Snežana Trifunović

Oxidation products of hyperforin from Hypericum perforatum

The isolation of two oxidation products of hyperforin from the aerial parts of Hypericum perforatum and their structure determination by means of 2D NMR methods is reported. The products had the same 1-(2-methyl-1-oxopropyl)-2,12-dioxo-3,10 beta-bis(3-methyl-2-butenyl)-11 beta-methyl-11 alpha-(4-methyl-3-pentenyl)-5-oxatricyclo[6.3.1.0(4,8)]-3-dodec ene skeleton. In addition, one of them, with the same number of carbons as hyperforin (C35H52O5), contained a 1-methyl-l-hydroxyethyl group in the 6 beta-position, whereas the other compound (a hemiacetal, C32H46O5), presumably a degradation product of hyperforin, exhibited a 6-hydroxy function. The latter was an inseparable mixture of 6 alpha- and 6 beta-hydroxy epimers undergoing (according to phase sensitive NOESY) mutual interconversion.

Diarylheptanoids from the bark of black alder inhibit the growth of sensitive and multi-drug resistant non-small cell lung carcinoma cells.

An extended study of minor diarylheptanoids from the bark of black alder has resulted in the isolation of twenty diarylheptanoids, ten of which have not previously been reported (14-18, 20-24). The structures and configurations of all compounds were elucidated by NMR, HRESIMS, UV, IR, and CD. The anti-cancer potency of twenty diarylheptanoids and four previously isolated compounds (7, 10, 12, 13) was investigated in human non-small cell lung carcinoma cell lines (sensitive and multi-drug resistant variants) as well as in normal human keratinocytes. Diarylheptanoids with a p-coumaroyl group, 14 and 18, platyphylloside (1), platyphyllonol-5-O-β-D-xylopyranoside (2), alnuside B (4) and hirsutenone (9) exhibited strong anti-cancer activity, considerably higher than diarylheptanoid curcumin, which served as a positive control. Compounds 4, 9, 14, and 18 displayed significant selectivity towards the cancer cells. Structure/activity analysis of twenty-four closely related diarylheptanoids revealed a high dependence of cytotoxic action on the presence of a carbonyl group at C-3. Substitution of a heptane chain on C-5 and a number of hydroxyl groups in the aromatic rings also emerged as a significant structural feature that influenced their cytotoxic potential.

Further degradation product of hyperforin from Hypericum perforatum (St. John's Wort)

Repeated examination of the aerial parts of Hypericum perforatum yielded a new degradation product of hyperforin (1) namely deoxyfurohyperforin A (2), together with the previously identified furohyperforin (3), furoadhyperforin (4), furohyperforin A (5a and 5b), pyrano[7,28-b]hyperforin (6) and 3-methyl-4,6-di(3-methyl-2-butenyl)-2-(2-methyl-1-oxopropyl)-3-(4-methyl-3-pentenyl)-cyclohexanone (7). The antimicrobial activity of the compounds 3, 5a and 5b, 6 and 7 was tested against Staphylococcus aureus, Candida albicans, Bacillus subtilis and Escherichia coli.

Diarylheptanoids from Alnus glutinosa Bark and Their Chemoprotective Effect on Human Lymphocytes DNA

A study of secondary metabolites from the bark of Alnus glutinosa led to the isolation of fourteen diarylheptanoids: oregonin (1), platyphylloside (2), rubranoside A (3), rubranoside B (4), hirsutanonol (5), hirsutenone (6), hirsutanonol-5-O-β-D-glucopyranoside (7), platyphyllonol-5-O-β-D-xylopyranoside (8), aceroside VII (9), alnuside A (10), alnuside B (11), 1,7-bis-(3,4-dihydoxyphenyl)-5-hydroxy-heptane-3-O-β-D-xylopyranoside (12), (5S)-1-(4-hydroxyphenyl)-7-(3,4-dihydroxyphenyl)-5-O-β-D-glucopyranosyl-heptan-3-one (13), and (5S)-1,7-bis-(3,4-dihydroxyphenyl)-5-O-β-D-[6-(3,4-dimethoxycinnamoylglucopyranosyl)]-heptan-3-one (14). All of the diarylheptanoids, except 1 and 5, were found in A. glutinosa for the first time, while 13 and 14 were new compounds. The structures were determined by spectroscopic techniques: 1D and 2D NMR, HR-ESI-MS, FTIR, UV, and CD. All isolated compounds were analyzed for an in vitro protective effect on chromosome aberrations in peripheral human lymphocytes using the cytokinesis-block micronucleus assay. The majority of them, including the new compounds 13 and 14, exerted a pronounced effect in decreasing DNA damage in human lymphocytes. Diarylheptanoids 1, 2, 5, 13, and 14 at a concentration of 1 µg/mL decreased the frequency of micronuclei by 52.8 %, 43.8 %, 63.6 %, 44.4 %, and 56.0 %, respectively, exerting a much stronger effect than the synthetic protector amifostine (17.2 %, c = 1 µg/mL).

Antiproliferative activity and QSAR studies of a series of new 4-aminomethylidene derivatives of some pyrazol-5-ones.

Twenty five 4-aminomethylidene derivatives obtained from 3-phenyl-2-pyrazolin-5-one and 1,3-diphenyl-2-pyrazolin-5-one were synthesized and tested for their antiproliferative activity against human breast cancer MDA-MB-361 and MDA-MB-453 cell lines. The compounds derived from 1,3-diphenyl-2-pyrazolin-5-one exhibited the most remarkable activity in the treatment of both cell lines. In vitro antiproliferative activities were accompanied by an important apoptotic fraction of both cell lines; also, compounds inhibited key endothelial cell functions implicated in invasion and angiogenesis. QSAR methods were performed in order to analyze the influence of structural features of the compounds investigated on the antiproliferative potential on MDA-MB-361 and MDA-MB-453 cancer cells. One-parameter heuristic analysis was performed and different whole molecule and fragmental descriptors were considered for rationalization of mechanism of interaction of these compounds with active place of hypothetical target included in tumorigenesis.

Synthesis, cytotoxic activity and DNA-interaction studies of novel anthraquinone-thiosemicarbazones with tautomerizable methylene group.

A series of novel anthraquinone-thiosemicarbazone derivatives in a tautomerizable keto-imine form was synthesized and tested for their in vitro cytotoxic activity against human cancer cells (HeLa, MDA-MB-361, MDA-MB-453, K562, A549) and human normal MRC-5 cells. Several compounds efficiently inhibited cancer cell growth at micromolar concentrations, especially against K562 and HeLa cells. As determined by flow cytometric analysis, anthraquinone-thiosemicarbazone caused significant increase in the number of sub-G1 phase of HeLa cells and apoptosis in a concentration-dependent manner. Also, inhibition of caspase-3, -8, and -9 with specific caspase inhibitors reduced the apoptosis mediated by the tested compounds in HeLa cells. All anthraquinone-thiosemicarbazones exhibit calf thymus DNA-binding activity, but no cleavage of plasmid DNA was observed.

Synthesis and antioxidant activity of 1,3,4-oxadiazoles and their diacylhydrazine precursors derived from phenolic acids

Eight 1,3,4-oxadiazole derivatives containing phenolic acid moieties (7a–h) and eight of their diacylhydrazine precursors (6a–h) were synthesized, characterized using spectroscopic methods and examined by scavenging of stable DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals. The most potent phenolic 1,3,4-oxadiazoles showed better DPPH scavenging activity in comparison with their corresponding diacylhydrazine precursors as a result of participation of both aromatic rings and a 1,3,4-oxadiazole moiety in resonance stabilization of the formed phenoxyl radical. Four diacylhydrazines (6d, 6e, 6g, and 6h) and four 1,3,4-oxadiazoles (7d, 7e, 7g and 7h) with the best DPPH scavenging activity, were chosen for further evaluation of their antioxidant potential through various assays. The investigated compounds exerted pronounced ABTS radical scavenging capacity, moderate to good H2O2 scavenging properties and strong ferric ion reducing capacity. Further in vitro evaluation of the antioxidant properties of the most active compounds demonstrated their protective effects in normal lung fibroblasts MRC-5 against hydrogen peroxide induced oxidative stress. Diacylhydrazine 6h increased two times the activity of glutathione peroxidase in treated cells in comparison with a control sample and did not affect the superoxide dismutase activity.

Diarylheptanoids from Green Alder Bark and Their Potential for DNA Protection

Nine diarylheptanoids, 1–9, catechin (11), and a phenolic glucoside, 10, were isolated from the bark of green alder (Alnus viridis). Four of the isolated compounds, i.e., 2, 5, 8, 10, are new. The structures of 1–11 were determined on the basis of spectroscopic data. All isolated compounds were evaluated for their in vitro protective effects on chromosome aberrations in peripheral human lymphocytes using cytokinesis‐block micronucleus (CBMN) assay. Almost all of them exerted a pronounced effect of decreasing DNA damage of human lymphocytes, acting stronger than the known synthetic protector amifostine.

Pyrrolizidine Alkaloids and Fatty Acids from the Endemic Plant Species Rindera umbellata and the Effect of Lindelofine-N-oxide on Tubulin Polymerization

The examination of the aerial parts, roots, and seeds of the endemic plant Rindera umbellata is reported in this paper for the first time. Phytochemical investigation of R. umbellata led to the isolation and characterization of ten pyrrolizidine alkaloids and eleven fatty acids in the form of triglycerides. Pyrrolizidine alkaloids 1–9 were found in the aerial parts, 7 and 8 in the roots, and 6–10, together with eleven fatty acids, in the seeds of this plant species. The structures of compounds 1–10 were established based on spectroscopic studies (1H- and 13C-NMR, 2D NMR, IR and CI-MS). After trans-esterification, methyl esters of the fatty acids were analyzed using GC-MS. The effect of lindelofine-N-oxide (7) on tubulin polymerization was determined.

Stereochemistry and conformations of natural 1,2-epoxy-guaianolides based on 1D and 2D NMR data and semiempirical calculations

From detailed study of 1D and 2D NMR spectra of ten natural 1,2‐epoxyguaianolides (bis‐1,2:3,4‐epoxyguaianolides and guaianolide‐1,2‐epoxychlorohydrins), we identified general spectral traits helpful for stereochemical assignment of such sesquiterpene lactones. We found that the chemical shifts of certain 1H and 13C nuclei are consistently dependent on the configuration of 1,2‐epoxy‐ring which could be used as a simple rule for establishing this configuration. Then, from 1D and 2D (COSY, NOESY, HMQC, HMBC) NMR data, applying the observed rule, the structure and stereochemistry of two new, diastereomeric guaianolide‐1,2‐epoxychlorohydrins, isolated from Achillea serbica, are determined. The NMR data, namely, nuclear overhauser enhancement (NOE) correlations, pointed out two conformations of guaianolides cycloheptane ring. The semiempirical calculations (AM1 and PM3 methods), performed in order to gain additional information regarding conformations, resulted in three geometries of investigated lactones. Even so, the conformations derived from the NMR data agreed well with those calculated by semiempirical methods. Copyright