Molecular properties prediction and synthesis of novel 1,3,4-oxadiazole analogues as potent antimicrobial and antitubercular agents

In the present investigation, a series of 1,5-dimethyl-2-phenyl-4-{[(5-aryl-1,3,4-oxadiazol-2-yl)methyl]amino}-1,2-dihydro-3H-pyrazol-3-one were subjected to molecular properties prediction, drug-likeness by Molinspiration (Molinspiration, 2008) and MolSoft (MolSoft, 2007) software, lipophilicity and solubility parameters using ALOGPS 2.1 program. The compounds followed the Lipinski ‘Rule of five’ were synthesized for antimicrobial and antitubercular screening as oral bioavailable drugs/leads. Maximum drug-likeness model score (0.95) was found for compound, 4a. All the synthesized compounds were characterized by IR, NMR and mass spectral analysis followed by antimicrobial and antimycobacterial screening. Among the title compounds, compound 4d showed pronounced activity against Mycobacterium tuberculosis H₃₇Rv and isoniazid resistant M. tuberculosis (INHR-TB) with minimum inhibitory concentrations (MICs) 0.78 μM and 1.52 μM, respectively. The compound, 4a showed maximum activity against all bacterial strains with MIC 4–8 μg/mL comparable to standard drug ciprofloxacin, while the compounds, 4e and 4k showed maximum antifungal activity with MIC 8–16 μg/mL less active than standard drug fluconazole.     

Synthesis and evaluation of antitubercular activity of glycosyl thio- and sulfonyl acetamide derivatives

A series of glycosyl thioacetamide and glycosyl sulfonyl acetamide derivatives have been prepared following a convenient reaction protocol and evaluated for their antitubercular activity against Mycobacterium tuberculosis H₃₇Rv. Amongst 32 compounds evaluated 3 compounds were effective in inhibiting mycobacterial growth at MIC of 6.25 μg/mL, 6 compounds at MIC of 3.125 μg/mL and 1 compound at MIC of 1.56 μg/mL. All active compounds were found nontoxic in Vero cell lines and mice bone marrow macrophages.     

Synthesis of azatricyclodiones & octahydro-benzo[f]isoindoles and their antimicrobial evaluation

A series of azatricyclodiones and octahydro-benzo[f]isoindoles have been synthesized by (4+2) Diels-Alder cycloaddition of maleimides with furfuryl amine. Reaction of azatricyclodiones with isocyanates led to the respective ureides. All of the compounds were screened against a number of bacteria and fungi. One of the compounds (2) displayed moderate antitubercular activity while two compounds (2) and (4) inhibited the fungal growth at 25 μg/mL.     

Phytochemical,Antiplasmodial, Cytotoxic and Antimicrobial Evaluation of a Southeast Brazilian Brown Propolis Produced by Apis mellifera Bees

Seven phenolic compounds (ferulic acid, caffeic acid, 4-methoxycinnamic acid, 3,4-dimethoxycinnamic acid, 3-hydroxy-4-methoxybenzaldehyde, 3-methoxy-4-hydroxypropiophenone and 1-O,2-O-digalloyl-6-O-trans-p-coumaroyl-β-D-glucopyranoside), a flavanonol (7-O-methylaromadendrin), two lignans (pinoresinol and matairesinol) and six diterpenic acids/alcohol (19-acetoxy-13-hydroxyabda-8(17),14-diene, totarol, 7-oxodehydroabietic acid, dehydroabietic acid, communic acid and isopimaric acid) were isolated from the hydroalcoholic extract of a Brazilian Brown Propolis and characterized by NMR spectral data analysis. The volatile fraction of brown propolis was characterized by CG-MS, composed mainly of monoterpenes and sesquiterpenes, being the major α-pinene (18.4 %) and β-pinene (10.3 %). This propolis chemical profile indicates that Pinus spp., Eucalyptus spp. and Araucaria angustifolia might be its primary plants source. The brown propolis displayed significant activity against Plasmodium falciparum D6 and W2 strains with IC₅₀ of 5.3 and 9.7 μg/mL, respectively. The volatile fraction was also active with IC₅₀ of 22.5 and 41.8 μg/mL, respectively. Among the compounds, 1-O,2-O-digalloyl-6-O-trans-p-coumaroyl-β-D-glucopyranoside showed IC₅₀ of 3.1 and 1.0 μg/mL against D6 and W2 strains, respectively, while communic acid showed an IC₅₀ of 4.0 μg/mL against W2 strain. Cytotoxicity was determined on four tumor cell lines (SK-MEL, KB, BT-549, and SK-OV-3) and two normal renal cell lines (LLC-PK1 and VERO). Matairesinol, 7-O-methylaromadendrin, and isopimaric acid showed an IC₅₀ range of 1.8–0.78 μg/mL, 7.3–100 μg/mL, and 17–18 μg/mL, respectively, against the tumor cell lines but they were not cytotoxic against normal cell lines. The crude extract of brown propolis displayed antimicrobial activity against C. neoformans, methicillin-resistant Staphylococcus aureus, and P. aeruginosa at 29.9 μg/mL, 178.9 μg/mL, and 160.7 μg/mL, respectively. The volatile fraction inhibited the growth of C. neoformans at 53.0 μg/mL. The compounds 3-hydroxy-4-methoxybenzaldehyde, 3-methoxy-4-hydroxypropiophenone and 7-oxodehydroabietic acid were active against C. neoformans, and caffeic and communic acids were active against methicillin-resistant Staphylococcus aureus.     

Novel isoniazid embedded triazole derivatives: Synthesis,antitubercular and antimicrobial activity evaluation

In the present study, a series of new isoniazid embedded triazole derivatives have been synthesized. These compounds were evaluated for their in vitro antitubercular and antimicrobial activities. Among the screened compounds, six have exhibited potent antitubercular activity against Mycobacterium tuberculosis H37Rv strain with MIC value 0.78 μg/mL, whereas, three compounds have displayed activity with MIC value ranging from 1.56 to 3.125 μg/mL. The cytotoxicity of the active compounds was studied against RAW 264.7 cell line by MTT assay and no toxicity was observed even at 25 μg/mL concentration. The five compounds have displayed good antimicrobial activities. Molecular docking have been performed against mycobacterial InhA enzyme to gain an insight into the plausible mechanism of action which could pave the way for our endeavor to identify potent antitubercular candidates. We believe that further optimization of these molecules may lead to potent antitubercular agents.     

Design,synthesis and in vivo/in vitro screening of novel chlorokojic acid derivatives

A series of novel Mannich bases of chlorokojic acid (2-chloromethyl-5-hydroxy-4H-pyran-4-one) were synthesized and their biological activities were investigated. Anticonvulsant activity results according to phase-I tests of Antiepileptic Drug Development (ADD) Program revealed that compound 13 was the most effective one at 4?h against subcutaneous pentylenetetrazole (scPTZ)-induced seizure test. Antimicrobial activities were evaluated in vitro against bacteria and fungi by using broth microdilution method. The antitubercular activities against Mycobacterium tuberculosis and M. avium were discussed with Resazurin microplate assay (REMA). The antimicrobial activity results indicated that compounds 1 and 12 (MIC: 8–16 µg/mL) showed higher activity against Gram negative bacteria while compound 12 had MIC: 4–16 µg/mL against Gram positive bacteria. Compound 1 was the most active one with MIC values of 8–32 µg/mL against fungi. Mannich bases also exhibit significant antitubercular activity in a MIC range of 4 to 32 µg/mL, especially compound 18 against M. avium.     

Design of potent fluoro-substituted chalcones as antimicrobial agents

Owing to ever-increasing bacterial and fungal drug resistance, we attempted to develop novel antitubercular and antimicrobial agents. For this purpose, we developed some new fluorine-substituted chalcone analogs (3, 4, 9–15, and 20–23) using a structure–activity relationship approach. Target compounds were evaluated for their antitubercular efficacy against Mycobacterium tuberculosis H37Rv and antimicrobial activity against five common pathogenic bacterial and three common fungal strains. Three derivatives (3, 9, and 10) displayed significant antitubercular activity with IC₅₀ values of ≤16,760. Compounds derived from trimethoxy substituent scaffolds with monofluoro substitution on the B ring of the chalcone structure exhibited superior inhibition activity compared to corresponding hydroxy analogs. In terms of antimicrobial activity, most compounds (3, 9, 12–14, and 23) exhibited moderate to potent activity against the bacteria, and the antifungal activities of compounds 3, 13, 15, 20, and 22 were comparable to those of reference drugs ampicillin and fluconazole.     

Monoamine oxidase inhibition by monoterpene indole alkaloids and fractions obtained from Psychotria suterella and Psychotria laciniata

Alkaloid fractions of Psychotria suterella (SAE) and Psychotria laciniata (LAE) as well as two monoterpene indole alkaloids (MIAs) isolated from these fractions were evaluated against monoamine oxidases (MAO-A and -B) obtained from rat brain mitochondria. SAE and LAE were analysed by HPLC-PDA and UHPLC/HR-TOF-MS leading to the identification of the compounds 1, 2, 3 and 4, whose identity was confirmed by NMR analyses. Furthermore, SAE and LAE were submitted to the enzymatic assays, showing a strong activity against MAO-A, characterized by IC₅₀ values of 1.37?±?1.05 and 2.02?±?1.08 μg/mL, respectively. Both extracts were also able to inhibit MAO-B, but in higher concentrations. In a next step, SAE and LAE were fractionated by RP-MPLC affording three and four major fractions, respectively. The RP-MPLC fractions were subsequently tested against MAO-A and -B. The RP-MPLC fractions SAE-F3 and LAE-F4 displayed a strong inhibition against MAO-A with IC₅₀ values of 0.57?±?1.12 and 1.05?±?1.15 μg/mL, respectively. The MIAs 1 and 2 also inhibited MAO-A (IC₅₀ of 50.04?±?1.09 and 132.5?±?1.33 μg/mL, respectively) and -B (IC50 of 306.6?±?1.40 and 162.8?±?1.26 μg/mL, respectively), but in higher concentrations when compared with the fractions. This is the first work describing the effects of MIAs found in neotropical species of Psychotria on MAO activity. The results suggest that species belonging to this genus could consist of an interesting source in the search for new MAO inhibitors.     

Protein glycation inhibitory activities of Lawsonia inermis and its active principles

The protein glycation inhibitory activity of ethanolic extract of Lawsonia inermis (henna) plant tissues was evaluated in vitro using the model system of bovine serum albumin and glucose. Protein oxidation and glycation are posttranslational modifications that are implicated in the pathological development of many age-related disease processes. This study investigated the effects of Lawsonia inermis ethanolic extract and its components, on protein damage induced by a free radical generator in in vitro assay system. We found that alcoholic extract of Lawsonia inermis can effectively protect against protein damage and showed that its action is mainly due to Lawsone. In addition, the presence of gallic acid also plays an important role in the protective activity against protein oxidation and glycation. Two known compounds, namely, Lawsone and gallic acid previously isolated from this plant were subjected to glycation bioassay for the first time. It was found that the alcoholic extract, lawsone (1) and gallic acid (2) showed significant inhibition of Advanced Glycated End Products (AGEs) formation and exhibit 77.95%, 79.10% and 66.98% inhibition at a concentration of 1500 μg/mL, 1000 μg/mL and 1000 μM respectively. Lawsonia inermis, compounds 1 and 2 were found to be glycation inhibitors with IC₅₀ 82.06 ± 0.13 μg/mL, 67.42 ± 1.46 μM and 401.7 ± 6. 23 μM respectively. This is the first report on the glycation activity of these compounds and alcoholic extract of Lawsonia inermis.     

Synthesis,identification and in vitro biological evaluation of some novel quinoline incorporated 1,3-thiazinan-4-one derivatives

The present study describes the synthesis of two new series of 3-hydroxy-N-(4-oxo-2-phenyl-1,3-thiazinan-3-yl)-8-(trifluoromethyl)quinoline-2-carboxamide derivatives (4a–j) and 3-((7-chloroquinolin-4-ylamino)methyl)-2-phenyl-1,3-thiazinan-4-one derivatives (5a–7j). All the compounds were synthesized in moderate to good yield by one-pot three component cyclo-condensation reaction. The newly synthesized compounds were characterized by FT-IR, ¹H, ¹³C NMR and elemental analysis. The compounds were screened for their in vitro antibacterial activity against a panel of pathogenic bacterial strains, antitubercular activity against Mycobacterium tuberculosis H₃₇Rv and also for their in vitro antimalarial activity against Plasmodium falciparum. Among the synthesized compounds two of them (4f and 5f) showed excellent antibacterial activity against C. tetani at 15.6 μg/mL. Some of them exhibited excellent antitubercular (4f & 5f) and good antimalarial (4f, 5f & 6f) activity compared with the first line drugs.     

Chemical Composition and Antioxidant,Antiparasitic, Cytotoxicity and Antimicrobial Potential of the Algerian Limonium Oleifolium Mill. Essential Oil and Organic Extracts

This work aimed to investigate, for the first time, the chemical composition, antioxidant, antiparasitic, cytotoxicity, and antimicrobial activities of the aromatic plant Limonium oleifolium Mill. essential oil (EO) and organic extracts. L. oleifolium aerial parts essential oil was analyzed by GC-FID and GC-MS, and 46 constituents representing 98.25±1.12 % of the oil were identified. γ-Muurolene (10.81±0.07 %), cis-caryophyllene (7.71±0.06 %), o-cymene (7.07±0.01 %) and α-copaene (5.02±0.05 %) were the essential oil main compounds. The antioxidant activity of L. oleifolium EO and organic extracts (MeOH, CHCl₃, AcOEt, BuOH) was explored using 2,2-diphenyl-1-picrylhydrazyl (DPPH), ABTS, β-carotene/linoleic acid, cupric reducing antioxidant capacity (CUPRAC), and ferric reducing power assays. The results showed that L. oleifolium EO exhibit antioxidant capacity (IC₅₀=17.40±1.32 μg/mL for DPPH assay, IC₅₀=29.82±1.08 μg/mL for β-carotene assay, IC₅₀=25.23±1.01 μg/mL for ABTS assay, IC₅₀=9.11±0.08 μg/mL for CUPRAC assay and IC₅₀=19.41±2.06 mg/mL for reducing power assay). Additionally, the EO showed significant activity against trophozoite form of Acanthamoeba castellanii (IC₅₀=7.48±0.41 μg/mL) and promastigote form of Leishmania amazonensis (IC₅₀=19.36±1.06 μg/mL) and low cytotoxicity on murine macrophages (LC₅₀ 90.23±1.09 μg/mL), as well as good antimicrobial activity against Staphylococcus aureus, Escherichia coli, Klebsiella oxytoca, and Pseudomonas aeruginosa. These results suggest that L. oleifolium essential oil is a valuable source of bioactive compounds presenting antioxidant, antiparasitic, and antimicrobial activities. Furthermore, it is considered nontoxic.     

New Pterosin Sesquiterpenes and Antitubercular Constituents from Pteris ensiformis

Two new pterosin sesquiterpenes, (2S)‐13‐hydroxypterosin A ( 1 ) and (2S,3S)‐12‐hydroxypterosin Q ( 2 ), were isolated from the whole plants of Pteris ensiformis, together with six known compounds. The structures of 1 and 2 were determined through extensive 1D/2D‐NMR and MS analyses. Compound 2 exhibited antitubercular activity (MIC 6.25 μg/ml) against Mycobacterium tuberculosis H₃₇Rv in vitro.     

Dihydroisocoumarins and Phenylglycosides from Scorzonera longiana,Their Antimicrobial Activities and Molecular Docking Studies

Five new phenyl dihydroisocoumarin glycosides ( 1 – 5 ) and two known compounds ( 6 – 7 ) were identified from the butanol fraction of Scorzonera longiana. The structures of 1 – 7 were elucidated based on spectroscopic methods. Antimicrobial, antitubercular, and antifungal evaluation of compounds 1 – 7 were carried out using the microdilution method against nine microorganisms. Compound 1 was active only against Mycobacterium smegmatis (Ms) with a MIC value of 14.84 μg/mL. All tested compounds ( 1 – 7 ) were active against Ms but only compounds 3–7 were active against fungi (C. albicans, S. cerevisiae) with MIC values of 25.0–125 μg/mL. In addition, molecular docking studies were conducted against Ms DprE1 (PDB ID: 4F4Q), Mycobacterium tuberculosis (Mbt) DprE1 (PDB ID: 6HEZ), and arabinosyltransferase C (EmbC, PDB ID: 7BVE) enzymes. Compounds 2 , 5 , and 7 are the most effective Ms 4F4Q inhibitors. Compound 4 was the most promising inhibitory activity on Mbt DprE with the lowest binding energy of −9,9 kcal/mol.     

Synthesis and evaluation of chromenyl barbiturates and thiobarbiturates as potential antitubercular agents

A novel series of barbiturate and thiobarbiturate analogs of 2-benzoyl-3-methyl-5-oxo-5H-furo[3,2-g]chromene-6-carbaldehydes (3a-g and 4a-d, respectively) and 6-methyl-4,8-dioxo-4,8-dihydropyrano[3,2-g]chromenes (7a-c), were synthesized and evaluated for their antitubercular activities against Mycobacterium tuberculosis H37RV, and cytotoxicity (CC₅₀) in the VERO cell MABA assay. The results indicate that the furanochromene series of compounds (3a-g and 4a-d) showed only weak to moderate antitubercular activity. However, the pyranochromene analog 7b showed good antitubercular activity (IC₉₀: 5.9 μg/mL) and cytotoxicity (CC₅₀: 14.27 μg/mL). The antitubercular activity of 7b was superior to the antituberculosis drug, pyrazinamide (PZA; IC₉₀: >20 μg/mL). Analog 7b was considered to be a lead compound for subsequent structural optimization.     

Bis(oxyphenylene)benzimidazoles: a novel class of anti-Plasmodium falciparum agents

A small library of 26 2,2′-[alkane-α,ω-diylbis(oxyphenylene)]bis-1H-benzimidazoles has been prepared and evaluated against Giardia intestinalis, Entamoeba histolytica, Trypanosoma brucei rhodesiense, Trypanosoma cruzi, Leishmania donovani, and Plasmodium falciparum. Among the tested compounds, eight derivatives (17, 19, 20, 24, 27, 30, 32 and 35) exhibited an anti-Plasmodium falciparum activity characterized by IC₅₀ values in the range of 180–410 nM (0.11–0.21 μg/mL) and selectivity indexes (IC₅₀ rat skeletal myoblasts L6 cells vs IC₅₀P. falciparum K1 strain) varying between 92 and more than 450. Two of the eight novel drug leads, namely compounds 19 and 32, were also active against G. intestinalis and L. donovani with selectivity indexes of 122 and >164 respectively.     

New AZT Analogues Having 5′-Alkylsulfonyl Groups: Synthesis and Anti-HIV Activity

New derivatives of azidothymidine (AZT) substituted by alkyl and alkylsulphonyl groups at N-3 and C-5′, respectively, have been synthesized. The new synthesized derivatives showed remarkable anti-HIV-1 and HIV-2 activity in MT-4 cells. Compounds 8 and 10 have IC₅₀ values of 0.83 and 0.31 μg/mL against HIV-1 with therapeutic index of 83 and 403, respectively, and IC₅₀ values of 0.93 and 0.29 μg/mL against HIV-2 with therapeutic index of 74 and 431, respectively. This means that compounds 8 and 10 were cytotoxic to MT-4 cells at CC₅₀ of 69.2 μg/mL and 125 μg/mL, respectively.     

Synthesis and Biological Evaluation of Novel Carbazole Hybrids as Promising Antimicrobial Agents

Two series of carbazole analogs of 8‐methoxy‐N‐substituted‐9H‐carbazole‐3‐carboxamides (series 1) and carbazolyl substituted rhodanines (series 2) were synthesized through facile synthetic routes. All the final compounds from these two series were evaluated for their preliminary in vitro antifungal and antibacterial activity against four fungal (Candida albicans, Cryptococcus neoformans, Cryptococcus tropicalis and Aspergillus niger) and four bacterial (Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa) strains, respectively. Among the tested compounds, three compounds of series 1 displayed promising antifungal and antibacterial activity, especially against C. neoformans and S. aureus. In addition, one compound of series 1 displayed notable antimicrobial activity (MIC: 6.25 μg/mL) against clinical isolates of C. albicans and C. neoformans (MIC: 12.5 μg/mL). From the second series, four compounds exhibited significant antifungal and antibacterial activity, especially against C. neoformans and S. aureus. The most active compound of series 2 displayed a prominent antimicrobial activity against C. neoformans (MIC: 3.125 μg/mL) and S. aureus (MIC: 1.56 μg/mL), respectively.     

Synthesis and Antileishmanial Activity of 3-Imidazolylalkylindoles. Part I

The present study was designed to investigate conazoles as new antileishmanial agents. Several 3-imidazolylalkylindoles were prepared under mild reaction conditions and pharmacomodulation at N1 and C5 of the indole ring and at the level of the alkyl chain (R) was carried out starting from the corresponding 3-formylindoles 7–10. All target imidazolyl compounds 38–52 were evaluated in vitro against Leishmania mexicana promastigotes; ketoconazole, amphotericin B and meglumine antimoniate were used as references. Eight out of fifteen compounds (40, 43, 44, 47, 48, 50, 51 and 52) exerted similar activity to ketoconazole, with IC₅₀ values in the range of 2.10–3.30?μg/mL. However the most potent compound, 1-(2-bromobenzyl)-3-(1H-imidazol-1-ylmethyl)-1H-indole (38), exhibited IC₅₀ value (0.011±0.003?μg/mL) 270-fold lower than that of ketoconazole. Four compounds (38, 43, 50 and 52) were also tested against intracellular amastigotes of L. mexicana; compound 38 exhibited the highest activity with an IC₅₀ value of 0.018±0.004?μg/mL.     

Design,synthesis and antimycobacterial activity evaluation of natural oridonin derivatives

In an effort to develop novel potent antitubercular drugs, thirty-one oridonin derivatives were designed and prepared. All the compounds obtained were screened for their in vitro activities against Mycobacterium phlei, Mycobacterium smegmatis and Mycobacterium marinum. Among them, thirteen compounds showed significant inhibitory activity against M. phlei with MICs less than 2 μg/mL. Compounds 2k, 8d, 10c, 10d containing trans-cinnamic acid moiety were the most potent (MIC = 0.5 μg/mL), comparable to the well-known antitubercular drug streptomycin. The preliminary structure–activity relationships (SARs) were also analyzed.     

Synthesis and evaluation of in vitro antiviral activity of 2-[3-(substituted phenyl)-4,5-dihydro-1H-5-pyrazolyl]benzofuran-3-yl chloride derivatives

3-Chlorobenzofuran-2-carbaldehyde was condensed with substituted acetophenone by using the Claisen-Schmidt condensation to obtain 3-(3-chlorobenzofuran-2-yl)-1-(substituted phenyl)-2-propen-1-one (2a-m) which upon further treatment with hydrazine hydrate gave 2-[3-(substituted phenyl)-4,5-dihydro-1H-5- pyrazolyl)benzofuran-3-yl chloride derivatives (3a-m). All the newly synthesized derivatives were evaluated in vitro for cytotoxicity and antiviral activity in Crandell-Rees Feline Kidney cell, human embryonic lung (HEL) cell, HeLa cell and Vero cell cultures against different viruses. Several compounds, i.e. 2f, 2g, 2i, 2m, 3b, 3d, 3g, 3h and 3m proved quite cytotoxic to the host cells (minimum cytotoxic concentration: 1-10 μg/mL). No specific antiviral activity [50% antivirally effective concentration (EC₅₀) ≥ 5-fold lower than the minimum cytototoxic concentration] was observed for any of the compounds.