In vitro antimicrobial activity of extracts and compounds isolated from Cladonia uncialis

Heptane (Hep), diethyl ether (Et₂O), acetone (Me₂CO) and methanolic (MeOH) extracts, as well as ( ? )-usnic acid and squamatic acid, were obtained from thallus of Cladonia uncialis (Cladoniaceae). The antimicrobial activities of these extracts, ( ? )-usnic acid and squamatic acid, were tested against reference strains: Staphylococcus aureus, Escherichia coli and Candida albicans. In addition, Me₂CO extract was analysed against 10 strains of Methicillin-resistant S. aureus (MRSA) isolated from patients. All extracts exerted antibacterial activity against the reference strain S. aureus, comparably to chloramphenicol [minimum inhibitory concentration (MIC) = 5.0 μg/mL]. The Me₂CO extract exhibited the strongest activity against S. aureus (MIC = 0.5 μg/mL), higher than ( ? )-usnic acid, whereas squamatic acid proved inactive. The Me₂CO extract showed potent antimicrobial activity against MRSA (MIC 2.5–7.5 μg/mL). Also no activity of C. uncialis extracts against E. coli and C. albicans was observed.     

In vitro pharmacological screening of three newly synthesised pyrimidine derivatives

The antibacterial and antifungal activities of three new pyrimidine derivatives, namely, 2,6-bis(4,6-dimethylpyrimidin-2-ylthio)benzene-1,4-diol (1),3,5-bis(4,6-dimethylpyrimidin-2-ylthio)-2-methylbenzene-1,4-diol (2) and 3,5-bis(4,6-dimethylpyrimidin-2-ylthio)-2-methoxybenzene-1,4-diol (3), synthesised by electrochemical method are presented here. The compounds were screened for their activities against Gram-positive and Gram-negative bacteria, Bacillus subtilis, Staphylococcusaureus, Escherichia coli and a pathogenic fungus Aspergillus niger. The results show that these compounds have significant activity against these bacteria and fungus. The minimum inhibitory concentration of compound 1 was determined as 62.5 μg/mL against B. subtilis, 125 μg/mL against E. coli and 250 μg/mL against S. aureus establishing its promising activities higher than susceptible ranges.     

Flavonoids from Plinia cauliflora (Mart.) Kausel (Myrtaceae) with antifungal activity

Plinia cauliflora is a plant species with edible fruits but its chemical composition is not totally known yet although former studies showed its potential as antifungal agent. This work aimed the chemical analysis of the leaves, the activity against fungi species and evaluated cytotoxicity. Extract was obtained with 70% ethanol. An ethyl acetate fraction was obtained and glycosylated quercetin and myricetin were isolated. Samples were tested against Candida species, dermatophytes and entomopathogenic fungi. Cytotoxicity was evaluated against fibroblast cells. Extract showed good activity against C. albicans (minimum inhibitory concentration at 156 μg/mL), C. parapsilosis (78 μg/mL), C. krusei (19 μg/mL), Trichophyton rubrum (78 μg/mL) and Microsporum canis (156 μg/mL). Isolated compounds were more active against C. krusei and T. rubrum. The extract, which was the more active sample, demonstrated low cytotoxic effect and encourage more studies against rising non-albicans species and dermatophyte T. rubrum.     

Chemical composition and biological activities of Iranian Achillea wilhelmsii L. essential oil: a high effectiveness against Candida spp. and Escherichia strains

In the case of Achillea wilhelmsii, 30 compounds were identified representing 94.48% of the total oil with a yield of 0.82% w/w. The major constituents of the oil were described as α-thujene (6.11%), α-pinene (5.11%), sabinene (5.23%), p-cymene (7%), 1,8-cineole (6%), linalool (10%), camphor (8.43%), thymol (18.98%) and carvacrol (20.13%). A. wilhelmsii oil exhibited higher antibacterial and antifungal activities with a high effectiveness against Escherichia coli and Candida albicans with the lowest minimum inhibitory concentration and minimum bactericidal concentration/minimum fungicidal concentration value (2 ± 0.0–2 ± 0.0 g/mL, 1 ± 0.5–1 ± 0.5 g/mL), respectively. Results showed that A. wilhelmsii oil exhibits a higher activity in each antioxidant system with a special attention for β-carotene bleaching test (IC₅₀: 19 μg/mL) and reducing power (EC₅₀: 10 μg/mL). Antioxidant activity-guided fractionation of the oil was carried out by TLC-bioautography screening and fractionation resulted in the separation of main antioxidant compounds which were identified as thymol (65%) and carvacrol (19%). In conclusion, these results support the use of the essential oil and its main compounds for their antioxidant properties and antimicrobial activity.     

Antimicrobial compounds from root,stem bark and seeds of Melia volkensii

Three compounds, toosendanin (1), kulactone (2) and scopoletin (3), were isolated from either the root bark and/or the stem bark of Melia volkensii. Their structures were determined on the basis of spectroscopic data generated and by comparison with data from the literature. 1 and 2, isolated for the first time from M. volkensii, exhibited significant (p < 0.05) activity against Escherichia coli with minimum inhibitory concentration of 12.5 μg/mL, close to that of neomycin (6.25 μg/mL). The compounds also exhibited high activity against Aspergillus niger (MIC 6.25 μg/mL compared to 2.5 μg/mL for clotrimazole). Dichloromethane and methanol seed, hexane stem bark and methanol root bark extracts exhibited activities towards Escherichia coli, Staphylococcus aureus, Aspergillus niger and Plasmodium falciparum, respectively. Antimicrobial activity of the plant towards A. niger, P. falciparum and S. aureus is reported for the first time in the current work.     

Composition and antimicrobial activity of the essential oil from the branches of Jacaranda cuspidifolia Mart. growing in Sichuan,China

This study represents the first report on the chemical composition and antimicrobial activity of the essential oil from the branches of Jacaranda cuspidifolia Mart. Thirty-three compounds were identified by Gas Chromatography-Mass Spectrometry (GC-MS) and the major constituents of the essential oil were Palmitic acid (31.36%), (Z) ? 9,17-Octadecadienal (12.06%), Ethyl palmitate (3.81%), Perhydrofarnesyl acetone (2.07%), γ-Maaliene (1.88%), and Cedro (1.42%) and 9,12-Octadecadienoic acid ethyl ester (1.42%). The in vitro antimicrobial activities of the essential oil were evaluated by the disc diffusion method, and the inhibition zones against Escherichia coli, Staphylococcus aureus and Candida albicans were 7.10, 8.20 and 7.25 mm, respectively. The oil showed moderate activities against E. coli, S. aureus and C. albicans with minimum inhibition concentration (MIC) values of 17.3 mg/mL, 12.9 mg/mL and 16.0 mg/mL, respectively.     

GC×GC/qMS analyses of Campomanesia guazumifolia (Cambess.) O. Berg essential oils and their antioxidant and antimicrobial activity

The present study investigated the essential oil obtained from Campomanesia guazumifolia (Cambess.) O. Berg, an aromatic plant used in Brazilian folk medicine. The chemical composition was performed by GC×GC/qMS. The antioxidant and antimicrobial activities were evaluated by DPPH and BCB and, MIC assays, respectively. Sixty-eight compounds were identified in the oil, where the major compounds were bicyclogermacrene (15%), globulol (5%) and spathulenol (5%). Sesquiterpene hydrocarbons (29 compounds) and oxygenated sesquiterpenes (20 compounds) were the most representative classes of terpenes. DPPH (IC₅₀ value 26.1 ± 0.5 μg/mL) and BCB (68.3 ± 1.5%) values indicated a significant antioxidant activity. The essential oil strongly inhibited Staphylococcus aureus (MIC 15 ± 0.1 μg/mL), Escherichia coli (MIC 25 ± 0.2 μg/mL) and Candida albicans (MIC 5 ± 0.1 μg/mL). The results give a deeper understanding of the chemical composition and report for the first time the antioxidant and antimicrobial potential of the C. guazumifolia essential oil.     

Antimicrobial and Cytotoxicity Properties of 2,3-Dihydroxy-9,10-Anthraquinone Isolated from Streptomyces galbus (ERINLG-127)

Streptomyces galbus ERINLG-127 was isolated from the soil samples of the Marapalam forest, Nilgiris, India. The ethyl acetate extract was subjected to activity-guided fractionation by column chromatography over silica gel. This led to the isolation of 2,3-dihydroxy-9,10-anthraquinone as the active principle. The compound showed good antimicrobial activity against tested bacteria and fungi. The minimum inhibitory concentration values of isolated compound were 12.5 μg/mL against Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhimurium, K. pneumoniae (ESBL-3971), K. pneumoniae (ESBL-3894) and Staphylococcus aureus (MRSA). The compound showed prominent cytotoxic activity in vitro against A549 lung adenocarcinoma cancer cell line. It showed 75.1 % activity at the dose of 100 μg/mL with IC₅₀ value of 60 μg/mL. The isolated compound was subjected to molecular docking studies for the inhibition of TtgR and Topoisomerase IV enzymes which are targets for antimicrobials. Docking studies of the compound showed low docking energy indicating its usefulness as antimicrobial agent.     

Chemical composition,antioxidant and antimicrobial activity of the essential oil from the leaves of Macleaya cordata (Willd) R. Br.

The essential oil from the leaves of Macleaya cordata R.Br. obtained by hydrodistillation was analysed by gas chromatography/mass spectrometry. Sixty-eight compounds consisting of up to 92.53% of the essential oil were identified. Antioxidant activities of the essential oil were evaluated by using DPPH radical scavenging and β-carotene–linoleic acid assays. The essential oil showed moderate antioxidant activity. In addition, the essential oil exhibited potential antimicrobial activity against all tested microorganisms, with diameters of inhibition zones ranging from 8.7 ± 0.5 to 17.2 ± 1.2 mm and minimum inhibitory concentration values from 125 to 500 μg/mL. We selected the most sensitive bacterium Staphylococcus aureus as model to observe of the action of essential oils of M. cordata on the membrane structure by scanning electron microscopy. The treated cell membranes were damaged severely. The results presented here indicate that the essential oil of M. cordata may be potential sources of antioxidant and antimicrobial agents in the future.     

Antifungal activity of cinnamic acid and benzoic acid esters against Candida albicans strains

Candida albicans is an important opportunistic fungal pathogen capable of provoking infection in humans. In the present study, we evaluated the antifungal effect of 23 ester derivatives of the cinnamic and benzoic acids against 3 C. albicans strains (ATCC-76645, LM-106 and LM-23), as well as discuss their Structure–Activity Relationship (SAR). The antifungal assay results revealed that the screened compounds exhibited different levels of activity depending on structural variation. Among the ester analogues, methyl caffeate (5) and methyl 2-nitrocinnamate (10) were the analogues that presented the best antifungal effect against all C. albicans strains, presenting the same MIC values (MIC = 128 μg/mL), followed by methyl biphenyl-2-carboxylate (21) (MIC = 128, 128 and 256 μg/mL for C. albicans LM-106, LM-23, and ATCC-76645, respectively). Our results suggest that certain molecular characteristics are important for the antifungal action.     

Modulation of antibiotic activity by the hydroalcoholic extract from leaves of Caryocar coriaceum WITTM

The aim of this study was to identify the presence of tannins, phenols and flavonoids on the hydroalcoholic extract of Caryocar coriaceum leaves (HECCL) and to determine the antioxidant and antibacterial activity of this extract. The extract was tested alone (1024–1 μg/mL) or associated (MIC/8) with several antibiotics in order to identify any antibacterial activity against multiresistant bacterial strains (Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa). The existence of tannins, total phenols (901.31 mg/g) and flavonoids (89.68 mg/g) was confirmed in the HECCL. The presence of rutin and quercetin were confirmed by Thin-layer chromatography (TLC). Using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method, the antioxidant activity of the extract (9 μg/mL) was determined. Moreover, the Minimum Inhibitory Concentration (MIC) value found for HECCL was 1024 μg/mL and the association between HECCL (MIC/8) with benzylpenicillin significantly changed its minimum inhibitory concentration from 2500 to 625 μg/mL against E. coli.     

A new anthraquinone from Morinda elliptica Ridl.

A new anthraquinone, morinquinone, together with 18 known anthraquinones were isolated from the stems of Morinda elliptica Ridl. Their structures were elucidated on the basis of spectroscopic data. They each showed weak inhibitory activity against a susceptible strain of Staphylococcus aureus and a methicillin-resistant S. aureus. Damnacanthal was effective against Microsporum gypseum (MIC 1 μg/mL). Lucidin was active against Entamoeba histolytica (MIC 31.25 μg/mL) and Giardia intestinalis (MIC 7.8 μg/mL).     

A new antimicrobial and radical-scavenging glycoside from Paullinia pinnata var. cameroonensis

A new glycoside, pinnatoside A (1), together with two known compounds (2 and 3), were isolated from the stems of Paullinia pinnata. Their structures were elucidated on the basis of extensive spectroscopic analysis and chemical methods. Compound 1 showed significant antibacterial activity with a minimum inhibitory concentration (MIC) value of 1.56 μg/mL against Escherichia coli, and 2 displayed significant antibacterial activity with a MIC value of 1.56 μg/mL against Enterobacter aerogenes and E. coli. Equally, compound 1 exhibited the best radical-scavenging activity (RSa₅₀ = 25.07 ± 0.49 μg/mL).     

Antibacterial alkaloids from Artabotrys crassifolius Hook.f. & Thomson

Chloroform extract of bark of Artabotrys crassifolius Hook.f. & Thomson exhibited antibacterial activities against both American Type Culture Collection and clinical bacterial strains in vitro with zones of inhibition ranging from 7 to 14 mm. Further analysis of this extract yielded artabotrine, liridine, lysicamine and atherospermidine. Artabotrine displayed a broad array of antibacterial activity mostly against Gram-positive bacteria with minimum inhibitory concentration (MIC) values ranging from 1.25 μg/mL to 5 μg/mL. Of note, artabotrine, liridine and lysicamine are bactericidal against Gram-negative extended-spectrum beta-lactamase-producing Klebsiella with MIC values equal 2.5, 2.5 and 10 μg/mL, respectively, and minimum bactericidal concentrations values equal to 2.5, 5 and 20 μg/mL.     

A new antibacterial lupane ester from the seeds of Acokanthera oppositifolia Lam.

As a part of ongoing investigation of Acokanthera oppositifolia (Lam.) Codd., four compounds were isolated from its seeds, a new compound; lup-20(29)-en-3β-O-(3′-β-hydroxy) palmitate (1), three known compounds; a triterpene; lupeol (2), a cardiac glycoside; acovenoside A (3) and a sterol; β-sitosterol (4). Their structures were investigated using 1D & 2D- ¹H and ¹³CNMR spectroscopy. Antimicrobial potential of the compounds was evaluated against 10 microorganisms responsible for endocarditis. The minimum inhibitory concentration (MIC) of the compounds was determined using broth microdilution method. The new compound (1) evidenced significant antibacterial activity especially aganist Pseudomonas aeruginosa with (MIC 7.81 μg/ml). Lupeol (2) exhibited remarkable antimicrobial activity against Methicillin-resistant Staphylococcus aureus, Aspergillus fumigates and Candida albicans (MIC 3.9, 0.24 and 3.9 μg/ml, respectively). On the other hand, acovenoside A (3) inhibited the growth of Escherichia coli (MIC 0.98 μg/ml). We herein present the potential of A. oppositifolia as a cardioprotective agent against the microorganisms responsible for endocarditis.     

Anti-infective assessment of Senecio smithioides (Asteraceae) and isolation of 9-oxoeuryopsin,a furanoeremophilane-type sesquiterpene with antiplasmodial activity

The search for anti-infective activity in the antipyretic plant Senecio smithioides was conducted. Petroleum ether (PE), dichloromethane (CH₂Cl₂), ethyl acetate (EtOAc) and hydroethanolic (96% EtOH) extracts, and compounds 9-oxoeuryopsin (1), epoxydecompostin (2) and senecionine (3) were obtained from the aerial parts. All extracts and 1 were tested against chloroquine-resistant strain of Plasmodium falciparum (ref. chloroquine), Trypanosoma cruzi (ref. nifurtimox), Leishmania braziliensis, Leishmania amazonensis and Leishmania donovani (ref. pentamidine), Staphylococcus aureus and Escherichia coli (ref. gentamicin) and, Neurospora crassa and Candida albicans (ref. ketoconazole). The PE extract exhibited the strongest in vitro activity against Plasmodium falciparum IC₅₀ < 1.0 μg/mL. 1 was established as a potent antiplasmodial compound with an IC₅₀ = 1.2 μg/mL, 5.2 μM. Other antiparasitic activities were recorded for all extracts and 1. Antibacterial and antifungal activity was negligible.     

Chemical Composition Analysis and Antimicrobial Screening of the Essential Oil of a Rare Plant from Jordan: Ducrosia flabellifolia

The composition of the essential oil isolated from the fresh and dry leaves of Ducrosia flabellifolia Boiss. (Apiaceae) was determined by gas chromatography and gas chromatography–mass spectrometry using hydrodistillation and solid phase microextraction (SPME). The hydrodistilled oil of the fresh leaves yielded 38 components, accounting for 98.67% of the total oil content, while thirty components were detected from the fresh leaves by solid phase microextraction (94.85%). Fifty-one and 36 components were identified in the hydrodistilled and SPME oils of the dried leaves amounting to 98.78% and 94.52%, respectively. A total of 25 components accounting for 97.24% of the total composition were characterized in the SPME oil of the fresh flowers. Aliphatic compounds predominated in the volatile fractions of the leaves and flowers of both methods with n-decanol, n-decanal, and dodecanal as the main constituents. The α- and ß-pinene were the major monoterpenoids in the oils. The hydrodistilled oil was screened for its antimicrobial and antioxidant activities. The minimal inhibitory concentration of the volatile oil was determined using a microdilution method in 96 well plates against a panel of gram (+), gram (?) bacteria, and fungi. Overnight cultures of reference strains of Candida albicans, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were used as test microorganisms. The oil exhibited the best activity against C. albicans (MIC 234 µg/mL) and S. aureus (MIC 234 µg/mL) whereas weak activity was detected against E. coli and P. aeruginosa. No antioxidant activity could be detected.     

New coumarin derivatives from Ferula pseudalliacea with antibacterial activity

In this study, the antibacterial activity of disesquiterpene coumarin and sesquiterpene coumarins obtained from Ferula pseudalliacea roots was evaluated by determination of minimum inhibitory concentration using the broth micro-dilution method against seven pathogenic bacterial strains (Staphylococcus aureus ATCC 25,923, vancomycin resistant clinical strain of Enterococcus faecium, Bacillus cereus PTCC 1015, Escherichia coli ATCC 25,922, Pseudomonas aeruginosa PTCC 1430, clinical strain of Klebsiella pneumoniae and a clinical strain of Helicobacter pylori). The overall inhibitory activities of the compounds were higher against Gram positive tested bacteria. Sanandajin and ethyl galbanate demonstrated significant activity against H. pylori strain, as well as S. aureus strain in concentration of 64 μg/ml. Methyl galbanate inhibited vancomycin resistant strain of E. faecium in concentration of 64 μg/ml. The results of the present investigation indicated that disesquiterpene and sesquiterpene coumarins isolated from F. pseudalliacea root extract can be considered as potent antibacterial agents for pharmaceutical and food industries.     

Synthesis,Characterization, and Antimicrobial Screening of 4″‐methyl‐2,2″‐diaryl‐4,2′:4′,5″‐terthiazole Derivatives

A series of novel 4″‐methyl‐2,2″‐diaryl‐4,2′:4′,5″‐terthiazole ( 8a‐p ) derivatives has been synthesized and screened for antibacterial activity against four pathogenic bacteria, Escherichia coli, Pseudomonas flurescence, Staphylococcus aureus, and Bacillus subtilis. Among them, compounds 8a and 8j exhibited excellent antibacterial activity with minimum inhibitory concentration range of 1.0 to 5.3 μg/mL and compounds 8m and 8p exhibited moderate to good antibacterial activity with minimum inhibitory concentration range of 16.9 to 29.7 μg/mL against all tested strains. All the synthesized compounds were screened for their in vitro antifungal activity against Cocinida candida. Most of the compounds reported moderate antifungal activity. This study provides valuable directions to our ongoing endeavor of rationally designing more potent antimicrobial agent.     

Bioactivity and chemical characterisation of Lophostemon suaveolens – an endemic Australian Aboriginal traditional medicinal plant

Lophostemon suaveolens is a relatively unexplored endemic medicinal plant of Australia. Extracts of fresh leaves of L. suaveolens obtained from sequential extraction with n-hexane and dichloromethane exhibited antibacterial activity in the disc diffusion and MTT microdilution assays against Streptococcus pyogenes and methicillin sensitive and resistant strains of Staphylococcus aureus (minimum bactericidal concentration < 63 μg/mL). The dichloromethane extract and chromatographic fractions therein inhibited nitric oxide in RAW264.7 murine macrophages (IC₅₀ 3.7–11.6 μg/mL) and also PGE₂ in 3T3 murine fibroblasts (IC₅₀ 2.8–19.7 μg/mL). The crude n-hexane, dichloromethane and water extracts of the leaves and chromatographic fractions from the dichloromethane extract also showed modest antioxidant activity in the ORAC assay. GC–MS analysis of the n-hexane fraction showed the presence of the antibacterial compounds aromadendrene, spathulenol, β-caryophyllene, α-humulene and α-pinene and the anti-inflammatory compounds β-caryophyllene and spathulenol. Fractionation of the dichloromethane extract led to the isolation of eucalyptin and the known anti-inflammatory compound betulinic acid.