Evaluation of the antibacterial activity of the methylene chloride extract of Miconia ligustroides,isolated triterpene acids,and ursolic acid derivatives

The methylene chloride extract of Miconia ligustroides (DC.) Naudin (Melastomataceae), the isolated compounds ursolic and oleanolic acids and a mixture of these acids, and ursolic acid derivatives were evaluated against the following microorganisms: Bacillus cereus (ATCC 14579), Vibrio cholerae (ATCC 9458), Salmonella choleraesuis (ATCC 10708), Klebsiella pneumoniae (ATCC 10031), and Streptococcus pneumoniae (ATCC 6305). The microdilution method was used for determination of the minimum inhibitory concentration (MIC) during evaluation of the antibacterial activity. The methylene chloride extract showed no activity against the selected microorganisms. Ursolic acid was active against B. cereus, showing a MIC value of 20?μg/mL. Oleanolic acid was effective against B. cereus and S. pneumoniae with a MIC of 80?μg/mL in both cases. The mixture of triterpenes, ursolic and oleanolic acids, did not enhance the antimicrobial activity. However, the acetyl and methyl ester derivatives, prepared from ursolic acid, increased the inhibitory activity for S. pneumoniae.     

Synthesis and Antimicrobial Activity of the Hybrid Molecules between Sulfonamides and Active Antimicrobial Pleuromutilin Derivative

A series of novel hybrid molecules between sulfonamides and active antimicrobial 14‐o‐(3‐carboxy‐phenylsulfide)‐mutilin were synthesized, and their in vitro antibacterial activities were evaluated by the broth microdilution. Results indicated that these compounds displayed potent antimicrobial activities in vitro against various drug‐susceptible and drug‐resistant Gram‐positive bacteria such as Staphylococci and streptococci, including methicillin‐resistant Staphylococcus aureus, and mycoplasma. In particular, sulfapyridine analog ( 6c ) exhibited more potent inhibitory activity against Gram‐positive bacteria and mycoplasma, including Staphylococcus aureus (MIC = 0.016–0.063 μg/mL), methicillin‐resistant Staphylococcus aureus (MIC = 0.016 μg/mL), Streptococcus pneumoniae (MIC = 0.032–0.063 μg/mL), Mycoplasma gallisepticum (MIC = 0.004 μg/mL), with respect to other synthesized compounds and reference drugs sulfonamide (MIC = 8–128 μg/mL) and valnemulin (MIC = 0.004–0.5 μg/mL). Furthermore, comparison between MIC values of pleuromutilin‐sulfonamide hybrids 6a–f with pleuromutilin parent compound 3 revealed that these modifications at 14 position side chain of the pleuromutilin with benzene sulfonamide could greatly improve the antibacterial activity especially against Gram‐positives.     

In vitro analyses of the combination of high-dose doxycycline and antifungal agents against Candida albicans biofilms

The potential of antifungal agents used as antimicrobial lock therapy (ALT) for the conservative management of catheter-related candidemia has not been fully defined. We sought to determine the antifungal effect of high-dose doxycycline (DOX), alone or in combination with standard concentrations of amphotericin B (AMB), caspofungin (CAS) or fluconazole (FLC), against biofilms formed by Candida albicans in vitro. DOX alone (at 2048 μg/mL and 1024 μg/mL) demonstrated up to an 85% reduction of the metabolic activity of the C. albicans biofilm. Regardless of the concentration tested, FLC alone showed minimal activity (mean 22.9% reduction) against the C. albicans biofilm. When DOX 2048 μg/mL was used in combination with FLC, antifungal activity also increased up to 85%, suggesting an additive effect. DOX 128 μg/mL in combination with FLC demonstrated synergy (mean 58.3% reduction). The combination of DOX 2048 μg/mL or 512 μg/mL and AMB was superior to AMB alone at low concentrations (0.25–0.03125 μg/mL). However, DOX 128 μg/mL was antagonistic in combination with low concentrations of AMB. Maximal efficacy against the biofilm was observed with CAS at 8–0.25 μg/mL compared with FLC and AMB alone. A paradoxical effect (PE) occurred with CAS at 16 μg/mL, which showed a marked reduction in antifungal activity compared with lower concentrations of CAS. CAS at 16 μg/mL in combination with either DOX 2048 μg/mL or 512 μg/mL resulted in attenuation of the PE. These findings suggest that a high-dose DOX-based ALT strategy in combination with traditional antifungal agents may be useful for the treatment of C. albicans biofilms.     

Reynosin and santamarine: two sesquiterpene lactones from Ambrosia confertiflora with bactericidal activity against clinical strains of Mycobacterium tuberculosis

Context: Tuberculosis is primarily caused by Mycobacterium tuberculosis (Mtb). Previous studies have shown that the dichloromethanic extract of Ambrosia confertiflora DC (Asteraceae) inhibited Mtb.

Objective: To isolate the compounds responsible for the mycobactericidal activity against clinical Mtb strains.

Materials and methods: The dichloromethanic extract of aerial parts of A. confertiflora was separated using chromatography columns. Mycobactericidal activity of the isolated compounds was evaluated using the Alamar Blue bioassay (128–16?μg/mL, 7 days). Cytotoxicity was tested against normal cell line L929 using the MTT ([3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium]) assay (100–3.125?μg/mL, 48 h). Compound structures were elucidated by ¹H and ¹³C uni- and bidimensional NMR.

Results: Two sesquiterpene lactones (SQLs) with mycobactericidal activity were identified: santamarine and reynosin. Reynosin was the most active compound, with a minimal bactericidal concentration (MBC) of 128?μg/mL against the H37Rv, 366-2009 and 104-2010 Mtb strains and a minimal inhibitory concentration (MIC) of 64, 64, 128, 128 and 128?μg/mL against the H37Rv, 104-2010, 63-2009, 366-2009 and 430-2010 Mtb strains, respectively. Santamarine had MBCs of 128?μg/mL against the H3Rv and 104-2010 Mtb strains and MICs of 128?μg/mL against the H37Rv, 366-2009 and 104-2010 Mtb strains. We also isolated 1,10-epoxyparthenolide but only showed mycobacteriostatic activity (MIC 128?μg/mL) against the Mtb strain. Compounds were tested against the L929 cell line and the calculated selectivity index was <1.

Discussion and conclusions: This is the first report of the mycobactericidal activity of these compounds against clinical Mtb strains. It is also the first report of the isolation of 1,10-epoxyparthenolide from A. confertiflora. The anti-mycobacterial activity of A. confertiflora was attributed to the SQLs identified.     

Novel 3‐Substituted Ocotillol‐Type Triterpenoid Derivatives as Antibacterial Candidates

Plant‐derived triterpenoid saponins are involved in the plant defense system by targeting bacterial membranes. A series of ocotillol‐type triterpenoid derivatives were synthesized starting from PPD, one of the main components of Panax ginseng and their antibacterial activity against several representative bacteria were evaluated. Compounds 5 and 11 exhibited excellent antibacterial activity with MIC values of 1 μg/mL against Staphylococcus aureus and 8 μg/mL and 4 μg/mL against Bacillus subtilis, respectively. Furthermore, when compounds 5 and 11 were combined with two commercial antibiotics kanamycin and chloramphenicol, they showed strong synergistic activity at sub‐MIC levels against S. aureus USA300 and B. subtilis 168. Moreover, chloramphenicol turned from a bacteriostatic to a bactericidal agent when combined with compound 11 against B. subtilis 168.     

Design and synthesis of 4′‐((5‐benzylidene‐2,4‐dioxothiazolidin‐3‐yl)methyl)biphenyl‐2‐carbonitrile analogs as bacterial peptide deformylase inhibitors

Herein, we report the synthesis and screening of 4′‐((5‐benzylidene‐2,4‐dioxothiazolidin‐3‐yl)methyl)biphenyl‐2‐carbonitrile analogs 11(a–j) as bacterial peptide deformylase (PDF) enzyme inhibitors. The compounds 11b (IC₅₀ value = 139.28 μm ), 11g (IC₅₀ value = 136.18 μm ), and 11h (IC₅₀ value = 131.65 μm ) had shown good PDF inhibition activity. The compounds 11b (MIC range = 103.36–167.26 μg/mL), 11g (MIC range = 93.75–145.67 μg/mL), and 11h (MIC range = 63.61–126.63 μg/mL) had also shown potent antibacterial activity when compared with standard ampicillin (MIC range = 100.00–250.00 μg/mL). Thus, the active derivatives were not only PDF inhibitors but also efficient antibacterial agents. To gain more insight on the binding mode of the compounds with PDF enzyme, the synthesized compounds 11(a–j) were docked against PDF enzyme of Escherichia coli and compounds exhibited good binding properties. The results suggest that this class of compounds has potential for development and use in future as antibacterial drugs.     

Antifungal,anticancer, and docking studies of colchiceine complexes with monovalent metal cation salts

Complexes of colchiceine with monovalent cation perchlorates and iodides have been obtained and characterized by spectroscopic methods. DFT and spectroscopic studies reveal that the dihedral angle ω_{1‐1a‐12‐12a}, crucial for colchicine biological mechanism of action, that is, binding to tubulins depends on the diameter of the complexed metal cation. Biological tests indicated no antifungal properties of colchicine (it was active only toward A.pullulans), in contrast to its derivative—(colchiceine). Complexation of colchiceine with metal cations improved significantly the antifungal potency, even below MIC <1 μg/ml. The colchiceine complexes were more potent than colchiceine, and some of them were even more potent than the fungicidal standard IPBC. The highest potency of colchiceine complexes was noted against A. pullulans (MIC = 0.5 μg/ml). In contrast to the findings concerning antifungal potency, the anticancer studies showed complexes of colchicine more active (~IC₅₀ = 2 nM) than those of colchiceine (~IC₅₀ = 6 μM). MDA‐MB‐231 breast cancer cell lines and human lung fibroblasts CCD39Lu were also tested.     

Synthesis and antibacterial activity of N-[5-chlorobenzylthio-1,3,4-thiadiazol-2-yl] piperazinyl quinolone derivatives

A series ofN-[5-(chlorobenzylthio)-1,3,4-thiadiazol-2-yl] piperazinyl quinolone derivatives (4a-1) have been synthesized by reaction of piperazinyl quinolones with 5-chloro-2-(chloroben-zylthio)-1,3,4-thiadiazoles. Their structures were confirmed by elemental analysis, IR and NMR spectra. The antibacterial activities of4a-1 against a variety of Gram-positive and Gram-negative bacteria were determined. Several compounds showed a good antibacterial activity against Gram-positive bacteria among which, compound 4e with a 2-chlorobenzylthio moiety in ciprofloxacin derivative, exhibited high activities againstStaphylococcus aureus andStaphylococcus epidermidis (MIC=0.06 μg/mL). The structure-activity relationship (SAR) study revealed that the position of chlorine atom on benzyl moiety would dramatically affect the antibacterial activities of the synthesized compounds.     

Antimicrobial activity of pomegranate fruit constituents against drug-resistant Mycobacterium tuberculosis and β-lactamase producing Klebsiella pneumoniae

Abstract

Context: The global surge in multi-drug resistant bacteria and the imminence of tuberculosis pandemic necessitate alternative therapeutic approaches to augment the existing medications. Pomegranate, the fruit of Punica granatum Linn. (Punicaceae), widely recognized for potency against a broad spectrum of bacterial pathogens, deserves further investigation in this respect.

Objective: This study determines the therapeutic potential of pomegranate juice, extracts of non-edible peel prepared with methanol/water, and its four polyphenolic constituents, namely caffeic acid, ellagic acid, epigallocatechin-3-gallate (EGCG) and quercetin, against drug-resistant clinical isolates.

Materials and methods: Phenotypic characterisation of Mycobacterium tuberculosis, extended-spectrum β-lactamase (ESBL) and KPC-type carbapenemase producing Klebsiella pneumoniae was performed by biochemical and molecular methods. Resistance profiles of M. tuberculosis and K. pneumoniae were determined using LJ proportion and Kirby–Bauer methods, respectively. Pomegranate fruit extracts, and the compounds, were evaluated at a dose range of 1024–0.5?µg/mL, and 512–0.25?µg/mL, respectively, to determine minimum inhibitory (MIC) and bactericidal concentrations (MBC) against the drug-resistant isolates by the broth micro-dilution method.

Results: The peel extracts exhibited greater antimycobacterial activity (MIC 64–1024?μg/mL) than the potable juice (MIC 256?-?>?1024?μg/mL). EGCG and quercetin exhibited higher antitubercular (MIC 32–256?μg/mL) and antibacterial (MIC 64–56?μg/mL) potencies than caffeic acid and ellagic acid (MIC 64–512?μg/mL).

Discussion and conclusion: The pomegranate fruit peel and pure constituents were active against a broad panel of M. tuberculosis and β-lactamase producing K. pneumoniae isolates. EGCG and quercetin need further investigation for prospective application against respiratory infections.     

Antifungal properties of hypericin,hypericin tetrasulphonic acid and fagopyrin on pathogenic fungi and spoilage yeasts

Context: The role of hypericin-mediated photodynamic antimicrobial properties on pathogenic fungi and photodynamic therapy for human cancer cells is known. Antifungal properties of Hypericum perforatum L. (Hypericaceae) and Fagopyrum esculentum Moench. (Polygonaceae) extracts were also studied. The different polarities of solvents can cause complication in the identification of antifungal effects of separate biologically active compounds. In recent experimental work, we compared antifungal properties of purified hypericin, hypericin tetrasulphonic acid (hypericin?+?S) and fagopyrin, which is analogue of hypericin.

Objective: The antifungal properties of aromatic polyketide derivatives such as hypericin, hypericin?+?S and fagopyrin on the selected pathogenic fungi and spoilage yeasts have been studied.

Materials and methods: The antifungal properties of hypericin, hypericin?+?S and fagopyrin were determined using the broth microdilution method against a set of pathogenic fungi and spoilage yeasts including: Microsporum canis, Trichophyton rubrum, Fusarium oxysporum, Exophiala dermatitidis, Candida albicans, Kluyveromyces marxianus, Pichia fermentans and Saccharomyces cerevisiae. The tested concentrations of hypericin, hypericin?+?S and fagopyrin ranged from 750 to 0.011?μg/mL and MIC values were evaluated after 48?h incubation at 30?°C.

Results: The results confirm different antifungal properties of hypericin, hypericin?+?S and fagopyrin on the selected pathogenic fungi and spoilage yeasts. For pathogenic fungi, the minimum inhibitory concentrations of hypericin ranged 0.18–46.9?μg/mL, hypericin?+?S 0.18–750?μg/mL and fagopyrin 11.7–46.9?μg/mL. For spoilage yeasts, the MICs of hypericin and hypericin?+?S ranged 0.18–46.9 and 0.011–0.73?μg/mL, respectively.

Discussion and conclusion: The results obtained herein indicate that various chemical structures of hypericin, hypericin?+?S and fagopyrin can develop different antifungal properties.     

Screening of in vitro antimicrobial activity of plants used in traditional Indonesian medicine

Context: In many regions of Indonesia, there are numerous traditional herbal preparations for treatment of infectious diseases. However, their antimicrobial potential has been poorly studied by modern laboratory methods.

Objective: This study investigates in vitro antimicrobial activity of 49 ethanol extracts from 37 plant species used in Indonesian traditional medicine for treatment against Candida albicans, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus.

Materials and methods: The plants were collected from the Biopharmaca collection garden, Bogor, Indonesia. The plant material was dried, finely grounded, extracted using ethanol, concentrated, and the dried residue was dissolved in 100% DMSO. Antimicrobial activity was determined in terms of a minimum inhibitory concentration (MIC) using a broth microdilution method in 96-well microplates.

Results: The extract of Orthosiphon aristatus (Blume) Miq. (Lamiaceae) leaf produced the strongest antimicrobial effect, inhibiting the growth of C. albicans (MIC 128?μg/mL), S. aureus (MIC 256?μg/mL), E. faecalis (MIC 256?μg/mL) and P. aeruginosa (MIC 256?μg/mL). The leaf extract of Woodfordia floribunda Salisb. (Lythraceae) also exhibited significant effect against C. albicans (MIC 128?μg/mL), S. aureus (MIC 256?μg/mL) and E. faecalis (MIC 256?μg/mL). Rotheca serrata (L.) Steane &; Mabb. (Lamiaceae) leaf extract inhibited the growth of S. aureus (MIC 256 µg/mL) and C. albicans (MIC 256 µg/mL).

Discussion and conclusions: The leaf extract of O. aristatus and W. floribunda exhibited a significant anti-candidal effect. Therefore, both of these plants can serve as prospective source materials for the development of new anti-candidal agents.     

A Facile One‐Pot Synthesis of 2‐Arylamino‐5‐Aryloxylalkyl‐1,3,4‐Oxadiazoles and Their Urease Inhibition Studies

A one‐pot method for the synthesis of structural type urease inhibitors, 2‐amino‐1,3,4‐oxadiazoles, was developed. The structures of the compounds were established using spectroanalytical techniques and unambiguously confirmed by single‐crystal X‐ray analysis of compound 3o . The synthesized compounds were tested against jack beans urease, and most of the compounds ( 3c , 3g , 3j , 3k , 3n , 3r – 3v ) were found more active than the standard. The most potent compound ( 3u ) had an IC₅₀ value of 6.03 ± 0.02 μm as compared to the IC₅₀ value of the standard (thiourea; 22.0 ± 1.2 μm ). The prominent urease inhibition activity of these compounds may serve as an important finding in the development of less toxic and more potent antiulcer drugs. The compounds were also investigated against four bacterial strains, and some of the compounds ( 3g and 3r ) were found more potent than the standard drug (ciprofloxacin) against all the tested strains. The MIC value for compound 3g was 0.156 μmol/mL against the tested bacterial strains.     

Bioassay-guided fractionation and identification of α-amylase inhibitors from Syzygium cumini leaves

Context: Pancreatic α-amylase and α-glucosidase inhibitors serve as important strategies in the management of blood glucose. Even though Syzygium cumini (L.) Skeels (Myrtaceae) (SC) is used extensively to treat diabetes; scientific evidence on antidiabetic effects of SC leaves is scarce.

Objective: SC leaf extract was investigated for α-amylase inhibitory effect and continued with isolation and identification of α-amylase inhibitors.

Materials and methods: Bioassay-guided fractionation was conducted using in vitro α-amylase inhibitory assay (with 20–1000?μg/mL test material) to isolate the inhibitory compounds from ethyl acetate extract of SC leaves. Structures of the isolated inhibitory compounds were elucidated using ¹H NMR and ¹³C NMR spectroscopic analysis and direct TLC and HPLC comparison with authentic samples. Study period was from October 2013 to October 2015.

Results: An active fraction obtained with chromatographic separation of the extract inhibited porcine pancreatic α-amylase with an IC₅₀ of 39.9?μg/mL. Furthermore, it showed a strong inhibition on α-glucosidase with an IC₅₀ of 28.2?μg/mL. The active fraction was determined to be a 3:1 mixture of ursolic acid and oleanolic acid. Pure ursolic acid and oleanolic acid showed IC₅₀ values of 6.7 and 57.4?μg/mL, respectively, against α-amylase and 3.1 and 44.1?μg/mL respectively, against α-glucosidase.

Discussion and conclusions: The present study revealed strong α-amylase and α-glucosidase inhibitory effects of ursolic acid and oleanolic acid isolated from SC leaves for the first time validating the use of SC leaves in antidiabetic therapy.     

Preliminary studies on the antibacterial activity of crude extracts and alkaloids from species of Aspidosperma

Screening tests of hydroethanolic crude extracts of six species of Aspidosperma (Apocynaceae) against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, and Pseudomonas aeruginosa were performed. Aspidosperma ramiflorum Muell. Arg. showed good activity against Bacillus subtilis with MIC and MBC of 15.7 and 125?μg/mL, moderate activity against Staphylococcus aureus with MIC and MBC of 250 and 500?μg/mL, and weak activity against Escherichia coli with MIC and MBC of 1000?μg/mL. Aspidosperma pyricolum Muell. Arg. (MIC/MBC 125/250?μg/mL) and Aspidosperma olivaceum Muell. Arg. (MIC/MBC 250/?>?1000?μg/mL) displayed moderate antibacterial activity against Bacillus subtilis. Separation of the crude extract of Aspidosperma ramiflorum was performed according to the usual acid–base process, which produces alkaloid mixtures and closely related metabolites. The basic fraction was active against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli, with MICs of 31.2, 62.5, and 250?μg/mL, respectively. The basic fractions were more active than the acid fractions, probably because they contained some active alkaloids and/or closely related metabolites absent from the other fractions, or they contained a higher concentration of these active compounds.     

Antibacterial and Antifungal Activities of the Constituents of Flemingia paniculata.

Abstract

A salicylic acid derivative (1), a cinnamaldehyde (2), and six isoflavones (3–8) from the stem bark of Flemingia paniculata. Wall. (Leguminosae) were tested for antibacterial (both Gram-positive and Gram-negative) and antifungal activities. All the compounds showed significant activities against the test organisms having MIC values in the range of 1.57–200 μ g/mL. The highest potency (MIC = 1.57 μ g/mL) was exhibited by 3 against Staphylococcus aureus..     

Design,synthesis and biological evaluation of novel quinoline‐based carboxylic hydrazides as anti‐tubercular agents

In this study, seventeen novel quinoline‐based carboxylic hydrazides were designed as potential anti‐tubercular agents using molecular hybridization approach and evaluated in‐silico for drug‐likeness behavior. The compounds were synthesized, purified, and characterized using spectral techniques (like FTIR, ¹H NMR, and Mass). The in‐vitro anti‐tubercular activity (against Mycobacterium tuberculosisH37Ra) and cytotoxicity against human lung fibroblast cells were studied. Among the tested hydrazides, four compounds ( 6h , 6j , 6l, and 6m ) exhibited significant anti‐tubercular activity with MIC values below 20 μg/mL. The two most potent compounds of the series, 6j and 6m exhibited MIC values 7.70 and 7.13 μg/mL, respectively, against M. tuberculosis with selectivity index >26. Structure–activity relationship studies were performed for the tested compounds in order to explore the effect of substitution pattern on the anti‐tubercular activity of the synthesized compounds.     

Antibacterial activities of chemical constituents from the aerial parts of Hedyotis pilulifera

Context: Hedyotis pilulifera (Pit.) T.N. Ninh (Rubiaceae) has been used in Vietnamese ethnomedicine; the methanol extract exhibited antibacterial activity in our preliminary screening.

Objectives: In this study, compounds from H. pilulifera were isolated and their antibacterial activity in vitro was evaluated.

Materials and methods: The aerial parts of H. pilulifera (1.4?kg) were extracted with MeOH, suspended in water and ethyl acetate extract was chromatographed on a silica gel column. The structures of isolated compounds were elucidated by the combination analyses of spectroscopy including 1D-, 2D-NMR, HRMS and in comparison with the reported NMR data in the literature. All isolated compounds were evaluated for inhibitory effect using the microdilution method toward Staphylococcus aureus, Bacillus subtilis and Mycobacterium smegmatis, and MIC values were determined.

Results: Twenty compounds were isolated, including five triterpenoids, two steroids, two aromatic compounds, three fatty acids, one quinone derivative, one lignan glycoside, one ceramide and five glycolipids. Among these, oleanolic acid showed significant antibacterial activity against M. smegmatis with the MIC value of 2.5?μg/mL. Remarkably, rotungenic acid showed strong activity against S. aureus, B. subtilis, M. smegmatis with MIC values of 2.5, 2.5 and 1.25?μg/mL, respectively. Rotundic acid exhibited significant antibacterial activity against B. subtilis with the MIC value of 5?μg/mL. To the best of our knowledge, the antibacterial activity of rotungenic acid, stigmast-4-ene-3,6-dione and (2S,3S,4R,2′R)-2-(2′-hydroxytetracosanoylamino) octadecane-1,3,4-triol was reported for the first time.

Conclusions: Oleanolic acid, rotungenic acid, and rotundic acid were considered to be useful for developing new antimicrobial therapeutic agents for human.     

Anti-cryptococcal activity of ethanol crude extract and hexane fraction from Ocimum basilicum var. Maria bonita: mechanisms of action and synergism with amphotericin B and Ocimum basilicum essential oil

Context: Ocimum basilicum L. (Lamiaceae) has been used in folk medicine to treat headaches, kidney disorders, and intestinal worms.

Objective: This study evaluates the anti-cryptococcal activity of ethanol crude extract and hexane fraction obtained from O. basilicum var. Maria Bonita leaves.

Materials and methods: The MIC values for Cryptococcus sp. were obtained according to Clinical and Laboratory Standards Institute in a range of 0.3–2500?μg/mL. The checkerboard assay evaluated the association of the substances tested (in a range of 0.099–2500?μg/mL) with amphotericin B and O. basilicum essential oil for 48?h. The ethanol extract, hexane fraction and associations in a range of 0.3–2500?μg/mL were tested for pigmentation inhibition after 7?days of treatment. The inhibition of ergosterol synthesis and reduction of capsule size were evaluated after the treatment with ethanol extract (312?μg/mL), hexane fraction (78?μg/mL) and the combinations of essential oil?+?ethanol extract (78?μg/mL?+?19.5?μg/mL, respectively) and essential oil?+?hexane fraction (39.36?μg/mL?+?10?μg/mL, respectively) for 24 and 48?h, respectively.

Results: The hexane fraction presented better results than the ethanol extract, with a low MIC (156?μg/mL against C. neoformans T₄₄₄ and 312?μg/mL against C. neoformans H99 serotype A and C. gattii WM779 serotype C). The combination of the ethanol extract and hexane fraction with amphotericin B and essential oil enhanced their antifungal activity, reducing the concentration of each substance needed to kill 100% of the inoculum. The substances tested were able to reduce the pigmentation, capsule size and ergosterol synthesis, which suggest they have important mechanisms of action.

Conclusions: These results provide further support for the use of ethanol extracts of O. basilicum as a potential source of antifungal agents.     

In vitro activities of the newly synthesised ER-2 against clinical isolates of Mycobacterium tuberculosis susceptible or resistant to antituberculosis drugs

Two hundred isolates of Mycobacterium tuberculosis were evaluated for their susceptibility to a newly synthesised quinolone derivative, ER-2, compared with ciprofloxacin, ofloxacin, levofloxacin and moxifloxacin. ER-2 and moxifloxacin showed the greatest activity [MIC for 90% of strains tested (MIC₉₀) = 0.5 μg/mL], although levofloxacin and ciprofloxacin showed good activity with an MIC₉₀ of 1 μg/mL. More importantly, ER-2 showed excellent activity against M. tuberculosis H37Rv both in the lungs and spleen of mice, indicating the potential therapeutic value of ER-2 against M. tuberculosis.     

A new p-hydroxybenzoic acid derivative from an endophytic fungus Penicillium sp. of Nerium indicum

A new p-hydroxybenzoic acid derivative named 4-(2′R, 4′-dihydroxybutoxy) benzoic acid (1) was isolated from the fermentation of Penicillium sp. R22 in Nerium indicum. The structure was elucidated by means of spectroscopic (HR-ESI-MS, NMR, IR, UV) and X-ray crystallographic methods. The antibacterial and antifungal activity of compound 1 was tested, and the results showed that compound 1 revealed potent antifungal activity against Colletotrichum gloeosporioides, Alternaria alternata, and Alteranria brassicae with MIC value of 31.2 μg/ml.