Synthesis and Biological Evaluation of Some Pyridine Derivatives as Antimicrobial Agents

In this study, several pyridine derivatives were synthesized and evaluated for their in vitro antimicrobial activity against Gram-positive bacteria (Bacillus cereus and Staphylococcus aureus), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and fungi (Aspergillus niger and Candida albicans). The intermediate chalcone derivatives 2a,b were synthesized by condensation of pyrazole aldehydes 1a,b with acetophenone in alcoholic KOH. Cylization of 2a,b with ethyl cyanoacetate and ammonium acetate resulted in pyridine carbonitrile derivatives 3a,b. Furthermore, condensation of pyridine-4-carboxaldeyde, 4 with different amino-derivatives gave rise to pyridine derivatives 5a,b, 6a,b. The oxadiazole derivative 7a was prepared by cylization of 6a with acetic anhydride. Characterization of the synthesized compound was performed using IR, 1H NMR, 13C NMR spectra and elemental microanalyses. The antimicrobial test results revealed that compounds 5a, 6b and 7a (MIC = 50 μg/ml) exhibited half fold antibacterial activity compared to ampicillin (MIC = 25 μg/ml), against B. cereus. On the other hand, compound 3b (MIC = 25 μg/ml) showed an equivalent activity compared to miconazole (MIC = 25 μg/ml) against C. albicans and to clotrimazole (MIC = 100 μg/ml) against the clinical isolate C. albicans 6647. Moreover, this compound was further tested for its acute toxicity profile. The results showed that its oral and parentral LD50s are more than 300 mg/kg and 100 mg/kg, respectively. Therefore, compound 3b is a good candidate as antifungal agent with good acute toxicity profile, and deserves more investigation to find out its mechanism of action and bioavailability.Keywords: synthesis, pyridine derivatives, in vitro antibacterial, antifungal, acute toxicit

Physicochemical properties and bioactivity of extracts from the roe of New Zealand hoki and southern blue whiting

Various physicochemical properties of New Zealand hoki and southern blue whiting (SBW) roes and the biological activities of their extracts were investigated. Protein, moisture, and ash contents in both roes were similar; however, the lipid content of hoki roe was higher (p < 0.05) than SBW roe (11.0 ± 0.9 and 2.5 ± 0.1, respectively). Both fish roe extracts contained active protease inhibitors toward trypsin and papain. Neither of the roe extracts agglutinated erythrocytes, indicating the absence of lectins. Both fish roe extracts at 5 mg/mL concentration exhibited slight inhibitory effects on the proliferation of breast cancer cells, but neither of the roe extracts exhibited RNase or antifungal activity

PHNQ from Evechinus chloroticus sea urchin supplemented with calcium promotes mineralization in Saos-2 human bone cell line

Polyhydroxylated naphthoquinones (PHNQs), known as spinochromes that can be extracted from sea urchins, are bioactive compounds reported to have medicinal properties and antioxidant activity. The MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cell viability assay showed that pure echinochrome A exhibited a cytotoxic effect on Saos-2 cells in a dose-dependent manner within the test concentration range (15.625-65.5 μg/mL). The PHNQ extract from New Zealand sea urchin Evechinus chloroticus did not induce any cytotoxicity within the same concentration range after 21 days of incubation. Adding calcium chloride (CaCl₂) with echinochrome A increased the number of viable cells, but when CaCl2 was added with the PHNQs, cell viability decreased. The effect of PHNQs extracted on mineralized nodule formation in Saos-2 cells was investigated using xylenol orange and von Kossa staining methods. Echinochrome A decreased the mineralized nodule formation significantly (p < 0.05), while nodule formation was not affected in the PHNQ treatment group. A significant (p < 0.05) increase in mineralization was observed in the presence of PHNQs (62.5 μg/mL) supplemented with 1.5 mM CaCl₂. In conclusion, the results indicate that PHNQs have the potential to improve the formation of bone mineral phase in vitro, and future research in an animal model is warranted