SYNTHESIS AND ANTIMICROBIAL EVALUATION OF SOME NEW OXAZINE DERIVATIVES DERIVED FROM COUMARINYL CHALCONES

A series of novel substituted 3-(2-amino-6-phenyl-6H-1,3-oxazin-4-yl)-2H-chromen-2-ones(AO1-AO10) was synthesized upon refluxing ethanolic solution of substituted 3-cinnamoyl-2H chromen-2-one with urea in presence of 20 % NaOH. The intermediate chalcones, substituted 3-cinnamoyl-2H-chromen2-ones, were synthesized by condensing 3-acetyl coumarin with various substituted benzaldehydes in presence of 20 % NaOH. The structures of the final synthesized compounds were characterized by UV, IR, 1 H NMR and mass spectra. The antibacterial activity of the synthesized compounds was estimated by tube dilution method. The turbidity was observed for the synthesized compounds. Few compounds showed promising minimum inhibitory concentration by tube dilution method.

Synthesis, Docking and Antimicrobial Activity of Some New Coumarin Incorporated Thiazole Derivatives

Synthesis and screening of a series of new coumarin derivatives coupled with thiazole are performed for their antimicrobial properties. A series of new thiazolyl coumarin derivatives were synthesized upon refluxing 3-bromoaceytl coumarin, substituted benzaldehyde and thiosemicarbazide in the presence of glacial acetic acid. Substituted 3-acetyl coumarin undergoes bromination in the presence of bromine and chloroform to form 3-Bromoaceytl coumarin. The thiazolyl coumarin derivatives were characterized based on IR, 1H NMR, and Mass spectral data. The docking studies have been carried out against the enzyme DNA gyrase (1KZN). Compound SCT 2 showed the highest docking score -5.662 compared to other compounds. The final synthesized compounds were screened for their antibacterial activity by tube dilution method. Compound SCT 1 and SCT 2 showed significant antibacterial activity with minimum inhibitory concentration of 12.5µg/ml and 6.25µg/ml, respectively, compared to standard Cephalosporin. The MIC results suggest that compounds SCT 1 and SCT 2 showed promising antibacterial activity. So these compounds are interesting lead molecules for further synthesis as antimicrobial agents.

Synthesis, Insilico and Antibacterial Activity Studies of Substituted Dihydro-1, 2-Oxazole Benzopyran-2-One Hybrids

A series of substituted dihydro-1, 2-oxazole benzopyran-2-one (SR1-SR6) were synthesized through the intermediate substituted benzopyran-2-one chalcones and were characterized using spectral analysis. Compounds were docked with receptor DNA Gyrase B (PDB code: 5L3J) to know its interaction and binding energy; ranges -3.38 to -2.15 kcal/mol. Further these compounds were tested for antibacterial activity using tube dilution method and MIC values were observed; ranges 3.12 to 25 µg/ml. Compound 3-(5-(m-tolyl)-4,5-dihydroisoxazol-3-yl)-2H-chromen-2-one (SR3) showed the best interaction with binding energy -3.38 kcal/mol and antimicrobial activity having MIC 3.12 µg/ml. GRAPHICAL ABSTRACT

Synthesis and Antimicrobial Activity of Some New Coumarin Incorporated Pyridine-3-carbonitrile Derivatives

Drug resistance causes serious difficulties in the routine therapy for curing common microbial infections. Thus it is very essential to develop new antimicrobial agents which can offer alternative treatments. The development of potent and effective antimicrobial agents is of utmost importance to overcome the emerging multidrug resistance strains of bacteria and fungi. The technique involves Knoevenagel reaction between substituted salicylaldehyde and ethyl acetoacetate in presence of piperidine as catalyst to give 3-acetyl coumarin. The intermediate coumarinyl chalcones was synthesized by condensing with various substituted benzaldehyde in presence of ethanolic KOH. The final synthesized pyridine-3-carbonitrile derivative was prepared upon refluxing with coumarinyl chalcones with malononitrile in presence of ammonium acetate. All the newly synthesized compounds were assigned on the basis of IR, 1H NMR and mass spectral data. The finalsynthesized compounds were screened for their antibacterial activity tube dilution method. Most of the compounds showed promising MIC by tube dilution method as compared to standard Cephalosporin.

A Synthetic Approach, Characterization and Biological Evaluation of Novel 5-(Arylidene)-2-(5-methyl-1,3,4-thiadiazol-2-ylimino)thiazolidin-4-one Derivatives

The extensive biological potential of thiazolidin-4-one and 1,3,4-thiadiazole moieties, the novel string of 5-(arylidene)-2-(5-methyl-1,3,4-thiadiazol-2-ylimino)thiazolidin-4-one has been synthesized and characterized. The synthesized derivatives were screened for antimicrobial potential using serial tube dilution method. The results showed that all the synthesized compounds have significant biological activity against the microorganisms being tested. The antimicrobial activity of the compounds TA2, TA3, TA4, TA9, TA10 and TA20 against the tested microbial strains was promising. Compound TA4 (2-((5-methyl-1,3,4-thiadiazol-2-yl)imino)-5-(4-nitrobenzylidene)- thiazolidin-4-one) and TA2 (5-(4-chlorobenzylidene)-2-((5-methyl-1,3,4-thiadiazol-2-yl)imino)thiazolidin-4-one) showed promising antimicrobial activity against microbial strains. Compound TA9 (5-(4-(benzyloxy)benzylidene)-2-((5-methyl-1,3,4-thiadiazol-2-yl)imino)thiazolidin-4-one) was found to be the most effective towards B. subtilis. Compound TA10 (5-(3,4-dimethoxybenzylidene)-2-((5- methyl-1,3,4-thiadiazol-2-yl)imino)thiazolidin-4-one) was discovered to be the most potent against the Gram-negative bacteria. Compounds TA3 (5-(4-bromobenzylidene)-2-((5-methyl-1,3,4-thiadiazol- 2-yl)imino)thiazolidin-4-one) and TA20 (5-(2-bromobenzylidene)-2-((5-methyl-1,3,4-thiadiazol-2- yl)imino)thiazolidin-4-one) were the most effective compounds against the fungal strain.

Phytochemical Analysis and Antifungal Activity of Aqueous Leaf Extract of Trema guineensis (Ulmaceae), A Plant from the Ivoirian Pharmacopoeia

Trema guineensis is a woody plant distributed in tropical forest of which leaf and bark extracts are traditionally used for the treatment of various diseases including fever, bronchitis, and gastrointestinal disorders. Previous studies have highlighted their antibacterial activity. So, present work was designed to examine the phytochemical and antifungal properties of aqueous crude extract of T. guineensis leaves. The bioactive components extracted from leaves were tested against pathogenic fungi using the agar tube dilution method. Antifungal activity of aqueous leaves extracts was carried out against selected pathogenic fungal strains as Aspergillus fumigatus, Cryptococcus neoformans and Candida albicans. The phytochemical analysis of the aqueous crude extract revealed the presence of secondary metabolites widely reported as antifungal such as flavonoids, saponins, quinones, alkaloids, polyphenols. The results showed that the aqueous crude leaves extract of T. guineensis was effective in inhibiting the fungal growth and were active against A. fumigatus, C. neoformans and C. albicans with MIC and MFC ranged from 20 to 200 mg/mL and 100 to 400 mg/mL, respectively. The efficient antifungal activity of T. guineensis from the present investigation revealed that aqueous leaf crude extract of the selected plant had a moderate potential to inhibit the growth of pathogenic fungal strains. This finding showed that the aqueous extract of T. guineensis exerted an antifungal effect on C. albicans, A. fumigatus and C. neoformans and supports its traditional use in herbal medicine.

Synthesis and Antimicrobial Activities of Containing Sulfur Heterocyclic Curcumin Derivatives

Eight novel containing sulfur heterocyclic curcumins were synthesized and characterized by 1H-NMR, FTIR and MS spectroscopy. Their antimicrobial activities against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Aspergillus niger were also tested for MIC by using serial tube dilution method. The results showed that the antimicrobial activities of synthesized curcumin derivatives were better than curcumin. Especially, the compound 4-(1,3-dithiolan-2-ylidene)-1,7-di(thiophen-2-yl) hepta-1,6-diene-3,5- dione (2g) exhibited excellent the antimicrobial activities among these curcumin derivatives.

A Comparative Study of the Chemical Composition of the Extracts from Leaves, Stem Bark, and Root Bark of Cassia sieberiana: Antibacterial Activities

In Togo, the abusive use of the root of Cassia sieberiana D.C. in traditional medicine, contributes gradually to the rarefaction of the species. The general objective of this study is to promote the use of vital organs of Cassia sieberiana in traditional medicine in Togo. The identification of secondary metabolites of the extracts (cyclohexane, dichloromethane and methanol) was carried out by GC-MS and by CL-MS / MS. The antibiotic susceptibility test was performed according to the well diffusion method and the MICs and MBCs according to the tube dilution method. Compounds such as sitosterol α-acetate, β-sitosterol, emodin, chaetochromine, luteolin, (±) -catechin, naringenin 5-O-rhamnoside, guibourtinidol- (4 alpha-> 6) -catechin and (-) - epiafzelechin are found in the root and in the stem bark. The identified molecules give the different methanolic extracts, an antibacterial effect on all the germs tested. At the end of this study, it appears that the chemical composition of the stem bark is almost similar to that of the root bark. The leaves would be better placed for the treatment of bacteria tested.

Improved Methods of Extraction and In Vitro Evaluation of Antimicrobial Potential of Stem Bark of Terminalia arjuna

Background:he Terminalia arjuna has been reported for the antimicrobial activity using classical methods of extraction in the literature. As novel extraction methods have gained importance to carry out the extraction of different plant materials, hence it was planned to extract Terminalia arjuna stem bark in a better way and evaluate the change in antimicrobial activity of the improved extracts.Objective:The extraction and evaluation of antimicrobial activity of stem bark of Terminalia arjuna were performed, analyzed and compared using different extraction methods viz. RTE, SE and USAE in this article.Methods:The central composite design among the response surface methods was adopted to carry out the optimization of different parameters of ultrasound-assisted extraction. The central composite design was used for optimization and the values of parameters for an optimized batch of ultrasoundassisted extraction were 800 W power, 10 minutes time and 1:80 ratio of solid/solvent ratio. The invitro antimicrobial activity was performed using the tube dilution method taking ciprofloxacin and fluconazole as standard antibacterial and antifungal agents.Results:The value of estimated total percentage yield was 12.8 % which upon experimentation was obtained as 12.7 %. The extraction efficiency of USAE was found better as compared to the RTE and SE in terms of the extraction yield 4.2% and 6.8 % respectively. The extraction time of the conventional RTE and SE (2 days and 7 days) was also reduced to minutes (10 to 20 min.) in USAE hence was found to be better. The antimicrobial activity of the selected extracts was performed using tube dilution method on selected strains of bacteria S. aureus, B. subtilis, E. coli and fungal A. niger and C. albicans. The results obtained suggested that the USAE technique showed best results as compared to the other extraction methods and the standard drugs taken (MIC values of 3.12, 1.56, 3.12, 1.56 and 3.12 µg/mL respectively).Conclusion:Hence, it was concluded that ultrasound is an effective technique of extraction and has enhanced the antimicrobial principles of the Terminalia arjuna stem bark.