Isolation and antibacterial activity of anomanol B and other secondary metabolites from the stem bark of Anonidium mannii (Annonaceae).

A new Lanosta-7,9(11),22-trien-3,15,20-triol named Anomanol B 1, together with five known compounds: manniindole 2, arborinine 3, polycarpol 4, 8,9-dimethoxyphenanthridin-6(5H)-one 5 and 3-O-ß-D-glucopyranosyl-ß-sitosterol 6 were isolated from the stem bark extract of Anonidium mannii by routine chromatography techniques. 8,9-dimethoxyphenanthridin-6(5H)-one 5, was reported from natural origin for the first time. The structures of the compounds were established by comprehensive elucidation of spectroscopic data and by comparison with literature data. Evaluation of the isolates on Gram-negative bacteria such as Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, Providencia stuartii, and Pseudomonas aeruginosa showed that, compound 1 had weak antibacterial activity with minimal inhibitory concentrations (MIC) varying from 128 to 256 µg/mL. Compounds 3, 5, and 6 exhibited moderate to weak activity with MIC of 32 to 128 µg/mL and 64 to 256 µg/mL compared to the reference drug chloramphenicol which inhibited the growth of all studied bacteria with MIC values of 16 to 64 µg/mL.

Antibacterial secondary metabolites from Vernonia auriculifera Hiern (Asteraceae) against MDR phenotypes.

Purification of the aerial parts of Vernonia auriculifera Hiern afforded steroids (1-2), flavonoids (3-5), and polyalcohol (6). Their structures were determined using spectral evidences as well as by comparison with reported data. Iodonitrotetrazolium chloride (INT) colorimetric assay was used to assess the antibacterial activity of the extract and isolates against 13 pathogenic strains. The crude extract showed strong antibacterial activity (MIC < 100 µg/mL) against the tested bacterial strains. When combined with an efflux pump inhibitor phenylalanine beta naphthylamide (PAßN), the inhibition potency of the extract was substantially enhanced with the lowest MIC value at 4 µg/mL. Compounds 5 and 6 showed moderate activity (MIC < 100 µg/mL) against 12/13 (92.3%), and 8/13 (61.5%) bacterial strains, respectively. A minimal bactericidal concentration (MBC)/minimal inhibitory concentration (MIC) ratio ≤ 4 indicated their bactericidal effect against Escherichia coli, Enterbacter aerogenes, Klebsiella pneumoniae, Providencia stuartii, Pseudomonas aeruginosa, and Staphylococcus aureus.

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.

A New Chalcone and Antimicrobial Chemical Constituents of Dracaena stedneuri.

Microbial infections are leading causes of death and morbidity all over the world due to the development of the resistance to antibiotics by certain microorganisms. In this study, the chemical exploration of the ethanol (EtOH) extract of the aerial part of Dracaena stedneuri (Dracaenaceae) led to the isolation of one previously unreported chalcone derivative, i.e., 2',4'-dihydroxy-2,3'-dimethoxychalcone (1), together with 12 known compounds: 8-(C)-methylquercetagetin-3,6,3'-trimethyl ether (2), methylgalangine (3), quercetin (4), kaempferol (5), 6,8-dimethylchrysin (6), ombuine-3-O-rutinoside (4',7-dimethylquercetin-3-O-α-L-rhamnopyranosyl-(1 → 6) -ß-D-glucopyranoside) (7), alliospiroside A (8), ß-sitosterol 3-O-glucopyranoside (9), ishigoside (10), betulinic acid (11), oleanolic acid (12), and lupeol (13). The structures were determined by spectroscopic and spectrometric analysis including 1- and 2-Dimensional Nuclear Magnetic Resonance (1D- and 2D-NMR), High-Resolution Electrospray Ionization Mass Spectrometry (HRESIMS), and comparison with literature data. The isolated secondary metabolites and crude extract displayed antibacterial activity against some multidrug-resistant strains with minimal inhibitory concentration (MIC) values ranging from 32 to 256 µg/mL. The antibacterial activity of compound 13 against Enterobacter aerogenes ATCC13048 (MIC value: 32 µg/mL) was higher than that of chloramphenicol used as the reference drug (MIC = 64 µg/mL).

Antibacterial and antibiotic-potentiation activity of the constituents from aerial part of Donella welwitshii (Sapotaceae) against multidrug resistant phenotypes.

BACKGROUND: The rise of multidrug-resistant (MDR) bacteria is a real public health problem worldwide and is responsible for the increase in hospital infections. Donella welwitschii is a liana or shrub belonging to the family Sapotaceae and traditionally used to cure coughs. OBJECTIVE: This study was conducted with the objective to validate the medicinal properties of this plant, the aerial part was studied for its phytochemical composition using column and PTLC chromatography and exploring its antibacterial and antibiotic-modifying activity as well as those of its phytochemicals. METHODS: The structures of the compounds were elucidated from their physical and spectroscopic data in conjunction with literature. The antibacterial activity of the isolated metabolites was performed toward a panel of MDR Gram negative and Gram-positive bacteria. The broth micro-dilution method was used to determine antibacterial activities, efflux pump effect using the efflux pump inhibitor (EPI) (phenylalanine-arginine-ß-naphthylamide (PAßN)), as well as the modulating activity of antibiotics. Monitoring the acidification of the bacterial growth medium was used to study the effects of the samples on the bacterial proton-ATPase pumps and cellular ATP production. RESULTS: Eleven compounds were isolated including pentacyclic triterpenes, C-glucosyl benzophenones. With a MIC value < 10 µg/mL, diospyric acid (7) significantly inhibited the growth of Escherichia coli AG102, Enterobacter aerogenes ATCC13048, Klebsiella pneumoniae KP55, Providencia stuartii NEA16 and Staphylococcus aureus MRSA3. 28-hydroxy-ß-amyrin (8) significantly impaired the growth of Enterobacter aerogenes EA27, Klebsiella pneumoniae ATCC11296 and Staphylococcus aureus MRSA6; and oleanolic acid (9) strongly impaired the growth of Escherichia coli AG 102, Enterobacter aerogenes EA27 and Providencia stuartii PS2636. Diospyric acid (7) and 28-hydroxy-ß-amyrin (8) induced perturbation of H+-ATPase pump and inhibition of the cellular ATP production. Moreover, at MIC/2 and MIC/4, compounds 7, 8, and 9 strongly improved the antibacterial activity of norfloxacin, ciprofloxacin and doxycycline with antibiotic-modulating factors ranging between 2 and 64. CONCLUSION: The overall results of the current work demonstrate that diospyric acid (7), 28-hydroxy-ß-amyrin (8) and oleanolic acid (9) are the major bioactive constituents of Donella welwitschia towards Gram-negative bacteria expressing MDR phenotypes.

Botanicals and phytochemicals from the bark of Hypericum roeperianum (Hypericaceae) had strong antibacterial activity and showed synergistic effects with antibiotics against multidrug-resistant bacteria expressing active efflux pumps.

ETHNOPHARMACOLOGICAL RELEVANCE: Infections due to multidrug-resistant (MDR) bacteria constitute a real problem in the public health worldwide. Hypericum roeperianum Schimp. ex A. Rich (Hypericaceae) is used traditionally for treatment of various ailments such as abdominal pains, constipation, diarrhea, indigestion, nausea, and bacterial diseases. AIM OF THE STUDY: This study was aimed at investigating the antibacterial and antibiotic-modifying activity of the crude methanol extracts (HRB), ethyl-acetate soluble fraction (HRBa), residual material (HRBb), and 11 compounds from the bark of Hypericum roeperianum against multi-drug resistant (MDR) bacteria expressing active efflux pumps. MATERIALS AND METHODS: The antibacterial activity, the efflux pump effect using the efflux pump inhibitor (EPI), phenylalanine-arginine-ß-naphthylamide (PAßN), as well as the antibiotic-modifying activity of samples were determined using the broth micro-dilution method. Spectrophotometric methods were used to evaluate the effects of HRB and 8,8-bis(dihydroconiferyl) diferulate (11) on bacterial growth, and bacterial membrane damage, whereas follow-up of the acidification of the bacterial culture was used to study their effects on bacteria proton-ATPase pumps. RESULTS: The crude extract (HRB), HRBa, and HRBb had selective antibacterial activity with MICs ranging from 16 to 512 µg/mL. Phytochemical 11 displayed the best antibacterial activity (0.5 ≤ MIC ≤ 2 µg/mL). The activity of HRB and 11 in the presence of EPI significantly increased on the tested bacteria strains (up to 32-fold). The activity of cloxacillin (CLO), doxycycline (DOX), and tetracycline (TET), was considerably improved (up to 64-fold) towards the multidrug-resistant Enterobacter aerogenes EA-CM64 strain. The crude extract (HRB) and 11 induced the leakage of bacterial intracellular components and inhibited the proton-ATPase pumps. CONCLUSIONS: The crude extract (HRB) and 8,8-bis(dihydroconiferyl)diferulate from the bark of Hypericum roeperianum are good antibacterial candidates that deserve further investigations to achieve antibacterial drugs to fight infections involving MDR bacteria.

Cytotoxic Constituents of the Bark of Hypericum roeperianum towards Multidrug-Resistant Cancer Cells.

The global cancer burden remains a serious concern with the alarming incidence of one in eight men and one in eleven women dying in developing countries. This situation is aggravated by the multidrug resistance (MDR) of cancer cells that hampers chemotherapy. In this study, the cytotoxicity of the methanol extract (HRB), fractions (HRBa, HRBb, and HRBa1-5), and compounds from the bark of Hypericum roeperianum (HRB) was evaluated towards a panel of 9 cancer cell lines. The mode of action of the HRB and trichadonic acid (1) was also studied. Column chromatography was applied to isolate the constituents of HRB. The cytotoxicity of botanicals and phytochemicals was evaluated by the resazurin reduction assay (RRA). Caspase-Glo assay was used to evaluate the activity of caspases, and reactive oxygen species (ROS) (H2DCFH-DA) were assessed by flow cytometry. Phytochemicals isolated from HRB were trichadonic acid (1), fridelan-3-one (2), 2-hydroxy-5-methoxyxanthone (3), norathyriol (4), 1,3,5,6-tetrahydroxyxanthone (5), betulinic acid (6), 3'-hydroxymethyl-2'-(4″-hydroxy-3″,5″-dimethoxyphenyl)-5',6':5,6-(6,8-dihydroxyxanthone)-1',4'-dioxane (7), and 3'-hydroxymethyl-2'-(4″-hydroxy-3″,5″-dimethoxyphenyl)-5',6':5,6-(xanthone)-1',4'-dioxane (8). Botanicals HRB, HRBa, HRBa2-4, HRBb, and doxorubicin displayed cytotoxic effects towards the 9 tested cancer cell lines. The recorded IC50 values ranged from 11.43 µg/mL (against the P-glycoprotein (gp)-overexpressing CEM/ADR5000 leukemia cells) to 26.75 µg/mL (against HCT116 (p53+/+) colon adenocarcinoma cells) for the crude extract HRB. Compounds 1, 5, and doxorubicin displayed cytotoxic effects towards the 9 tested cancer cell lines with IC50 values varying from 14.44 µM (against CCRF-CEM leukemia cells) to 44.20 µM (against the resistant HCT116 (p53-/-) cells) for 1 and from 38.46 µM (against CEM/ADR5000 cells) to 112.27 µM (against the resistant HCT116 (p53-/-) cells) for 5. HRB and compound 1 induced apoptosis in CCRF-CEM cells. The apoptotic process was mediated by enhanced ROS production for HRB or via caspases activation and enhanced ROS production for compound 1. This study demonstrated that Hypericum roeperianum is a potential source of cytotoxic phytochemicals such as trichadonic acid and could be further exploited in cancer chemotherapy.

8,8-bis-(Dihydroconiferyl)-diferulate displayed impressive cytotoxicity towards a panel of human and animal cancer cells.

BACKGROUND: Recalcitrant cancers appear as a major obstacle to chemotherapy, prompting scientists to intensify the search for novel drugs to tackle the cell lines expressing multi-drug resistant (MDR) phenotypes. PURPOSE: The purpose of this study was to evaluate the antiproliferative potential of a ferrulic acid derivative, 8,8-bis-(dihydroconiferyl)-diferulate (DHCF2) on a panel of 18 cancer cell lines, including various sensitive and drug-resistant phenotypes, belonging to human and animals. The mode of induction of cell death by this compound was further studied. METHODS: The antiproliferative activity, autophagy, ferroptotic and necroptotic cell death were evaluated by the resazurin reduction assay (RRA). CCRF-CEM leukemia cells were used for all mechanistic studies. A caspase-Glo assay was applied to evaluate the activity of caspases. Cell cycle analysis (PI staining), apoptosis (annexin V/PI staining), mitochondrial membrane potential (MMP) (JC-1) and reactive oxygen species (ROS) (H2DCFH-DA) were assessed by flow cytometry. RESULTS: DHCF2 demonstrated impressive cytotoxic effects towards the 18 cancer cell lines tested, with IC50 values all below 6.5 µM. The obtained IC50 values were in the range of 1.17 µM (towards CCRF-CEM leukemia cells) to 6.34 µM (towards drug-resistant HCT116 p53-/- human colon adenocarcinoma cells) for DHCF2 and from 0.02 µM (against CCRF-CEM cells) to 122.96 µM (against multidrug-resistant CEM/ADR5000 leukemia cells) for the reference drug, doxorubicin. DHCF2 had IC50 values lower than those of doxorubicin, against CEM/ADR5000 cells and on some melanoma cell lines, such as MaMel-80a cells, Mel-2a cells, MV3 cells and SKMel-505 cells. DHCF2 induced autophagy as well as apoptosis in CCRF-CEM cells though caspases activation, MMP alteration and increase of ROS production. CONCLUSION: The studied diferulic acid, DHCF2, is a promising antiproliferative compound. It deserves further indepth investigations with the ultimate aim to develop a novel drug to fight cancer drug resistance.