Synthesis and antimicrobial activity of novel 5-amino-4-cyano-<Emphasis Type="Italic">1H</Emphasis>-pyrazole and quinazolin-4(<Emphasis Type="Italic">3H</Emphasis>)-one derivatives

New substituted aroylhydrazones (4a-f) were synthesized from the acid hydrazide (3) and the corresponding aldehyde or aldose. 5-Amino-4-cyano-1H-pyrazole derivatives (6a-f) were prepared by the reaction of the aroylhydrazones (4a-f) with malononitrile. The synthesized compounds were tested for antimicrobial activity against various bacteria and fungi and showed moderate to high inhibition activities. Compounds incorporating a sugar moiety as well as a pyrazolyl ring in their structure displayed the highest antimicrobial activity.     

Foetithiophenes C-F,thiophene derivatives from the roots of Ferula foetida

Abstract

Context: Ferula foetida Regel (Apiaceae) is an Iranian medicinal plant with various biological activities including antispasmodic and anthelmintic.

Objective: The sulfur compounds from the roots of F. foetida were isolated and characterized to test their cytotoxic and antimicrobial activities.

Materials and methods: The methanolic extract of the roots of F. foetida was fractionated using silica column chromatography. The components of each fraction were further purified using RP-HPLC. Their structures were elucidated by 1- and 2-D NMR spectroscopy as well as HREIMS. Their cytotoxic and antimicrobial activities were evaluated using Alamar Blue assay and broth microdilution method, respectively.

Results: Four new thiophene derivatives, namely foetithiophenes C-F (3–6), together with four known compounds, foetithiophenes A (1) and B (2), coniferaldehyde, and sinapic aldehyde, were isolated from the roots of F. foetida. Antimicrobial activities were observed in particular against the Gram-positive bacteria. The best antimicrobial activity was observed for compound 6 against B. cereus with a MIC value 50?µg/mL. The tested compounds did not show cytotoxic properties against MCF-7 and K562 cells.

Conclusion: Four new thiophene derivatives including foetithiophenes C-F (3–6) were characterized from the roots of F. foetida. Foetithiophene F (6) exhibited the most potent activity against the Gram-positive bacteria B. cereus.     

4H-1,4-benzothiazine, dihydro-1,4-benzothiazinones and 2-amino-5-fluorobenzenethiol derivatives: design, synthesis and in vitro antimicrobial screening

As part of our studies focused on the design and synthesis of new antimicrobial agents a series of 7‐fluoro‐3,4‐dihydro‐2H‐1,4‐benzothiazine derivatives ( 4a–4f , 4h ) and 7‐fluoro‐2H‐1,4‐benzothiazin‐3(4H)‐one analogues ( 4j–4o ) were synthesized and evaluated for their in vitro inhibitory activity against a representative panel of Gram‐positive and Gram‐negative bacteria strains and also toward selected fungi species. These compounds were prepared in one step from chloro‐substituted‐2‐amino‐5‐fluorobenzenethiol 6a–6c . The biological screening identified in compounds 4a , 4j and 4l the most promising results of both series showing an interesting antimicrobial activity. Our antibiotic investigation was also completed by testing the key intermediates 6a–6c . Surprisingly, 6a–6c emerged as the compounds exhibiting the highest antimicrobial activity by possessing a remarkable antibacterial effect against the Gram‐positive strains with MIC (minimal inhibitory concentration) values between 2 and 8 µg/mL and the fungi panel with MIC values between 2 and 8 µg/mL. These results may prove useful in the design of a novel pool of antimicrobial agents.     

Synthesis,in‐vitro Microbial and Cytotoxic Studies of New Benzimidazole Derivatives

Several new classes of benzimidazole derivatives were synthesized and evaluated for in‐vitro antimicrobial and cytotoxic activities. The results showed that all synthesized compounds exhibited moderate antimicrobial activity, and compounds 2 , 4 , and 13 displayed cytotoxic activity (as LD₅₀) at the concentration 1×10^–3 M against Artemia salina.     

Synthesis and in?vitro antimicrobial activity of benzo[b][1,4]thiazin-3(4H)-ones via smiles rearrangement

New benzo[b][1,4]thiazin-3(4H)-one derivatives (compounds 12a–p) were synthesized via Smiles rearrangement and assayed in vitro for their antimicrobial activity against Gram-positive, Gram-negative bacteria and fungi. The antimicrobial activity of the benzo[b][1,4]thiazin-3(4H)-ones showed, on the whole, potent toward all tested Gram-positive and Gram-negative microorganism (minimal inhibitory concentration ranging from 16 to 64 μg/ml), whereas weak effectiveness was exhibited against fungi. Data obtained suggested that 12g, 12i, and 12o exerted the best antibacterial activity against Gram-positive bacteria and compound 12b demonstrated the best inhibition of Gram-negative bacteria. These observations provide some predictions to design further antimicrobial active compounds prior to their synthesis following with molecular modeling studies.     

Synthesis,antibacterial and antifungal activities of novel thiazolidinyl sulfonamides of quinazolin-4(3<Emphasis Type="Italic">H</Emphasis>)ones

Some novel derivatives of quinazolinone including 2-[2-(2, 6-dichlorophenyl)amino]phenylmethyl-3-{4-[2-(substituted phenyl)-4-oxo-thiazolidin-3-yl]phenylsulfonamido-1-yl}-6-bromoquinazolin-4(3H)ones (4a – 4l) were prepared from 2-[2-(2, 6-dichlorophenyl) amino]phenylmethyl-3-{[4-(N-substituted arylidene)phenyl]-sulfonamide-1-yl}-6-bromo quinazolin-4(3H)ones (3a – 3l). Twenty four synthesized compounds were screened in vitro for their antibacterial and antifungal activities. Minimum inhibitory concentration (MIC) values of all the twenty four compounds were determined. Some of these compounds exhibited significant antimicrobial activity.     

Synthesis,antimicrobial evaluation,ot-QSAR and mt-QSAR studies of 2-amino benzoic acid derivatives

A series of 2-amino benzoic acid derivatives (1–28) were synthesized and evaluated for their in vitro antimicrobial activity against the panel of Gram positive, Gram negative bacterial and fungal strains. The results of antimicrobial studies indicated that, in general, the synthesized compounds were found to be bacteriostatic and fungistatic in action. QSAR studies performed by the development of one target and multi target models indicated that multi-target model was effective in describing the antimicrobial activity as well demonstrated the effect of structural parameters viz. LUMO, ³χ^v and W on antimicrobial activity of 2-amino benzoic acid derivatives.     

Synthesis of benzo[b][1,4]oxazin-3(4H)-ones via smiles rearrangement for antimicrobial activity

The benzo[b][1,4]oxazin-3(4H)-one derivatives, 1a–p, carrying F, Br, and Cl on the benzene ring, or benzyl, cyclohexyl, n-hexyl, and tetrafuryl methylene groups attached to nitrogen atom were synthesized via Smiles rearrangement and assayed in vitro for their antimicrobial activity against Gram-positive, Gram-negative bacteria, and fungi. The antimicrobial activity of the benzo[b][1,4]oxazin-3(4H)-ones showed, on the whole, potency toward all the tested Gram-positive and Gram-negative microorganism (MIC ranging from 16 to 64 μg/ml), whereas weak effectiveness was exhibited against fungi. Data obtained suggest that fluorine atom in the compounds, 1c, 1f, 1i plays an important role in enhancing the antimicrobial properties of this class of compounds. These observations provide some predictions to design further antimicrobial active compounds prior to their synthesis according to molecular modeling studies.     

Antimicrobial activities of some Thai traditional medical longevity formulations from plants and antibacterial compounds from Ficus foveolata

Context: Medicinal plants involved in traditional Thai longevity formulations are potential sources of antimicrobial compounds.

Objective: To evaluate the antimicrobial activities of some extracts from medicinal plants used in traditional Thai longevity formulations against some oral pathogens, including Streptococcus pyogenes, Streptococcus mitis, Streptococcus mutans, and Candida albicans. An extract that possessed the strongest antimicrobial activity was fractionated to isolate and identify the active compounds.

Materials and methods: Methanol and ethyl acetate extracts of 25 medicinal plants used as Thai longevity formulations were evaluated for their antimicrobial activity using disc diffusion (5?mg/disc) and broth microdilution (1.2–2500?µg/mL) methods. The ethyl acetate extract of Ficus foveolata Wall. (Moraceae) stems that exhibited the strongest antibacterial activity was fractionated to isolate the active compounds by an antibacterial assay-guided isolation process.

Results and discussion: The ethyl acetate extract of F. foveolata showed the strongest antibacterial activity with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 19.5–39.0 and 39.0–156.2?µg/mL, respectively. On the basis of an antibacterial assay-guided isolation, seven antibacterial compounds, including 2,6-dimethoxy-1,4-benzoquinone (1), syringaldehyde (2), sinapaldehyde (3), coniferaldehyde (4), 3β-hydroxystigmast-5-en-7-one (5), umbelliferone (6), and scopoletin (7), were purified. Among these isolated compounds, 2,6-dimethoxy-1,4-benzoquinone (1) exhibited the strongest antibacterial activities against S. pyogenes, S. mitis, and S. mutans with MIC values of 7.8, 7.8, and 15.6?µg/mL, and MBC values of 7.8, 7.8, and 31.2?µg/mL, respectively. In addition, this is the first report of these antibacterial compounds in the stems of F. foveolata.     

Anti-acne activities of pulsaquinone, hydropulsaquinone, and structurally related 1, 4-quinone derivatives

Quinone type compound, pulsaquinone 1, isolated from the aqueous ethanol extract of the roots of Pulsatilla koreana exhibited antimicrobial activities against an anaerobic non-spore-forming gram-positive bacillus, Propionibacterium acnes, which is related with the pathogenesis of the inflamed lesions in a common skin disease, acne vulgaris. Compound 1 was unstable on standing and thus converted to more stable compound 2, namely hydropulsaquinone by hydrogenation, whose activity was comparable to mother compound 1 (MIC for 1 and 2 against P. acnes: 2.0 and 4.0 μg/mL, respectively). Other structurally-related quinone derivatives (3–13) were also tested for structure-activity relationship against anaerobic and aerobic bacteria, and fungi. The antimicrobial activity was fairly good when the quinone moiety was fused with a nonpolar 6- or 7-membered ring on the right side whether or not conjugated (1,4-naphtoquinone derivatives 3–5), while simple quinone compounds 6–9 showed poor activity. It seems that the methoxy groups at the left side of the quinone function deliver no considerable antimicrobial effect.     

Synthesis and antimicrobial activity of new 1-[(tetrazol-5-yl)methyl] indole derivatives,their 1,2,4-triazole thioglycosides and acyclic analogs

New 1-[(tetrazol-5-yl)methyl]indole derivatives, their acyclic nucleoside analogs and the corresponding glycoside derivatives were synthesized. Furthermore, the [)(1,2,4-triazol-3-yl)methyl])-2H-tetrazole derivative as well as the corresponding thioglucoside were prepared. The synthesized compounds were tested for their antimicrobial activity against Aspergillus Niger, Penicillium sp, Candida albican, Bacillus subtilis, Streptococcus lacti, Escherichia coli, Pseudomonas sp., and streptomyces sp. Compounds 3, 5 and 19b exhibited potent antibacterial activity and compounds 4, 5 and 10 exhibited high activities against the tested fungi compared with fusidic acid.     

Synthesis,antioxidant and antimicrobial evaluation of simple aromatic esters of ferulic acid

Aromatic ester derivatives of ferulic acid where the phenolic hydroxyl is free (6a–d) or acetylated (5a–d) were evaluated for their antioxidant and antimicrobial properties. The superoxide radical scavenging capacity of compounds 5d and 6d–e (IC₅₀ of 0.19, 0.27 and 0.20 mM, respectively) was found to be twice as active as α-tocopherol (IC₅₀ = 0.51 mM). DPPH radical scavenging capacity was moderate and only found in compounds bearing free phenolic hydroxyl groups (6a–e). With regard to antimicrobial properties, compounds 6b and 6c displayed significant activity against Enterococcus faecalis (MICs = 16 μg/mL) and vancomycin-resistant E. faecalis (MIC for 6b, 32 and for 6c, 16 μg/mL). Compound 6c also demonstrated prominent activity against planktonic Staphylococcus aureus with a MIC value of <8 μg/mL and it inhibited bacterial biofilm formation by S. aureus with a MBEC value of <8 μg/mL, which was 64 and 128 times more potent than ofloxacin and vancomycin, respectively.     

Synthesis and antimicrobial activity of 1,2,3-triazoles containing quinoline moiety

A new series of substituted 1,2,3-triazoles (4a-n) were synthesized from 4-azido-2,8-bistrifluoromethylquinoline 2. The 1,3-dipolar cycloaddition reaction of 2 with ethyl acetoacetate afforded 1-(2,8-Bistrifluoromethylquinolin-4-yl)-5-methyl-1,2,3-triazole-4-carboxylic acid 3, which was then converted into its corresponding acid hydrazide 3a. Condensation of this hydrazide with different aromatic aldehydes resulted in the formation of Schiff’s bases, N-[1-Arylmethylene]-1-[2,8-bistrifluoromethylquinoline-4-yl]-5-methyl-1H-1,2,3-triazole-4-carbohydrazides (4a-n). These newly synthesized 1,2,3-triazole derivatives were characterized by analytical and spectral data. All the synthesized compounds were evaluated in vitro for their antibacterial and antifungal activity. A brief investigation of the structure activity relationships revealed that the nature of the substituent on position 4 of the triazole ring influences the antimicrobial activity. Among the newly synthesized compounds, the most active compound was 4n, which contained the 3-methylthien-2-yl moiety and showed a broad spectrum of antimicrobial activity against all the strains used for testing. Compounds 4b, 4c, 4e, 4f, 4h and 4l showed significant antimicrobial activity at the concentration of 6.25 μg/mL.     

Three new amino acid derivatives from edible mushroom Pleurotus ostreatus

Three new amino acid derivatives, oxalamido-L-phenylalanine methyl ester (1), oxalamido-L-leucine methyl ester (2), and lumichrome hydrolyzate (3), together with nine known compounds (4–12), were isolated from the solid culture of edible mushroom Pleurotus ostreatus. Their structures were elucidated on the basis of extensive spectroscopic analysis. The absolute configurations of 1 and 2 were established by the chiral synthesis and confirmed by circular dichroism (CD) analysis of their total synthesis products and natural isolates. All new compounds were evaluated for their antioxidant effects, antimicrobial activities, and cytotoxic activity. Compounds 1–3 showed weak antifungal activities against Candida albicans with minimum inhibitory concentration (MIC) value of 500 μg/ml.     

Synthesis,antimicrobial evaluation,and QSAR analysis of 2-isopropyl-5-methylcyclohexanol derivatives

A series of 2-isopropyl-5-methylcyclohexanol derivatives were synthesized and evaluated for their antibacterial activity against Gram-positive Staphylococcus aureus and Bacillus subtilis and Gram-negative Escherichia coli and in vitro antifungal activity against Candida albicans and Aspergillus niger. The results of antimicrobial activity demonstrated that the compounds 10, 20, and 21 were the most active ones among the synthesized compounds. The QSAR studies revealed the importance of dipole moment (μ), total energy (Te), and topological parameters (κ₁ and κ₃) in describing the antimicrobial activity of 2-isopropyl-5-methylcyclohexanol derivatives.     

Identification of highly potent α-glucosidase inhibitory and antioxidant constituents from Zizyphus rugosa bark: enzyme kinetic and molecular docking studies with active metabolites

Context: Previous studies have shown that extracts of Zizyphus rugosa Lam. (Rhamnaceae) bark contained phytoconstituents with antidiabetic potential to lower blood glucose levels in diabetic rats. However, there has been no report on the active compounds in this plant as potential antidiabetic inhibitors.

Objective: We evaluated the α-glucosidase inhibitory and antioxidant activities of Z. rugosa extract. Moreover, the active phytochemical constituents were isolated and characterized.

Materials and methods: The α-glucosidase inhibition of crude ethanol extract obtained from the bark of Z. rugosa was assayed as well as the antioxidant activity. Active compounds (1–6) were isolated, the structures were determined, and derivatives (2a–2?l) were prepared. All compounds were tested for their α-glucosidase inhibitory (yeast and rat intestine) and antioxidant (DPPH) activities.

Results: The active α-glucosidase inhibitors (1–6) were isolated from Z. rugosa bark and 12 derivatives (2a–2?l) were prepared. Compound 2 showed the most powerful yeast α-glucosidase inhibitory activity (IC₅₀ 16.3?μM), while compounds 3 and 4 display only weak inhibition toward rat intestinal α-glucosidase. Moreover, compound 6 showed the most potent antioxidant activity (IC₅₀ 42.8?μM). The molecular docking results highlighted the role of the carboxyl moiety of 2 for yeast α-glucosidase inhibition through H-bonding.

Discussion and conclusions: These results suggest the potential of Z. rugosa bark for future application in the treatment of diabetes and active compounds 1 and 2 have emerged as promising molecules for therapy.     

Dodecanoic acid derivatives: Synthesis, antimicrobial evaluation and development of one-target and multi-target QSAR models

In this study a series of dodecanoic acid derivatives (1–30) were synthesized and evaluated for in vitro antimicrobial activity against the panel of Gram positive, Gram negative bacterial and fungal strains. 4-Nitro phenyl dodecanoate (4) and quinolin-8-yl dodecanoate (5) emerged as most effective antibacterial agents, and 1-(4-benzylpiperazin-1-yl) dodecan-1-one (15) was found to be the most effective antifungal agent amongst the synthesized dodecanoic acid derivatives. Quantitative structure activity relationship (QSAR) studies performed by the development of one-target and multi-target models indicated that multi-target model was effective in describing the antimicrobial activity of dodecanoic acid derivatives as well demonstrated the importance of topological parameter, zero-order molecular connectivity index (⁰χ).     

Bioassay-guided isolation and evaluation of antimicrobial compounds from Ixora megalophylla against some oral pathogens

Context Ixora megalophylla Chamch. (Rubiaceae) is a new plant species recently found in southern Thailand. Ethyl acetate extracts of its leaves and stems showed antimicrobial activities.

Objectives To isolate and identify the antimicrobial compounds from I. megalophylla leaves and stems.

Materials and methods The dried leaves (1.7?kg) and stems (3.5?kg) were consecutively extracted with petroleum ether (5?L?×?4), ethyl acetate (5?L?×?3) and ethanol (5?L?×?4) under reflux conditions. The ethyl acetate extract was subjected to an antimicrobial assay guided isolation with Candida albicans and Streptococcus mutans. Compounds 1–10 were identified by ¹H NMR, ¹³C NMR and EI-MS. Minimal lethal concentration (MLC) against C. albicans and Streptococcus spp. was determined using a broth microdilution method for 48 and 24?h, respectively.

Results and discussion On the basis of the antimicrobial assay guided isolation, 10 known compounds, including vanillic acid (1), syringic acid (2), 4-hydroxy benzaldehyde (3), scopoletin (4), loliolide (5), syringaldehyde (6), sinapaldehyde (7), coniferaldehyde (8), syringaresinol (9) and 2,2′-dithiodipyridine (10), were identified. Compounds 1–5 were purified from the ethyl acetate extract of the leaves, while 6–9 and 10 were from the ethyl acetate and ethanol extracts of the stems, respectively. Among these isolates, 10 showed the strongest antibacterial activities against S. mutans and Streptococcus mitis, with minimum inhibitory concentrations (MICs) of 2–4?μg/mL, and MLC of 4?μg/mL, as well as having a weak antifungal activity against C. albicans (MIC of 125?μg/mL). This is the first report of the antimicrobial activities of 10.     

A new prenylated flavone from Pleione bulbocodioides

A new prenylated flavone, 3,5,7,3′-tetrahydroxy-8,4′-dimethoxy-6-(3-methylbut-2- enyl)flavone (1), together with three known flavone derivatives (2–4), two known dihydrophenanthrenes (5–6), two known lignin derivatives (7–8), and three known phenolic glycoside compounds (9–11) were isolated from the n-BuOH extract of Pleione bulbocodioides. High-resolution electrospray ionization mass spectroscopy (HRESIMS), FTIR spectroscopy, and NMR techniques were used to elucidate the structures of these compounds. Biological investigations showed that compound 5, 4,7-dihydroxy-2-methoxy-9,10-dihydrophenanthrene, exhibited potent anti-inflammatory activity on LPS-stimulated NO production in BV-2 microglial cells, with IC₅₀ value of 5.44 μM.     

Synthesis and Antimicrobial Evaluation of 6‐Alkylamino‐N‐phenylpyrazine‐2‐carboxamides

This work presents synthesis and antimicrobial evaluation of nineteen 6‐alkylamino‐N–phenylpyrazine‐2‐carboxamides. Antimycobacterial activity was determined against Mycobacterium tuberculosis H37Rv, M. kansasii and two strains of M. avium. Generally, the antimycobacterial activity increased with prolongation of simple alkyl chain and culminated in compounds with heptylamino substitution ( 3e , 4e ) with MIC = 5–10 μm against M. tuberculosis H37Rv. On the contrary, derivatives with modified alkyl chain (containing e.g. terminal methoxy or hydroxy group) as well as phenylalkylamino derivatives were mainly inactive. The most active compounds (with hexyl to octylamino substitution) were evaluated for their in vitro activity against drug‐resistant strains of M. tuberculosis and possessed activity comparable to that of the reference drug isoniazid. None of the tested compounds were active against M. avium. Some derivatives exhibited activity against Gram‐positive bacteria including methicillin‐resistant Staphylococcus aureus (best MIC = 7.8 μm ), while Gram‐negative strains as well as tested fungal strains were completely unsusceptible. Active compounds were tested for in vitro toxicity on various cell lines and in most cases were non‐toxic up to 100 μm .