Essential Oils-Based Antibacterial Agent Against Escherichia coli O157:H7 Biofilm on Cucumber

Quaternary Ammonium Salt Strategy and Molecular Docking Studies of Novel 5-Acyl-8-(Arylamino)-Quinolines by Acetyl and Methanesulfonyl Chloride for Dual Evaluation Bioactivity

Six quinoline derivatives containing quaternary ammonium salts and acyl chloride groups were synthesized from ethyl 8-chloro-[1,3]dioxolo[4,5-g]quinoline-7-carboxylate in several step. With berberine as the positive control, three human cancer cell lines (HCT-116, Hela and A549) and human normal liver L-02 cell lines were used to evaluate the cytotoxicity of the newly synthesized compounds in vitro. Compound (V-X) showed good antitumor activity, and the test result of compound (VII) was better than that of positive control group. In terms of antibacterial activity, compound (V-X) has obvious inhibitory effect on Staphylococcus aureus (ATCC 29213) and Escherichia coli (ATCC 8739), and its antibacterial activity is about 1-4 times that of positive control amoxicillin and 1-2 times that of ciprofloxacin. Among them, the most effective compounds (VII) and (X) have 4-fold the antibacterial activity of amoxicillin and 2-fold the antibacterial activity of ciprofloxacin.

Supplementary Information

The online version contains supplementary material available at 10.1134/S1068162023020097.

Origanum dubium (Cypriot Oregano) as a Promising Sanitizing Agent against Salmonella enterica and Listeria monocytogenes on Tomato and Cucumber Fruits

In recent years, the use of natural products such as essential oils (EOs) and other plant extracts for the preservation of fresh produce has attracted much interest from the food industry. Many endemic medicinal and aromatic plants, such as Cypriot oregano (Origanum dubium), present a plethora of properties that can be utilized by the fruit and vegetable sectors of the food industry. The purpose of the present study was to assess the effects of O. dubium EO and hydrosol (at different concentrations and durations of dipping application) for the preservation of tomato and cucumber fruit quality, and their effectiveness as sanitizing agents against two foodborne pathogens (Listeria monocytogenes and Salmonella enterica). The results of this study indicated that increased concentrations of EO, combined with a longer duration of application, resulted in less marketable fruit compared to hydrosol application. Interestingly, EO application at lower concentrations and shorter durations of application (i.e., 0.01% for 5 min) increased fruit antioxidant, ascorbic acid and carotenoid levels (for tomato fruit), suggesting an increase in the nutritional value of the treated fruit, compared to the control. EO and hydrosol were able to decrease the bacterial populations (both bacteria) on fruits. Both products were especially effective against L. monocytogenes, even seven days after their application and storage at 11 °C (up to an approx. 3 log reduction with the EO application). Overall, the results of this study suggest that the use of O. dubium EO and hydrosol could be considered as alternative sanitation means for tomatoes and cucumbers.

Validation of a method of broth microdilution for the determination of antibacterial activity of essential oils

OBJECTIVE

The aim of the present study was to adapt and optimize a broth microdilution method and compare it to the agar dilution method for the evaluation of activity of essential oils from medicinal plants against Gram-negative bacteria. Based on bibliographic research, active and not active oils were selected. The sensitivity and specificity were established as parameters for validation. The comparison between both methods was made using contingency analysis tables, based on the observed frequencies. For both methods, the minimum inhibitory concentration was determined against Escherichia coli strains, in an essential oil concentration range between 0.03 and 0.48% (v/v).

RESULTS

A stable emulsion formation was achieved with the addition of Tween 80 and constant agitation, guaranteeing the continuous contact of oil with bacteria (critical step in the microdilution method). The statistical analysis of results obtained with both methods presented a good sensitivity and specificity (100% in both cases), which let us correctly discriminate between active and non-active oils. The values obtained for the minimal inhibitory concentration were independent of the technique used. Finally, the obtained results show that the validated microtechnique allows important diminishment of time and resources for investigations dealing with essential oils or lipophilic extracts evaluation.

Quality Attributes and Storage of Tomato Fruits as Affected by an Eco-Friendly, Essential Oil-Based Product

The preservation of fresh produce quality is a major aim in the food industry since consumers demand safe and of high nutritional value products. In recent decades there has been a turn towards the use of eco-friendly, natural products (i.e., essential oils-EOs) in an attempt to reduce chemical-based sanitizing agents (i.e., chlorine and chlorine-based agents). The aim of this study was to evaluate the efficacy of an eco-friendly product (EP—based on rosemary and eucalyptus essential oils) and two different application methods (vapor and dipping) on the quality attributes of tomato fruits throughout storage at 11 °C and 90% relative humidity for 14 days. The results indicated that overall, the EP was able to maintain the quality of tomato fruits. Dipping application was found to affect less the quality attributes of tomato, such as titratable acidity, ripening index and antioxidant activity compared to the vapor application method. Vapor application of 0.4% EP increased fruit’s antioxidant activity, whereas tomatoes dipped in EP solution presented decreased damage index (hydrogen peroxide and lipid peroxidation levels), activating enzymes antioxidant capacity (catalases and peroxidases). Moreover, higher EP concentration (up to 0.8%) resulted in a less acceptable product compared to lower concentration (0.4%). Overall, the results from the present study suggest that the investigated EP can be used for the preservation of fresh produce instead of the current commercial sanitizing agent (chlorine); however, the method of application and conditions of application must be further assessed for every commodity tested.

Synthesis and characterization of quaternized agar in KOH/urea aqueous solution

Quaternized agar (QA) is synthesized in KOH/urea aqueous solution and shows low melting and gelling temperatures and antibacterial properties.