Evaluation of anti-quorum sensing and antibiofilm effects of secondary metabolites from Gambeya lacourtiana (De Wild) Aubr. & Pellegr against selected pathogens.

BACKGROUND: Microbial infections cause serious health problems especially with the rising antibiotic resistance which accounts for about 700,000 human deaths annually. Antibiotics which target bacterial death encounter microbial resistance with time, hence, there is an urgent need for the search of antimicrobial substances which target disruption of virulence factors such as biofilm and quorum sensing (QS) with selective pressure on the pathogens so as to avoid resistance. METHODS: Natural products are suitable leads for antimicrobial drugs that can inhibit bacterial biofilms and QS. Twenty compounds isolated from the medicinal plant Gambeya lacourtiana were evaluated for their antibiofilm and anti-quorum sensing effects against selected pathogenic bacteria. RESULTS: Most of the compounds inhibited violacein production in Chromobacterium violaceum CV12472 and the most active compound, Epicatechin had 100% inhibition at MIC (Minimal Inhibitory Concentration) and was the only compound to inhibit violacein production at MIC/8 with percentage inhibition of 17.2 ± 0.9%. Since the bacteria C. violaceum produces violacein while growing, the inhibition of the production of this pigment reflects the inhibition of signal production. Equally, some compounds inhibited violacein production by C. violaceum CV026 in the midst of an externally supplied acylhomoserine lactone, indicating that they disrupted signal molecule reception. Most of the compounds exhibited biofilm inhibition on Staphyloccocus aureus, Escherichia coli and Candida albicans and it was observed that the Gram-positive bacteria biofilm was most susceptible. The triterpenoids bearing carboxylic acid group, the ceramide and epicatechin were the most active compounds compared to others. CONCLUSION: Since some of the compounds disrupted QS mediated processes in bacteria, it indicates that this plant is a source of antibiotics drugs that can reduce microbial resistance.

Antiproliferative activity of a new xanthone derivative from leaves of Garcinia nobilis Engl.

A new xanthone, mboudiexanthone (1), together with five known compounds, euxanthone (2), isogarcinol (3), garcinol (4), betulinic acid (5) and zeorin (6) were isolated from the leaves of Garcinia nobilis Engl. The structures were determined by 1D and 2D NMR techniques and X-ray diffraction for 6. The in vitro antiproliferative properties of isolated compounds were evaluated against the human breast cancer cell line MCF-7. All compounds showed an antiproliferative activity with an IC50 value down to ∼11 µM for isogarcinol.

Natural Polyketides Isolated from the Endophytic Fungus Phomopsis sp. CAM212 with a Semisynthetic Derivative Downregulating the ERK/IκBα Signaling Pathways.

Three previously undescribed natural products, phomopsinin A - C (1:  - 3: ), together with three known compounds, namely, cis-hydroxymellein (4: ), phomoxanthone A (5: ) and cytochalasin L-696,474 (6: ), were isolated from the solid culture of Phomopsis sp. CAM212, an endophytic fungus obtained from Garcinia xanthochymus. Their structures were determined on the basis of spectroscopic data, including IR, NMR, and MS. The absolute configurations of 1: and 2: were assigned by comparing their experimental and calculated ECD spectra. Acetylation of compound 1: yielded 1A: , a new natural product derivative that was tested together with other isolated compounds on lipopolysaccharide-stimulated RAW 264.7 cells. Cytochalasin L-696,474 (6: ) was found to significantly inhibit nitric oxide production, but was highly cytotoxic to the treated cells, whereas compound 1: slightly inhibited nitric oxide production, which was not significantly different compared to lipopolysaccharide-treated cells. Remarkably, the acetylated derivative of 1: , compound 1A: , significantly inhibited nitric oxide production with an IC50 value of 14.8 µM and no cytotoxic effect on treated cells, thereby showing the importance of the acetyl group in the anti-inflammatory activity of 1A: . The study of the mechanism of action revealed that 1A: decreases the expression of inducible nitric oxide synthase, cyclooxygenase 2, and proinflammatory cytokine IL-6 without an effect on IL-1ß expression. Moreover, it was found that 1A: exerts its anti-inflammatory activity in lipopolysaccharide-stimulated RAW 264.7 macrophage cells by downregulating the activation of ERK1/2 and by preventing the translocation of nuclear factor κB. Thus, derivatives of phomopsinin A (1: ), such as compound 1A: , could provide new anti-inflammatory leads.

Lambertellin from Pycnoporus sanguineus MUCL 51321 and its anti-inflammatory effect via modulation of MAPK and NF-κB signaling pathways.

Lambertellin (1) and ergosta-5,7,22-trien-3-ol (2) were isolated from the solid rice fermentation of the plant pathogenic fungus Pycnoporus sanguineus MUCL 51321. Their structures were elucidated using comprehensive spectroscopic methods. The isolated compounds were tested on lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. Lambertellin (1) exhibited promising inhibitory activity against nitric oxide (NO) production with IC50 value of 3.19 µM, and it significantly inhibited the expression of inducible NO synthase (iNOS) and cyclooxygenase 2 (COX-2). Lambertellin (1) also decreased the expression of pro-inflammatory cytokines IL-6 and IL-1ß. The study of the mechanistic pathways revealed that lambertellin (1) exerts its anti-inflammatory effect in LPS-stimulated RAW 264.7 macrophage cells by modulating the activation of the mitogen activated protein kinase (MAPK) and nuclear factor κB (NF-κB) signaling pathways. Therefore, lambertellin (1) could be a promising lead compound for the development of new anti-inflammatory drugs.

Anticancer and antibacterial secondary metabolites from the endophytic fungus Penicillium sp. CAM64 against multi-drug resistant Gram-negative bacteria.

BACKGROUND: The emergence of multiple-drug resistance bacteria has become a major threat and thus calls for an urgent need to search for new effective and safe anti-bacterial agents. OBJECTIVES: This study aims to evaluate the anticancer and antibacterial activities of secondary metabolites from Penicillium sp., an endophytic fungus associated with leaves of Garcinia nobilis. METHODS: The culture filtrate from the fermentation of Penicillium sp. was extracted and analyzed by liquid chromatography-mass spectrometry, and the major metabolites were isolated and identified by spectroscopic analyses and by comparison with published data. The antibacterial activity of the compounds was assessed by broth microdilution method while the anticancer activity was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. RESULTS: The fractionation of the crude extract afforded penialidin A-C (1-3), citromycetin (4), p-hydroxyphenylglyoxalaldoxime (5) and brefelfin A (6). All of the compounds tested here showed antibacterial activity (MIC = 0.50 - 128 µg/mL) against Gramnegative multi-drug resistance bacteria, Vibrio cholerae (causative agent of dreadful disease cholera) and Shigella flexneri (causative agent of shigellosis), as well as the significant anticancer activity (LC50 = 0.88 - 9.21 µg/mL) against HeLa cells. CONCLUSION: The results obtained indicate that compounds 1-6 showed good antibacterial and anticancer activities with no toxicity to human red blood cells and normal Vero cells.

Antibacterial and cytotoxic cytochalasins from the endophytic fungus Phomopsis sp. harbored in Garcinia kola (Heckel) nut.

BACKGROUND: The continuous emergence of multidrug-resistant (MDR) bacteria drastically reduced the efficacy of our antibiotic armory and consequently, increased the frequency of therapeutic failure. The search for bioactive constituents from endophytic fungi against MDR bacteria became a necessity for alternative and promising strategies, and for the development of novel therapeutic solutions. We report here the isolation and structure elucidation of antibacterial and cytotoxic compounds from Phomopsis sp., an endophytic fungus associated with Garcinia kola nuts. METHODS: The fungus Phomopsis sp. was isolated from the nut of Garcinia kola. The crude extract was prepared from mycelium of Phomopsis sp. by maceration in ethyl acetate and sequentially fractionated by column chromatography. The structures of isolated compounds were elucidated on the basis of spectral studies and comparison with published data. The isolated compounds were evaluated for their antibacterial and anticancer properties by broth microdilution and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide methods respectively. The samples were also tested spectrophotometrically for their hemolytic properties against human red blood cells. RESULTS: The fractionation of the crude extract afforded three known cytochalasins including 18-metoxycytochalasin J (1), cytochalasins H (2) and J (3) together with alternariol (4). The cytochalasin compounds showed different degrees of antibacterial activities against the tested bacterial pathogens. Shigella flexneri was the most sensitive microorganism while Vibrio cholerae SG24 and Vibrio cholerae PC2 were the most resistant. Ampicillin did not show any antibacterial activity against Vibrio cholerae NB2, Vibrio cholerae PC2 and Shigella flexneri at concentrations up to 512 µg/mL, but interestingly, these multi-drug resistant bacterial strains were sensitive to the cytochalasin metabolites. These compounds also showed significant cytotoxic properties against human cancer cells (LC50 = 3.66-35.69 µg/mL) with low toxicity to normal non-cancer cells. CONCLUSION: The three cytochalasin compounds isolated from the Phomopsis sp. crude extract could be a clinically useful alternative for the treatment of cervical cancer and severe infections caused by MDR Shigella and Vibrio cholerae.

Anti-mycobacterial activity of polyketides from Penicillium sp. endophyte isolated from Garcinia nobilis against Mycobacteriumsmegmatis.

OBJECTIVE/BACKGROUND: According to estimates by the World Health Organization, there were 9.6 million new tuberculosis (TB) cases in 2014: 5.4 million among men, 3.2 million among women, and 1.0 million among children. There were also 1.5 million TB deaths. Although there are potent anti-TB molecules, the misuse of these drugs in addition to inconsistent or partial treatment have led to the development of multidrug-resistant TB and extensively drug-resistant TB. It is established that plants harbor microorganisms, collectively known as endophytes, which also produce metabolites. Exploring the as-yet untapped natural products from the endophytes increases the chances of finding novel and active compounds. The present study was aimed to investigate the antimycobacterial activity of the crude extract and compounds isolated from Penicillium sp. endophyte associated with Garcinia nobilis against Mycobacterium smegmatis. METHODS: Liquid culture obtained from the fermentation of Penicillium sp. was extracted using ethylacetate and the liquid chromatography-mass spectrometry monitored fractionation of crude extracts yielded six compounds. Their structures were elucidated with spectroscopic analyses including two-dimensional nuclear magnetic resonance, high resolution mass spectrometry by dereplication using Antibase, and by comparison to literature data. All compounds and the crude extract from the liquid medium were evaluated for their antimycobacterial activity against M. smegmatis. RESULTS: In this study, the activity of penialidins A-C (1-3), citromycetin (4), p-hydroxy phenyl glyoxalaldoxime (5), and Brefeldin A (6) were tested against nonpathogenic M. smegmatis. Penialidin C was the most active compound with a minimum inhibitory concentration of 15.6µg/mL. CONCLUSION: Isolated compounds from Penicillium sp. harbored in G. nobilis exhibited promising antimycobacterial activity against M. smegmatis thus supporting the immensity of the potential of antimycobacterial drug discovery from endophytes from medicinal plants. Penialidin C could further be investigated for antimycobacterial drug development.

Antibacterial and antioxidant xanthones and benzophenone from garcinia smeathmannii.

A new prenylated xanthone, 1,3,5,8-tetrahydroxy-2-(3-methybut-2-enyl)-4-(3,7-dimethylocta-2,6-dienyl) xanthone (1), and a new benzophenone (2), together with four known xanthone derivatives, cheffouxanthone (3), smeathxanthone A (4), smeathxanthone B (5), ananixanthone (6), and two pentacyclic triterpenes, epi-friedelinol (7) and friedelin (8), were isolated from the stem bark of Garcinia smeathmannii. The structures of the compounds were elucidated on the basis of 1D and 2D NMR experiments, and compound 2 was further characterized and confirmed by single X-ray analysis. Compounds 1, 2, and 3 exhibited the most prominent antibacterial activity against gram-positive Enterococcus faecalis with minimal inhibitory concentration values of 8, 8, and 2 µg/mL, respectively, while compounds 1, 3, 4, and 6 showed the capacity to scavenge free radicals.

A new xanthone derivative from twigs of Garcinia nobilis.

Phytochemical investigation of the twigs of Garcinia nobilis led to the isolation of a new xanthone, named l-hydroxy-2,5-dimethoxyxanthone (1), together with 15 known compounds (2-16). The structures of the new and known compounds were established by means of spectroscopic methods and by comparison with previously reported data. The structure of compound 1 was confirmed by X-ray diffraction data. Compounds 1-16 were tested for their cytotoxic activity against human cervix carcinoma cell line KB-3-1. Compounds 5 and 11 showed moderate activity while others showed weak biological activity in these cytotoxicity assays. Compounds 4 and 9 were found to be inactive.

A new sphingolipid and furanocoumarins with antimicrobial activity from Ficus exasperata.

From the methanol extract of the stem bark of Ficus exasperata, a new sphingolipid named Ficusamide, (2S,3S,4R,11E)-2-[(2',3'-dihydroxyhexacosanoylamino)]-11-octadecene-1,3,4-triol (1), along with three known furanocoumarins, (S)-(-) oxypeucedanin hydrate (2), (R)-(+) oxypeucedanin hydrate (3), bergapten (5-methoxypsoralen) and six other known compounds, were isolated. Their structures were characterized basing on spectroscopic methods and chemical evidence. Compounds (1-3) were analyzed for their antimicrobial activity. Ficusamide (1) showed wick activity (minimal inhibitory concentration (MIC)=312.5 µg/mL) against Escherichia coli, while the furanocoumarins (2) and (3) showed significant activity (MIC=9.76 µg/mL) against Bacillus cereus, Candida albicans and Microsporum audouinii.

Cytotoxicity of natural compounds isolated from the seeds of Garcinia afzelii.

The new compounds guttiferone O ( 1) and 3-methoxycheffouxanthone ( 2) have been isolated from the seeds of Garcinia afzelii Engl., together with nine known compounds: 2-hydroxy-1,7-dimethoxyxanthone ( 3), smeathxanthone A ( 4), 1,5-dihydroxyxanthone ( 5), 1,6-dihydroxy-5-methoxyxanthone ( 6), cheffouxanthone ( 7), 1,3,5-trihydroxyxanthone ( 8), smeathxanthone B ( 9), isoxanthochymol ( 10) and guttiferone E ( 11). Their structures were elucidated by means of 1D and 2D-NMR techniques. All the isolates showed high cytotoxic activity and were found inactive when tested against HIV and influenza viruses.

Inhibitory effect of macabarterin, a polyoxygenated ellagitannin from Macaranga barteri, on human neutrophil respiratory burst activity.

An ellagitannin with a 2,4-acyl group, named macabarterin (1), and a new ellagic acid glycoside, 3-O-methylellagic acid 4-O-ß-d-xylopyranoside (2), were isolated from the stem bark extract of Macaranga barteri along with five known phenolic compounds, ellagic acid (3), 3-O-methylellagic acid (4), gallic acid (5), methyl gallate (6), and scopoletin (7). The structures of 1 and 2, as well as those of the known compounds, were elucidated on the basis of spectroscopic data and by comparison with reported data. Compounds 1-5 and 7 were tested for their anti-inflammatory potential in a cell-based respiratory burst assay, compound 1 being found an inhibitor of the superoxides produced in the cellular system.

Polyanxanthone A, B and C, three xanthones from the wood trunk of Garcinia polyantha Oliv.

Three xanthones, polyanxanthone A (1), B (2) and C (3) have been isolated from the methanol extract of the wood trunk of Garcinia polyantha, along with five known xanthones: 1,3,5-trihydroxyxanthone (4); 1,5-dihydroxyxanthone (5); 1,3,6,7-tetrahydroxyxanthone (6); 1,6-dihydroxy-5-methoxyxanthone (7) and 1,3,5,6-tetrahydroxyxanthone (8). Their structures were determined by means of 1D- and 2D-NMR techniques. Some of the above compounds were screened for their anticholinesterase activity on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes.