Dehydrozingerone, chalcone, and isoeugenol analogues as in vitro anticancer agents

Twenty-eight compounds related to dehydrozingerone (1), isoeugenol (3), and 2-hydroxychalcone (4) were synthesized and evaluated in vitro against human tumor cell replication. Except for isoeugenol analogues 27-35, most compounds exhibited moderate or strong cytotoxic activity against KB, KB-VCR (a multidrug-resistant derivative), and A549 cell lines. In particular, chalcone 15 showed significant cytotoxic activity against the A549 cell line with an IC50 value of 0.6 microg/mL. Furthermore, dehydrozingerone analogue 11 and chalcones 16 and 17 showed significant and similar cytotoxic activity against both KB (IC50 values of 2.0, 1.0, and 2.0 microg/mL, respectively) and KB-VCR (IC50 values of 1.9, 1.0, and 2.0 microg/mL, respectively) cells, suggesting that they are not substrates for the P-glycoprotein drug efflux pump.     

Antimalarial compounds from Kniphofia foliosa roots

During the course of screening Ethiopian medicinal plants for their antimalarial properties, it was found that the dichloromethane extract of the roots of Kniphofia foliosa Hochst. (Asphodelaceae), which have long been used in the traditional medicine of Ethiopia for the treatment of abdominal cramps and wound healing, displayed strong in vitro antiplasmodial activity against the chloroquine-sensitive 3D7 strain of Plasmodium falciparum with an ED50 value of 3.8 microg/mL and weak cytotoxic activity against KB cells with an ED50 value of 35.2 microg/mL. Five compounds were isolated from the roots and evaluated for their in vitro antimalarial activity. Among the compounds tested, 10-(chrysophanol-7'-yl)-10-(xi)-hydroxychrysopanol-9-anthrone and chryslandicin, showed a high inhibition of the growth of the malaria parasite, P. falciparum with ED50 values of 0.260 and 0.537 microg/mL, respectively, while the naphthalene derivative, 2-acetyl-1-hydroxy-8-methoxy-3-methylnaphthalene, exhibited a less significant antimalarial activity with an ED50 value of 15.4 microg/mL. To compare the effect on the parasite with toxicity to mammalian cells, the cytotoxic activities of the isolated compounds against the KB cell line were evaluated and 10-(chrysophanol-7'-yl)-10-(xi)-hydroxychrysopanol-9-anthrone and chryslandicin displayed very low toxicity with ED50 values of 104 and 90 microg/mL, respectively. This is the first report of the inhibition of the growth of P. falciparum by anthraquinone-anthrone dimers and establishes them as a new class of potential antimalarial compounds with very little host cell toxicity.     

Search for antiviral activity in higher plant extracts

In the course of our search for plant natural products as antiviral agents, extracts of ten plants from the Iberian Peninsula were tested for antiviral activity against herpes simplex type I (HSV-1), vesicular stomatitis virus (VSV) and poliovirus type 1. Aqueous extracts of five of these medicinal plants, namely Nepeta nepetella (150-500 microg/mL), Nepeta coerulea (150-500 microg/mL), Nepeta tuberosa (150-500 microg/mL), Dittrichia viscosa (50-125 microg/mL) and Sanguisorba minor magnolii (50-125 microg/mL), showed a clear antiviral activity against two different DNA and RNA viruses, i.e. HSV-1 and VSV. Only the medicinal plant Dittrichia viscosa was active against an additional virus, poliovirus type 1.     

Antitumor agents. 203. Carbazole alkaloid murrayaquinone A and related synthetic carbazolequinones as cytotoxic agents

Murrayaquinone A (1) and murrayafoline A (3), isolated from the root bark of Murraya euchrestifolia, were identified as cytotoxic compounds. Murrayaquinone A (1) demonstrated significant cytotoxicity against SK-MEL-5 and Colo-205 cells, with ED(50) values of 2.58 and 3.85 microg/mL, respectively. In contrast, murrayafoline A (3) exhibited marginal or weak cytotoxicity against SK-MEL-5, Colo-205, HCT-8, KB, and A-549 tumor cell lines, with ED(50) values ranging from 5.31 to 7.52 microg/mL. In total, 20 carbazole alkaloids (1-20), isolated previously by Furukawa et al. from various plant sources were also evaluated for their cytotoxic profiles in the NCI's human disease-oriented, 60-cell line, in vitro antitumor screening protocol. Compounds 3 and 15 showed potent cell-line selective cytotoxicity against MOLT-4 cells, with log GI(50) values of -8.60 and -8.49 M, respectively, while 12 demonstrated better selectivity against the colon cancer subpanel. Moreover, synthetic 2-methyl- or 3-methyl-carbazolequinone derivatives with various substituents in the A-ring were evaluated against KB, SK-MEL-5, Colo-205, and HCT-8 tumor cells. 6-Methoxy- (21), 6-methyl- (22), and 6-chloro- (24) 3-methyl-carbazolequinones demonstrated significant cytotoxicity against SK-MEL-5 cells, with ED(50) values of 0.55, 0.66, and 0.83 microg/mL, respectively. Compounds 21 and 22 were also significantly cytotoxic toward KB cells, with ED(50) values of 0.76 and 0.92 microg/mL, respectively, and 21 displayed a similar level of toxicity against Colo-205 cells (ED(50) 0.87 microg/mL).     

Antiprotozoal activities of heterocyclic-substituted xanthones from the marine-derived fungus Chaetomium sp

Investigations of the marine-derived fungus Chaetomium sp. led to the isolation of the new natural products chaetoxanthones A, B, and C (1-3). Compounds 1 and 2 are substituted with a dioxane/tetrahydropyran moiety rarely found in natural products. Compound 3 was identified as a chlorinated xanthone substituted with a tetrahydropyran ring. The configurational analysis of these compounds employed CD spectroscopy, modified Mosher's method, and selective NOE gradient measurements. Compound 2 showed selective activity against Plasmodium falciparum with an IC50 value of 0.5 microg/mL without being cytotoxic toward cultured eukaryotic cells. Compound 3 displayed a moderate activity against Trypanosoma cruzi with an IC50 value of 1.5 microg/mL.     

Anti-babesial and anti-plasmodial compounds from Phyllanthus niruri

Bioassay-guided fractionation of boiled aqueous extracts from the whole plant of Phyllanthus niruri led to the isolation of 1-O-galloyl-6-O-luteoyl-alpha-d-glucose (1), with IC(50) values of 4.7 microg/mL against Babesia gibsoni and 1.4 microg/mL against Plasmodium falciparum in vitro. The known compounds beta-glucogallin (2), quercetin 3-O-beta-d-glucopyranosyl-(2-->1)-O-beta-d-xylopyranoside (3), beta-sitosterol, and gallic acid were also isolated. Structures of these compounds were elucidated on the basis of their chemical and spectroscopic data.     

Cytotoxic lignans from the stem bark of Magnolia officinalis

Three new lignans, 4'-methoxymagndialdehyde ( 1), 4'-methoxymagnaldehyde B ( 2), and 4'-methoxymagnaldehyde E ( 3), were isolated from hexane- and EtOAc-soluble fractions of the stem bark of Magnolia officinalis, together with eight known compounds ( 4- 11). The structures of compounds 1- 3 were determined on the basis of spectroscopic and physicochemical data analysis. Compounds 1- 11 were tested in vitro for their cytotoxic activity against the K562, HeLa, and A549 cancer cell lines. Among the compounds tested, compound 1 showed the most potent cytotoxic activity against these cancer cell lines, with IC50 values of 3.9, 1.5, and 3.7 microg/mL, respectively.     

Cytotoxic and antioxidant activities of alkylated benzoquinones from Maesa lanceolata

The natural and semi-synthetic analogs of substituted 1,4-benzoquinones were evaluated for in vitro cytotoxic and antioxidant activities. Maesanin, dihydromaesanin, maesanin dimethyl ether and isomeric mixtures of 3-[(Z)-10'-pentadecenyl]-benzoquinone derivatives exhibited cytotoxic activity against HL-60 cell line (IC50 values 4.5, 2.2, 0.43 and 2.8 microg/mL, respectively), while it was found to be inactive against ROS (Reactive Oxygen Species) generation in HL-60. In contrast, the isomeric acylated benzoquinones with shorter alkyl substituents, namely, 2-acetoxy-5-hydoxy-6-methyl-3-tridecyl-1,4-benzoquinone and 2-hydoxy-5-acetoxy-6-methyl-3-tridecyl-1,4-benzoquinone showed most prominent antioxidant and antiproliferative effect on HL-60 (IC50 values 6.2 and 2.2 microg/mL, respectively), as well as cytotoxicities against SK-MEL, KB, BT-549 and SK-OV-3 carcinomas (IC50 values <1.1-4.2 microg/mL). All benzoquinones were found to be inactive against cell aggregation and cell adhesion assays, thus showing no effect on immune responses and inflammation.     

Antiplasmodial activity of selected sudanese medicinal plants with emphasis on Acacia nilotica.

Twenty-two plant organs from eleven plants comprising five families were extracted and screened for antiplasmodial activity in vitro against Plasmodium falciparum 3D7 (chloroquine sensitive) and Dd2 (chloroquine resistant and pyrimethamine sensitive). Fifty nine percent of plant extracts from 22 extracts exerted activity on P. falciparum strain 3D7 with an IC(50) less than 50 microg/mL, whereas 43% of plant extracts showed an IC(50) value within 50 microg/mL on Dd2 strains. Plant extracts from Gardenia lutea, Haplophyllum tuberculatum, Cassia tora, Acacia nilotica and Aristolochia bracteolata possessed IC(50) values less than 5 microg/mL on both tested strains. Bioassay guided fractionation of A. nilotica revealed that the ethyl acetate extract possessed the highest activity (IC(50) = 1.5 microg/mL). Fraction 2 (R(f) = 0.75) prepared by preparative chromatography showed the highest activity on P. falciparum (IC(50) = 1.7 microg/mL). Phytochemical analysis indicated that the most active phase contained terpenoids and tannins and was devoid of alkaloids and saponins. The effect of plant extracts on lymphocyte proliferation showed low toxicity to the human cells. This plant has been subjected to long term clinical trials in folk medicine and is a promising plant.     

In vitro leishmanicidal activity of naturally occurring chalcones

A variety of chalcones have been shown to exhibit activity against Leishmania parasites. In contrast to synthetic or semisynthetic chalcones, only a few plant-derived compounds have been investigated. To provide a scientific rational for the antiprotozoal potency of plants used in ethnomedicine and containing chalcones, and in the search for new antiprotozoal drugs, we have carried out a primary screening for in vitro leishmanicidal activity of 20 chalcones isolated from plants. The compounds were tested against extracellular promastigotes of Leishmania donovani, L. infantum, L. enrietii and L. major, and against intracellular amastigote L. donovani residing within murine macrophages. Against the extracellular Leishmania (L. donovani), most compounds were active with EC(50) values between 0.07 and 2.01 microg/mL. Some of these chalcones, 2',4'-dihydroxy-4-methoxychalcone, 2'-hydroxy-3,4-dimethoxychalcone and 2-hydroxy-4,4'-dimethoxychalcone also significantly inhibited the intracellular survival of L. donovani parasites with EC(50) values between 0.39 and 0.41 microg/mL. When tested against murine bone marrow-derived macrophages as a mammalian host cell control, all compounds with antileishmanial activities also proved to be cytotoxic to varying extents (EC(50) 0.19-2.06 microg/mL). Correlations between molecular structures and antileishmanial activity are discussed in detail. Specific compounds are illustrated with emphasis on their mode of action and potential for the development of selective antiprotozoal agents.     

Inhibition of phospholipase cgamma1 and cancer cell proliferation by triterpene esters from Uncaria rhynchophylla

Investigation of the hooks of Uncaria rhynchophylla resulted in isolation of six phospholipase Cgamma1 (PLCgamma1) inhibitors (1-6). The structures of these compounds were elucidated as pentacyclic triterpene esters by spectroscopic and chemical analysis. Three of them, namely uncarinic acids C (1), D (2), and E (3), are newly reported as natural products. All the compounds showed dose-dependent inhibitory activities against PLCgamma1 in vitro with IC(50) values of 9.5-44.6 microM and inhibited the proliferation of human cancer cells with IC(50) values of 0.5-6.5 microg/mL.     

Antimalarial activity of some plants traditionally used in Meru district of Kenya

Ten plant extracts commonly used by the Meru community of Kenya were evaluated for the in vitro antiplasmodial, in vivo antimalarial, cytotoxicity and animal toxicity activities. The water and methanol extracts of Ludwigia erecta and the methanol extracts of Fuerstia africana and Schkuhria pinnata exhibited high antiplasmodial activity (IC(50) < 5 microg/mL) against chloroquine sensitive (D6) and resistant (W2) Plasmodium falciparum clones. The cytotoxicity of these highly active extracts on Vero E6 cells were in the range 161.5-4650.0 microg/mL with a selectivity index (SI) of 124.2-3530.7. In vivo studies of these extracts showed less activity with chemosuppression of parasitaemia in Plasmodium berghei infected mice of 49.64-65.28%. The methanol extract of Clerodendrum eriophyllum with a lower in vitro activity (IC(50) 9.51-10.56 microg/mL) exhibited the highest chemosuppression of 90.13%. The methanol and water extracts of Pittosporum viridiflorum were toxic to mice but at a lower dose prolonged survival of P. berghei infected mice (p < 0.05) with no overt signs of toxicity. However, the extracts were cytotoxic (SI, 0.96-2.51) on Vero E6 cells. These results suggest that there is potential to isolate active non-toxic antimalarial principles from these plants.     

Antibacterial activities and cytotoxicity of terpenoids isolated from Spirostachys africana

Spirostachys africana Sond. stem bark is used traditionally for the treatment of diarrhoea and dysentery in Limpopo Province of South Africa. Bioassay-guided fractionation of ethanolic extract from bark of Spirostachys africana led to the isolation of four known compounds, two triterpenoids, compound 1 [d-Friedoolean-14-en-oic acid (3-acetyl aleuritolic acid)] and compound 2 (Lupeol), and two diterpenes, compound 3 [ent-2,6alpha-dihydroxy-norbeyer-1,4,15-trien-3-one (diosphenol 2)] and compound 4 (ent-3beta-hydroxy-beyer-15-ene-2-one). Isolated compounds were tested for antibacterial activity using micro-dilution method. Compound 1, exhibited minimum inhibitory concentration (MIC) of 50 microg/ml against Staphylococcus aureus, Salmonella typhy, Vibrio cholera, Escherichia coli and Shigella dysentery. Compound 2 was not active against all tested microorganisms at 200 microg/ml, which was the highest concentration tested. At this concentration, all four compounds were not active against Shigella sonnei. Cytotoxicity of ethanol crude extracts and isolated compounds from Spirostachys africana was determined using the sodium-2,3-bis-[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) assay on Vero cells. Compounds 2 and 3, isolated from Spirostachys africana, had up to three times higher [50% inhibitory concentration (IC(50) values; 300.9 and 308.9 microg/ml)] than the ethanol crude extracts (102.8 microg/ml) suggesting higher toxicity of the crude extract as compared to these two compounds. In contrast, compounds 1 and 4 were not cytotoxic to Vero cell lines (African green monkey) in vitro at the concentrations tested (IC(50)>400 microg/ml). This is the first report on the antibacterial activity and cytotoxicity of purified compounds from Spirostachys africana.     

Prenylated phenolics from Ganoderma fornicatum

Three new prenylated phenolic compounds, fornicins A-C (1-3), were obtained from the fruiting bodies of Ganoderma fornicatum. The structure elucidation was achieved by interpretation of spectroscopic data. These compounds exhibited moderate cytotoxic activity with IC(50) values of 15 to 30 microg/mL in Hep-2 cells.     

Screening of selected plant extracts for in vitro inhibitory activity on human immunodeficiency virus

As part of our screening of anti-AIDS agents from natural sources, extracts of 15 medicinal plants widely used in the folk medicines of North America and Europe were evaluated in vitro. Most of the extracts tested were relatively nontoxic to human lymphocytic MT-2 cells, but only the extracts of Hysopp officinalis and Dittrichia viscosa exhibited anti-HIV activity in an in vitro MTT assay. The 50% hydroalcohol extract of Hysopp officinalis and the aqueous extract of Dittrichia viscosa showed inhibitory effects against HIV-1 induced infections in MT-2 cells at concentrations ranging from 50 to 100 microg/mL and 25 to 400 microg/mL, respectively. Both extracts showed no appreciable cytotoxicity at these concentrations.     

Screening of plant extracts for antiprotozoal and cytotoxic activities

Methanolic and aqueous extracts derived from 43 plant species, selected either from ethnobotanical or chemotaxonomical data, were screened for their antiprotozoal activity against Leishmania donovani and Trypanosoma brucei brucei. The cytotoxic activity against KB cells was also determined. Eight extracts had IC50 values of less than 10 microg/ml against Leishmania donovani. The most active was Triclisia patens with an IC50 value of 1.5 microg/ml against Leishmania donovani. Annona purpurea and Alstonia macrophylla had IC50 values below 10 microg/ml against Trypanosoma brucei brucei. Annona purpurea was the most cytotoxic against KB cells.     

Isolation and identification of cytotoxic compounds from the wood of Pinus resinosa

Methanol extracts of wood from Pinus resinosa were found to be selectively cytotoxic against human lung carcinoma cells, A549 (IC50 41 +/- 6 microg/mL), human colorectal adenocarcinoma cells, DLD-1 (IC50 47 +/- 4 microg/mL) in comparison with healthy cells, WS1 (IC50 130 +/- 11 microg/mL). Five known compounds were isolated and identified by 1H, 13C NMRspectroscopy and HR-ESI-MS mass spectrometry as, pinosylvin monomethyl ether (1), pinosylvin (2), pinosylvin dimethyl ether (3), pinobanksin (4) and (-)-norachelogenin (5). Compound 4 was isolated for the first time in P. resinosa. The cytotoxicity of compounds 1-5 was evaluated against A549, DLD-1 and WS1. Compound 1 exhibited the strongest cytotoxicity against both tumor cell lines and the healthy cell line with an IC50 of 25 +/- 4 microm for A549, 20 +/- 1 microm for DLD-1 and 34 +/- 3 microm for WS1.     

Isolation, structures, and structure - cytotoxic activity relationships of withanolides and physalins from Physalis angulata

Phytochemical investigation of Physalis angulata was initiated following primary biological screening. Fractionation of CHCl3 and n-BuOH solubles of the MeOH extract from the whole plant was guided by in vitro cytotoxic activity assay using cultured HONE-1 and NUGC cells and led to the isolation of seven new withanolides, withangulatins B-H (1-7), and a new minor physalin, physalin W (8), along with 14 known compounds, including physaprun A, withaphysanolide, dihydrowithanolide E, physanolide A, withaphysalin A, and physalins B, D, F, G, I, J, T, U, and V. New compounds (1-8) were fully characterized by a combination of spectroscopic methods (1D and 2D NMR and MS) and the relative stereochemical assignments based on NOESY correlations and analysis of coupling constants. Biological evaluation of these compounds against a panel of human cancer cell lines showed broad cytotoxic activity. Withangulatin B (1) and physalins D (10) and F (11) displayed potent cytotoxic activity against a panel of human cancer cell lines with EC50 values ranging from 0.2 to 1.6 microg/mL. Structure-activity relationship analysis indicated that withanolides and physalins with 4beta-hydroxy-2-en-1-one and 5beta,6beta-epoxy moieties are potential cytotoxic agents.     

Antiprotozoal and cytotoxic screening of 45 plant extracts from Democratic Republic of Congo

AIM OF THE STUDY: To evaluate in vitro the antiprotozoal and cytotoxic activities of 80% methanol extract from 45 medicinal plants collected in Sankuru (Democratic Republic of Congo) against Trypanosoma brucei brucei, Trypanosoma cruzi and the chloroquine-sensitive Ghanaian strain of Plasmodium falciparum, and MRC-5 cell lines respectively. MATERIAL AND METHODS: Different extracts were obtained by maceration of each plant part used with 80% methanol for 24h. The mixture was filtered and evaporated in vacuo to give corresponding dried extract. The activity against Trypanosoma brucei brucei and Trypanosoma cruzi were performed in 96 well tissue plates each containing 10 microl aqueous plant extract dilutions (100 to 0.01 microg/ml) with 10 microl of the parasite suspension cultured in Hirumi medium supplemented with 10% foetal calf serum, a solution of 2% penicillin/streptomycin (2% P/S) After 4 days incubation with Almar bluea solution, fluorescence was measured at 500 nm emission and 530 nm excitation and results expressed as percentage reduction in parasite compared to control wells. The antiplasmodial activity of was assessed in vitro against the chloroquine-sensitive Ghanaian strain of Plasmodium falciparum cultured in RPMI-1640 medium by the lactate deshydrogenase assay in the presence of plant extracts (50 to 0.01 microg/ml). Cell-lines MRC-5 were cultured in MEM medium supplemented with 20mM l-glutamine, 16.5mM NaHCO(3), 5% foetal calf serum and 2% P/S solution. After 4h incubation, cell proliferation/viability was spectrophotomecally assessed at 540 nm after addition of MTT. In each assay, the IC50 value for each sample was derived by the drug concentration-response curves. RESULTS: The extracts from Alcornea cordifolia leaves, Momordica charantia whole plant, Omphalocarpum glomerata, root bark and Piptadia africanum stem bark showed good antiprotozoal activity against Trypanosoma brucei brucei with IC50 values from 0.7 to 7 microg/ml. Only Piptadenia africanum extract showed a pronounced antiprotozoal activity against Trypanosoma cruzi (IC50=4.0+/-06 microg/ml). The extracts from Alchornea cordifolia, Polyathia swaveleons stem bark, Sapium cornutum stem bark and Triclisia giletii stem bark exhibited a pronounced antiplasmodial activity against P. falciparum Ghanaian strain with IC50 values ranging from 0.5 to 3.0 microg/ml. Piptadenia africanum extract was the most cytotoxic sample (CC50=0.25 microg/ml) with poor selectivity against all selected protozoa (SI<10) while other active extracts did not show a significant cytotoxic effect against MCR-5 cell-lines with good selectivity according to the case. CONCLUSION: These active plant extracts are selected for extensive studies leading to the isolation of active constituents.     

In vitro antileishmanial and antimalarial activities of tetrahydrofuran lignans isolated from Nectandra megapotamica (Lauraceae)

Seven tetrahydrofuran lignans, isolated from Nectandra megapotamica (Lauraceae), were evaluated for their in vitro antileishmanial and antimalarial activities. Among the evaluated compounds, machilin-G (1a) and veraguensin (2a) showed the highest antileishmanial activities, displaying for both compounds an IC(50) value of 18 microg/mL and an IC(90) value of 36 microg/mL, while galgravin (1b), nectandrin-A (1c), nectandrin-B (1d), calopeptin (2b) and ganshisandrine (3) were inactive against Leishmania donovani. In the antimalarial assay against Plasmodium falciparum, it was observed that calopeptin (2b) displayed moderate activity, with IC(50) values of 3800 ng/mL (D6 clone) and 3900 ng/mL (W2 clone), while the lignans 1a-1d, 2a and 3 were inactive. In order to compare the effect on the parasites with toxicity to mammalian cells, the cytotoxic activity of the isolated compounds were evaluated against the Vero cells, showing that all evaluated tetrahydrofuran lignans exhibited no cytotoxicity at the maximum dose tested.