Synthesis of 3-(4-substituted benzoylmethyl)-2-benzoxazolinones and screening antimicrobial activities

A number of 3-(4-substituted benzoylmethyl)-2-benzoxazolinones have been synthesized by reacting with 2-benzoxazolinone and 4-substituted phenacyl bromide in ethanol. Their chemical structures were confirmed by IR, 1H NMR and elemental analysis. For screening antimicrobial activity, minimum inhibitory concentration (MIC) values were determined against two Gram positive, one Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus) and three yeast-like the fungi (Candida albicans, Candida krusei, Candida parapsilosis).     

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.     

New N-arylamino biquinoline derivatives: microwave-assisted synthesis and their antimicrobial activities

A new series of N-arylamino biquinoline derivatives 5a–x were synthesized under microwave irradiation technique in good yields compared with conventional method and screened for their antimicrobial activity. All the synthesized compounds have been established by elemental analysis, IR, ¹H NMR, ¹³C NMR and mass spectral data. In vitro antimicrobial activity was carried out against three Gram-positive bacteria (Bacillus subtilis, Clostridium tetani, Streptococcus pneumoniae), three Gram-negative bacteria (Escherichia coli, Salmonella typhi, Vibrio cholerae) and two fungal species (Aspergillus fumigatus, Candida albicans) using broth microdilution method. Of the compounds studied, compound 5u exhibited promising antimicrobial activity against Streptococcus pneumoniae and Salmonella typhi.     

Novel analogues of sydnone: synthesis, characterization and antibacterial evaluation

New sydnone derivatives bearing a substituted phenyl ring at the 3-position have been synthesized. Two separate series of 3-(carboxyphenyl)sydnone derivatives have been prepared by cyclization of the corresponding N-nitroso-N-(carboxyphenyl)-glycine 3. The obtained 3-(carboxyphenyl)sydnones 4 were subjected to a series of different chemical reactions on the carboxylic acid group. Compound 5, the potassium salt of 4a, was reacted with alpha-chloroacetanilide derivatives 6 to give the corresponding esters 7. On the other hand, the acid hydrazide 9 was condensed with different aromatic aldehydes to give the corresponding arylidene derivatives 10. The synthesized compounds were tested for their antibacterial activities against both gram-positive and gram-negative organisms. Some of the test compounds exhibited high activity; among them, 10d is considered to be a lead compound possessing high broad-spectrum antibacterial activity.     

Synthesis of 3- or 4-phenyl-1,8-naphthyridine derivatives and evaluation of antimycobacterial and antimicrobial activity

A series of 3- or 4-phenyl-1,8-naphthyridine derivatives variously substituted in the positions 2, 6 and 7 were synthesized and evaluated for in vitro evaluation for their antimycobacterial activity as part of a TAACF TB screening program under the direction of the US National Institute of Health, NIAID division. Several compounds showed an interesting activity when tested at a concentration of 6.25 microg/ml against Mycobacterium tuberculosis H(37)Rv and in particular compounds 2a, 4a,d, 8a,d and 8i, exhibit a % inhibition from 91 to 99. Among these, compounds 2a, 8a and 8d appeared to have a good activity with minimum inhibitory concentrations (MICs) of 6.25 microg/ml. On the basis of the biological results, the most effective substituent in position 2 or 7 seems to be the piperidinyl group. The introduction of a morpholinyl group either in position 2 or 7 of the heterocycle ring caused a decrease in activity. The 1,8-naphthyridine derivatives were also tested in vitro for their antimicrobial activity against Staphylococcus aureus as Gram-positive bacteria and Escherichia coli as Gram-negative bacteria.     

Anticancer and antimicrobial activities of scorpion venoms and their peptides

Scorpion venom is a natural biological resource that contains several components, which are not only responsible for death but also have a potential therapeutic activity. Scorpion venom has been used as traditional and folk therapy in various pathophysiological conditions. Now, many scorpion venom components have been purified and identified. Based on the available structural and functional information of these components, the scientists can produce new venom-derived medications with potential therapeutic activity against many important diseases. This review focused on the importance of scorpion venoms and their peptides against cancer and microbes.     

Synthesis and antimicrobial activities of some new nitroimidazole derivatives

In this study, some new nitroimidazole derivatives were obtained from 2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethylamine dihydrochloride (4) and 1-(2-bromoethyl)-2-methyl-5-nitroimidazole (5), which were prepared using metronidazole. Compound 4 was reacted with arylisothiocyanates (6) to obtain 1-[2-(2-methyl-5-nitroimidazol-1-yl)ethyl]-3-arylthioureas (7) and the latter with alpha-bromoacetophenones (8) to give 3-[2-(2-methyl-5-nitroimidazol-1-yl)ethyl]-2-arylimino-4-aryl-4-thiazolines (9). Also 1-[2-(2-methyl-5-nitroimidazol-1-yl)ethyl]-2-phenyl-4-arylideneimidazolin-5-ones (11) were prepared by reaction of 4 with 2-phenyl-4-arylidene-5-oxazolones (10). The reaction of the other starting material 5 with 5-arylidenethiazolidin-2,4-dione (12) gave 3-[2-(2-methyl-5-nitroimidazol-1-yl)ethyl]-5-arylidenethiazolidin-2,4-dione (13) derivatives. Structural elucidation of the compounds was performed by IR, 1H-NMR and MASS spectroscopic data and elemental analysis results. Antimicrobial activities of the compounds were examined and moderate activity was obtained.     

Antimycobacterial activity of 1-substituted indolizines

Indolizine derivatives were tested as antimycobacterials against Mycobacterium tuberculosis H(37)Rv (ATCC 27294)in BACTEC 12B medium using the Microplate Alamar Blue Assay. The most active compounds examined carry an alpha-hydroxybenzyl substituent in the indolizine 1-position. MICs against Mycobacterium tuberculosis for these compounds were 6.25 microg/mL     

Antiproliferative and antimicrobial activities of alkylbenzoquinone derivatives from Ardisia kivuensis

Context: Medicinal plants are continuously screened for their pharmacological properties. Despite the diversity and the numerous phytochemicals found in Ardisia (Myrsinaceae) species, its full biological potential has not been fully explored.

Objective: Four naturally occurring alkylbenzoquinone derivatives, namely ardisiaquinone N (1), ardisiaquinone J (2), ardisiaquinone K (3) and a mixture of ardisiaquinone P (4) and K (3) from Ardisia kivuensis Taton (Myrsinaceae) were investigated in vitro for their cytotoxicity and antimicrobial activity.

Materials and methods: Minimal inhibitory concentration (MIC) was determined using the broth micro-dilution assay. Tumor cells growth inhibition was performed by sulphorhodamine B (SRB) assay while sub-diploid DNA fraction was measured by flow cytometry.

Results: Compounds 1, 2 and 3 showed significant antimicrobial activity against two Gram-positive bacteria and one fungus (with MICs varying between 3.12 and 6.25?µg/ml). The four compounds exhibited remarkable antiproliferative activity against the leukemia cell line TPH-1 with IC₅₀ inhibition values between 2 and 2.1?µg/ml. Cytotoxic activity was found to be related to apoptosis induction.

Discussion and conclusion: These findings suggest that natural compounds herein studied are interesting potential candidates for the development of new therapeutic agents, especially against leukemia and Gram-positive bacterial infections.     

下呼吸道葡萄球菌感染的耐药性分析和治疗对策

目的通过对2002年1月至2005年12月期间，临床下呼吸道标本分离到的423株葡萄球菌进行耐药性分析，以了解葡萄球菌的耐药情况，指导临床合理使用抗生素。方法用VITEK系统对所分离的葡萄球菌进行鉴定，按美国临床实验室标准委员会推荐的标准方法（K—B法）进行药敏试验。结果423株葡萄球菌中凝固酶阴性葡萄球菌（CNS）325株。占76．8％．其中耐甲氧西林凝固酶阴性葡萄球菌（MRCNS）311株．检出率为95．7％，耐甲氧西林的金黄色葡萄球菌（MRSA）的检出率为76．5％。MRS对万古霉素100％敏感，对利福平和呋喃妥因敏感性高。结论我院MRS检出率高，应重视对MRS耐药性监测。治疗MRS引起的严重呼吸道感染应首选万古霉索。合理应用抗生素是延缓细菌耐药性的关键。     

Synthesis and potent antimicrobial activities of some novel retinoidal monocationic benzimidazoles

Several 2-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-yl)-1H-benzimidazole-5-carboxamidine analogues were synthesized for their antibacterial and antifungal activities against S. aureus, Methicillin-resistant S. aureus (MRSA), C. albicans, and C. krusei. MIC values of the targeted compounds 43-58 are comparable to those of Fluconazole and Sultamicillin. The most potent compounds, 51 and 53, showed MIC values as 0.78 and 1.56 microg/mL against S. aureus and C. albicans, respectively.     

Synthesis and antimicrobial activities of N-chloroacetyl-2,6-diarylpiperidin-4-ones

An array of new N-chloroacetyl-2,6-diarylpiperidin-4-ones has been synthesised and their antibacterial activity against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and Salmonella typhi, and antifungal activity against Cryptococcus neoformans, Candida albicans, Rhizopus sp., Aspergillus flavus, and Aspergillus niger examined. Compounds 14 against P. aeruginosa, 15 against S. typhi, 16 against S. aureus, and 19 against B. subtilis showed marked antibacterial activity. Similarly, compounds 15 and 19 against A. niger and 19 against A. flavus exerted significant antifungal activities.     

Synthesis of 4-aminoantipyrine Schiff bases and their antimicrobial activities

Various compounds of 4-aminoantipyrine Schiff bases (M₁–M₁₂) were synthesized via a condensation reaction of 4-aminoantipyrine with different benzaldehydes through a conventional method of refluxing the mixture for 3–4 h. The synthesizedSchiff bases were characterized by using elemental analyses, FT-IR, UV-Vis, Mass, ¹H and ¹³C NMR spectroscopy. The antimicrobial activity of the synthesized Schiff bases was investigated against 12 bacterial strains(Mycobacterium smegmatis, Bacillus cereus, Bacillus subtilis, Enterococcus faecalis, Staphylococcus epidermidis, Klebsiella pneumonia, Escherichia coli, Enterobacter cloacae,Klebsiella oxytoca, Proteus vulgaris, Enterobacter aerogenes, and Pseudomonas aeruginosa), and antifungal activities were tested against seven fungal strains (Aspergillus flavus, Aspergillus carbonarious, Aspergillus parasiticus, Aspergillus fumigatus,Aspergillus niger, Fusarium verticillioides and Fusarium proliferatum). The antimicrobial activities of the synthesized compounds were compared with standard streptomycin and nalidixicacid. The results obtained from antibacterial assay indicated that M₁–M₁₂ inhibited potential growth of Proteus vulgaris with minimum inhibitory concentrations (MICs) ranging from 15.6–250 µg/mL compared with the standard nalidixic acid with an MIC of 500 µg/mL. Moreover, we could conclude that most of the tested compounds experienced mild to low activities at 15.6 µg/mL. Their activities could be attributed to their low concentrations.The antifungal analysis showed that the tested fungi were not sensitive to the prepared Schiff bases at the prepared concentration of 500 µg/mL. Therefore, we recommended further analysis on both cytotoxicity and minimum bactericidal concentration (MBC) to ascertain their potential effects against human cells.     

Evaluation of antimicrobial activities of several mannich bases and their derivatives

The aim of this study was to evaluate the antimicrobial activities of several Mannich bases and their derivatives against pathogenic bacteria and fungi. 3-Dimethylamino-1-phenyl-1-propanone hydrochloride (Ig1) as mono-Mannich base, bis(beta-aroylethyl)methylamine hydrochlorides (B1, B5) as bis-Mannich bases, 3-aroyl-4-aryl-1-methyl-4-piperidinol hydrochlorides (C1, C5) as piperidinol derivatives, which are structural isomers of bis-Mannich bases, N,N'-Bis(3-dimethylamino-1-phenylpropylidene)hydra zine dihydrochlorides (D1) as azine derivative of mono-Mannich base Ig1, and some representative quaternary derivatives (Ig4 and C6), which are quaternary derivatives of Ig1 and C1, respectively, have been synthesized. Aryl parts were phenyl in B1 and C1, and 2-thienyl in B5 and C5. Bis-Mannich bases and quaternary Mannich bases were found to be effective antifungal derivatives. Quaternary mono-Mannich base Ig4 has shown twice the amount of higher antifungal potency against the human pathogenic fungus Microsporum canis compared with the reference drug amphotericin-B and it had equal potency against many other fungi species pathogenic in humans and plants. Ig4 was effective against Staphylococcus aureus among the bacteria tested. Preparation of bis-Mannich bases and qua ternization procedure seemed suitable chemical modifications to prepare effective antifungal compounds. Especially quaternary derivatives Ig4, and to some extent C6, seem to be model compounds to develop new antimicrobial agents for further studies.     

Synthesis of certain substituted quinoxalines as antimicrobial agents (part II)

Several fused triazolo and ditriazoloquinoxaline derivatives such as 1-aryl-4-chloro-[1,2,4]triazolo[4,3-a]quinoxalines (3a-d), 4-alkoxy[1,2,4]triazolo[4,3-a]quinoxalines (4a,b), 4-substituted-amino-[1,2,4] triazolo[4,3-a]quinoxalines (5a-h), 1-(aryl)-[1,2,4]triazolo[4,3-a]quinoxalin-4(5H)-thione (6), 4-(arylidenehydrazino)1-phenyl-[1,2,4]triazolo[4,3-a]quinoxalines (10a-e) and [1,2,4]ditriazolo[4,3-a:3',4'-c]quinoxaline derivatives (11-13) have been synthesized and some of these derivatives were evaluated for antimicrobial and antifungal activity in vitro. It was found that compounds 3a and 9b possess potent antibacterial activity compared to the standard tetracycline.     

Influence of extraction methods on antimicrobial activities of lignin-based materials: A review

Lignin is an abundant biomass-derived polymer that can be utilized as an antimicrobial agent. However, its antimicrobial properties depend on the method used for its extraction. Amongst the extracted lignin, lignin-based materials including nanomaterials are often favoured due to their unique properties and mode of action in suppressing microbial growth by targeting the cell membrane of bacteria. This lignin is generally obtained through chemical extraction from a variety of natural sources using different methods. However, their extraction methods, in relation to their antibacterial properties, have not been well documented. Here, we present an overview of alternative methods of extracting lignin and their potential influence on antimicrobial properties of the lignin. Shortcomings of the extraction methods as well as potential solutions for process optimisation are also discussed.     

7-Hydroxy-coumarin derivatives: synthesis, characterization and preliminary antimicrobial activities

A new series of 7-O-coumarinyl alkenoates were synthesized from 7-hydroxyl-coumarin and fatty acids using DCC and DMAP as catalyst. The synthesized compounds were characterized on the basis of their spectral data. All the target compounds were evaluated for their in vitro antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Streptococcus pyogene, Pseudomonas aeruginosa, Salmonella typhimurium, Escherichia coli and fungal cultures of Candida albicans, Candida krusei, Candida parapsilosis and Cryptococcus neoformans. The minimum inhibitory concentration (MIC) was determined for the test compounds as well as for reference standards. Among the tested compounds, 7-O-coumarinyl (9Z, 12R)-12-hydroxyoctadec-9-enoate and 7-O-coumarinyl (12Z, 9R)-9-hydroxyoctadec-12-enoate showed the most potent antifungal as well as antibacterial activities.     

Characterization of the phenolic composition and antimicrobial activities of Turkish medicinal plants

In this paper, antibacterial and antimycobacterial activity of five Labiatae plant methanol extracts, commonly used for treating cold, stomachache, and sore throat, Salvia fruticosa Mill., Salvia tomentosa Mill., Sideritis albiflora Hub.-Mor. (endemic), Sideritis leptoclada O. Schwarz & P.H. Davis, (endemic), and Origanum onites L., were investigated, and their phenolic compounds were determined by HPLC. Antibacterial activity was analyzed against Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Bacillus cereus, Escherichia coli, Salmonella typhimurium, Enterobacter aerogenes, and Klebsiella pneumoniae. Antimycobacterial activity was assayed against Mycobacterium tuberculosis. The best antibacterial activity (MIC 640 μg/mL) was shown against S. typhimurium and E. aerogenes by S. fruticosa; E. coli, and S. typhimurium, E. aerogenes by S. tomentosa; S. typhimurium, and E. aerogenes by S. leptoclada and S. typhimurium, E. aerogenes and S. epidermidis by O. onites, respectively. The best antimycobacterial activity (MIC 196 μg/mL) was shown by S. tomentosa. S. fruticosa (MIC 392 μg/mL) and O. onites (MIC 784 μg/mL) showed moderate activity against M. tuberculosis. S. albiflora, with low level rosmarinic acid and carvacrol content, showed inhibition against bacteria except K. pneumoniae, B. cereus and M. tuberculosis. The correlation between in vitro activity and ethnobotanical usage was evaluated.     

无患子皂苷的提取及抑菌性研究

目的 优化无患子皂苷的提取工艺,并测定提取物的抑菌活性.方法 本研究起止时间为2018年3月至2019年3月.以乙醇为提取剂,采用超声波辅助法,通过正交试验对无患子皂苷的提取工艺进行研究;采用滤纸片扩散法测定提取物对细菌和真菌的抑制效果.结果 无患子皂苷的最佳提取工艺是以70％的乙醇为提取溶剂,料液比为1:5,超声提取60 min,共提取3次;无患子皂苷提取物对金黄色葡萄球菌、枯草芽孢杆菌和大肠杆菌等细菌的抑菌效果不明显,但可以显著抑菌真菌的生长,对青霉菌、白色念珠菌和黑曲霉的最小抑菌浓度分别为0.05 g/mL、0.11 g/mL和0.44 g/mL(生药材/提取液).结论 无患子皂苷的超声辅助提取法工艺稳定,提取物得率高,且对真菌抑菌效果显著,有很好的开发价值.