Synthesis,antiproliferative activity and molecular docking of thiocolchicine urethanes

A number of naturally occurring compounds such as paclitaxel, vinblastine, combretastatin, and colchicine exert their therapeutic effect by changing the dynamics of tubulin and its polymer form, microtubules. The identification of tubulin as a potential target for anticancer drugs has led to extensive research followed by clinical development of numerous compounds from several families. In this paper we report on the design, synthesis and in vitro evaluation of a group of thiocolchicine derivatives, modified at ring-B, labelled here compounds 4–14. These compounds have been obtained in a simple reaction of 7-deacetyl-10-thiocolchicine 3 with eleven different alcohols in the presence of triphosgene. These novel agents have been checked for anti-proliferative activity against four human cancer cell lines and their mode of action has been confirmed as colchicine binding site inhibition (CBSI) using molecular docking. Molecular simulations provided rational tubulin binding models for the tested compounds. On the basis of in vitro tests, derivatives 4–8 and 14 demonstrated the highest potency against MCF-7, LoVo and A549 tumor cell lines (IC₅₀ values = 0.009–0.014 μM). They were more potent and characterized by a higher selectivity index than several standard chemotherapeutics including cisplatin and doxorubicin as well as unmodified colchicine. Further, studies revealed that colchicine and its several derivatives arrested MCF-7 cells in mitosis, while its selected derivatives caused microtubule depolymerization.     

SYNTHESIS AND STUDY OF CONFORMATIONALLY RESTRICTED 3′-DEOXY-3′,4′-EXO-METHYLENE NUCLEOSIDE ANALOGUES

Hitherto unknown restricted 3′-deoxy-3′,4′-exo-methylene nucleoside derivatives bearing the nucleic acid naturally occurring pyrimidine bases have been synthesized. The compounds were tested for their activity against HIV, HBV, and several RNA viruses, but they did not show significant antiviral effect.     

Flavonoids and polyacetylenes in Dahlia tenuicaulis

5,7,4′-Trimethoxyflavanone, 5-hydroxy-7,4′-dimethoxyflavanone, 2′-hydroxy-4,4′,6′-trimeth-oxychalcone, and a new naturally occurring compound, 5,7,4′-trimethoxyflavan-4-ol have been isolated from the leaves of Dahlia tenuicaulis Sorensen. Two chalcones, 4,2′,4′-trihydroxychalcone and 3,2′,4′-trihydroxy-4-methoxychalcone, and 5-hydroxy-7,4′-dimethoxyflavanone have been isolated from the flower heads. Minute amounts of the polyacetylene 1,3-diacetoxy-tetradeca-4,6-diene-8,10,12-triyne have been found in both leaves and flower heads, whereas 1-acetoxy-tetradeca-4,6-diene-8,10,12-triyne was present only in the flower heads.     

Phenolic constituents of Semecarpus anacardium

GLC-MS analysis of methylated bhilawanol from S. anacardium nuts and its oxidation product, the methyl ester of an aromatic carboxylic acid, conclusively proved that it contains more than seven closely related compounds. Two of them are major components which were isolated and shown to be 1-pentadec-Δ^5′-enyl-2,3-dimethoxybenzene (I) and 1-pent biflavanoids A, B and C have been also isolated from defatted nuts of S. anacardium. The first of these has been characterized as its methyl ethers. A₁ and A₂, for which biflavanone structures (VI) and (VII) are suggested on the basis of chemical and spectral evidence. The biflavanones B and C have been also characterized as their methyl ethers. Suggested structures are O-methyl derivatives of a IB-3′, IIA-8-binaringenin (XIV) for the former and IB-3′, IIA-8-biliquiritigenin (XV) for the latter.     

Polyacetylenes from Chrysanthemum leucanthemum

Fifteen acetylenic compounds have been isolated and characterized from the flower heads of Chrysanthemum leucanthemum L. Five of these acetylenes have not previously been published as naturally occurring compounds. These are: 1,7(c)-hexadecadien-10,12,14-triyne; 1,8(c)-heptadecadien-11,13,15-triyne; 4(c)-tridecen-7,9,11-triyn-l-ol; 1,8(t)-hexadecadien-10,12,14-triyn-(6·7)-oxirane; and [3(t),5(t)-tridecadien-7,9,11-triyn-l-yl]-3-methyl-2-butenoate. The first three compounds are interesting since they are important intermediates in previously postulated biogenetic pathways. Ten acetylenes have been identified from the roots of the same plant, all of these having different structures from those of the flower heads. One of the acetylenes, [3(t), 5(t)-tridecadien-7,9,11-triyn-l-yl]-3-methylbutyrate, from the roots has never been reported as a naturally occurring compound.     

A general method for characterizing naturally occurring folate compounds, illustrated by characterizing Torula yeast (Candida utilis) folates

A method previously found suitable for the chromatographic separation and identification of simpler folates has been extended and found suitable for separating and characterizing all the complex polyglutamyl folyl derivatives occurring naturally. Folates were characterized employing the combined use of analytical DEAE-cellulose chromatography, folylpoly-γ-glutamyl carboxypeptidase digestion, and differential microbiological growth response studies. An observed relation between the log phosphate concentration of the eluting buffer and the number of γ-glutamyl residues in successive pteroylpoly-γ-glutamyl derivatives provides a simple tool for a rapid and accurate identification of folate compounds from their elution profile. Twelve folate compunds present in Torula yeast (Candida utilis) were characterized employing this method; 80% of the total folates appeared to be pteroylpolyglutamates. The method characterizes not only the number of γ-glutamyl residues but also the state of reduction of the pteridine ring and the nature of the 1-C substituents attached.     

Design,synthesis and anticancer activities of stilbene-coumarin hybrid compounds: Identification of novel proapoptotic agents

The naturally occurring coumarins and resveratrol, attract great attention due to their wide range of biological properties, including anticancer, antileukemic, antibacterial and anti-inflammatory activities; moreover, their cancer chemopreventive property have been recently emphasized. A novel class of hybrid compounds, obtained by introducing a substituted trans-vinylbenzene moiety on a coumarin backbone, was synthesized and evaluated for the antitumor profile. A number of derivatives showed a good antiproliferative activity, in some cases higher to that of the reference compound resveratrol. The most promising compounds in this series were 14 and 17, endowed with excellent antiproliferative and proapoptotic activities. The present study suggests that the 7-methoxycoumarin nucleus, together with the 3,5-disubstitution pattern of the trans-vinylbenzene moiety, are likely promising structural features to obtain excellent antitumor compounds endowed with a apoptosis-inducing capability.     

Carbon-13 NMR spectroscopy of steroidal sapogenins and steroidal saponins

The ¹³C NMR chemical shifts of 130 naturally occurring steroidal sapogenins and saponin derivatives published up to 1983 are listed and a number of methods for signal assignment are explained. The utility of ¹³C NMR spectral analysis for the structure elucidation of these compounds is discussed.     

The antibacterial properties of 6-tuliposide B. Synthesis of 6-tuliposide B analogues and structure–activity relationship

6-Tuliposide B is a secondary metabolite occurring specifically in tulip anthers. Recently, a potent antibacterial activity of 6-tuliposide B has been reported. However, its molecular target has not yet been established, nor its action mechanism. To shed light on such issues, 6-tuliposide B and tulipalin B analogues were synthesized and a structure–activity relationship (SAR) was examined using a broad panel of bacterial strains. As the results of SAR among a total of 25 compounds, only tulipalin B and the compounds having 3′,4′-dihydroxy-2′-methylenebutanoate (DHMB) moieties showed any significant antibacterial activity. Moreover, the 3′R analogues of these compounds displayed essentially the same activities as 6-tuliposide B and the structure of the 3′R-DMBA moiety was the same as that of the proposed active moiety of cnicin. These results suggest that 6-tuliposide B has the same action mechanism as proposed for cnicin and bacterial MurA is one of the major molecular targets of 6-tuliposide B.     

Natural and semisynthetic oxyprenylated aromatic compounds as stimulators or inhibitors of melanogenesis

It has been very recently shown how naturally occurring oxyprenylated coumarins are effective modulators of melanogenesis. In this short communication we wish to generalize the potentialities as skin tanning or whitening agents of a wider panel of natural and semisynthetic aromatic compounds, including coumarins, cinnamic and benzoic acids, cinnamaldehydes, benzaldehyde, and anthraquinone derivatives. A total number of 43 compounds have been tested assaying their capacity to inhibit or stimulate melanin biosynthesis in cultured murine Melan A cells. The wider number of chemicals herein under investigation allowed to depict a detailed structure-activity relationship, as the following: (a) benzoic acid derivatives are slightly pigmenting agent, for which the effect is more pronounced in compounds with longer O-side chains; (b) independently from the type of substitution, cinnamic acids are able to increase melanin biosynthesis, while benzaldehydes are able to decrease it; (c) coumarins with a 3,3-dimethylallyl or shorter skeletons as substituents in position 7 are tanning agents, while coumarins with farnesyloxy groups are whitening ones; (d) double oxyprenylation in position 6 and 7 and 3,3-dimethylallyl or geranyl skeletons have slight depigmenting capacities, while farnesyl skeletons tend to marginally increase the tanning effect; (e) the presence of electron withdrawing groups (acetyl, COOH, and -Cl) and geranyl or farnesyl oxyprenylated chains respectively in positions 3 and 7 of the coumarin nucleus lead to a whitening effect, and finally (f) oxyprenylated anthraquinones have only a weak depigmenting capacity.     

Detoxification of naturally occurring chromenes in larvae of the generalist herbivore Spodoptera littoralis (Noctuidae)

Five naturally occurring chromenes from the Asteraceae including the insecticidal compounds precocene II (1) and encecalin (2) were administered to last instar larvae of Spodoptera littoralis via the food or by topical contact. Metabolites formed and excreted via the frass were analysed by GC-MS and by direct comparison with reference compounds obtained by partial synthesis. In total 28 different metabolites were identified, many of them reported here for the first time. All metabolites detected originated from phase I reactions (most probably catalysed by Cytochrom P-450-dependent monooxygenases) by hydroxylation, demethylation or reduction of the parent chromenes. The resulting metabolites can be regarded as detoxification products based on previous structure-activity studies. The increased polarity of the metabolites will furthermore facilitate their excretion by the larvae compared to the more apolar parent chromenes. The largest number of metabolites (eight for each compound) was detected following oral treatment with precocene II and encecalin respectively. 3-Monool as well as 3,4-trans-diol derivatives predominated in the frass of larvae treated with the latter compounds whereas the 6-hydroxyethyl derivatives were the major metabolites of the other chromenes investigated. The patterns of metabolites originating from precocene II or encecalin were the same following oral application or topical treatment.     

Phenolic diterpenoids of podocarpus ferrugineus and other podocarps

19-Hydroxyferruginol and 19-acetoxyferruginol, two new naturally occurring phenolic diterpenoids, have been isolated from the heartwood of Podocarpus ferrugineus. Totarol and its derivatives have been obtained from Podocarpus affinis, P. falcatus, P. koordersii, Dacrycarpus vieillardii and Decussocarpus comptonii and podocarpic acid from Falcatifolium taxoides.     

Synthesis and antiviral evaluation of thieno[3,4-d]pyrimidine C-nucleoside analogues of 2′,3′-dideoxy- and 2′,3′-dideoxy-2′,3′-didehydro-adenosine and -inosine

Several thieno[3,4-d]pyrimidine derivatives, including four hitherto unknown 2′,3′-dideoxy- and 2′,3′-dideoxy-2′,3′-didehydro-C-nucleoside analogues of adenosine and inosine have been synthesized. When evaluated in cell culture experiments against human immunodeficiency virus, none of the tested compounds exhibited any significant antiviral effect, while two of them showed some cytotoxicity.     

Biological activity of new flavonoid from <Emphasis Type="Italic">Hieracium pilosella</Emphasis> L.

Hieracium pilosella L. (Asteraceae) is a well-known plant used in ethno-medicine as its inflorescences are particularly rich in beneficial polyphenolics. This research aimed to elucidate the structure of a new flavone glycoside isolated from the inflorescences of Hieracium pilosella and evaluate its antioxidant, antimicrobial and antiproliferative activities. The chromatographic methods were successfully applied to isolate the new flavonoid. Its structure was determined by subsequent UV, NMR and MS experiments and identified as isoetin 4′-O-β-D-glucopyranoside. Free radical scavenging capacity was examined by measuring the scavenging activity of the new isoetin derivative on 2,2-diphenyl-1-picrylhydrazyl (DPPH). The compound was also screened for spectrum of antimicrobial activity using the agar well diffusion method. Minimum inhibitory concentration (MIC) for Pseudomonas aeruginosa ATCC 9027 was performed by the micro-dilution broth method. The antiproliferative effect of tested glycoside was assessed in two human tumor cell lines derived from lung (A549) and colon (HT-29) carcinoma and cell proliferation was determined by means of MTT method. The tested compound showed high antiradical activity, reducing the DPPH? with EC₅₀ 7.9 μM (3.7 µg/ml) and exhibited narrow antimicrobial spectrum among tested microorganisms. The compound was active against Pseudomonas aeruginosa ATCC 9027 (MIC 125 μg/ml) which is prone to causing infections that are difficult to treat due to it developing extremely rapid antibiotic resistance. In the antiproliferative studies, cell proliferation of the colon (HT-29) carcinoma cell line was significantly decreased after exposure to the compound. The results indicate that isoetin 4′-O-β-D-glucopyranoside possesses antioxidant capacity and very promising antibacterial activity and could have uses as an effective antipseudomonal agent as well a antiproliferative agent.     

Kinetic studies on the reduction of cytochrome c: reaction with organic oxy-compounds

A range of organic hydroxy compounds, many of them naturally occurring, have been assayed for their ability to reduce the electron transfer protein cytochrome c. Those with conjugated hydroxyl systems e.g. catechol, acted as reducing agents while those which were phenol-like, either by separation of conjugation e.g. resorcinol or by having only one free hydroxyl group, did not. Rapid reaction kinetic investigations of the reaction of rhodizonic acid with cytochrome c revealed rapid reduction of the protein. The dianion of rhodizonic acid is the most reactive species in agreement with results obtained with catecholato compounds. The pH-dependence of this reaction is discussed in terms of the complex solution chemistry of rhodizonic acid.     

Synthesis and biological activities of marine terpene-adenine hybrids and synthetic analogs

Marine sponges (Agelas sp., Raspailia sp.) produce bioactive metabolites, which can be regarded as hybrids between a terpenoid and an adenine derivative. Three sub classes are known: Agelasines, agelasimines and asmarines. Currently 19 agelasines or closely related structures, two agelasimines and 11 asmarines are published. The two agelasimines have been prepared by total synthesis, the same is true for some of the agelasines, but none of the asmarines have been synthesized so far. Agelasines are associated with antimicrobial and antineoplastic activities. Several analogs have been prepared, which are even more potent than the naturally occurring compounds, and interesting leads for treatment of for instance tuberculosis, Chagas disease and leishmaniasis have been identified. Also antifouling agents and biofilm inhibitors have been found among agelasines and analogs. Agelasines inhibits Na,K-ATPase and other ATPases, but how relevant this is for their mechanism of action, as antimicrobial and antineoplastic agents, are currently poorly understood. Agelasimines A and B display antineoplastic activity and they have the ability to inhibit smooth muscle contraction. Synthetic analogs with both antimicrobial and anticancer activities are known. Biological activities of asmarines are far less studied than those of agelasines and agelasimines, but some of them are claimed to be cytotoxic compounds.     

Caffeoylquinic Acids: Separation Method,Antiradical Properties and Cytotoxicity

Twelve chlorogenic acid derivatives and two flavones were isolated from Moquiniastrum floribundum (Asteraceae, other name: Gochnatia floribunda). Compounds were evaluated in relation to their cytotoxicity and antiradical properties. Cytotoxicity was not observed for compounds, however, chlorogenic acid derivatives showed antiradical activity and were more active than the Trolox standard. Quinic acid esterified with caffeoyl group at C‐4 position showed higher antiradical activity compared to acylation at C‐3 or C‐5 positions. Additional caffeoyl groups esterified in quinic acid increase the antiradical activity observed for 4‐caffeoylquinic acid. Excepted to 3,4‐dicaffeoylquinic acid methyl ester, methyl ester derivatives show higher capacity of trapping radicals than their respective acids. Consequently, the presence of caffeoyl group at C‐4 position of quinic acid is suggested as fundamental to obtain the highest antiradical activity.     

Determination of the linkages in some methylated,sialic acid-containing,meningococcal polysaccharides by mass spectrometry

The application of gas-liquid chromatography-mass spectrometric (g.l.c.-m.s.) analysis to a number of sialic acid-containing polysaccharides of meningococcal origin has been studied. Methylation of these polysaccharides by the Hakomori conditions resulted in both O- and N-methylation. Methanolysis of the methylated polysaccharides from serogroup C [(2→9)-linked], colominic acid [(2→8)-linked], and serogroups Y and W-135 [both (1→4)-linked], yielded the respective 4,7,8,4,7,9-, and 7,8,9-tri-O-methyl derivatives of methyl N-acetyl-N-methyl-β-D-neuraminate methyl glycoside. As model compounds, methyl N-acetyl-4,7,8,9-tetra-O-methyl-α-D-neuraminate methyl glycoside and its N-methyl derivative were also synthesized. All of the methylated derivatives could be identified on the basis of their typical fragmentation-patterns, indicating that this method is applicable to the determination of the position of linkages to sialic acid residues in biopolymers.     

Neue sesquiterpene,triterpene, flavanone und andere aromatische verbindungen aus Flourensia heterolepis

The investigation of a further Flourensia species afforded in addition to already known compounds 12 new sesquiterpene acids isolated as their methyl esters, a new eudesmane diol, four lupane derivatives and two flavanones, two cinnamic acid derivatives, also isolated as methyl esters and a ketone. The structures are elucidated mainly by spectroscopic methods and by some chemical transformations. Several of the compounds isolated are more or less similar to those isolated from other Flourensia species; the considerable amounts of eudesmanes, however, are unusual. The overall picture of the genus is still relatively uniform. Close relationships to Helianthella are obvious, while to Helianthus, placed in the same subtribe, no clear relations are visible.     

Isolation,characterization and cytotoxic activity of benzophenone glucopyranosides from Mahkota Dewa (Phaleria macrocarpa (Scheff.) Boerl)

Two benzophenone glucopyranosides have been isolated from the nut shell part of Mahkota Dewa. The structures were identified as 2,4′,6-trihydroxy-4-methoxy-benzophenone-2-O-β-d-glucoside (Mahkoside A) and 2,4′,6-trihydroxy-4-methoxy-6″-acetyl-benzophenone-2-O-β-d-glucoside (Mahkoside B). Mahkoside B was recognized as a novel compound. Furthermore, a series of benzophenone glucopyranoside derivatives (compounds 3–18) were synthesized and their bioactivities were characterized. Our results demonstrated that compound 18 has significant cytotoxicity against two esophageal cancer cell lines, stomach cancer cell line and prostate cancer cell line, with IC₅₀ less than 10 μM, indicating its potential activity against cancer cells.