Antimicrobial and Antioxidant Activities of Natural Compounds: Enhance the Safety and Quality of Food

Ferulic acid production from wheat bran by integration of enzymatic pretreatment and a cold-adapted carboxylesterase catalysis

High-value chemical production from natural lignocellulose transformation is a reliable waste utilization approach. A gene encoding cold-adapted carboxylesterase in Arthrobacter soli Em07 was identified. The gene was cloned and expressed in Escherichia coli to obtain a carboxylesterase enzyme with a molecular weight of 37.2 KDa. The activity of the enzyme was determined using α-naphthyl acetate as substrate. Results showed that the optimum enzyme activity of carboxylesterase was at 10 °C and pH 7.0. It was also found that the enzyme could degrade 20 mg enzymatic pretreated de-starched wheat bran (DSWB) to produce 235.8 μg of ferulic acid under the same conditions, which was 5.6 times more than the control. Compared to the chemical strategy, enzymatic pretreatment is advantageous because it is environmentally friendly, and the by-products can be easily treated. Therefore, this strategy provides an effective method for high-value utilization of biomass waste in agriculture and industry.

Carvacrol Selective Pressure Allows the Occurrence of Genetic Resistant Variants of Listeria monocytogenes EGD-e

Essential oils and their constituents, such as carvacrol, are potential food preservatives because of their great antimicrobial properties. However, the long-term effects of these compounds are unknown and raise the question of whether resistance to these antimicrobials could emerge. This work aims to evaluate the occurrence of genetic resistant variants (RVs) in Listeria monocytogenes EGD-e by exposure to carvacrol. Two protocols were performed for the RVs selection: (a) by continuous exposure to sublethal doses, where LmSCar was isolated, and (b) by reiterative exposure to short lethal treatments of carvacrol, where LmLCar was isolated. Both RVs showed an increase in carvacrol resistance. Moreover, LmLCar revealed an increased cross-resistance to heat treatments at acid conditions and to ampicillin. Whole-genome sequencing identified two single nucleotide variations in LmSCar and three non-silent mutations in LmLCar. Among them, those located in the genes encoding the transcriptional regulators RsbT (in LmSCar) and ManR (in LmLCar) could contribute to their increased carvacrol resistance. These results provide information regarding the mode of action of this antimicrobial and support the importance of knowing how RVs appear. Further studies are required to determine the emergence of RVs in food matrices and their impact on food safety.

Quality grade evaluation and related antioxidant activity research of different medicinal parts of Catalpa fruit

Catalpa fruit is a traditional Chinese medicine used in the treatment of diuresis and detumescence; however one-sided quantitative or qualitative investigation limits its overall quality evaluation. Hence, this study proposed to qualitatively and quantitatively evaluate the quality consistency of Catalpa fruit from the perspectives of chromatography and spectroscopy. First, the fusion fingerprints of 15 batches of Catalpa fruit pericarp and 15 batches of Catalpa fruit seed were established by high performance liquid chromatography (HPLC) and ultraviolet (UV) spectroscopy in equal weights, respectively, to avoid the unilaterality of a single analytical technique. The different medicinal parts of Catalpa fruit were graded and evaluated based on a systematically quantified fingerprint method, and the quality of the pericarp and seed was further investigated. The results revealed that the quality of most pericarp and seed samples was within the acceptable level range (grade ≤ 5), and that seed quality was clearly superior to pericarp quality. Furthermore, according to the research findings, the content of p-hydroxybenzoic acid in Catalpa fruit pericarp was generally higher than that in Catalpa fruit seed, while the content of catalposide was generally lower than that in Catalpa fruit seed. Additionally, the fingerprint-efficacy relationship with HPLC was discussed by binary correlation analysis, which indicated that catalposide had the strongest antioxidant activity. This study demonstrated that the analytical techniques based on chromatographic fingerprinting, spectral fingerprinting and antioxidant activity provided new theoretical foundation as well as technical guidance for Catalpa fruit quality control and rational utilization.

A Flavonoid-Rich Extract of Sambucus nigra L. Reduced Lipid Peroxidation in a Rat Experimental Model of Gentamicin Nephrotoxicity

The use of gentamicin (GM) is limited due to its nephrotoxicity mediated by oxidative stress. This study aimed to evaluate the capacity of a flavonoid-rich extract of Sambucus nigra L. elderflower (SN) to inhibit lipoperoxidation in GM-induced nephrotoxicity. The HPLC analysis of the SN extract recorded high contents of rutin (463.2 ± 0.0 mg mL-1), epicatechin (9.0 ± 1.1 µg mL-1), and ferulic (1.5 ± 0.3 µg mL-1) and caffeic acid (3.6 ± 0.1 µg mL-1). Thirty-two Wistar male rats were randomized into four groups: a control group (C) (no treatment), GM group (100 mg kg-1 bw day-1 GM), GM+SN group (100 mg kg-1 bw day-1 GM and 1 mL SN extract day-1), and SN group (1 mL SN extract day-1). Lipid peroxidation, evaluated by malondialdehyde (MDA), and antioxidant enzymes activity-superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX)-were recorded in renal tissue after ten days of experimental treatment. The MDA level was significantly higher in the GM group compared to the control group (p < 0.0001), and was significantly reduced by SN in the GM+SN group compared to the GM group (p = 0.021). SN extract failed to improve SOD, CAT, and GPX activity in the GM+SN group compared to the GM group (p > 0.05), and its action was most probably due to the ability of flavonoids (rutin, epicatechin) and ferulic and caffeic acids to inhibit synthesis and neutralize reactive species, to reduce the redox-active iron pool, and to inhibit lipid peroxidation. In this study, we propose an innovative method for counteracting GM nephrotoxicity with a high efficiency and low cost, but with the disadvantage of the multifactorial environmental variability of the content of SN extracts.

In vitro toxicological evaluation of mesoporous silica microparticles functionalised with carvacrol and thymol

The cytotoxicity of carvacrol- and thymol-functionalised mesoporous silica microparticles (MCM-41) was assessed in the human hepatocarcinoma cell line (HepG2). Cell viability, lactate dehydrogenase (LDH) activity, reactive oxygen species (ROS) production, mitochondrial membrane potential (ΔΨm), lipid peroxidation (LPO) and apoptosis/necrosis analyses were used as endpoints. The results showed that both materials induced cytotoxicity in a time- and concentration-dependent manner, and were more cytotoxic than free essential oil components and bare MCM-41. This effect was caused by cell-particle interactions and not by degradation products released to the culture media, as demonstrated in the extract dilution assays. LDH release was a less sensitive endpoint than the MTT (thiazolyl blue tetrazolium bromide) assay, which suggests the impairment of the mitochondrial function as the primary cytotoxic mechanism. In vitro tests on specialised cell functions showed that exposure to sublethal concentrations of these materials did not induce ROS formation during 2 h of exposure, but produced LPO and ΔΨm alterations in a concentration-dependent manner when cells were exposed for 24 h. The obtained results generally support the hypothesis that the carvacrol- and thymol-functionalised MCM-41 microparticles induced toxicity in HepG2 cells by an oxidative stress-related mechanism that resulted in apoptosis through the mitochondrial pathway.

Anacyclus pyrethrum var. pyrethrum (L.) and Anacyclus pyrethrum var. depressus (Ball) Maire: Correlation between Total Phenolic and Flavonoid Contents with Antioxidant and Antimicrobial Activities of Chemically Characterized Extracts

In this work, two varieties of Anacyclus pyrethrum (L.) including Anacyclus pyrethrum var. pyrethrum (L.) and Anacyclus pyrethrum var. depressus (Ball) Maire were evaluated for their mineral and chemical compositions, total phenolic and flavonoid contents, and antimicrobial and antioxidant activities using hydroalcoholic extracts from their different parts (leaves, capitula, roots, and seeds). The phytochemical and mineral compositions were carried out using standard methods. The antioxidant activity was determined using the DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2-azino-bis 3-ethylbenzothiazolin-6-sulfonic acid), and FRAP (ferric reducing antioxidant power) tests. The antimicrobial activity was assayed using the agar diffusion, minimum inhibitory concentration, and minimum bactericidal concentration methods. The results of the chemical analysis showed that both varieties contained interesting mineral and chemical compositions with potentially active compounds; among them, N-isobutyl-2,4-heptadiene-6-monoynamide and cinnamic acid were detected in the Anacyclus pyrethrum var. pyrethrum (L.) only while thiadiazolo [5,4-d] pyrimidin-7-amine and N-isobutyl-2,4-undecadiene-8,10-diynamide compounds were limited to the Anacyclus pyrethrum var. depressus (Ball) Maire. In vitro antioxidant and antimicrobial activities of the two varieties demonstrated that the different parts had prominent antioxidant and antimicrobial properties. The principal component analysis (PCA) showed great similarity in the activity of the leaves, capitula, and seeds of both plants and a high difference in roots. Anacyclus pyrethrum var. pyrethrum roots were characterized by a high content in phenols and flavonoids and better antibacterial activities compared to Anacyclus pyrethrum var. depressus (Ball) Maire roots, which were characterized by better antioxidant activities. From this study, it can be concluded that the two varieties of Anacyclus pyrethrum (L.) showed promising mineral and chemical compositions with antioxidant and antimicrobial properties.