Synthesis and screening of (E)-1-(β-D-galactopyranosyl)-4-(aryl)but-3-ene-2-one against Mycobacterium tuberculosis

A series of galactose-derived aryl enones were synthesised and screened against Mycobacterium tuberculosis H₃₇Rv. Preliminary results were promising with MIC values in the range 1.56-12.5 μg/mL.     

Design,synthesis and antitubercular evaluation of novel 2-substituted-3H-benzofuro benzofurans via palladium–copper catalysed Sonagashira coupling reaction

A series of novel natural product like 2-substiuted-3H-benzofurobenzofurans designed by molecular hybridization were synthesized in very good yields. The key reactions involved in the synthesis are iodination of 2-dibenzofuranol using iodine monochloride followed by palladium–copper catalyzed Sonagashira-coupling of 1-iododibenzofuran-2-ol with various alkyl and aryl acetylenes. Among the all 10 new compounds screened for in vitro anti-mycobacterial activity against Mycobacterium tuberculosis H37Rv, 2-(4-methoxy-2-methyl phenyl)-3H-benzofuro[3,2-e]benzofuran (7c) was found to be most active with MIC 3.12 μg/mL and has shown lower cytotoxicity with good therapeutic index.     

Synthesis and antitubercular evaluation of novel substituted aryl and thiophenyl tethered dihydro-6H-quinolin-5-ones

A series of novel aryl and thiophenyl tethered dihydro-6H-quinolin-5-ones have been synthesized in very good yields through CeCl₃·7H₂O-NaI catalyzed one-pot condensation of β-enaminones derived from the respective methyl ketones; 1,3-cyclohexanedione & 5,5-dimethyl-1,3-cyclohexanedione and ammonium acetate refluxing in 2-propanol. Dihydro-6H-quinolin-5-ones 3a-f was further derivatized to the respective hydroxymethyl analogs using proline as an organocatalyst in aqueous media. Among the all 18 compounds screened for in vitro antimycobacterial activity against Mycobacterium tuberculosis H₃₇Rv (MTB), dihydro-6H-quinolin-5-ones 4e and 4f were found to be most active with MIC 3.13 μg/mL.     

Design, synthesis and antimycobacterial activity of cinnamide derivatives: a molecular hybridization approach

A series of cinnamide derivatives was designed as potential antimycobacterial agents using molecular hybridization approach. The diamine moiety, a key feature of ethambutol and its other analogs, and certain structural features of cerulenin and cinnamic acid were hybridized to obtain cinnamide derivatives. The minimum inhibitory concentration (MIC) of all synthesized compounds was determined against M. tuberculosis H₃₇R_v using Resazurin Microtitre plate Assay (REMA) method. The synthesized molecules showed good to moderate activity with MIC in the range of 5-150 μM and good safety profile. Additionally, the most potent compound 1a, having MIC 5.1 μM exhibited synergy with rifampicin.     

Microwave assisted one-pot synthesis of highly potent novel isoniazid analogues

A series of novel isoniazid (INH) analogues were synthesized by microwave assisted one pot reaction of INH, various benzaldehydes and dimedone in water with catalytic amount of DBSA. The synthesized compounds were evaluated for their anti-TB activity against Mycobacterium tuberculosis H37Rv (MTB) and multi-drug resistant Mycobacterium tuberculosis (MDR-TB). Among the 29 compounds, compound N-[9-[2-(benzyloxy)phenyl]-3,3,6,6-tetramethyl-1,8-dioxo-2,3,4,5,6,7,8,9-octahydro-10(1H)-acridinyl]isonicotinamide (12) inhibited MTB with MIC of <0.17 μM and MDR-TB with MIC of 0.69 μM.     

Ganoderol B: A potent α-glucosidase inhibitor isolated from the fruiting body of Ganoderma lucidum

α-Glucosidase inhibitor has considerable potential as a diabetes mellitus type 2 drug because it prevents the digestion of carbohydrates. The search for the constituents reducing α-glucosidase activity led to the finding of active compounds in the fruiting body of Ganoderma lucidum. The CHCl₃ extract of the fruiting body of G. lucidum was found to show inhibitory activity on α-glucosidase in vitro. The neutral fraction, with an IC₅₀ of 88.7 μg/ml, had stronger inhibition than a positive control, acarbose, with an IC₅₀ of 336.7 μg/ml (521.5 μM). The neutral fraction was subjected to silica gel column chromatography and repeated p-HPLC to provide an active compound, (3β,24E)-lanosta-7,9(11),24-trien-3,26-diol (ganoderol B). It was found to have high α-glucosidase inhibition, with an IC₅₀ of 48.5 μg/ml (119.8 μM).     

Synthesis and antitubercular evaluation of amidoalkyl dibenzofuranols and 1H-benzo[2,3]benzofuro[4,5-e][1,3]oxazin-3(2H)-ones

A new class of amidoalkyl dibenzofuranols and 1H-benzo[2,3]benzofuro[4,5-e][1,3]oxazin-3(2H)-ones was synthesized in very good yields through polyphosphoric acid supported on silica (PPA-SiO₂) catalyzed one-pot three component condensation of 2-dibenzofuranol; aromatic aldehydes and acetamide or benzamide or urea under solvent free conditions. At 125 °C the reaction led to the formation of amidoalkyl dibenzofuranols 5a-k where as at 160 °C cyclization take place to give oxazin-3(2H)-one analogues 6a-e. Screening all the 16 compounds for in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (MTB) resulted 1-((4-chlorophenyl)(2-hydroxydibenzo[b,d]furanyl)methyl)urea 5h; 1-((4-bromophenyl)(2-hydroxydibenzo[b,d]furanyl)methyl)urea 5i; 1-phenyl-1H-benzo[2,3]benzo furo[4,5-e][1,3]oxazin-3(2H)-one 6a (MIC 3.13 μg/mL) and 1-(4-chlorophenyl)-1H-benzo[2,3]benzofuro[4,5-e][1,3]oxazin-3(2H)-one 6b; 1-(4-bromophenyl)-1H-benzo[2,3]benzofuro [4,5-e][1,3]oxazin-3(2H)-one 6c (MIC 1.56 μg/mL) as most active antitubercular agents.     

Design,synthesis, and bioevaluation of a novel class of (E)-4-oxo-crotonamide derivatives as potent antituberculosis agents

A series of novel (E)-4-oxo-2-crotonamide derivatives were designed and synthesized to find potent antituberculosis agents. All the target compounds were evaluated for their in vitro activity against Mycobacterium tuberculosis H₃₇Rv(MTB). Results reveal that 4-phenyl moiety at part A and short methyl group at part C were found to be favorable. Most of the derivatives displayed promising activity against MTB with MIC ranging from 0.125 to 4?µg/mL. Especially, compound IIIa16 was found to have the best activity with MIC of 0.125?μg/mL against MTB and with MIC in the range of 0.05–0.48?µg/mL against drug-resistant clinical MTB isolates.     

Design,synthesis and in vitro anti-mycobacterial evaluation of gatifloxacin-1H-1,2,3-triazole-isatin hybrids

A set of novel gatifloxacin-1H-1,2,3-triazole-isatin hybrids 6a-l was designed, synthesized and evaluated for their in vitro anti-mycobacterial activities against M. tuberculosis (MTB) H₃₇Rv and MDR-TB as well as cytotoxicity. The results showed that all the targets (MIC: 0.025–3.12 μg/mL) exhibited excellent inhibitory activity against MTB H₃₇Rv and MDR-TB, but were much more toxic (CC₅₀: 7.8–62.5 μg/mL) than the parent gatifloxacin (GTFX) (CC₅₀: 125 μg/mL). Among them, 61 (MIC: 0.025 μg/mL) was 2–32 times more potent in vitro than the references INH (MIC: 0.05 μg/mL), GTFX (MIC: 0.78 μg/mL) and RIF (MIC: 0.39 μg/mL) against MTB H₃₇Rv. The most active conjugate 6 k (MIC: 0.06 μg/mL) was 16–>2048 times more potent than the three references (MIC: 1.0–>128 μg/mL) against MDR-TB. Both of the two hybrids warrant further investigations.     

Synthesis and in vitro antitubercular activity of a series of quinoline derivatives

A series of 33 quinoline derivatives have been synthesized and evaluated for their in vitro antibacterial activity against Mycobacterium tuberculosis H₃₇Rv using the Alamar Blue susceptibility test and the activity expressed as the minimum inhibitory concentration (MIC) in μg/mL. Compounds 5e and 5f exhibited a significant activity at 6.25 and 3.12 μg/mL, respectively, when compared with first line drugs such as ethambutol and could be a good starting point to develop new lead compounds in the fight against multi-drug resistant tuberculosis.     

α-Glucosidase inhibition and antihyperglycemic activity of prenylated xanthones from Garcinia mangostana

An ethanol extract of the fruit case of Garcinia mangostan, whose most abundant chemical species are xanthones, showed potent α-glucosidase inhibitory activity (IC₅₀ = 3.2 μg/ml). A series of isolated xanthones (1-16) demonstrated modest to high inhibition of α-glucosidase with IC₅₀ values of 1.5-63.5 μM. In particular, one hitherto unknown xanthone 16 has a very rare 2-oxoethyl group on C-8. Kinetic enzymatic assays with a p-nitrophenyl glucopyranoside indicated that one of them, compound (9) exhibited the highest activity (K_i = 1.4 μM) and mixed inhibition. Using, a physiologically relevant substrate, maltose, as substrate, many compounds (6, 9, 14, and 15) also showed potent inhibition which ranged between 17.5 and 53.5 μM and thus compared favorably with deoxynojirimycin (IC₅₀ = 68.8 μM). Finally, the actual pharmacological potential of the ethanol extract was demonstrated by showing that it could elicit reduction of postprandial blood glucose levels. Furthermore, the most active α-glucosidase inhibitors (6, 9, and 14) were proven to be present in high quantities in the native seedcase by a HPLC chromatogram.     

Application of click chemistry towards an efficient synthesis of 1,2,3-1H-triazolyl glycohybrids as enzyme inhibitors

An efficient synthesis of novel 1,2,3-1H-triazolyl glycohybrids with two or more than two sugar units or a chromenone moiety via copper-catalysed azide–alkyne cycloaddition (CuAAC), a 1,3-dipolar cycloaddition of glycosyl azides to 2,3-unsaturated alkynyl glycosides or propargyloxy coumarins is described. The synthesised glycohybrids were screened for their α-glucosidase, glycogen phosphorylase and glucose-6-phosphatase inhibitory activities. A few of the glycohybrids showed promising inhibitory activities against these enzymes.     

Synthesis and biological evaluation of novel 1,2,3-triazole derivatives as anti-tubercular agents

A library of seventeen novel 1,2,3-triazole derivatives were efficiently synthesized in excellent yields by the popular ‘click chemistry’ approach and evaluated in vitro for their anti-tubercular activity against Mycobacterium tuberculosis H37Ra (ATCC 25177 strain). Among the series, six compounds exhibited significant activity with minimum inhibitory concentration (MIC) values ranging from 3.12 to 0.78 μg/mL and along with no significant cytotoxicity against MBMDMQs (mouse bone marrow derived macrophages). Molecular docking of the target compounds into the active site of DprE1 (Decaprenylphosphoryl-β-d-ribose-2′-epimerase) enzyme revealed noteworthy information on the plausible binding interactions.     

A microwave-assisted facile regioselective Fischer indole synthesis and antitubercular evaluation of novel 2-aryl-3,4-dihydro-2H-thieno[3,2-b]indoles

A series of novel 2-aryl-3,4-dihydro-2H-thieno[3,2-b]indoles has been synthesised regioselectively in good yields from the reaction of 5-aryldihydro-3(2H)-thiophenones and arylhydrazine hydrochloride. This reaction is found to be assisted by microwaves. The thieno[3,2-b]indoles were evaluated for their in vitro activity against Mycobacterium tuberculosis H37Rv (MTB) and multi-drug resistant M. tuberculosis (MDR-TB). Among 22 compounds screened, [2-(2,4-dichlorophenyl)-7-fluoro-3,4-dihydro-2H-thieno[3,2-b]indole] (6t) was found to the most active compound with MIC of 0.4 μg/mL against MTB and MDR-TB.     

Design,synthesis and evaluation of 1,2,3-triazole-adamantylacetamide hybrids as potent inhibitors of Mycobacterium tuberculosis

A series of novel 1,2,3-triazole-adamantylacetamide hybrids 5a–u, designed by combining bioactive fragments from antitubercular I-A09 and substituted adamantyl urea, were synthesized using copper catalyzed click chemistry. N-(1-Adamantyl)-2-azido acetamide 3 prepared from 1-adamantylamine was reacted with a series of alkyl/aryl acetylenes in the presence of copper sulfate and sodium ascorbate to give new analogues 5a–u in very good yields. Evaluation of all new compounds for in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv (ATCC27294), resulted N-(1-adamantan-1-yl)-2-(4-(phenanthren-2-yl)-1H-1,2,3-triazol-1-yl)acetamide (5t) as most promising lead MIC: 3.12 μg/mL) with selectivity index >15.     

Synthesis and antimycobacterial activity of highly functionalized tetrahydro-4(1H)-pyridinones

A series of 35 2e,3e,6e-triaryltetrahydro-4(1H)-pyridinones, 2e,3e,5e,6e-tetraaryltetrahydro-4(1H)-pyridinones and their N-nitroso and N-cyano analogs have been prepared. All these 35 compounds obtained were screened for their in vitro activity against Mycobacterium tuberculosis H37Rv (MTB). Among them, the N-nitrosopyridinones are found to be more active against MTB than the corresponding N-CN analogs, which, in turn, were slightly more active than NH analogs. In particular, the N-nitroso compounds, 3d, 4b and 4e with halogen-bearing phenyl rings at 2,6-positions showed maximum activity with MIC values of 3.97, 3.11 and 3.11 μM, being more efficacious than the first line anti-TB drugs, ciprofloxacin, ethambutol and pyrazinamide. A general trend has also been discerned in all the three classes of NH, N-CN and N-NO compounds, in each of which those bearing four aryl rings display higher activity than that having three analogously substituted aryl rings disclosing that lipophilicity could be an important factor underlying antimycobacterial activity.     

Inhibition of β-carbonic anhydrases with ureido-substituted benzenesulfonamides

A series of sulfonamides was prepared by reaction of sulfanilamide with aryl/alkyl isocyanates. The ureido-substituted benzenesulfonamides showed a very interesting profile for the inhibition of several carbonic anhydrases (CAs, EC 4.2.1.1) such as the human hCA II and three β-CAs from pathogenic fungal or bacterial species. The Candida albicans enzyme was inhibited with potencies in the range of 3.4-3970 nM, whereas the Mycobacterium tuberculosis enzymes Rv1284 and Rv3273 were inhibited with K_is in the range of 4.8-6500 nM and of 6.4-6850 nM, respectively. The structure-activity relationship for this class of inhibitors is rather complex, but the main features associated with effective inhibition of both α- and β-CAs investigated here have been delineated. The nature of the moiety substituting the second ureido nitrogen is the determining factor in controlling the inhibitory power, probably due to the flexibility of the ureido linker and the possibility of this moiety to orientate in different subpockets of the active site cavities of these enzymes.     

Antitubercular activity of α,ω-diaminoalkanes,H2N(CH2)nNH2

A series of 11 α,ω-diaminoalkanes, (H₂N(CH₂)_nNH₂, n = 2–12) have been evaluated for their in vitro antibacterial activity against Mycobacterium tuberculosis H37Rv. Compounds, (H₂N(CH₂)_nNH₂, n = 9–12), exhibited a very good activities in the range 2.50–3.12 μg/mL, which can be compared with that of the first line drug, ethambutol (3.12 μg/mL). These results and a preliminary QSAR study can be considered an important start point for the rational design of new leads for anti-TB compounds.     

Potent alpha-glucosidase inhibitors purified from the red alga Grateloupia elliptica

Diabetes mellitus is a most serious and chronic disease whose incidence rates are increasing with incidences of obesity and aging of the general population over the world. One therapeutic approach for decreasing postprandial hyperglycemia is to retard absorption of glucose by inhibition of α-glucosidase. Two bromophenols, 2,4,6-tribromophenol and 2,4-dibromophenol, were purified from the red alga Grateloupia elliptica. IC₅₀ values of 2,4,6-tribromophenol and 2,4-dibromophenol were 60.3 and 110.4 μM against Saccharomyces cerevisiae α-glucosidase, and 130.3 and 230.3 μM against Bacillus stearothermophilus α-glucosidase, respectively. In addition, both mildly inhibited rat-intestinal sucrase (IC₅₀ of 4.2 and 3.6 mM) and rat-intestinal maltase (IC₅₀ of 5.0 and 4.8 mM). Therefore, bromophenols of G. elliptica have potential as natural nutraceuticals to prevent diabetes mellitus because of their high α-glucosidase inhibitory activity.     

1,3-Azoles from ortho-naphthoquinones: Synthesis of aryl substituted imidazoles and oxazoles and their potent activity against Mycobacterium tuberculosis

Twenty-three naphthoimidazoles and six naphthoxazoles were synthesised and evaluated against susceptible and rifampicin- and isoniazid-resistant strains of Mycobacterium tuberculosis. Among all the compounds evaluated, fourteen presented MIC values in the range of 0.78 to 6.25 μg/mL against susceptible and resistant strains of M. tuberculosis. Five structures were solved by X-ray crystallographic analysis. These substances are promising antimycobacterial prototypes.