Microwave-assisted synthesis of antimicrobial dihydropyridines and tetrahydropyrimidin-2-ones: novel compounds against aspergillosis

Ten 4-aryl-1,4-dihydropyridine and three 4-aryl-1,2,3,4-tetrahydropyrimidin-2-one derivatives have been synthesized and examined for their activity against pathogenic strains of Aspergillus fumigatus and Candida albicans. Although none of the three compounds belonging to pyrimidin-2-one series showed any activity against two pathogens, two of the compounds of the dihydropyridine series, that is, diethyl 4-(4-methoxyphenyl)-2,6-dimethyl-1,4-dihydropyridin-3,5-dicarboxylate and dimethyl 4-(4-methoxyphenyl)-2,6-dimethyl-1,4-dihydropyridin-3,5-dicarboxylate, exhibited significant activity against A. fumigatus in disc diffusion, microbroth dilution and percent spore germination inhibition assays. The most active diethyl dihydropyridine derivative exhibited a MIC value of 2.92 microg/disc in disc diffusion and 15.62 microg/ml in microbroth dilution assays. The MIC(90) value of the most active compound by percent germination inhibition assay was found to be 15.62 microg/ml. The diethyl dicarboxylate derivative of dihydropyridine also exhibited appreciable activity against C. albicans. The in vitro toxicity of the most active diethyl dihydropyridine derivative was evaluated using haemolytic assay, in which the compound was found to be non-toxic to human erythrocytes even at a concentration of 625 microg/ml. The standard drug amphotericin B exhibited 100% lysis of erythrocytes at a concentration almost 16 times less than the safer concentration of the most active dihydropyridine derivative.     

Synthesis and antibacterial activity of substituted 1,2,3,4-tetrahydropyrazino [1,2-a] indoles

A series of substituted 1,2,3,4-tetrahydropyrazino [1,2-a] indole derivatives have been synthesized and tested against the Gram positive and Gram negative strains of bacteria namely Staphylococcus aureus (MTCCB 737), Salmonella typhi (MTCCB 733), Pseudomonas aeruginosa (MTCCB 741), Streptomyces thermonitrificans (MTCCB 1824) and Escherichia coli (MTCCB 1652). All synthesized compounds showed mild to moderate activity. However, compounds 4d-f were found to have potent activity against pathogenic bacteria used in the study. Their MIC ranged from 3.75 to 60 microg/disc. In vitro toxicity tests demonstrated that toxicity of 4d-f was not significantly different than that of gentamycin. However, at higher concentration (1000-4000 microg/ml) difference was highly significant.     

Synthesis and antimicrobial activity of 3-arylamino-1-chloropropan-2-ols

A series of nine 3-arylamino-1-chloropropan-2-ols 2a-2i were synthesized and their anti-fungal activity against pathogenic strains of Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger and Candida albicans, and antibacterial activity against four pathogenic bacterial strains of Salmonella typhi, Pseudomonas aeruginosa, Streptococcus pneumonae and Staphylococcus aureus were evaluated using different assay systems. 1-Chloro-3-(4'-chlorophenylamino)-propan-2-ol was found to be the most active anti-fungal compound against three pathogenic strains under study, i.e., A. fumigatus, A. flavus and A. niger; the compound showed more than 90% inhibition of growth of A. fumigatus at a concentration of 5.85 microg/ml in disc diffusion assay. Interestingly, 1-chloro-3-(4'-chlorophenylamino)-propan-2-ol did not show any toxicity up to a concentration of 4000 microg/ml. Although 1-chloro-3-(4'-chlorophenylamino)-propan-2-ol was about 8 times less active than the standard compound amphotericin B, its toxicity was many more fold less than the toxicity of amphotericin B. Further, 1-chloro-3-(2',6'-dichlorophenylamino)-propan-2-ol and 1-chloro-3-(3',5'-dichlorophenylamino)-propan-2-ol were found to be the most active compounds against C. albicans. In the anti-microbial assay, 1-chloro-3-(2',4'-dichlorophenylamino)-propan-2-ol and 1-chloro-3-(3',5'-dichlorophenylamino)-propan-2-ol were found to be the most active compounds against Salmonella typhi and 1-chloro-3-(3',4'-dichlorophenylamino)-propan-2-ol was found to be the most active compound against P. aeruginosa. Although, the activities of 1-chloro-3-(2',4'-dichlorophenylamino)-propan-2-ol and 1-chloro-3-(3',5'-dichlorophenylamino)-propan-2-ol are about half the activity of the standard anti-bacterial compound tetracycline, these compounds also were many fold less toxic than the standard drug.     

Pyrazino[1,2-a]indoles as novel high-affinity and selective imidazoline I(2) receptor ligands

1,2,3,4-Tetrahydropyrazino[1,2-a]indoles are described as a novel class of I(2) imidazoline receptor ligands. In particular, 8-methoxy-1,2,3,4-tetrahydropyrazino[1,2-a]indole (8-OMe THPI; 3c) binds with high affinity at I(2) imidazoline receptors (K(i)=6.2 nM) and with exceptional (> or =1000-fold) selectivity relative to its affinity for I(1) imidazoline receptors, alpha(2)adrenergic receptors, and 5-HT(2A) and 5-HT(2C) serotonin receptors.     

Synthesis and evaluation of demethoxyviridin derivatives as potential antimicrobials

The in vitro antibacterial and antifungal activities of demethoxyviridin and some synthetic analogues were evaluated by the agar diffusion method. The minimum inhibitory concentrations (MIC) of the active compounds were also determined by the agar dilution method. Demethoxyviridin (1) showed moderate antibacterial activity against most of the strains tested. 1alpha-Hydroxydemethoxyviridin (3) showed antibacterial activity and the most potent in vitro antifungal activity with MIC of 20 microg/ml (0.062 mM) against Aspergillus niger, A. fumigatus, A. flavus, A. parasiticus, Fusarium solani, F. graminarum, Geotrichum candidum whereas 5'-methylfuro-(4',3',2'-4,5,6)androst-5-ene-3,17-dione (7) exhibited very weak antifungal activity against Candida albicans only.     

In vitro activity of a new triazole antifungal agent,Sch 56592, against clinical isolates of filamentous fungi

Sch 56592 is a new triazole derivative that possesses potent, broad-spectrum antifungal activity. We evaluated the in vitroactivity of Sch 56592 compared with that of itraconazole, amphotericin B and 5-fluorocytosine against 51 clinical isolates of filamentous fungi, including Aspergillus flavus(10), A. fumigatus(12), Fusariumspp. (13), Rhizopus spp. (6), Pseudallescheria boydii(5), and one isolate each of Acremoniumspp., A. niger, A. terreus, Paecilomycesspp., and Trichodermaspp. In vitrosusceptibility testing was performed using the microdilution broth method outlined in the NCCLS 27-A document. Sch 56592 was highly active against A. flavus(MIC₉₀, 0.25 μg/ml), A. fumigatus(MIC₉₀, 0.12 μg/ml), P. boydii(MIC₅₀, 1 μ/ml) and Rhizopusspp (M1C₅₀, 1 μg/ml). By comparison with itraconazole, Sch 56592 was four- to eight-fold more active against isolates of Aspergillusand both compounds showed equipotent in vitroactivity against P. boydiiand Rhizopusspp. Sch 56592 was four- to 16-fold more active than amphotericin B against Aspergillusspp. and P. boydiiand both antifungal drugs displayed similar activity against Rhizopusspp. Overall, Sch 56592 showed good in vitroactivity against all isolates tested (MIC, ≤ 2 μg/ml) except isolates of Fusarium(MIC range, 1–>4 μg/ml). On the basis of these data Sch 56592 has promising activity against Aspergillus spp. and other species of filamentous fungi that are likely to be encountered clinically. Additional in vitroand in vivostudies are warranted. This revised version was published online in June 2006 with corrections to the Cover Date.     

Triphenyltin salicylate-antimicrobial effect and resistance--the pyrophosphatase connection

The effect of Triphenyltin salicylate (TPS) was tested against six bacteria, Escherichia coli, Staphylococcus aureus, Shigella flexneri, Pseudomonas aeruginosa, Klebsiella pneumoniae and Salmonella typhi and five fungi, Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Rhodotorula spp. and Saccharomyces spp. Sensitivity tests were determined with 5-500 microg/ml of TPS. All organisms were sensitive to the compound except Klebsiella pneumoniae, Pseudomonas aeruginosa, Rhodotorula spp. and Saccharomyces spp. The minimum dose of TPS that can kill 50% of the susceptible microorganisms is in the range 5-50 microg/ml. Membrane bound pyrophosphatase(s) from the organisms was non-competitively inhibited by 5 microM TPS with Ki values of 7.6, 18, 8.8 and 6.9 microM for Escherichia coli, Shigella flexneri, Aspergillus niger, and Aspergillus fumigatus, respectively. The physiological index of efficiency of the enzyme (Vmax/KM) for TPS susceptible organisms was reduced by 17-68% in the presence of 5-10 microM of the compound. In contrast the index for the non-susceptible organisms was unaffected. The mode of action of TPS is discussed.     

Design and synthesis of spiro[indole-thiazolidine]spiro[indole-pyrans] as antimicrobial agents

A series of novel spiro[indole-thiazolidine]spiro[indole-pyran] derivatives were synthesized from N-(bromoalkyl)indol-2,3-diones via monospiro-bisindole intermediates; the two indole nuclei being connected via N-(CH(2))(n)-N linker. Synthesized compounds were evaluated for their antimicrobial activities in vitro against three Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, and Staphylococcus epidermis), four Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and Klebsiella pneumonia) as well as four fungi (Aspergillus niger, Aspergillus fumigatus, Aspergillus flavus, and Candida albicans) using Cup plate method. Bis spiro-indoles exhibited stronger antibacterial and antifungal efficiency than their corresponding mono spiro-indoles. Compound 10e, the most active derivative was shown to inhibit the growth of all bacterial strains and two fungal strains (A. niger and C. albicans).     

An acylated phloroglucinol with antimicrobial properties from Helichrysum caespititium

A new acylated form of a phloroglucinol with significant antimicrobial properties was isolated by bioactivity guided fractionation from Helichrysum caespititium (Asteraceae). The structure elucidation, and conformation of the new phloroglucinol, 2-methyl-4-[2',4',6'-trihydroxy-3'-(2-methylpropanoyl) phenyl]but-2-enyl acetate, was established by high field NMR spectroscopic and MS data. The compound inhibited growth of Bacillus cereus, B. pumilus, B. subtilis and Micrococcus kristinae at the very low concentration of 0.5 microg/ml and Staphylococcus aureus at 5.0 microg/ml. Six fungi tested were similarly inhibited at low MICs, Aspergillus flavus and A. niger (1.0 microg/ml), Cladosporium chladosporioides (5 microg/ml), C. cucumerinum and C. sphaerospermum (0.5 microg/ml) and Phylophthora capsici at 1.0 microg/ml.     

Investigations on anti-Aspergillus properties of bacterial products

AIMS: To investigate the anti-Aspergillus properties of bacterial products. METHODS AND RESULTS: In the present study, 12 bacterial strains were screened for antifungal activity against Aspergilli. The culture supernatant and lysates of Pseudomonas aeruginosa, Bacillus cereus, Escherichia coli (BL21, DH5alpha, HB101, XL Blue), Klebsiella pneumoniae, Streptomyces thermonitrificans, Streptococcus pneumoniae, Enterobacter aerogenes, Staphylococcus aureus and Salmonella typhi were examined for antifungal activity in protein concentration ranging from 1000.0 to 7.8 microg ml-1 using microbroth dilution assay. The lysate of Salm. typhi and E. coli BL21 exhibited the maximum activity against Aspergillus fumigatus, Aspergillus flavus and Aspergillus niger. Their in vitro minimum inhibitory concentrations (MICs) were found to be 15.6-31.2 microg ml-1 by microbroth dilution and spore germination inhibition assays. In disc diffusion assay, a concentration of 3.1 microg disc-1 of Salm. typhi lysate showed significant activity against Aspergilli. Escherichia coli BL21 exhibited similar activity at 6.2 microg disc-1. The work on identification of molecule endowed with antimycotic properties is in progress. CONCLUSION: The products of Salm. typhi and E. coli demonstrated significant activity against Aspergillus species. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first time that E. coli has been reported for anti-Aspergillus activity. It could be an important source of biologically active compounds useful for developing better new antifungal drugs/or probiotics.     

布洛芬对曲霉的体外抗真菌活性评价

目的观察布洛芬对曲霉临床分离株的体外抗真菌活性。方法分别用微量液基稀释法和纸片扩散法,测定布洛芬对10株烟曲霉、黄曲霉和土曲霉的抗菌活性。结果微量液基稀释法显示布洛芬对曲霉的最低抑菌浓度（MIC）范围为1000～2000μg/mL,最低杀菌浓度（MFC）范围为2000～8000μg/mL;纸片扩散法也显示布洛芬有体外抗曲霉活性：48h时,1000μg布洛芬对曲霉产生的抑菌圈直径为（20.1±3.89）mm。结论布洛芬有体外抗曲霉活性。     

Standardization and characterization of antigens for the diagnosis of aspergillosis

The aim of this study was to develop and characterize antigens for the diagnosis of aspergillosis. Nine strains of Aspergillus species Aspergillus fumigatus , Aspergillus flavus , and Aspergillus niger were grown in Sabouraud and Smith broth to produce exoantigens. The antigens were tested by immunodiffusion against sera from patients with aspergillosis and other systemic mycoses. The protein fraction of the antigens was detected by SDS-PAGE; Western blot and representative bands were assessed by mass spectrometry coupled to a nano Acquity UltraPerformance LC and analyzed by the Mascot search engine. Concurrently, all sera were tested with Platelia Aspergillus EIA. The most reactive antigens to sera from patients infected by A. fumigatus were produced by A. fumigatus MG2 Sabouraud and pooled A.?fumigatus Sabouraud samples, both with a sensitivity of 93% and specificity of 100% and 97%, respectively. Aspergillus niger and A. flavus antigens were reactive against A. niger and A. flavus sera, each one with a sensitivity and specificity of 100%. Two proteins, probably responsible for antigenic activity, β-glucosidase in A. fumigatus and α-amylase in A. niger were attained. The commercial kit had a specificity of 22%, sensitivity of 100%, positive predictive value of 48%, and negative predictive value of 100%. The antigens produced showed high sensitivity and specificity and can be exploited for diagnostics of aspergilloma.     

3-[Benzimidazo- and 3-[benzothiadiazoleimidazo-(1,2-c)quinazolin-5-yl]-2H-chromene-2-ones as potent antimicrobial agents

A series of 3-[benzimidazo(1,2-c)quinazolin-5-yl]-2H-chromene-2-one (6a-6f) and 3-[benzothiadiazole- imidazo(1,2-c)quinazolin-5-yl]-2H-chromene-2-one derivatives (7a-7f) that incorporate a variety of substituents at the 6- and/or 8-positions of the coumarin moieties have been synthesized utilizing cellulose sulfuric acid as an efficient catalyst under both conventional heating and microwave irradiation procedures. These analogs were evaluated for their antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Streptococcus pyogenes (Gram-positive bacteria), Escherichia Coli, Klebsiella pneumonia, Salmonella typhimurium (Gram-negative bacteria), and Aspergillus niger, Candida albicans, and Aspergillus flavus (Fungi). Two analogs, 6c (a 6,8-dichloro analog, MIC([SA]) = 2.5 μg/mL; MIC([ST]) = 2.5 μg/mL) and 7d (a 6,8-dibromo analog, MIC([ST]) = 2.5 μg/mL) were identified as potent antibacterial agents, and two analogs, 6b (a 6-bromo analog, MIC([AF]) = 10 μg/mL) and 6d (a 6,8-dibromo analog, MIC([AF]) = 15 μg/mL; MIC([CA]) = 15μg/mL), were identified as potent antifungal agents. Based on the MIC data, analogs 6b, 6c, 6d, and 7d were identified as the most potent antimicrobial agents in the series.     

Novel ofloxacin derivatives: synthesis, antimycobacterial and toxicological evaluation

Thirty novel 9-fluoro-2,3-dihydro-8,10-(mono/di-sub)-3-methyl-8-nitro-7-oxo-7H-[1,4]oxazino[2,3,4-ij]quinoline-6-carboxylic acids were synthesized from 2,3,4,5-tetrafluoro benzoic acid and evaluated for in vitro and in vivo antimycobacterial activities against Mycobacterium tuberculosis H37Rv (MTB), multi-drug resistant Mycobacterium tuberculosis (MDR-TB), and Mycobacterium smegmatis (MC(2)) and also tested for the ability to inhibit the supercoiling activity of DNA gyrase from mycobacteria. Among the synthesized compounds, 10-[2-carboxy-5,6-dihydroimidazo[1,2-a]pyrazin-7(8H)-yl]-9-fluoro-2,3-dihydro-3-methyl-8-nitro-7-oxo-7H-[1,4]oxazino[2,3,4-ij]quinoline-6-carboxylic acid was found to be the most active compound in vitro with MIC99 of 0.19 microM and 0.09 microM against MTB and MTR-TB, respectively. In the in vivo animal model also the same compound decreased the bacterial load in lung and spleen tissues with 1.91 and 2.91--log10 protections, respectively, at the dose of 50mg/kg body weight. Compound 10-[(4-((4-chlorophenyl)(phenyl)methyl)piperazin-1-yl)]-9-fluoro-2,3-dihydro-3-methyl-8-nitro-7-oxo-7H-[1,4]oxazino[2,3,4-ij]quinoline-6-carboxylic acid was found to be the most active in the inhibition of the supercoiling activity of DNA gyrase with an IC(50) of 10.0 microg/mL. The results demonstrate the potential and importance of developing new oxazino quinolone derivatives against mycobacterial infections.     

Culture supernatants of patient-derived Aspergillus isolates have toxic and lytic activity towards neurons and glial cells

Infection of the central nervous system by the ubiquitous fungi Aspergillus spp. is a life-threatening disease. Therefore we investigated the mechanism of brain damage by fungal infection. To examine whether secretory factors of Aspergillus isolates derived from patients can induce death of different brain cells, culture supernatants of Aspergillus fumigatus, Aspergillus flavus, Aspergillus terreus and Aspergillus niger were added to different astrocytes as well as to the neuroblastoma cell line SK-N-SH, and to the microglial cell line CHME. All four fungal species were shown to secrete toxic factors with neurons being most sensitive against these factors. Very low amounts and short incubation times are sufficient to induce irreversible cell damage, indicating that secreted factors might also affect distant brain regions. Further characterization of the toxic factors revealed that A. fumigatus and A. terreus produced small, heat-stable components whereas the toxic activity of A. niger filtrates was triggered by a high molecular mass factor which could be inactivated by heat. The active component of A. flavus had a molecular mass similar to that of A. niger but was heat-stable and had a significantly lower activity. Taken together these results indicate that secretion of different necrotizing factors might contribute to brain lesions in patients with cerebral aspergillosis.     

Synthesis and antimicrobial activity of N-alkyl and N-aryl piperazine derivatives

A series of substituted piperazine derivatives have been synthesized and tested for antimicrobial activity. The antibacterial activity was tested against Staphylococcus aureus (MTCCB 737), Pseudomonas aeruginosa (MTCCB 741), Streptomyces epidermidis (MTCCB 1824) and Escherichia coli (MTCCB 1652), and antifungal activity against Aspergillus fumigatus, Aspergillus flavus and Aspergillus niger. All synthesized compounds showed significant activity against bacterial strains but were found to be less active against tested fungi. In vitro toxicity tests demonstrated that compounds 4d and 6a showed very less toxicity against human erythrocytes.     

Specificity of antigens from pathogenic Aspergillus species. II. Studies with line immunoelectrophoresis

Somatic (mycelial) and metabolic (culture filtrate) antigens of Aspergillus flavus, A. fumigatus, A. nidulans, A. niger and A. terreus were compared by line immunoelectrophoresis with sera from patients with allergic bronchopulmonary aspergillosis (ABPA) or aspergilloma, or from immunized animals. Number of lines observed when tested with human sera were similar for somatic and metabolic preparations of A. fumigatus, but up to 33 lines were present when both types of antigens were tested simultaneously. Cross-reactions between heterologous antigens and sera from patients with aspergilloma or ABPA were uncommon. In contrast, cross-reactions were common when standard antisera prepared in animals against heterologous species of Aspergillus were tested against A. fumigatus antigens. Lines of identity between homologous antigens and those from A. fumigatus were observed in 5 of 9 lines obtained with A. flavus, 4 of 16 lines of A. nidulans, 4 of 9 lines of A. niger and 4 of 8 lines of A. terreus.     

曲霉生物膜的形成过程与结构特征

目的 研究曲霉生物膜的形成过程和结构特征.方法 我们利用一个曲霉生物膜体外模型研究其形成过程和结构特征.将200 μL浓度为1×10<'5>孢子/mL的受试曲霉(烟曲霉AF293,黄曲霉BMU03940,土曲霉BMU00802,黑曲霉BMU04689)的孢子悬液加到24孔组织培养板中的无菌塑料细胞培养盖玻片上,37℃孵育不同时间(0、2、4、8、10、12、16、18、24、48、72 h),加入25 μmol/L的FUN-1室温避光染色后,用波长488 nm激光激发,通过共聚焦激光扫描显微镜观察曲霉生物膜的形成过程;再用波长为488 am和633 am激光同时激发,将两个波长下的图像叠加后观察曲霉生物膜的活力;利用:XYZ轴成像观察其结构特征.在上述不同的时间点用钙荧光白染色后,用波长为405 nm的紫外光激发,观察曲霉生物膜细胞外基质的产生.结果 烟曲霉AF293在第4 h即开始有散在的孢子黏附于盖玻片上;8 h时孢子开始萌芽,10～12 h菌丝延长形成单细胞层;16～20 h菌丝缠绕形成多层立体结构;24 h形成一个具有复杂的三维立体结构特征的多细胞菌落,菌丝有序排列,细胞外基质弥散的分布在菌丝的周围;48～72 h生物膜逐渐成熟.成熟的烟曲霉生物膜是由细胞外基质包裹的有序排列的菌丝形成的复杂立体结构.黄曲霉BMU03940、土曲霉BMU00802、黑曲霉BMU04689与烟曲霉AF293有类似的生物膜发育阶段,包括黏附、孢子萌芽、菌丝延长、菌丝有序排列形成三维立体结构.结论 烟曲霉、黄曲霉、土曲霉和黑曲霉在体外都能形成典型的生物膜,它的形成过程和结构特征与其他真菌生物膜类似.     

吸水链霉菌BS-112产生的抗真菌活性物质的分离纯化与结构鉴别

【目的】分离纯化吸水链霉菌(Streptomyces hygroscopicus)BS-112产生的抗真菌活性物质,究明各活性组分的结构,测定其对黄曲霉的抑制作用,为该菌株及其产生的抗真菌活性物质的应用提供依据。【方法】通过大孔吸附树脂柱层析、硅胶柱层析及制备HPLC等方法,对该菌株产生的抗真菌活性物质进行分离纯化;利用质谱(MS)和核磁共振谱(NMR)解析各活性组分的结构;采用微量液体稀释法测定各活性组分对黄曲霉的最小抑菌浓度(MIC)和最小杀菌浓度(MFC)。【结果】从BS-112菌株发酵液中分离获得4个抗真菌活性组分,利用波谱技术确定其结构分别为Tetrins A和B、Tetramycins A和B。96孔板法测得这4个化合物对黄曲霉的MIC分别为3.13μg/mL、12.56μg/mL、1.56μg/mL、6.25μg/mL,MFC分别为6.25μg/mL、25.0μg/mL、3.13μg/mL、12.56μg/mL。【结论】BS-112菌株产生的抗真菌活性物质由Tetrins A和B、Ttramycins A和B 4个化合物组成,它们对黄曲霉均具有良好的抑制作用。     

Synthesis and evaluation of antitubercular activity of imidazo[2,1-b][1,3,4]thiadiazole derivatives

A series of 2,6-disubstituted and 2,5,6-trisubstituted imidazo[2,1-b][1,3,4]thiadiazoles were synthesized, the structures of the compounds were elucidated and screened for antitubercular activity against Mycobacterium tuberculosis H37Rv using the BACTEC 460 radiometric system, antibacterial activity against Escherichia coli and Bacillus cirrhosis, and antifungal activity against Aspergillus niger and Penicillium wortmanni. Among the tested compounds 2-(2-furyl)-6-phenylimidazo[2,1-b][1,3,4] thiadiazole-5-carbaldehyde (6c) and (2-cyclohexyl-6-phenylimidazo[2,1-b][1,3,4]thiadiazol-5-yl)methanol (7a) have shown the highest (100%) inhibitory activity. Compounds 6a, 6b, 7c, and 8a exhibited moderate antitubercular activity with percentage inhibition 36, 30, 15, and 20, respectively, at a MIC of >6.25 microg/ml.