Characterization of Lacticaseibacillus rhamnosus, Levilactobacillus brevis and Lactiplantibacillus plantarum Metabolites and Evaluation of Their Antimicrobial Activity against Food Pathogens

Lactic acid bacteria (LAB) play an important role as natural food preservatives. However, the characterization of the variety of their metabolites is limited. The objective of this study was to determine the production of specific metabolites of Lacticaseibacillus rhamnosus, Levilactobacillus brevis and Lactiplantibacillus plantarum by an optimized liquid chromatography with an ultraviolet/diode detection (HPLC-UV/DAD) method and to investigate their potential antimicrobial activity against specific food pathogens. Based on the results of this study, the main metabolites detected in Levilactobacillus brevis were 103.4 μg mL−1 DL-p-Hydroxyphenyllactic acid (OH-PLA) and 2.59 μg mL−1 vanillic acid, while 216.2 μg mL−1 OH-PLA, 19.0 μg mL−1 salicylic acid, 3.7 μg mL−1 vanillic acid, 6.9 μg mL−1 ferulic acid, 4.2 μg mL−1 benzoic acid and 1.4 μg mL−1 4-Hydrocinnamic acid were identified in the Lactiplantibacillus plantarum strain and 147.6 μg mL−1 OH-PLA and 4.9 μg mL−1 ferulic acid were identified in Lacticaseibacillus rhamnosus. This study provides alternative approaches for the molecules involved in the antimicrobial activity of food microorganism fermentation. These molecules may be used as antimicrobial ingredients in the food industry instead of conventional chemical preservatives.

SYNTHESIS OF 4-(3H)-QUINAZOLINONES FOR POTENTIAL ANTIMICROBIAL ACTIVITY

Quinazolinones are of considerable research interest since their discovery and are found in large numbers as naturally occurring alkaloids. They are reported to exhibit a wide range of useful biological activities like antibacterial, antiviral, antimalarial, anticancer, anticonvulsant, antihypertensive, antidiabetic, antihistamine and anti-inflammatory. There are several new reports on quinazolinone analogues showing a diverse spectrum of biological activities. A new series of 2-styryl 4(3H)- quinazolinone analogues were synthesized using anthranilamide, acetyl chloride and substituted aromatic benzaldehyde. The synthesized analogues (IVa-IVj) were purified by chromatography and characterized by spectroscopy. They were screened for antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Pseudomonas vulgaris, Staphylococcus aureus and Bacillus subtilis using moxifloxacin as the reference standard and for antifungal activity against Candida albicans and Aspergillus niger using ketoconazole as the reference standard. The results indicated that IVa and IVj were active against E. coli, IVd against B. subtilis, IVb against S. aureus and IVa, IVb and IVe against C. albicans. The synthesized analogues did not exhibit activity against A. niger. The 2-styryl 4(3H)- quinazolinone series was found to show good activity against the selected bacterial strains and can serve as good templates for design and synthesis of more potent antibacterial and antifungal entities.

Potential Application of Phage ɸ11 Lytic Proteins in Rapid Detection and Elimination of Staphylococcus aureus

The increasing antibiotic resistance conferred by Staphylococcus aureus to multiple potential antibiotics has become a serious issue of concern and threat to mankind worldwide. In light of this, phage lytic proteins have been reported which show potential antimicrobial activity against pathogenic microorganisms that could be a promising alternative to antibiotics to eradicate the antibiotic resistant problems. This review discusses the various applications of S. aureus phage lytic proteins and the potentiality of aureophage phi 11 endolysin and virion associated peptidoglycan hydrolase (VAPGH) against staphylococcus strains. Phage Phi11 endolysin harbors two enzymatically active domain; cysteine and histidine-dependent amidohydrolase/peptidase (CHAP) and Amidase 2 at the N-terminus and a cell wall binding domain (CBD) SH3 5 at the C-terminus, while virion associated peptidoglycan hydrolase (VAPGH) has two catalytic domains, CHAP and Glucosaminidase (Mannosyl-glycoprotein endo-beta-N-acetylglucosaminidase) at its N-terminal and C-terminal, respectively.

Exploration of BAY 11-7082 as a novel antibiotic

Exposure of the Gram-negative pathogen Pseudomonas aeruginosa to sub-inhibitory concentrations of antibiotics increases formation of biofilms. We exploited this phenotype to identify molecules with potential antimicrobial activity in a biofilm-based high-throughput screen. The anti-inflammatory compound BAY 11-7082 induced dose-dependent biofilm stimulation, indicative of antibacterial activity. We confirmed that BAY 11-7082 inhibits growth of P. aeruginosa and other priority pathogens, including methicillin-resistant Staphylococcus aureus (MRSA). We synthesized 27 structural analogues, including a series based on the related scaffold 3-(phenylsulfonyl)-2-pyrazinecarbonitrile (PSPC), 10 of which displayed increased anti-Staphylococcal activity. Because the parent molecule inhibits the NLR Family Pyrin Domain Containing 3 (NLRP3) inflammasome, we measured the ability of select analogues to reduce IL-1β production in mammalian macrophages, identifying minor differences in the structure-activity relationship for the anti-inflammatory and antibacterial properties of this scaffold. Although we could evolve stably resistant MRSA mutants with cross resistance to BAY 11-7082 and PSPC, their lack of shared mutations suggested that the two molecules could have multiple targets. Finally, we showed that BAY 11-7082 and its analogues potentiate the activity of penicillin G against MRSA, suggesting that this scaffold may serve as an interesting starting point for the development of antibiotic adjuvants.

5-[4-(tert-Butyl)cyclohexylidene]-2-thioxothiazolidin-4-one

The Knoevenagel reaction is an essential synthetic tool in the organic and medicinal chemistry of thiazolidin-4-one derivatives. In the present work, the application of ethylenediamine diacetate (EDDA) as an effective catalyst for the interaction of 2-thioxothiazolidin-4-one with 4-(tert-butyl)cyclohexanone is proposed. The structure of novel synthesized 5-[4-(tert-butyl)cyclohexylidene]-2-thioxothiazolidin-4-one (yield 61%) was confirmed by 1H-, 13C-NMR, LC-MS, IR, and UV spectra. Drug-like properties of the synthesized compound were evaluated in silico using the SwissAdme, and their potential antimicrobial activity against 15 strains of Gram-positive and Gram-negative bacteria as well as yeasts was evaluated in vitro. The synthesized compound possesses satisfactory drug-like parameters and promising antimicrobial properties and presents interest as a prospective intermediate for the forthcoming design of biologically active small molecules.

Citrus scented natural essential oils for crystal salt deodorant

Alum natural mineral salt is the world's leading crystal deodorant which works in removing unpleasant body smell. Some other products attempt to block the sweat pores with harmful chemicals such as aluminum chlorohydrates or aluminum zirconium. However, crystal is hypoallergenic deodorant that is healthy, safe, and effective in inhibiting odor formation on the axillary. The light scent infused with natural essential oils might enhance the properties of the crystal deodorant and its antimicrobial activity in fighting against body odor bacteria. This study was conducted to evaluate the potential antimicrobial activity of both citrus essential oils and alum salt. The essential oils were extracted from Citrus aurantifolia, and Citrus sinensis peels by water-steam distillation and analysed using gas chromatography-mass spectrometry (GC-MS). Antibacterial assay against Escherichia coli was carried out on the extracted essential oils using paper disc diffusion assay. Results showed that no lead and cadmium constituents were detected, while low concentration of iron (0.993 ± 0.0059 ppm) and copper (0.134 ± 0.0078 ppm) were detected in the crystal salt (15% w/v). D-limonene, decanal and citral were major components responsible for the citrus scents aroma. The C. aurantifolia essential oil and 15% w/v alum salt were active against E. coli with inhibitory zones at 7.23 ± 0.15 mm and 11.13 ± 0.51 mm respectively. The citrus scented crystal deodorant was successfully developed and tested.