Aim: To evaluate the antimicrobial and antioxidant activities of bioactive compounds isolated from Annona muricata (Linn.) leaf extract. Study Design: In vitro antimicrobial assay of bioactive compounds isolated from solvent fractions of plant leaf extract against selected clinical bacterial and fungal isolates. Antioxidant assay of plant leaf extract. Place and Duration of Study: All the work was carried out in the Departments of Chemistry and Microbiology, Obafemi Awolowo University, Ile-Ife, Nigeria between March, 2015 and January, 2016. Methodology: Isolation of bioactive compounds was by column and thin layer chromatographic techniques. Isolated compounds were characterized by nuclear magnetic resonance spectroscopic analysis. Antimicrobial activities were evaluated by disc diffusion and broth microdilution methods while antioxidant activity was investigated using the 2,2-dipheny-1-picrylhydrazyl (DPPH) radical-scavenging assay. Results: Two compounds kaempferol-3-O-glucoside (1) and 1-(4-Hydroxyphenyl)-3-Phenylpropan-1-one (2) were isolated from the ethyl acetate fraction of leaf extract of A. muricata. The two compounds showed broad spectrum antimicrobial activities with zones of inhibition ranging from 26.00 ± 1.73 to 31 ± 1.00 mm and 17.33 ± 1.15 to 31.33 ± 1.15 mm respectively, for compounds 1 and 2 for the test bacteria species and 15.33 ± 1.15 to 31.33 ± 1.15 mm and 17.67 ± 0.58 to 29.67 ±1.53 mm respectively, for compounds 1 and 2 for the test fungi. Minimum inhibitory concentrations ranged between 0.625-5.00 µg/mL and 1.25-5.00 µg/ml respectively, for compounds 1 and 2. Minimum bactericidal concentrations ranged between 2.5-10.00 µg/mL for both compounds which compared favourably with the reference drugs used. DPPH radical-scavenging activities were IC50 = 13.41 ± 0.64 µg/mL and 7.42 ± 0.90 µg/mL for compounds 1 and 2 respectively, compared with IC50 = 51.99 ± 1.44 µg/ml obtained for the standard ascorbic acid. The results show that both isolated compounds from A. muricata leaf possess in vitro antimicrobial and antioxidant properties and they may be useful as active ingredients in antimicrobial drug formulations and as agents for the control of free radical-related pathological disorders.
A mixture of 2,3-dichloroquinoxaline 1[1] (5.0 g, 25 mmol) and diethanolamine 2 (12 mL, 125 mmol) was heated to 130° C for 3 h, with magnetic stirring. The reaction mixture was cooled to room temperature and then poured into 300 mL of water. The resulting solid was filtered and then recrystallized from water to give white crystals of 2-(1,4-oxazino[2,3-b]quinoxalin-4-yl)ethanol 3 (5.3 g, 91%).
Alzheimer's disease is a chronic and progressive neurodegenerative disease which occurs due to lower levels of acetylcholine neurotransmitters, and results in a gradual decline in memory and other cognitive processes. Acetylcholinesterase and butyrylcholinesterase have been reported to be the primary regulators of the acetylcholine levels in the brain. Evidence shows that acetylcholinesterase activity decreases in Alzheimer's disease, while activity of butyrylcholinesterase elevate in advanced Alzheimer's disease, which suggests a key involvement of butyrylcholinesterase in acetylcholine hydrolysis during Alzheimer's disease symptoms. In order to sustain the level of remaining acetylcholine, acetylcholinesterase and butyrylcholinesterase inhibitors may be used. Therefore, inhibiting the activity of butyrylcholinesterase may be an effective way to control Alzheimer's disease associated disorders. In this study, eleven 3-methylquinoxaline-2-hdrazones were synthesized from the reactions of 3-methylquinoxaline-2-hydrazine with different substituted aromatic ketones and aromatic aldehyde. All the newly synthesized compounds have been characterized on the basis of IR, 1 H-NMR and 13 H-NMR spectral data as well as physical data. All the synthesized compounds were biologically evaluated against cholinesterases (acetylcholinesterase and butyrylcholinesterase). Compounds 2-12 were found to be a good selective inhibitor for acetycholinesterase and butyrylcholinesterase. Among the series, compounds 6 (IC 50 =170 ± 30 µg/mL) and 10 (IC 50 =180 ± 10 µg/mL) were found to be the most active inhibitors against acetylcholinesterase, while compounds 2 (IC 50 =780 ± 10 µg/mL), 5 (IC 50 =550 ± 10 µg/mL) and 6 (IC 50 =790 ± 10 µg/mL), were found to be most active inhibitor against butyrylcholinesterase. The IC 50 values for all the synthesized compounds were lower than standard, eserine (IC 50 =70 ± 20 µg/mL). Their considerable acetylcholinesterase and butyrylcholinesterase inhibitory activities makes them a good candidate for the development of selective acetycholinesterase and butyrylcholinesterase inhibitors.
The review article attempts to give recent advances on quinoxaline and its derivatives. Some pathways to the synthesis of quinoxaline, quinoxaline-2-one and quinoxaline-2,3-dione were reported using simple reactive quinoxaline synthon. In addition, the reactions, biological and technological applications of derivatives of quinoxaline and related compounds were reported.
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