No abstract

Currently, researchers have given special attention to the synthesis of hetero cyclic compounds with nitrogen and oxygen five in five or sixmembered ring systems. This is mainly due to their wide range of biological activities. Hence, in this study, isoxazoline, pyrazole and bypyrimidine derivatives were synthesized from flavonoids, previously isolated from Polygonum senegalense and Psiadia panctulata, and assessed for their antifungal activity. A flavone was reacted with hydrazine hydrate to afford a pyrazole analogue 5methoxy2(5(2,3,4,5tetramethoxyphenyl)1Hpyrazol3yl)benzene1,3 diol (1) Two isoxazoline derivatives namely, 2(4,5dihydro5phenylisoxazol 3yl)5methoxybenzene1,3diol (2) and 2(4,5dihydro5phenylisoxazol 3yl)3,5dimethoxyphenol (3) were successfully synthesized by the reaction of chalcones with hydroxylamine hydrochloride. An oxime derivative (4) was also generated from a similar procedure. A reaction between a chalcone and thiourea gave a bypyrimidine derivative, 4,5dihydro6(2,4 dihydroxy3,6dimethoxyphenyl)4phenylpyrimidine2(1H)thione (5). The products were then assessed for their antibacterial and antifungal activity.All compounds showed no significant activity except compound 2 that demonstrated activity against standard antibacterial agent, Streptococcus aureus with IC 50 value of 7.56 and antifungal Candida neoformans, Candida krusei and Candida glabrata strains with IC 50 values 8.01, 8.11 and 13.74 μg/mL respectively. We, therefore, recommend synthetic optimization of com pound 2 as a potential antimicrobial agent.

Hypericum revolutum subsp. keniense is a plant mainly used to treat diarrhoea, rheumatism, nervous disorders, and wounds in African traditional medicine. The objective of the current work was to establish antibacterial, antioxidant potency, and chemical composition of essential oil from the leaves and flowers of Hypericum revolutum subsp. keniense. The oils were isolated by steam distillation. Antibacterial activity against methicillin-resistant Staphylococcus aureus, Staphylococcus aureus (ATCC 12393), Escherichia coli (ATCC 25922), Acinetobacter baumannii (ATTC 19606), Salmonella enteritidis (NCTC12023), Salmonella typhimurium (ATCC 14028), Pseudomonas aeruginosa (ATCC 15442), and Haemophilus influenzae (ATCC 49766) was carried out by agar disk diffusion and microtiter broth dilution methods. Antioxidant activities of the essential oils were examined by different methods, DPPH, FRAP, and H2O2 assays. Chemical characterization was performed using gas chromatography interfaced with mass spectrometry, Fourier-transform infra-red (FTIR) spectroscopy, and quantification of phenolics and flavonoids by Folin–Ciocalteu reagent and aluminium nitrate, respectively. The oils showed potential antibacterial activity with mean zone of inhibition ranging from 20.67 ± 0.33 to 32.00 ± 1.00 mm at 100% oil concentration against the tested bacteria. Furthermore, the minimum inhibitory concentrations (MICs) in all the tested microorganisms were in the range from 250 to 15.6250 μg/ml. The essential oils derived from the leaves revealed varied antioxidant activity levels with the different methods of assay. The IC50 of values obtained from the three methods, DPPH, FRAP, and H2O2 were ˃1000 μg/ml, 0.31 μg/ml, and 12.33 μg/ml, respectively. Caryophyllene (22.1%) and 2, 3, 4-trimethylhexane were the major chemical components of the essential oils derived from the leaves and flowers, respectively. FTIR spectroscopy of the essential oils from the leaves and flowers showed similarity at peaks for hydroxyl, unsaturated olefinic, and amine functional groups. Further findings indicated that the total phenolic and flavonoid contents essential oils derived from leaves were 130.4 6 ± 10.5 mg GAE/g dry weight and 0.911 ± 0.04 mg CE/g dry weight, respectively. It was therefore concluded that essential oils from the leaves and flowers of H. revolutum subsp. keniense have compounds that have antibacterial and antioxidant potency.

Hypericum revolutum subsp. keniense is a plant mainly used to treat diarrhoea, rheumatism, nervous disorders and wounds in African traditional medicine. The objective of the current work was to establish antibacterial, antioxidant potency and chemical composition of essential oil from the leaves and flowers of Hypericum revolutum subsp. keniense. The oils were isolated by steam distillation. Antibacterial activity against methicillin-resistant Staphylococcus aureus, Staphylococcus aureus (ATCC 12393), Escherichia coli (ATCC 25922), Acinetobacter baumannii (ATTC 19606), Salmonella Enteritidis (NCTC12023), Salmonella Typhimurium (ATCC 14028), Pseudomonas aeruginosa (ATCC 15442), and Haemophilus influenzae (ATCC 49766) were done by Agar Disk Diffusion and Microtiter Broth Dilution methods. Antioxidant activities of the essentail oils were examined by different methods, DPPH, FRAP and H2O2 assays. Chemical characterization was done using Gas Chromatography interfaced with Mass Spectrometry, Fourier-Transform Infra-red (FTIR) spectroscopy and the quantification of phenolics and flavonoids by Folin-Ciocalteu reagent and Aluminium nitrate respectively. The oils showed potential antibacterial activity with mean zone of inhibition ranging from 20.67 ± 0.33 to 32.00 ± 1.00 mm at 100 % oil concentration against the tested bacteria. Furthermore, the minimum inhibitory concentrations (MICs) in all the tested microorganisms were in the range of 250 to 15.6250 µg/ml. The essential oils derived from th leaves revealed varied antioxidant activity levels with the different methods of assay. The IC50 of values obtained from the three methods, DPPH, FRAP and H2O2 were ˃1000 µg/ml, 0.31 µg/ml and 12.33 µg/ml respectively. Caryophyllene (22.1 %) and 2,3,4-trimethylhexane were the major chemical components of the essential oils derived from the leaves and flowers respectively. FTIR spectroscopy of the essential oils from the leaves and flowers showed similarity at peaks for hydroxyl, unsaturated olefinic and amine functional groups. Further findings indicated that the total phenolic and flavonoid contents essential oils derived from leaves were 130.4 6 ± 10.5 mg GAE/g dry weight and 0.911 ± 0.04 mg CE/g dry weight respectively. It was therefore concluded that essential oils from the leaves and flowers of H. revolutum subsp. keniense have compounds that have antibacterial and antioxidant potency.

This paper describes the semi-synthesis and anti-microbial activity of novel pyrazoline derivatives of Polygonum senegalense chalcones. The study was carried out on the understanding that heterocycles with pyrazoline ring systems are known to possess a broad spectrum of biological activities. The derivatives were afforded by refluxing mixtures of chalcones and phenylhydrazine, hydrazine hydrate, and / or acetic acid in DMSO or ethanol at low temperatures between 40-60°C in an oil-bath. The products were characterized in by 1 H-NMR (200 or 400 MHz), 13 C-NMR spectroscopy and ESI-HRMS. NMR data was described in detail for each derivative. The compounds 6-15 have been screened for their in vitro anti-bacterial activity against one gram positive bacteria (S. aureus) and anti-fungal activity against five strains C. krusei, C. neoformans, and C. glabrata. They all showed insignificant antimicrobial activities with lower IC 50 as compared to positive control, except compound 7 that demonstrated moderate antifungal activity with IC 50 values ranging between 8.01 -13.74 µg/mL against C. krusei, C. neoformans and C. glabrata. The compound also showed antibacterial activity of IC 50 value 7.56µg/mL against S. aureus. Based on these findings, we recommend that compound 7 should undergo further structural modification in order to optimize its anti-microbial activity.