Synthesis and biological evaluation of amino analogs of Ludartin: Potent and selective cytotoxic agents

Diverse amino analogs of Ludartin, a cytotoxic guaianolide and a position isomer of an anticancer drug, Arglabin were prepared through Michael type addition at its highly active α-methylene-γ-lactone motif. The semisynthetic derivatives were subjected to sulphorhodamine B cytotoxicity assay against a panel of four different human cancer cell lines viz. lung (A-549), leukemia (THP-1), prostate (PC-3) and colon (HCT-116) to look into structure–activity relationship. Few of the analogs displayed potent selective cytotoxicity compared to the parent molecule-Ludartin (1). (11R)-13-(Diethyl amine)-11,13-dihydroludartin (6) and (11R)-13-(piperidine)-11,13-dihydroludartin (10) showed almost same cytotoxicity against leukemia cell lines (THP-1) as that of parent molecule-Ludartin, but were more active against colon (HCT-116) cancer cells. (11R)-13-(Morpholine)-11,13-dihydroludartin (11) displayed selectively better cytotoxicity against Leukemia cancer cells (THP-1) exhibiting IC₅₀ of 2.8 μM. (11R)-13-(6-Nitroindazole)-11,13-dihydroludartin (17) was four times more potent than Ludartin with selective cytotoxic effects against prostate cancer cells (2.2 μM) while as (11R)-13-(6-nitroindazole)-11,13-dihydroludartin (18) exhibited three-fold selective cytotoxicity for Lung (A-549) cancer cell lines exhibiting IC₅₀ of 2.6 μM.     

α-Santalol derivatives from Santalum album and their cytotoxic activities

A bioassay-guided fractionation of the heartwood of Santalum album led to the isolation of seven α-santalol derivatives including (9S,10E)-9-hydroxy-α-santalal, (10R,11S)-10,11-dihydroxy-α-santalol, (9E)-11,13-dihydroxy-α-santalol, and (10E)-12-hydroxy-α-santalic acid. Their structures were determined on the basis of results of spectroscopic analysis, including two-dimensional (2D) NMR spectroscopic data. The isolated compounds and derivatives were evaluated for cytotoxicity against HL-60 human promyelocytic leukemia cells and TIG-3 normal human diploid fibroblasts. Of these (9S,10E)-9-hydroxy-α-santalal, exhibited tumor-selective cytotoxicity. The apoptosis induction properties of sesquiterpenes with cytotoxic potency in HL-60 cells are also described.     

Guaianolides from Saussurea affinis

Cynaropicrin, 11βH-11,13-dihydrodesacylcynaropicrin, aguerins A and B, isoamberboin and the new guaianolides saussureolide and 11βH-11,13-dihydrodesacylcynaropicrin 8-β-d-glucoside were isolated from Saussurea affinis.     

Antimalarial sesquiterpene lactones from Distephanus angulifolius

Combined use of bioassay-guided fractionation based on in vitro antiplasmodial assay and dereplication based on HPLC-PDA-MS-SPE-NMR led to isolation of (6S,7R,8S)-14-acetoxy-8-[2-hydroxymethylacrylat]-15-helianga-1(10),4,11(13)-trien-15-al-6,12-olid and (5R,6R,7R,8S,10S)-14-acetoxy-8-[2-hydroxymethylacrylat]-elema-1,3,11(13)-trien-15-al-6,12-olid, along with vernodalol, vernodalin, and 11,13β-dihydroxyvernodalin from extract of Distephanus angulifolius. All compounds were identified by spectroscopic methods, including 1D and 2D homo- and heteronuclear NMR experiments. The isolated compounds showed IC₅₀ values in the range 1.6-3.8 μM and 2.1-4.9 μM against chloroquine sensitive D10 and chloroquine resistant W2 Plasmodium falciparum strains, respectively.     

Sesquiterpenes and diterpenes from Ambrosia arborescens

Six compounds, eudesm-11(13)-en-4β,9β-diol, 15R,16-dihydroxy-3-oxoisopimar-9(11)-ene, 15S,16-dihydroxy-3-oxoisopimar-9(11)-ene, 1α-hydroxy-7-oxo-iso-anhydrooplopanone, 10α-hydroxy-11,13-dihydro-5-epi-psilostachyin, and 4β-hydroxypseudoguaian-12,6-olide 4-O-β-d-glucopyranoside, together with 12 known sesquiterpenes, were isolated from the leaves of Ambrosia arborescens. Structures were elucidated by 1D and 2D NMR spectroscopy including 1D-TOCSY, DQF-COSY, 2D-ROESY, HSQC, and HMBC experiments, as well as by ESI mass spectrometry. The absolute configuration of the 15,16-diol moiety in 15R,16-dihydroxy-3-oxoisopimar-9(11)-ene and 15S,16-dihydroxy-3-oxoisopimar-9(11)-ene was determined using Snatzke’s method. All compounds were evaluated for antiproliferative activity.     

Biosynthesis of pisatin: Experiments with enantiomeric precursors

Feeding experiments in cupric chloride-treated Pisum sativum pods and seedlings have demonstrated the preferential incorporation of (+)-(6aS,11aS)-[³H]maackiain over (?)-(6aR, 11aR)-[¹⁴C]maackiain into (+)-(6aR, 11aR)-pisatin, establishing that the 6a-hydroxylation of pterocarpans proceeds with retention of configuration. (+)- (6aR,11aR)-6a-hydroxymaackiain was similarly incorporated much better than (?)-(6aS,11aS)-6a- hydroxymaackiain. Where (?)-isomers were incorporated, optical activity measurements on the pisatin produced indicated significant synthesis of (?)-pisatin as well as the normal (+)-pisatin. 7,2′-Dihydroxy-4′,5′- methylenedioxyisoflav-3-ene and both enantiomers of 7,2′-dihydroxy-4′,5′-methylenedioxyisoflavan were poor precursors of pisatin.     

Guaianolides and elemanolides from Vernonia anthelmintica

Two new guaianolides, (1R,4R,5S,6R,7R,8S)-8,15-dihydroxyguaia-10(14),11(13)-dien-12,6-olide (1) and (1R,4R,5S,6R,7R,8S,11S)-8,15-dihydroxyguaia-10(14)-en-6,12-olide (2), and two known elemanolides, (4S,5R,6R,7R,8S,10R,11S)-11,13-dihydrovernolepin (3) and (5R,6R,7R,8S,10R,11S)-melitensin (4) were isolated from the aerial parts of Vernonia anthelmintica Willd. The structures of these compounds were determined on the basis of IR, UV, MS, 1D-NMR and 2D-NMR, and their absolute configurations were deduced using the CD exciton chirality method and single-crystal X-ray diffraction. The possible biosynthetic relationships of compounds 1–4 are postulated. Compounds 1–4 were evaluated for their cytotoxicity against HL-60 and SMMC-7721 cell lines.     

Abietane diterpenoids from Isodon inflexus

Four abietane diterpenoids, inflexanin C, inflexanin D, inflexuside A and inflexuside B, were isolated from the aerial parts of Isodon inflexus. Their respective structures were established by NMR, mass spectrometry and CD as (+)-(1S,4R,5S,7S,8S,10S,13S)-1,7,18-trihydroxy-abieta-9(11)-ene-12-one 1-monoacetate, (+)-(1S,4R,5S,10S,13S)-1,18-dihydroxy-abieta-7,9(11)-diene-12-one 1-monoacetate, (−)-(1S,5S,10S,11R,13R)-1,11,13-trihydroxy-abieta-8-ene-7-one 1-O-β-d-glucopyranoside and (−)-(1S,5S,10S,11R,13R)-1,11,13-trihydroxy-abieta-8-ene-7-one 1-O-(2-O-coumaroyl)-β-d-glucopyranoside. All compounds showed strong inhibitory activity against nitric oxide (NO) production in RAW264.7 lipopolysaccaride (LPS)-activated macrophages.     

Dolabellane diterpenoids from Aglaia odorata

Dolabellane diterpenoids, (1R,3E,7E,10S,11S,12R)-dolabella-3,7-dien-10,18-diol (1), (1R,3S,7E,11S,12R)-dolabella-4(16),7-dien-3,18-diol (2), (1R,7E,11S,12R)-18-hydroxydolabella-4(16),7-dien-3-one (3), (1R,3S,4S,7E,11S,12R)-3,4-epoxydolabella-7-en-18-ol (4), and (1R,3R,7E,11S,12R)-dolabella-4(16),7,18-trien-3-ol (5), were obtained from the ornamental plant Aglaia odorata. Their structures were characterized on the basis of spectroscopic analyses and further confirmed by X-ray diffraction. Compounds 1 and 5 showed weak cytotoxicity against the human myeloid leukemia HL-60, hepatocellular carcinoma SMMC-7721, and lung cancer A-549 cells.     

Vanadium-catalyzed transformation of 13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoic acid: Structural studies on epoxy alcohols and trihydroxy acids

Treatment of methyl 13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoate with vanadium oxyacetylacetonate led to the formation of two diastereometric α,β-epoxy alcohols, i.e. methyl 11(R), 12(R)-epoxy-13(S)-hydroxy-9(Z)-octadecenoate and methyl 11(S), 12(S)-epoxy-13(S)-hydroxy-9(Z)-octadecenoate. The epoxy alcohols underwent spontaneous hydrolysis into isomeric trihydroxyesters. The first mentioned epoxy alcohol afforded methyl 9(R), 12(S), 13(S)- and methyl 9(S), 12(S), 13(S)-trihydroxy-10(E)-octadecenoates as major hydrolysis products whereas the latter epoxy alcohol afforded methyl 9(R), 12(R), 13(S)- and methyl 9(S), 12(R)-13(S)-trihydroxy-10(E)-octadecenoates as major compounds. Smaller amounts of diastereomeric methyl 11,12,13-trihydroxy-9-octadecenoates were also formed from both epoxy alcohols. The vanadium-catalyzed conversion of 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid (13(S)HPOD) (methyl ester) into α,β-epoxy alcohols and their further conversion into trihydroxy derivatives offers a model system for similar transformations of certain poly-unsaturated fatty acids recently described in the fungus, Saprolegnia parasitica.     

Biochemical Characterization of the Oxygenation of Unsaturated Fatty Acids by the Dioxygenase and Hydroperoxide Isomerase of Pseudomonas aeruginosa 42A2

We have studied oxygenation of fatty acids by cell extract of Pseudomonas aeruginosa 42A2. Oleic acid ((9Z)-18:1) was transformed to (10S)-hydroperoxy-(8E)-octadecenoic acid ((10S)-HPOME) and to (7S,10S)-dihydroxy-(8E)-octadecenoic acid (7,10-DiHOME). Experiments under oxygen-18 showed that 7,10-DiHOME contained oxygen from air and was formed sequentially from (10S)-HPOME by isomerization. (10R)-HPOME was not isomerized. The (10S)-dioxygenase and hydroperoxide isomerase activities co-eluted on ion exchange chromatography and on gel filtration with an apparent molecular size of ∼50 kDa. 16:1n-7, 18:2n-6, and 20:1n-11 were also oxygenated to 7,10-dihydroxy fatty acids, and (8Z)-18:1 was oxygenated to 6,9-dihydroxy-(7E)-octadecenoic acid. A series of fatty acids with the double bond positioned closer to ((6Z)-18:1, (5Z,9Z)-18:2) or more distant from the carboxyl group ((11Z)-, (13Z)-, and (15Z)-18:1) were poor substrates. The oxygenation mechanism was studied with [7S-²H]18:1n-9, [7R-²H]18:2n-6, and [8R-²H]18:2n-6 as substrates. The pro-R hydrogen at C-8 was lost in the biosynthesis of (10S)-HPODE, whereas the pro-S hydrogen was lost and the pro-R hydrogen was retained at C-7 during biosynthesis of the 7,10-dihydroxy metabolites. Analysis of the fatty acid composition of P. aeruginosa revealed relatively large amounts of (9E/Z)-16:1 and (11E/Z)-18:1 and only traces of 18:1n-9. We found that (11Z)-18:1 (vaccenic acid) was transformed to (11S,14S)-dihydroxy-(12E)-octadecenoic acid and to a mixture of 11- and 12-HPOME, possibly due to reverse orientation of (11Z)-18:1 at the active site compared with oleic acid. The reaction mechanism of the hydroperoxide isomerase suggests catalytic similarities to cytochrome P450.     

Acid-catalyzed transformation of 13(S)-hydroperoxylinoleic acid into epoxyhydroxyoctadecenoic and trihydroxyoctadecenoic acids

Acid treatment of (13S)-(9Z,11E)-13-hydroperoxy-9,11-octadecadienoic acid in tetrahydrofuran-water solvent afforded mainly (11R,12R,13S)-(Z)-12,13-epoxy-11-hydroxy-9-octadecenoic acid, diastereomeric (Z)-11,12,13-trihydroxy-9-octadecenoic acids and four isomers of (E)-9,12,13(9,10,13)-trihydroxy-10(11)-octadecenoic acid. Other minor products were oxooctadecadienoic, (E)-9(13)-hydroxy-13(9)-oxo-10(11)-octadecenoic and (E)-12-oxo-10-dodecenoic acids. A heterolytic mechanism for acid catalysis was indicated, even though most of the products characterized also have been observed as a result of homolytic decomposition of the hydroperoxide via an oxy radical. Most of the products found in this study have been observed as metabolites of (13S)-(9Z,11E)-13-hydroperoxy-9,11-octadecadenoic acid in biological systems, and analogous compounds have been reported as metabolites of (12S)-(5Z,8Z,10E, 14Z)-12-hydroperoxy-5,8,10,14-hydroperoxy-5,8,10,14-eicosatetraenoic acid in either blood platelets or lung tissue.     

Stereochemistry of lepidopteran sex pheromone biosynthesis: a comparison of fatty acid-CoA Δ11-(Z)-desaturases in Bombyx mori and Manduca sexta female moths

The absolute stereochemistry of fatty acid (FA) desaturation in Bombyx mori and Manduca sexta female pheromone glands (PGs), catalysed by FA-CoA Δ11-(Z)-desaturases, was determined using chiral, specifically labelled palmitic acids {[2,2,3,4,5,5,6,6,7,8,9,9,11,12−²H₁₄]–(11R,12S)−1 and [2,2,3,4,5,5,6,6,7,8,9,9,11,12−²H₁₄]–(11S,12R)−1)} as metabolic probes. The (11R,12S)−1 acid was converted in PGs of treated virgin females to labelled methyl (11Z)-hexadecenoate ([²H₁₄]−2, Mw=282 Da). In incubations with the opposite enantiomer two deuterium atoms from (11S,12R)−1 were removed, yielding [²H₁₂]−2 of Mw=280 Da. These results were confirmed by methylthiolation of [²H₁₄]−2 and [²H₁₂]−2 with a dimethyl disulfide/iodine mixture. Mass spectra of the DMDS adducts directly showed the distribution of deuterium atoms in the labelled methyl esters of 2. The data consistently indicate, that the studied insects possess Δ11-(Z)-desaturases with pro-(R) C(11)-H and pro-(R) C(12)-H stereospecificity, catalysing a syn-elimination of two hydrogen atoms.     

Two new cytotoxic eudesmane sesquiterpenoids from Artemisia anomala

Two new eudesmane sesquiterpenoids artanoate (1) and eudesmanomolide (2) were isolated from the aerial parts of Artemisia anomala S. Moore. Their structures were elucidated as methyl (4R, 5S, 6S, 7S, 10R)-1-oxo-4, 6-dihydroxy-eudesma-2, 11 (13)-dien-12-oate (1) and (1R, 5R, 6R, 10R)-3, 13-diacetoxy-1-hydroxy-3, 7(11)-diene-12, 6-olide (2) on the basis of extensive spectroscopic analyses. Compound 1 showed cytotoxicity against HCT-8 cell lines with IC₅₀ value of 9.13 μM, and compound 2 exhibited inhibitory activities against HCT-8 and A549 cell lines with IC₅₀ values of 3.76 and 5.49 μM, respectively.     

Gene Deletion of 7,8-Linoleate Diol Synthase of the Rice Blast Fungus: STUDIES ON PATHOGENICITY, STEREOCHEMISTRY, AND OXYGENATION MECHANISMS*

Linoleate diol synthases (LDS) are heme enzymes, which oxygenate 18:2n-6 sequentially to (8R)-hydroperoxylinoleic acid ((8R)-HPODE) and to (5S,8R)-dihydroxy-, (7S,8S)-dihydroxy-, or (8R,11S)-dihydroxylinoleic acids (DiHODE). The genome of the rice blast fungus, Magnaporthe oryzae, contains two genes with homology to LDS. M. oryzae oxidized 18:2n-6 to (8R)-HPODE and to (7S,8S)-DiHODE, (6S,8R)-DiHODE, and (8R,11S)-HODE. Small amounts of 10-hydroxy-(8E,12Z)-octadecadienoic acid and traces of 5,8-DiHODE were also detected by liquid chromatography-mass spectrometry. The contribution of the 7,8-LDS gene to M. oryzae pathogenicity was evaluated by replacement of the catalytic domain with hygromycin and green fluorescent protein variant (SGFP) cassettes. This genetically modified strain Δ7,8-LDS infected rice leaves and roots and formed appressoria and conidia as the native fungus. The Δ7,8-LDS mutant had lost the capacity to biosynthesize all the metabolites except small amounts of 8-hydroxylinoleic acid. Studies with stereospecifically deuterated linoleic acids showed that (8R)-HPODE was formed by abstraction of the pro-S hydrogen at C-8 and antarafacial oxygenation, whereas (7S,8S)-DiHODE and (8R,11S)-DiHODE were formed from (8R)-HPODE by suprafacial hydrogen abstraction and oxygenation at C-7 and C-11, respectively. A mac1 suppressor mutant (Δmac1 sum1–99) of M. oryzae, which shows cAMP-independent protein kinase A activity, oxygenated 18:2n-6 to increased amounts of (10R)-HPODE and (5S,8R)-DiHODE. Expression of the 7,8-LDS gene but not of the second homologue was detected in the suppressor mutant. This suggests that PKA-mediated signaling pathway regulates the dioxygenase and hydroperoxide isomerase activities of M. oryzae.     

Absolute configuration of the pyrrolizidine alkaloid acetylgynuramine

The absolute configuration of the pyrrolizidine alkaloid acetylgynuramine was determined by X-ray diffraction to be (?)-(1aR,6bR,10R,11S)-9,14-dioxo-10-hydroxy-13-cis-ethylidene-11-methoxyacetyl-10-methyl-1a,2,3,6b-tetrahydro-5H-pyrrolizino-(1a,6b,6a,b,c)-1,8-dioxa-cyclododecane.     

黄斑卷蛾雄蛾对性信息素的行为反应

分别在风洞中和田间观察了黄斑卷蛾Acleris fimbriana Thunberg et Becklin雄蛾对合成性信息素三种成分（E11,13-14∶Ald, E11,13-14∶Ac和E11-14∶Ac）及其不同组合的行为反应。在风洞中,主要活性成分E11,13-14∶Ald能引起雄蛾完成从兴奋到搜索释放源的行为反应,但雄蛾对单个组分E11,13-14∶Ac 或 E11-14∶Ac不呈现任何行为反应。当释放源为双组分 E11,13-14∶Ald＋E11,13-14∶Ac （6∶4）或三组分E11,13-14∶Ald＋E11,13-14∶Ac＋E11-14∶Ac（6∶4∶1）时,可以明显增加雄蛾定向飞行和到达释放源的数量。三组分 E11,13-14∶Ald＋E11,13-14∶Ac＋E11-14∶Ac的比例为6∶4∶1时,500 μg剂量效果最好。田间试验结果表明,E11,13-14∶Ald单独使用表现出良好的诱蛾活性,其诱蛾量为活雌蛾的1.9倍,而E11,13-14∶Ac和E11-14∶Ac则不具有诱蛾活性。E11,13-14∶Ac对E11,13-14∶Ald有明显的增效作用,三组分E11,13-14∶Ald＋E11,13-14∶Ac＋E11-14∶Ac（6∶4∶1）诱芯的诱蛾效果最好。     

Design,synthesis and biological evaluation of novel bicyclo[1.1.1]pentane-based ω-acidic amino acids as glutamate receptors ligands

A novel series of bicyclo[1.1.1]pentane-based ω-acidic amino acids, including (2S)- and (2R)-3-(3′-carboxybicyclo[1.1.1]pentyl)alanines (8 and 9), (2S)- and (2R)-2-(3′-carboxymethylbicyclo[1.1.1]pentyl)glycines (10 and 11), and (2S)- and (2R)-3-(3′-phosphonomethylbicyclo[1.1.1]pentyl)glycines (12 and 13), were synthesized and evaluated as glutamate receptor ligands. Among them, (2R)-3-(3′-phosphonomethylbicyclo[1.1.1]pentyl)glycine (13) showed relatively high affinity and selectivity at the NMDA receptor. The results are also discussed in light of pharmacophoric modelling studies of NMDA agonists and antagonists.     

Glucosinolates in seeds of Neslia paniculata

The glucosinolate fraction in seeds of Neslia paniculata (L.) Desv., subsp. thracica (Velen.) Bornmüller, (Cruciferae), has been isolated and subjected to enzymic hydrolysis. The isothiocyanates thus produced have been separated and identified as cheirolin (II), (R)-9-methylsulfinylnonyl (III), (R)-10-methylsulfinyldecyl (IV), and (R)-11-methylsulfinylundecyl isothiocyanate (V), the last of which has not been previously encountered as a natural compound.     

Estrogenic and anti-estrogenic compounds from the Thai medicinal plant, Smilax corbularia (Smilacaceae)

From the rhizomes of Smilax corbularia Kunth. (Smilacaceae), 11 compounds, (2R,3R)-2″-acetyl astilbin, (2R,3R)-3″-acetyl astilbin, (2R,3R)-4″-acetyl astilbin, (2R,3R)-3″-acetyl engeletin, (2R,3S)-4″-acetyl isoastilbin, 2-(4-hydroxyphenyl)-3,4,9,10-tetrahydro-3,5-dihydroxy-10-(3,4-dihydroxyphenyl)-(2R,3R,10R)-2H,8H-benzo [1,2-b:3,4-b′] dipyran-8-one, 2-(4-hydroxyphenyl)-3,4,9,10-tetrahydro-3,5-dihydroxy-10-(3,4-dihydroxyphenyl)-(2R,3R,10S)-2H, 8H-benzo [1,2-b:3,4-b′] dipyran-8-one, 3,4-dihydro-7-hydroxy-4-(3,4-dihydroxyphenyl)-5-[(1E)-2-(4-hydroxyphenyl) ethenyl]-2H-1-benzopyran-2-one, 3,4-dihydro-7-hydroxy-4-(3,4-dihydroxy-phenyl)-5-[(1E)-2-(3,4-dihydroxyphenyl) ethenyl]-2H-1-benzopyran-2-one, 3,4-dihydro-7-hydroxy-4-(4-hydroxy-3-methoxyphenyl)-5-[(1E)-2-(4-hydroxyphenyl) ethenyl]-2H-1-benzopyran-2-one, and 5,7,3′,4′-tetrahydroxy-3-phenylcoumarin along with 34 known compounds were isolated and characterized as 19 flavonoids, 14 catechin derivatives, 6 stilbene derivatives, and 6 miscellaneous substances. All isolates had their estrogenic and anti-estrogenic activities determined using the estrogen-responsive human breast cancer cell lines MCF-7 and T47D. The major constituents were recognized as flavanonol rhamnosides by the suppressive effect on estradiol induced cell proliferation at a concentration of 1 μM. Meanwhile, flavanonol rhamnoside acetates demonstrated estrogenic activity in both MCF-7 and T47D cells at a concentration of 100 μM, and they enhanced the effects of co-treated E2 on T47D cell proliferation at concentrations of more than 0.1 μM.