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Ashraf Taha Khalil

Publications and source records attributed to Ashraf Taha Khalil.

16 recordsLinked to original sources
PubMed2006

Isolation of aureol from Smenospongia sp. and cytotoxic activity of some aureol derivatives.

The sesquiterpene aureol (1) was isolated by chromatographic fractionation of a non-polar extract from Smenospongia sp. Methylation of aureol yielded 5'-O-methyl-aureol (2) while the prepared acylation products of aureol were 5'-O-acetyl-aureol (3), 5'-O-benzoyl-aureol (4), 5'-O-(4-fluoro-benzoyl)-aureol (5), 5'-O-(4-chlorobenzoyl)-aureol (6), 5'-O-(4-methylbenzoyl)-aureol (7), 5'-O-nicotinoyl-aureol (8), aureol-N,N-dimethylthiocarbamate (9), 5'-O-(2-furoylcarbonyl)-aureol (10), 5'-O-(2-thienoylcarbonyl-aureol (11). The structures of aureol as well as its ten derivatives were established through spectral analysis. The in vitro cytotoxic activities of the eleven compounds were evaluated against Hepa59T/VGH, KB and Hela tumor cell lines.

Animals↗
PubMed2006

Benzylamides from Salvadora persica.

A phytochemical investigation of stems from Salvadora persica resulted in the first isolation of four benzylamides from a natural source. The isolated compounds were identified as butanediamide, N1,N4-bis(phenylmethyl)-2(S)-hydroxy-butanediamide (1), N-benzyl-2-phenylacetamide (2), N-benzylbenzamide (3) and benzylurea (4). The structure elucidation was accomplished using spectroscopic methods, especially 2D NMR and HREIMS. Compound 2 revealed a significant inhibitory effect on human collagen-induced platelet aggregation, and a moderate antibacterial activity against Escherichia coli.

Amides↗
PubMed2006

Xenicane-type diterpenes with cytotoxicity from Xenia florida.

Chromatographic investigation of an acetone extract of the octocoral Xenia florida afforded three new xenicane diterpenes, namely, florxenilide A (1), florxenilide B (2), and florxenilide C (3), in addition to seven known xenicane diterpenes and two known cadinene sesquiterpenes. Structures were elucidated through spectroscopic analysis, especially 2D NMR, and chemical derivatization. The absolute configuration of 1 was determined by NOESY, CD, and Mosher's methods. Florxenilides A (1) and B (2) exhibited cytotoxicity against human colon cancer (WiDr) cells at 4.5 and 3.7 muM, respectively.

Animals↗
PubMed2005

New gemacranolides from Eupatorium hualienense.

Phytochemical investigation of Eupatorium hualienense (C. H. Ou, S. W. Chung, C. I. Peng) has resulted in the isolation of the new sesquiterpene lactones 1-5, named eupahualins A-E, along with the known heliangolide eupasimplicin B (6). The structures of the isolated compounds were established through detailed spectral analyses, especially by means of 2D-NMR techniques. Compounds 1-4 and 6 showed significant activities against cell lines of human chronic myelogenous leukemia (K562) and human bone cancer (U2OS).

Antineoplastic Agents↗
PubMed2005

Three new taxane diterpenoids from Taxus sumatrana.

Phytochemical investigation of taxane diterpenoidal content of an acetone extract of the leaves and twigs of Taxus sumatrana has resulted in the isolation of three new taxoid compounds, tasumatrols E (1), F (2), and G (3) together with 13 known taxanes (5-16). The structures of these taxanes as well as their derivatives were established on the basis of spectroscopic analyses, especially 1D and 2D NMR. Compounds 1, 2, 12, and 16 exhibited significant cytotoxicity against human A-498, NCI-H226, A549, and PC-3 tumor cells.

Antineoplastic Agents, Phytogenic↗
PubMed2005

Cytotoxic sesquiterpene lactones from Eupatorium kiirunense, a coastal plant of Taiwan.

Phytochemical investigation of Eupatorium kiirunense has resulted in the isolation of eight new sesquiterpene lactones, constituted by five germacranolides, eupakirunsins A-E (1-5), and three heliangolides, eupaheliangolide A (6), 15-acetoxyheliangin (7), and 3-epi-heliangin (8), in addition to the known heliangin (9) and 8,10-epoxy-9-acetoxythymol angelate (10). The structures of the new compounds were established through detailed analysis of their spectroscopic data. Compounds 6, 8, and 9 exhibited cytotoxicity against human oral epidermoid (KB), cervical epitheloid (Hela), and liver (hepa59T/VGH) carcinoma cells.

Antineoplastic Agents, Phytogenic↗
PubMed2005

Two new sesquiterpene lactones from Ixeris chinensis.

Phytochemical investigation of Ixeris chinensis NAKAI (Asteraceae) has resulted in the isolation of a new guaianolide-type sesquiterpene lactone, ixerochinolide (1) as well as the related glucoside, ixerochinoside (2). In addition, the known guaianolides, 8beta-hydroxy-3-oxo-guaia-4(15),10(14),11(13)-trien-1alpha,5alpha,6beta,7alphaH-12,6-olide (8beta-hydroxydehydrozaluzanin), 8beta,15-dihydroxy-2-oxo-guaia-1(10),3,11(13)-trien-5alpha,6beta,7alphaH-12,6-olide (lactucin), 3beta,8alpha,10alpha-trihydroxy-guaia-4(15),11(13)-dien-1alpha,5alpha,6beta,7alphaH-12,6-olide (10alpha-hydroxy-10,14-dihydro-desacylcynaropicrin) and 3beta-D-glucopyranosyloxy-8beta-(p-hydroxyphenylacetyloxy)-guaia-4(15),10(14),11(13)-trien-1alpha,5alpha,6beta,7alphaH-12,6-olide (8-epicrepioside) were identified. The structures were determined on the basis of spectral analyses, especially 1- and 2D NMR. Compound 1 exhibited significant cytotoxicity against human PC-3 tumor cells.

Asteraceae↗
PubMed2005

Bioactive pyranoxanthones from the roots of Calophyllum blancoi.

Phytochemical investigation of the roots of Calophyllum blancoi growing in Taiwan resulted in the isolation of three new pyranoxanthones, blancoxanthone (1), acetyl blancoxanthone (2) and 3-hydroxyblancoxanthone (3), in addition to two known pyranoxanthones, pyranojacaeubin (4) and caloxanthone (5). Structural characterization of the isolated compounds was determined by spectral analyses especially 2-D NMR. Biological study of the isolated xanthones revealed that blancoxanthone (1) exhibited significant anti-coronavirus activity.

Acetylation↗
PubMed2004

Vibsane diterpenoids from the leaves and flowers of Viburnum odoratissimum.

In addition to the five known compounds 5-epi-vibsanin H, vibsanins C, H, and G, and aldovibsanin B, four new diterpenes, 5-epi-vibsanin G (1), 18-O-methylvibsanin G (2), vibsanin M (3), and aldovibsanin C (4), were isolated from an acetone extract of the leaves and flowers of Viburnum odoratissimum by bioassay-directed fractionation. In addition, two acetyl derivatives 5 and 6 were obtained from the naturally occurring diterpenes. The structures of the new compounds were established on the basis of NMR spectral analysis, including COSY, HMQC, HMBC, and NOESY correlations. The compounds were evaluated for cytotoxicity against human nasopharyngeal carcinoma (HONE-1) tumor cells and human gastric cancer (NUGC-3) cells.

Antineoplastic Agents, Phytogenic↗
PubMed2004

New cytotoxic clerodane diterpenoids from the leaves and twigs of Casearia membranacea.

Bioassay-guided fractionation of an EtOAc-soluble extract of Casearia membranacea has resulted in the isolation of six new clerodane diterpenes, caseamembrins A-F (1-6), and a known compound, rel-(2S,5R,6R,8S,9S,10R,18S,19R)-diacetoxy-18,19-epoxy-6-hydroxy-2-(2-methylbutanoyloxy)cleroda-3,13(16),14-triene (7). The structures of 1-6 were established on the basis of extensive 1D and 2D NMR spectroscopic analysis. In addition, the new derivatives, 8 and 9, were prepared by acylation of 7 and 3, respectively. The isolated diterpenoids and their derivatives were tested against human prostate (PC-3) and hepatoma (Hep3B) cancer cells. Compounds 1, 3-5, and 7 exhibited cytotoxicity against both tumor cells, with IC(50) values below 3 micromicro, while compounds 2, 6, 8, and 9 were less effective.

Acetylation↗
PubMed2004

New regio- and stereoselective O-deacetylated and epoxy products of taxanes isolated from Taxus mairei.

Deacylation of a taxoid mixture isolated from the roots of Taxus mairei followed by chromatographic fractionation resulted in the isolation of three new taxoid derivatives, 2alpha,9alpha,10beta-triacetoxy-5alpha,14beta-dihydroxy-4(20),11(12)-taxadiene (1), 9alpha,10beta-diacetoxy-2alpha,5alpha,14beta-trihydroxy-4(20),11(12)-taxadiene (2), and 9alpha,10beta-diacetoxy-2alpha,5alpha,14beta-trihydroxy-4,20-epoxy,11(12)-taxene (3). Epoxidation of 2 afforded 9alpha,10beta-diacetoxy-2alpha,5alpha,14beta-trihydroxy-4,20:11,12-diepoxytaxane (6), while epoxidation of 4 yielded 9alpha,10beta-diacetoxy-5alpha,13alpha-dihydroxy-4,20-epoxy,11(12)-taxene (7) and 9alpha,10beta-diacetoxy-5alpha,13alpha-dihydroxy-4,20:11,12-diepoxytaxane (8). The structures were elucidated by detailed analysis of their NMR spectra. The structure and relative stereochemistry of 7 was confirmed by X-ray crystallography.

Crystallography, X-Ray↗
PubMed2004

Two new cytotoxic clerodane diterpenoids from Casearia membranacea.

In addition to casearlucin A (3), two new clerodane diterpenes, caseamembrols A (1) and B (2) have been isolated from the leaves and twigs of Casearia membranacea by bioassay-guided fractionation. The structures of the new compounds were established on the basis of extensive 1D- and 2D-NMR spectroscopic analysis. Compounds 1-3 exhibited significant cytotoxicity against human prostate (PC-3) cancer cells.

Antineoplastic Agents, Phytogenic↗
PubMed2004

Chromanones and dihydrocoumarins from Calophyllum blancoi.

Chromatographic fractionation of the acetone extract of the seeds of Calophyllum blancoi yielded six pyranochromanone derivatives; apetalic acid (1), isoapetalic acid (2), apetalic acid methyl ester (3), apetalic acid 5-O-acetate (4), isoapetalic methyl ester (5), and isoapetalic acid 5-O-acetate (6). In addition, one new dihydrocoumarin derivative, isorecedensolide (7), was also isolated together with recedensolide (8). The structures of the isolated compounds were established through analysis of NMR spectral data including 2D techniques as well as other physical and spectroscopic methods. Compounds 3, 4, 5, 7, and 8 showed mild activity against KB (human oral epidermoid carcinoma) and Hela (human cervical epitheloid carcinoma) tumor cell lines.

Anthraquinones↗
PubMed2003

Chemical constituents from the Hydrangea chinensis.

Two quinazolone alkaloids, (+)-febrifugine (1) and isofebrifugine (2), along with three coumarin derivatives, 6-hydroxy coumarin (3), skimmin (5), and umbelliferone-7-O-alpha-L-rhamnopyranosyl(1-->4)-beta-D-glucopyranoside (6), were isolated from the roots of Hydrangea chinensis. Compound 6 is a new compound. In addition, umbelliferone (4), linoleic acid (7), two steroidal glycosides (8, 9), three furfural derivatives (10-12), and butyl-beta-D-fructofuranoside (13) were isolated from the leaves of the same plant. The structures of all isolates were elucidated by spectral methods.

Coumarins↗
PubMed2003

Antiplatelet and anti-HIV constituents from Euchresta formosana.

Phytochemical investigation of the methanol extract of Euchresta formosana resulted in the isolation of thirty-four compounds. Compounds 1, 3-12, 15, 27, 29 and 32-24 were isolated from this species for the first time. These compounds were identified by spectral analyses and tested for antiplatelet aggregation and anti-HIV activities. Among these compounds, tectorigenin (1), 3',4',5-trihydroxyisoflavone (3), and euchretin F (19) were the most effective antiplatelet aggregation compounds; they inhibited both AA- (arachidonic acid) and collagen-induced platelet aggregation. Meanwhile, flemiphyllin (B), quercetin (13), euchretin M (23), and formosanatin C (26) inhibited HIV replication in H9 lymphocyte cells.

Animals↗