1,2-dihydroacronycine glycosides were synthetized, by condensation of the racemic aglycone with appropriate glycoside donors. Their effect on the inhibition of L1210 cell proliferation were evaluated. Results. Compounds 6a, 6b, 11a, 11b, and 12a, 12b, including a halogenated sugar moiety displayed activities of the same order of magnitude as acronycine itself. Compounds 7a, 7b, and 8a, 8b, bearing a 2,3,6-trideoxy-3-azido-L-lyxo- and L-arabino-hexopyranose unit respectively, were significantly more potent than acronycine in inhibiting cell proliferation. Conclusions. The activity of 2-hydroxy-1,2-dihydroacronycine glycosides seems to be related to the lipophilicity of the sugar unit.