Inhibitory effects of 190 compounds against SARS-CoV-2 Mpr o protein: Molecular docking interactions.

COVID-19 has caused many deaths since the first outbreak in 2019. The burden on healthcare systems around the world has been reduced by the success of vaccines. However, population adherence and the occurrence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants are still challenging tasks to be affronted. In addition, the newly approved drug presents some limitations in terms of side effects and drug interference, highlighting the importance of searching for new antiviral agents against SARS-CoV-2. The SARS-CoV-2 main protease (Mpr o ) represents a versatile target to search for new drug candidates due to its essential role in proteolytic activities responsible for the virus replication. In this work, a series of 190 compounds, composed of 27 natural ones and 163 synthetic compounds, were screened in vitro for their inhibitory effects against SARS-CoV-2 Mpro . Twenty-five compounds inhibited Mpro with inhibitory constant values (Ki ) between 23.2 and 241 µM. Among them, a thiosemicarbazone derivative was the most active compound. Molecular docking studies using Protein Data Bank ID 5RG1, 5RG2, and 5RG3 crystal structures of Mpro revealed important interactions identified as hydrophobic, hydrogen bonding and steric interactions with amino acid residues in the active site cavity. Overall, our findings indicate the described thiosemicarbazones as good candidates to be further explored to develop antiviral leads against SARS-CoV-2. Moreover, the studies showed the importance of careful evaluation of test results to detect and exclude false-positive findings.

Cytotoxicity of seputhecarpan D, thonningiol and 12 other phytochemicals from African flora towards human carcinoma cells.

BACKGROUND: Despite the remarkable progress in cancer therapy in recent years, this disease still remains a serious public health concern. The use of natural products has been and continues to be one of the most effective ways to fight malignancies. The cytotoxicity of 14 compounds from African medicinal plants was evaluated in four human carcinoma cell lines and normal fibroblasts. The tested samples included: ß-spinasterol (1), friedelanone (2), 16ß-hydroxylupeol (3), ß-amyrin acetate (4), lupeol acetate (5), sequoyitol (6), rhamnitrin (7), europetin 3-O-rhamnoside (8), thonningiol (9), glyasperin F (10), seputhecarpan B (11), seputhecarpan C (12), seputhecarpan D (13) and rheediaxanthone A (14). METHODS: The neutral red uptake (NR) assay was used to evaluate the cytotoxicity of samples; caspase-Glo assay, flow cytometry for cell cycle analysis and mitochondrial membrane potential (MMP) as well as spectrophotometry to measure levels of reactive oxygen species (ROS) were performed to detect the mode of action of compounds 9 and 13 in MCF-7 breast adenocarcinoma cells. RESULTS: Compounds 3, 9-13 displayed cytotoxic effects against the four tested cancer cell lines with IC50 values below 85 µM. Compounds 9 and 13 had IC50 values below 10 µM in 4/4 and 3/4 tested cell lines respectively. The IC50 values varied from 0.36 µM (against MCF7 cells) to 5.65 µM (towards colon carcinoma DLD-1 cells) for 9, from 9.78 µM (against MCF7 cells) to 67.68 µM (against HepG2 cells) for 13 and 0.18 µM (towards HepG2 cells) to 72 µM (towards Caco-2 cells) for the reference drug, doxorubicin. Compounds 9 and 13 induced cell cycle arrest in Go/G1 whilst doxorubicin induced arrest in G2/M. The two molecules (9 and 13) also induced apoptosis in MCF-7 cells through activation of caspases 3/7 and 9 as well as enhanced ROS production. CONCLUSION: Compounds 9 and 13 are good cytotoxic phytochemicals that should be explored more in future to develop a cytotoxic drug to fight human carcinoma.

ESI-MS2 and Anti-inflammatory Studies of Cyclopropanic Triterpenes. UPLC-ESI-MS and MS2 Search of Related Metabolites from Donella ubanguiensis.

INTRODUCTION: Triterpenes are one of the largest secondary metabolites groups spread in the plant kingdom with various skeletons. These metabolites have showed various bioactivities including anti-inflammatory activity. OBJECTIVE: The study aims to explore the mass spectrometry fragmentation of donellanic acids A-C (DA A-C), three compounds identified from Donella ubanguiensis; in addition, the fragmentation behaviour of these metabolites will serve as a fingerprint to search and characterise triterpenes congeners in fruits, bark and wood crude extracts of D. ubanguiensis. This work was prompted by the anti-inflammatory activity on leukocyte migration, exudate concentrations and myeloperoxidase activity obtained for DA A-B. METHODOLOGY: The bioactivity was performed on mouse model of pleurisy induced by carrageenan and the parameters were analysed by veterinarian automated cell counter and colorimetric assays. While the tandem mass analyses of DA A-C were carried out by a direct infusion ESI-QTOF-MS/MS, the extracts were studied by UPLC-ESI-QTOF-MS and UPLC-ESI-QTOF-MS/MS. RESULTS: DA A displayed interesting anti-inflammatory activity by inhibiting leukocyte migration, exudate concentrations and myeloperoxidase activity (p < 0.05) while DA B was weakly active (p > 0.05). Moreover, the diagnostic of the MS2 behaviour of DA A-C in conjunction with the chromatograms and the obtained MS2 data of the crude extract led to the characterisation of three cyclopropane triterpenes (T1-T3) and six saponins (T4-T9) from the fruits, the bark, and the wood extracts. CONCLUSIONS: Donella species deserve more investigation since metabolites related to the anti-inflammatory compound (DA A) could be identified. Copyright © 2016 John Wiley & Sons, Ltd.

Individual and combined antiparasitic effect of six plant metabolites against Leishmania amazonensis and Trypanosoma cruzi.

Six plant metabolites including isobavachalcone (1), 4-hydroxylonchocarpine (2), and (E)-1-(2,2-dimethyl-2H-chromen-6-yl)-3-(4-hydroxyphenyl)prop-2-en-1-one (3), 6,8-(di-3-methyl-but-2-enyl)eriodictyol (4), damnacanthal (5), and buesgenine (6) were evaluated for their leishmanicidal and trypanocidal activities against intracellular amastigotes of Leishmania amazonensis and Trypanosoma cruzi. Compounds 2-4 and 6 displayed antileishmanial activity while 3 and 5 showed trypanocidal effect. The leishmanicidal activity of 6 was expressed with the lowest IC50 (5.70µg/mL) whereas the most trypanocidal metabolite (5) showed its activity with IC50 at 11.14µg/mL. In addition, antiprotozoal effect of mixtures of 1-6 prepared at different ratios (3:1, 1:1, and 1:3) was also investigated. Interestingly, 1 and 2 initially inactive against T. cruzi, displayed trypanocidal activities when mixed together. This activity increased when 3 (13.63µg/mL) was combined with 1 in ratios 1:1 (10.01µg/mL) and 3:1 (7.78µg/mL). Moreover, the leishmanicidal effect of 4 against L. amazonensis increased in the mixture 6/4 (1:3).

Antibacterial and antibiotic-resistance modifying activity of the extracts and compounds from Nauclea pobeguinii against Gram-negative multi-drug resistant phenotypes.

BACKGROUND: Multi-drug resistance of Gram-negative bacteria constitutes a major obstacle in the antibacterial fight worldwide. The discovery of new and effective antimicrobials and/or resistance modulators is necessary to combat the spread of resistance or to reverse the multi-drug resistance. In this study, we investigated the antibacterial and antibiotic-resistance modifying activities against 29 Gram-negative bacteria including multi-drug resistant (MDR) phenotypes of the methanol extracts from Nauclea pobeguiinii leaves (NPL), Nauclea pobeguiinii bark (NPB) and six compounds from the bark extract, identified as 3-acetoxy-11-oxo-urs-12-ene (1), p-coumaric acid (2), citric acid trimethyl ester (3), resveratrol (4), resveratrol ß- D -glucopyranoside (5) and strictosamide (6). METHODS: The broth microdilution method was used to determine the minimal inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC) of crude extracts and compounds as well as the antibiotic-resistance modifying effects of MPB and 4. RESULTS: MIC determinations indicate values ranging from 32-1024 µg/mL for NPB and NPL on 89.7 % and 69.0 % of the tested bacterial strains respectively. MIC values below 100 µg/mL were obtained with NPB against Escherichia coli ATCC10536, AG100 and Enterobacter aerogenes CM64 strains. The lowest MIC value for crude extracts of 32 µg/mL was obtained with NPB against E. coli ATCC10536. Compound 4 was active all tested bacteria, whilst 1, 3 and 6 displayed weak and selective inhibitory effects. The corresponding MIC value (16 µg/mL) was obtained with 4 against Klebsiella pneumoniae KP55 strain. Synergistic effects of the combination of NPB with chloramphenicol (CHL), kanamycin (KAN) as well as that of compound 4 with streptomycin (STR) and ciprofloxacin (CIP) were observed. CONCLUSION: The present study provides information on the possible use of Nauclea pobeguinii and compound 4 in the control of Gram-negative bacterial infections including MDR phenotypes. It also indicates that NPB and 4 can be used as naturally occurring antibiotic-resistance modulators to tackle MDR bacteria.

Antibacterial and antibiotic-modulation activity of six Cameroonian medicinal plants against Gram-negative multi-drug resistant phenotypes.

BACKGROUND: Bacterial Infections involving multi-drug resistant (MDR) phenotypes constitute a worldwide health concern. The present work was designed to assess the antibacterial properties of the methanol extracts of six medicinal plants (Anthocleista schweinfurthii, Nauclea latifolia, Boehmeria platyphylla, Caucalis melanantha, Erigeron floribundus and Zehneria scobra) and the effects of their associations with antibiotics on MDR Gram-negative bacteria over-expressing active efflux pumps. METHODS: The antibacterial activities and the ability to potentiate antibiotic effects of the methanol extracts the tested plants were evaluated in vitro against twenty eight Gram-negative bacteria expressing MDR phenotypes, using broth microdilution method. The phytochemical screening of these extracts was also performed using standard methods. RESULTS: All tested extracts displayed moderate to low antibacterial activity on at least 14.3 % of the 28 tested bacteria, with MIC values ranged from 128 to 1024 µg/mL. The best antibacterial spectrum was observed with Naulcea latifolia bark extract. Extracts from A. schweinfurthii fruits, N. latifolia stem bark, Z. scobra and N. latifolia leaves showed synergistic effects with many antibiotics against MDR bacteria. CONCLUSION: The overall results of the present study provide information for the possible use of the studied plants, especially Nauclea latifolia in the control of Gram-negative bacterial infections including MDR species as antibacterials as well as resistance modulators.

Thonningiiflavanonol A and thonningiiflavanonol B, two novel flavonoids, and other constituents of Ficus thonningii Blume (Moraceae).

A phytochemical study of Ficus thonningii has led to the isolation of two previously unreported compounds, thonningiiflavanonol A and thonningiiflavanonol B together with 16 known compounds: shuterin, naringenin, syringic acid, p-hydroxybenzoic acid, genistein, 5,7,3',4',5'-pentahydroxyflavanone, luteolin, methylparaben, aromadendrin, garbanzol, dihydroquercetin, 5,7,3'-trihydroxyflavanone, ß-sitosterol, sitosterolglucoside, lupeol acetate, and taraxerol. Their structures were elucidated on the basis of spectroscopic data. The new compounds and extracts displayed potent antioxidant activity.

Cytotoxicity of selected Cameroonian medicinal plants and Nauclea pobeguinii towards multi-factorial drug-resistant cancer cells.

BACKGROUND: Malignacies are still a major public concern worldwide and despite the intensive search for new chemotherapeutic agents, treatment still remains a challenging issue. This work was designed to assess the cytotoxicity of six selected Cameroonian medicinal plants, including Nauclea pobeguinii and its constituents 3-acetoxy-11-oxo-urs-12-ene (1), p-coumaric acid (2), citric acid trimethyl ester (3), resveratrol (4), resveratrol ß- D -glucopyranoside (5) and strictosamide (6), against 8 drug-sensitive and multidrug-resistant (MDR) cancer cell lines. METHODS: The resazurin reduction assay was used to evaluate the cytotoxicity of the crude extracts and compounds, whilst column chromatography was used to isolate the constituents of Nauclea pobeguinii. Structural characterization of isolated compounds was performed using nuclear magnetic resonance (NMR) spectroscopic data. RESULTS: Preliminary experiments on leukemia CCRF-CEM cells at 40 µg/mL showed that the leaves and bark extracts from Tragia benthamii, Canarium schweinfurthii, Myrianthus arboreus, Dischistocalyx grandifolius and Fagara macrophylla induced more than 50 % growth of this cell line contrary to the leaves and bark extracts of N. pobeguinii. IC50 values below or around 30 µg/mL were obtained with leaves and bark extracts of N. pobeguinii towards two and five, respectively, of the 8 tested cancer cell lines. The lowest IC50 value was obtained with the bark extract of N. pobeguinii against HCT116 (p53 (-/-) ) colon cancer cells (8.70 µg/mL). Compounds 4 and 6 displayed selective activity on leukemia and carcinoma cells, whilst 1-3 were not active. IC50 values below 100 µM were recorded with compound 5 on all 9 tested cancer cell lines as well as with 4 against 7 out of 8 and 6 against 2 out of 8 cell lines. Collateral sensitivity was observed in CEM/ADR5000 leukemia cells, MDA-MB-231-BCRP breast adenocarcinoma cells (0.53-fold), HCT116 (p53 (+/+) ) cells, human U87MG.ΔEGFR glioblastome multiforme cells to the methanolic bark extract of N. pobeguinii, as well as in MDA-MB-231-BCRP cells and HCT116 (p53 (+/+) ) cells and U87MG.ΔEGFR cells (0.86-fold) to compound 5. CONCLUSIONS: The results of this study demonstrate the cytotoxicity of six Cameroonian medicinal plants, Canarium schweinfurthii, Dischistocalyx grandifolius, Tragia benthamii, Fagara macrophylla, Myrianthus arboreus and Nauclea pobeguinii. We also demonstrated the antiproliferative potential of Nauclea pobeguinii against drug-resistant cancer cell lines. Resveratrol and its glucoside are the major cytotoxic constituents in the bark of Nauclea pobeguinii.

Cytotoxicity of four Aframomum species (A. arundinaceum, A. alboviolaceum, A. kayserianum and A. polyanthum) towards multi-factorial drug resistant cancer cell lines.

BACKGROUND: The search for natural products as potential cytotoxic agents has yielded promising candidates. However multidrug resistance (MDR) is still a major hurdle for patients receiving chemotherapy. In the present study, we evaluated the cytotoxicity of the methanol extracts of four dietary Aframomum plant species (A. arundinaceum, A. alboviolaceum, A. kayserianum and A. polyanthum) against nine sensitive and MDR cancer cell lines. We have also identified the bioactive constituents of A. arundinaceum. METHODS: The cytotoxicity of the methanol extracts of the above plants was determined using a resazurin reduction assay. Chromatographic techniques were used to isolate the constituents of A. arundinaceum. RESULTS: A preliminary experiment on leukemia CCRF-CEM cells at 40 µg/mL showed that the extracts from A. kayserianum and A. alboviolaceum as well as the isolated compounds namely compounds aframodial (1), 8(17),12-labdadien-15,16-dial (2), galanolactone (3), 1-p-menthene-3,6-diol (6) and 1,4-dimethoxybenzene (7) were less active, inducing more than 50% growth of this cell line contrary to A. polyanthum and A. arundinaceum extracts, galanals A (4) and B (5), naringenin (8) and kaempferol-3,7,4'-trimethylether (9). The IC50 values below or around 30 µg/mL were recorded with A. arundinaceum extract against eight of the nine tested cancer cell lines. This extract as well as compound 8 displayed IC50 values below 40 µg/mL towards the nine tested cancer cell lines whilst A. polyanthum extract, compounds 4, 5 and 9 showed selective activities. Collateral sensitivity (hypersensitivity) was observed with A. arundinaceum extract towards leukemia CEM/ADR5000 cells and glioblastoma U87MG.ΔEGFR compared to their respective sensitive counterparts CEM/CEM and U87MG. CONCLUSION: The results of this study provide evidence of the cytotoxicity selected Aframomum species as well as a baseline information for the potential use of Aframomum arundinaceum in the fight against drug sensitive and otherwise drug-resistant cancers.

Excelsoside: a new benzylic diglycoside from the leaves of Milicia excelsa.

A new benzylic diglycoside was isolated from the leaves of Milicia excelsa and identified as 3,4-dimethoxybenzyl beta-D-xylopyranosyl (1 --> 2)-beta-D-glucopyranoside (1). It was obtained together with four known secondary metabolites including lupeol acetate (2), ursolic acid (3), triacontyl (E)-ferulate (4), and 2-(3,5-dihydroxyphenyl)benzofuran-5,6-diol (5). Their structures were determined based on their spectroscopic data and by comparison with those reported in the literature.

Elatumic acid: a new ursolic acid congener from Omphalocarpum elatum Miers (Sapotaceae).

A new triterpene diastereomer, 1, of the previously reported 3beta,6beta,19alpha-trihydroxy-urs-12-en-28-oic acid-24-carboxylic acid methyl ester was obtained from the stem bark of Omphalocarpum elatum Miers (Sapotaceae) along with a-amyrin acetate (2), spinasterol (3), spinasterol 3-O-beta-D-glucopyranoside (4), and tormentic acid (5). The structures of the isolates were established on the basis of NMR and mass spectrometric data and by comparison with those previously reported in the literature. Compound 1 showed weak antibacterial activity against E. aerogenes ATCC13048 and EA3, K. pneumoniae ATCC29916, and P aeruginosa; it also displayed moderate cytotoxicity against CCRF-CEM, CEM/ADR5000, and MDA-MB231 cells.

Chemical constituents of Croton oligandrum (Euphorbiaceae).

A new clerodane diterpene derivative named crotonoligaketone was obtained from the stem bark of Croton oligandrum along with eight known compounds including crotonadiol, imbricatadiol, crotonzambefuran B, 7-acetoxytrachiloban-18-oic acid, 3-O-acetylaleuritolic acid, lupeol, beta-sitosterol, and stigmasterol. The structures of the isolated compounds were established on the basis of their spectral data and by comparison with those reported in the literature.

Aframomumlabdane, a new bislabdane diterpenoid from Aframomum arundinaceum (zingiberaceae).

A previously undescribed bislabdane diterpenoid namely aframomumlabdane (1), was isolated from the seed of Aframomum arundinaceum together with seven known compounds (2 - 8). Their structures were established based on a comprehensive analysis of HR-ESI-MS, in conjunction with their 1D and 2D-NMR data. Compound 1 was evaluated for its cytotoxic activity against four cancer cell lines: A549, HepG2, SPC212 and DLD-1. The best activity was observed against SPC212 lung cancer cell line with an IC50 value of 0.52 µM.

The genus Canthium: A comprehensive summary on its traditional use, phytochemistry, and pharmacological activities.

Canthium Lam. is a genus of flowering plants of the Rubiaceae family with about 80-102 species mainly distributed in Asia, tropical and subtropical Africa. The genus is closely related to Keetia E. Phillips and Psydrax Gaertn. and plants of this genus are used in folk medicine for the treatment of diarrhea, worms, leucorrhoea, constipation, snake bites, diabetes, hypertension, venereal diseases, and malaria. The present review covers a period of 52 years of biological and chemical investigations into the genus Canthium and has resulted in the isolation of about 96 secondary metabolites and several reported biological properties. For the Rubiaceae family, iridoids were reported as being the chemotaxonomic markers of this genus (∼25%). Other reported classes of compounds include alkaloids, flavonoids, phenolic compounds, cyanogenic glycosides, coumarins, sugar alcohols, lignans, triterpenoids, and benzoquinones. The main reported pharmacological properties of most species of this genus include antioxidant, antiplasmodial, antipyretic, anti-inflammatory, antidiabetic, neuroprotective and antimicrobial activities with the latter being the most prominent. Considering the diversity of compounds reported from plants of this genus and their wide range of biological activities, it is considered to be worthy to further investigate them for the discovery of potentially new and cost effective drugs.

A new flavone from the roots of Milicia excelsa (Moraceae).

A new flavonoid identified as 2-(2,4-dihydroxyphenyl)-5-hydroxy-8,8-dimethyl-4H,8H-pyrano[2,3-f]chromen-4-one (2'-hydroxyatalantoflavone) (1) was obtained from the roots of Milicia excelsa along with five known compounds including atalantoflavone (2), neocyclomorusin (3), 6-geranylnorartocarpetin (4), cudraxanthone I (5), and betulinic acid (6). The structures of the isolates were established on the basis of their spectral data and by comparison with those reported in the literature.

Cytotoxicity of the methanol extracts and compounds of Brucea antidysenterica (Simaroubaceae) towards multifactorial drug-resistant human cancer cell lines.

BACKGROUND: Cancer remains a global health concern and constitutes an important barrier to increasing life expectancy. Malignant cells rapidly develop drug resistance leading to many clinical therapeutic failures. The importance of medicinal plants as an alternative to classical drug discovery to fight cancer is well known. Brucea antidysenterica is an African medicinal plant traditionally used to treat cancer, dysentery, malaria, diarrhea, stomach aches, helminthic infections, fever, and asthma. The present work was designed to identify the cytotoxic constituents of Brucea antidysenterica on a broad range of cancer cell lines and to demonstrate the mode of induction of apoptosis of the most active samples. METHODS: Seven phytochemicals were isolated from the leaves (BAL) and stem (BAS) extract of Brucea antidysenterica by column chromatography and structurally elucidated using spectroscopic techniques. The antiproliferative effects of the crude extracts and compounds against 9 human cancer cell lines were evaluated by the resazurin reduction assay (RRA). The activity in cell lines was assessed by the Caspase-Glo assay. The cell cycle distribution, apoptosis via propidium iodide (PI) staining, mitochondrial membrane potential (MMP) through 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide (JC-1) staining, and the reactive oxygen species (ROS) via 2´,7´-dichlorodihydrofluoresceine diacetate (H2DCFH-DA) staining, were investigated by flow cytometry. RESULTS: Phytochemical studies of the botanicals (BAL and BAS) led to the isolation of seven compounds. BAL and its constituents 3, (3-(3-Methyl-1-oxo-2-butenyl))1H indole (1) and hydnocarpin (2), as well as the reference compound, doxorubicin, had antiproliferative activity against 9 cancer cell lines. The IC50 values varied from 17.42 µg/mL (against CCRF-CEM leukemia cells) to 38.70 µg/mL (against HCT116 p53-/- colon adenocarcinoma cells) for BAL, from 19.11 µM (against CCRF-CEM cells) to 47.50 µM (against MDA-MB-231-BCRP adenocarcinoma cells) for compound 1, and from 4.07 µM (against MDA-MB-231-pcDNA cells) to 11.44 µM (against HCT116 p53+/+ cells) for compound 2. Interestingly, hypersensitivity of resistant cancer cells to compound 2 was also observed. BAL and hydnocarpin induced apoptosis in CCRF-CEM cells mediated by caspase activation, the alteration of MMP, and increased ROS levels. CONCLUSION: BAL and its constituents, mostly compound 2, are potential antiproliferative products from Brucea antidysenterica. Other studies will be necessary in the perspective of the discovery of new antiproliferative agents to fight against resistance to anticancer drugs.

Phosphodiesterase I-inhibiting Diels-Alder adducts from the leaves of Morus mesozygia.

A new 2-arylbenzofuran derivative, (+)-dimethylsmoracin O (1), and three new Diels-Alder type adducts, mesozygins A­C (2­4), in addition to eight known compounds, artonin I (5), chalcomaracin (6), norartocarpetin (7), moracin L (8), mulberrofuran F (9), moracin M (10), moracin C (11), and morachalcone A (12),were isolated from the leaves of Morus mesozygia Stapf. Structures were elucidated by spectroscopic data analyses. Compounds 2-7 displayed a potent phosphodiesterase I inhibitory activity.

Antimicrobial activities of the methanol extract and compounds from the twigs of Dorstenia mannii (Moraceae).

BACKGROUND: Dorstenia mannii (Moraceae) is a medicinal herb used traditionally for the treatment of many diseases. In the present study, the methanol extract of D. mannii and nine of its isolated compounds, namely dorsmanin A (1), B (2), C (3), D (4), E (6), F (7), G (8) dorsmanin I (9) and 6,8-diprenyleriodictyol (5), were tested for their antimicrobial activities against yeast, Mycobacteria and Gram-negative bacteria. METHODS: The microplate alamar blue assay (MABA) and the broth microdilution method were used to determine the minimal inhibitory concentration (MIC) and minimal microbicidal concentration (MMC) of the above extract and compounds on a panel of bacterial species. RESULTS: The results of the MIC determinations demonstrated that the methanol extract as well as compounds 3 and 8 were able to prevent the growth of all the fourteen studied microorganisms within the concentration range of 4 to 1024 µg/ml. The lowest MIC value for the methanol extract (64 µg/ml) was obtained on Candida albicans. The lowest value for individual compounds (4 µg/ml) was recorded with compounds 3 on Pseudomonas aeruginosa PA01 and 7 on Eschericia coli ATCC strain. The MIC values recorded with compounds 3 on P. aeruginosa PA01, 6 on C. albicans,7 on P. aeruginosa PA01 and K. pneumoniae ATCC strain and C. albicans,and 8 on P. aeruginosa PA01, PA124, P. stuartii, M. tuberculosis MTCS1 were lower than or equal to those of the reference drugs. MMC values not greater than 1024 µg/ml were recorded on all studied microorganisms with compounds 3 and 8. CONCLUSION: The overall results of the present investigation provided evidence that the crude extract of D. mannii as well as some of its compounds such compounds 3 and 8 could be a potential source of natural antimicrobial products.

(2E,4R,5R,6S)-2-(4,5,6-Trihy-droxy-cyclo-hex-2-en-1-yl-idene)acetonitrile.

The crystal structure of the title compound, C(8)H(9)NO(3), is characterized by a complex three-dimensional hydrogen-bond network in which every mol-ecule is connected to six symmetry-related neighbours.

Antibacterial and antibiotic-potentiation activities of the hydro-ethanolic extract and protoberberine alkaloids from the stem bark of Enantia chlorantha against multidrug-resistant bacteria expressing active efflux pumps.

ETHNOPHARMACOLOGICAL RELEVANCE: Enantia chlorantha is traditionally used to treat various ailments including rickettsia fever, cough and wounds, typhoid fever, infective hepatitis, jaundice, and urinary tract infections. AIM OF THE STUDY: To isolate the antibacterial constituents of the hydro-ethanolic extract of the stem bark of E. chlorantha (ECB) and to evaluate the antibacterial and antibiotic-modifying activities of ECB and its constituents against the multidrug-resistant (MDR) phenotypes. MATERIALS AND METHODS: Chromatographic methods were used to isolate the constituents of ECB and Spectroscopic methods were used to elucidate the chemical structures of the isolated compounds. The antibacterial activity of samples was determined by the broth microdilution method while spectrophotometric methods were used to evaluate the effects of ECB and its most active constituent on bacterial growth. Their effects on bacterial proton-ATPase pumps was assessed through the acidification of the bacterial culture medium. RESULTS: Six protoberberine alkaloids were isolated and identified as columbamine (1), pseudocolumbamine (2), jathrorrhizine (3), palmitine (4), 4,13-dihydroxy-3,9,10-trimethoxyprotoberberine (5), and 13-hydroxy-2,3,9,10-tetramethoxyprotoberberine (6). The crude extract (ECB) inhibited the growth of all the tested MDR bacteria, with the minimal inhibitory concentration (MIC) values below 100 µg/mL obtained against Escherichia coli ATCC 10536, AG 102, Enterobacter aerogenes EA 27, Klebsiella pneumoniae ATCC 11296 and KP 55, Providencia stuartii NEA 16, and Staphylococcus aureus MRSA3 and MRSA6. Compound 1 had the best antibacterial effects with MIC values ranging from 16 to 64 µg/mL. The efflux pump inhibitor (EPI), phenylalanine-arginine-ß naphthylamide (PAßN) significantly improved the activity of compounds 1-6. Compounds 1-3 significantly potentiated the antibacterial activity of antibiotics such norfloxacin (NOR), ciprofloxacin (CIP), and doxycycline (DOX) against the tested MDR bacteria. CONCLUSION: The crude extract (ECB) and its isolated compounds 1-6 are potential antibacterial products from Enantia chlorantha. They could be explored more to develop the antibacterial agents that could be used alone or in combination with antibiotics to overcome MDR phenotypes.