Cancer Chemopreventive Agents Discovered by Activity-Guided Fractionation: An Update

Chemical and biological comparison of different sections of Uncaria rhynchophylla (Gou-Teng)

Uncaria rhynchophylla (Gou-Teng in Chinese) is officially documented in Chinese pharmacopoeia as one of the authentic sources for the crude drug of Gou-Teng which has long been used for mental and cardiovascular diseases. Indole alkaloids are the characteristic constituents responsible for the desired hypotensive effect; however, the psychiatric active constituents of Gou-Teng are still unclear. According to traditional Chinese medicine theory, only the hook-bearing stems of U. rhynchophylla are used as the crude materials for Gou-Teng, while its leaves and fruits are scarcely used. The present study aimed to compare the metabolic fingerprints of different parts (hooks, stems, leaves and fruits) of U. rhynchophylla by LC-DAD-MS/MS analysis and further evaluate their psychiatric activities on HEK293 cell line in vitro. A total of 38 constituents including 26 alkaloids, six flavonoids, two triterpenoids, two chlorogenic acid analogs and two other compounds were characterized. The different parts of U. rhynchophylla can be well differentiated from their chemical profiles. Leaves displayed the most potent activity on both MT₁ and MT₂ receptors, with agonistic rates of 39.7% and 97.6%. For 5-HT_1A and 5-HT_2C receptors, hooks showed the strongest activity with agonistic rates of 92.6% and 83.1%, respectively. This investigation provided valuable information for understanding the chemical divergence between different parts of U. rhynchophylla, and their substantial bases for psychiatric purposes.

Characterization of the phytochemical constituents of Taif rose and its antioxidant and anticancer activities

Ward Taifi (Taif rose) is considered one of the most important economic products of Taif, Saudi Arabia. In this study both fresh and dry Taif rose were biologically and phytochemically investigated. The 80% methanol extracts and n-butanol fractions of dry and fresh Taif rose had high radical scavenging activity toward artificial 1,1-diphenyl picrylhydrazyl (DPPH)(•) radical with SC50 values range 5.86-12.24 µg/ml whereas the aqueous fractions showed weak activity. All samples had in vitro anticancer activity toward HepG2 with IC50 < 20 µg/ml which fall within the criteria of the American Cancer Institute. High positive correlation appeared between the antioxidant activity and total phenolics whereas there is no correlation between total phenolics and anticancer activity. The LC-ESI(- ve)-MS analysis of all extracts indicate the presence of phenolic compounds belonging to hydrolysable tannins and flavonol glycosides. In conclusion, the presence of this is considered to be the first phytochemical report that identifies the major compounds in dry and fresh roses using HPLC-ESI-MS. The methanol extracts and its n-butanol and aqueous fractions for both fresh and dry Taif rose could be used as preventive and therapeutic effective natural agents for diseases in which free radicals involved after more in vitro and in vivo studies.

Genetic variation of Fusarium oxysporum isolates forming fumonisin B(1) and moniliformin

Thirty single-spore isolates of a toxigenic fungus, Fusarium oxysporum, were isolated from asparagus spears and identified by species-specific polymerase chain reaction (PCR) and translation elongation factor 1-α (TEF) sequence analysis. In the examined sets of F. oxysporum isolates, the DNA sequences of mating type genes (MAT) were identified. The distribution of MAT idiomorph may suggest that MAT1-2 is a predominant mating type in the F. oxysporum population. F. oxysporum is mainly recognised as a producer of moniliformin-the highly toxic secondary metabolite. Moniliformin content was determined by high-performance liquid chromatography (HPLC) analysis in the range 0.05-1,007.47 μg g(-1) (mean 115.93 μg g(-1)) but, also, fumonisin B(1) was detected, in the concentration range 0.01-0.91 μg g(-1) (mean 0.19 μg g(-1)). There was no association between mating types and the mycotoxins biosynthesis level. Additionally, a significant intra-species genetic diversity was revealed and molecular markers associated with toxins biosynthesis were identified.

Synthesis and Biological Evaluation of (±)-Abyssinone II and Its Analogues as Aromatase Inhibitors for Chemoprevention of Breast Cancer

An efficient and economical synthesis of the naturally occurring aromatase inhibitor abyssinone II was performed. The synthesis features an optimized aromatic prenylation reaction in which an arylcopper intermediate is reacted with prenyl bromide to afford a key intermediate that was converted to a prenylated aromatic aldehyde. Condensation of the aldehyde with an o-hydroxyacetophenone under Claisen-Schmidt conditions afforded a chalcone that was deprotected and cyclized in the presence of sodium acetate in refluxing ethanol to afford (+/-)-abyssinone II. The synthesis proved to be versatile enough to provide an array of abyssinone II derivatives that were evaluated as aromatase inhibitors. Methylation of the 4'-hydroxyl group of (+/-)-abyssinone II resulted in a significant increase in aromatase inhibitory activity, and further smaller increases in activity resulted from the methylation of the 7-hydroxyl group and removal of the prenyl side chain. As a result of these structural changes, the most active flavanone of the series was 20 times more potent than (+/-)-abyssinone II (IC50 40.95 microM).

Limnophilaspiroketone, a highly oxygenated phenolic derivative from Limnophila geoffrayi

A highly oxygenated phenolic spiroketone, limnophilaspiroketone (1), was isolated from the aerial parts of Limnophila geoffrayi collected in Thailand. The structure of 1 was determined based on spectroscopic data interpretation. This novel isolate, obtained as a major secondary metabolite constituent, was verified as a racemate using the Mosher ester method.

Combining ethnopharmacology and virtual screening for lead structure discovery: COX-inhibitors as application example

Virtual screening of large libraries of organic compounds combined with pharmacological high throughput screening is widely used for drug discovery in the pharmaceutical industry. Our aim was to explore the efficiency of using a biased 3D database comprising secondary metabolites from antiinflammatory medicinal plants as a source for the virtual screening. For this study pharmacophore models of cyclooxygenase I and II (COX-1, COX-2), key enzymes in the inflammation process, were generated with structure-based as well as common feature based modeling, resulting in three COX hypotheses. Four different multiconfomational 3D databases limited in molecular weight between 300 and 700 Da were applied to the screening in order to compare and analyze the obtained hit rates. Two of them were created in-house (DIOS, NPD). The database DIOS consists of 2752 compounds from phytochemical reports of antiinflammatory medicinal plants described by the ethnopharmacological source 'De material medica' of Pedanius Dioscorides, whereas NPD contains almost 80,000 compounds gathered arbitrarily from natural sources. In addition, two available multiconformational 3D libraries comprising marketed and development drug substances (DWI and NCI), mainly originating from synthesis, were used for comparison. As a test of the pharmacophore models' capability in natural sources, the models were used to search for known COX inhibitory natural products. This was achieved with some exceptions, which are discussed in the paper. Depending on the hypothesis used, DWI and NCI library searches produced hit rates in the range of 6.6% to 13.7%. A slight increase of the number of molecules assessed for binding was achieved with the database of natural products (NPD). Using the biased 3D database DIOS, however, the average increase of efficiency reached 77% to 133% compared to the hit rates resulting from WDI and NCI. The statistical benefit of a combination of an ethnopharmacological approach with the potential of computer aided drug discovery by in silico screening was demonstrated exemplified on the applied targets COX-1 and COX-2.

Constituents of Asparagus officinalis evaluated for inhibitory activity against cyclooxygenase-2

As part of a project directed toward the discovery of new cancer chemopreventive agents from plants, two new natural products, asparagusic acid anti-S-oxide methyl ester (1) and asparagusic acid syn-S-oxide methyl ester (2), a new acetylenic compound, 2-hydroxyasparenyn [3',4'-trans-2-hydroxy-1-methoxy-4-[5-(4-methoxyphenoxy)-3-penten-1-ynyl]-benzene] (3), as well as eleven known compounds, asparenyn (4), asparenyol (5), (+/-)-1-monopalmitin (6), ferulic acid (7), 1,3-O-di-p-coumaroylglycerol (8), 1-O-feruloyl-3-O-p-coumaroylglycerol (9), blumenol C, (+/-)-epipinoresinol, linoleic acid, 1,3-O-diferuloylglycerol, and 1,2-O-diferuloylglycerol, were isolated from an ethyl acetate-soluble fraction of the methanol extract of the aerial parts of Asparagus officinalis (Asparagus), using a bioassay based on the inhibition of cyclooxygenase-2 to monitor chromatographic fractionation. The structures of compounds 1-3 were elucidated by 1D- and 2D-NMR experiments ((1)H NMR, (13)C NMR, DEPT, COSY, HMQC, HMBC and NOESY). All the isolates were evaluated for their inhibitory effects against both cyclooxygenase-1 and -2, with the most active compound being linoleic acid.

Potential cancer chemopreventive constituents of the leaves of Macaranga triloba

Activity-guided fractionation of the leaves of Macaranga triloba, using an in vitro bioassay based on the inhibition of cyclooxygenase-2, resulted in the isolation of a rotenoid, 4,5-dihydro-5'alpha-hydroxy-4'alpha-methoxy-6a,12a-dehydro-alpha-toxicarol (1), as well as 12 known compounds, (+)-clovan-2beta,9alpha-diol, ferulic acid, 3,7,3',4'-tetramethylquercetin, 3,7,3'-trimethylquercetin, 3,7-dimethylquercetin, abscisic acid, 1beta,6alpha-dihydroxy-4(15)-eudesmene, 3beta-hydroxy-24-ethylcholest-5-en-7-one, loliolide, scopoletin, taraxerol, and 3-epi-taraxerol. The structure of compound 1 was determined using spectroscopic methods. All isolates were evaluated for their potential to inhibit cyclooxygenases-1 and -2 by measuring PGE(2) production, and to induce quinone reductase in cultured Hepa 1c1c7 mouse hepatoma cells.

Phenolic compounds obtained from stems ofcouepia ulei with the potential to induce quinone reductase

Activity-guided fractionation of the EtOAc-soluble extract of the stems of Couepia ulei, using a bioassay based on the induction of quinone reductase (QR) in cultured Hepa 1c1c7 mouse hepatoma cells led to the isolation of two active compounds, a new natural product, erythro-2,3-bis(4-hydroxy-3-methoxyphenyl)-3-ethoxypropan-1-ol (1), and a known compound, evofolin-B (2), along with five inactive compounds all of known structure, viz., betulinic acid, oleanolic acid, pomolic acid, (+/-)-syringaresinol, and ursolic acid. These isolates were identified by analysis of physical and spectral data. Compounds 1 and 2 exhibited QR inducing activity, with observed CD (concentration required to double induction) values of 16.7 and 16.4 microM, respectively.

Potential cncer chemopreventive flavonoids from the stems of Tephrosia toxicaria

A new butenylflavanone, (2S)-5-hydroxy-7-methoxy-8-[(E)-3-oxo-1-butenyl]flavanone (1), and a new rotenoid, 4',5'-dihydro-11,5'-dihydroxy-4'-methoxytephrosin (2), as well as three active flavonoids of previously known structure, isoliquiritigenin (3), genistein (4), and chrysoeriol (5), along with nine known inactive compounds, alpha-toxicarol (6), sumatrol, 6a,12a-dehydro-alpha-toxicarol, 11-hydroxytephrosin, obovatin, marmesin, lupenone, benzyl benzoate, and benzyl trans-cinnamate, were isolated from an ethyl acetate-soluble extract of the stems of Tephrosia toxicaria, using a bioassay based on the induction of quinone reductase (QR) in cultured Hepa 1c1c7 mouse hepatoma cells to monitor chromatographic fractionation. The structures of compounds 1 and 2 were elucidated by spectroscopic data interpretation. All isolates were evaluated for their potential cancer chemopreventive properties utilizing an in vitro assay to determine quinone reductase induction. Selected compounds were tested in a mouse mammary organ culture assay to evaluate the inhibition of 7,12-dimethylbenz[a]anthracene (DMBA)-induced preneoplastic lesions.

Constituents of the stem bark of Pongamia pinnata with the potential to induce quinone reductase

Activity-guided fractionation of the petroleum ether and ethyl acetate extracts of the stem bark of Pongamia pinnata, using cultured Hepa 1c1c7 mouse hepatoma cells to evaluate quinone reductase (QR) inducing activity, led to the isolation of four new flavanone derivatives (1-4), one new flavone (5), one new chalcone (6), and 13 known compounds of the flavonoid, terpenoid, and fatty acid types. The structures of 1-6 were characterized on the basis of the interpretation of their spectroscopic data. The absolute stereochemistry of compounds 1-4 was determined from their CD data and by Mosher ester determination. All isolates obtained were evaluated in the quinone reductase induction assay.

Isolation and absolute stereochemistry of coussaric acid, a new bioactive triterpenoid from the stems of Coussarea brevicaulis

Coussaric acid (1), a triterpenoid based on an ursane skeleton, and an oleanane-type triterpene acid, 3-epi-spathodic acid (2), as well as four known compounds, barbinervic acid, scutellaric acid, stigmasterol and stigmasterol glucoside, have been isolated from an EtOAc-soluble extract of the stems of Coussarea brevicaulis. The structures of compounds 1 and 2 were elucidated on the basis of spectroscopic investigation, and single-crystal X-ray crystallography was used to confirm the structure of 1. The absolute stereochemistry of 1 was established by chemical transformations and by the Mosher ester procedure. The potential of the isolates and chemical transformation products to induce quinone reductase was evaluated in mouse Hepa lclc7 hepatoma cells.

Compounds obtained from sida acuta with the potential to induce quinone reductase and to inhibit 7,12-dimethylbenz[a]anthracene-induced preneoplastic lesions in a mouse mammary organ culture model

Activity-guided fractionation of the EtOAc-soluble extract of the whole plants of Sida acuta using a bioassay based on the induction of quinone reductase (QR) in cultured Hepa 1c1c7 mouse hepatoma cells, led to the isolation of ten active compounds of previously known structure, quindolinone (1), cryptolepinone (2), 11-methoxyquindoline (3), N-trans-feruloyltyramine (4), vomifoliol (5), loliolide (6), 4-ketopinoresinol (7), scopoletin (8), evofolin-A (9), and evofolin-B (10), along with five inactive compounds of known structure, ferulic acid, sinapic acid, syringic acid, (+/-)-syringaresinol, and vanillic acid. These isolates were identified by physical and spectral data measurement. A new derivative of quindolinone, 5,10-dimethylquindolin-11-one (1a) was synthesized and characterized spectroscopically. Of the active substances, compounds 1-3 and 1a exhibited the most potent QR activity, with observed CD (concentration required to double induction) values ranging from 0.01 to 0.12 microg/mL. Six compounds were then evaluated in a mouse mammary organ culture assay, with cryptolepinone (2), N-trans-feruloyltyramine (4), and 5,10-dimethylquindolin-11-one (1a) found to exhibit 83.3, 75.0, and 66.7% inhibition of 7,12-dimethylbenz[a]anthracene-induced preneoplastic lesions, respectively, at a dose of 10 microg/mL.