In Vitro Antioxidant Properties and Phenolic Profile of Acid Aqueous Ethanol Extracts from Torreya grandis Seed Coat

Torreya grandis is an important economic forestry product in China, whose seeds are often consumed as edible nuts, or used as raw materials for oil processing. To date, as an important by-product of Torreya grandis, comprehensive studies regarding the Torreya grandis seed coat phenolic composition are lacking, which greatly limits its in-depth use. Therefore, in the present study, the Torreya grandis seed coat was extracted by acid aqueous ethanol (TE), and NMR and UHPLC-MS were used to identify the major phenolics. Together with the already known phenolics including protocatechuic acid, catechin, epigallocatechin gallate, and epicatechin gallate, the unreported new compound 2-hydroxy-2-(4-hydroxyphenylethyl) malonic acid was discovered. The results of the antioxidant properties showed that both TE and 2-hydroxy-2-(4-hydroxyphenylethyl) malonic acid exhibited strong ABTS, DPPH, and hydroxyl radical-scavenging activity, and significantly improved the O/W emulsion’s oxidation stability. These results indicate that the TE and 2-hydroxy-2-(4-hydroxyphenylethyl) malonic acid could possibly be used in the future to manufacture functional foods or bioactive ingredients. Moreover, further studies are also needed to evaluate the biological activity of TE and 2-hydroxy-2-(4-hydroxyphenylethyl) malonic acid to increase the added value of Torreya grandis by-products.     

Functional Bacterial Amyloids: Understanding Fibrillation,Regulating Biofilm Fibril Formation and Organizing Surface Assemblies

Functional amyloid is produced by many organisms but is particularly well understood in bacteria, where proteins such as CsgA (E. coli) and FapC (Pseudomonas) are assembled as functional bacterial amyloid (FuBA) on the cell surface in a carefully optimized process. Besides a host of helper proteins, FuBA formation is aided by multiple imperfect repeats which stabilize amyloid and streamline the aggregation mechanism to a fast-track assembly dominated by primary nucleation. These repeats, which are found in variable numbers in Pseudomonas, are most likely the structural core of the fibrils, though we still lack experimental data to determine whether the repeats give rise to β-helix structures via stacked β-hairpins (highly likely for CsgA) or more complicated arrangements (possibly the case for FapC). The response of FuBA fibrillation to denaturants suggests that nucleation and elongation involve equal amounts of folding, but protein chaperones preferentially target nucleation for effective inhibition. Smart peptides can be designed based on these imperfect repeats and modified with various flanking sequences to divert aggregation to less stable structures, leading to a reduction in biofilm formation. Small molecules such as EGCG can also divert FuBA to less organized structures, such as partially-folded oligomeric species, with the same detrimental effect on biofilm. Finally, the strong tendency of FuBA to self-assemble can lead to the formation of very regular two-dimensional amyloid films on structured surfaces such as graphite, which strongly implies future use in biosensors or other nanobiomaterials. In summary, the properties of functional amyloid are a much-needed corrective to the unfortunate association of amyloid with neurodegenerative disease and a testimony to nature’s ability to get the best out of a protein fold.     

Functionalization of a Rigid Divalent Ligand for LecA,a Bacterial Adhesion Lectin

The bacterial adhesion lectin LecA is an attractive target for interference with the infectivity of its producer P. aeruginosa. Divalent ligands with two terminal galactoside moieties connected by an alternating glucose-triazole spacer were previously shown to be very potent inhibitors. In this study, we chose to prepare a series of derivatives with various new substituents in the spacer in hopes of further enhancing the LecA inhibitory potency of the molecules. Based on the binding mode, modifications were made to the spacer to enable additional spacer–protein interactions. The introduction of positively charged, negatively charged, and also lipophilic functional groups was successful. The compounds were good LecA ligands, but no improved binding was seen, even though altered thermodynamic parameters were observed by isothermal titration calorimetry (ITC).     

Potential of Carvacrol and Thymol in Reducing Biofilm Formation on Technical Surfaces

Polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), and stainless steel (SS) are commonly used in medicine and food production technologies. During contact with microorganisms on the surface of these materials, a microbial biofilm is formed. The biofilm structure is difficult to remove and promotes the development of pathogenic bacteria. For this reason, the inhibition of biofilm formation in medical and food production environments is very important. For this purpose, five naturally occurring compounds were used for antimicrobial screening tests. The two with the best antimicrobial properties were chosen to inhibit the biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa. After 3 days of exposure, thymol reduced the amount of biofilm of Pseudomonas aeruginosa within the range of 70–77% and 52–75% for Staphylococcus aureus. Carvacrol inhibited the formation of biofilms by up to 74–88% for Pseudomonas aeruginosa and up to 86–100% for Staphylococcus aureus. Those phenols decreased the enzyme activity of the biofilm by up to 40–100%. After 10 days of exposure to thymol, biofilm formation was reduced by 80–100% for Pseudomonas aeruginosa and by about 79–100% for Staphylococcus aureus. Carvacrol reduced the amount of biofilm by up to 91–100% for Pseudomonas aeruginosa and up to 95–100% for Staphylococcus aureus.     

The Effect of Selected Bee Products on Adhesion and Biofilm of Clostridioides difficile Strains Belonging to Different Ribotypes

There is an ongoing search for alternative treatments for Clostridioides difficile infections. The aim of the study was to investigate the antibacterial and antibiotic activity of bee products against C. difficile strains with different polymerase chain reaction ribotypes (RTs). The minimum inhibitory concentration (MICs) of Manuka honey 550+, goldenrod honey, pine honey, and bee bread were determined by the broth dilution method. C. difficile adhesion to HT-29, HT-29 MTX, and CCD 841 CoN cell lines was assessed. Biofilm was cultured in titration plates and visualized by confocal microscopy. The MICs of Manuka honey for C. difficile 630 and ATCC 9689 strains and control strain, M 120, were 6.25%, 6.25%, and 1.56% (v/v), respectively; of goldenrod honey, 50%, 50%, and 12.5%, respectively; of pine honey, 25%, 25%, and 25%, respectively; and of bee bread, 100 mg/L, 50 mg/L, and 100 mg/L, respectively. Manuka honey (1%) increased adhesion of C. difficile RT176 strains, and one strain of RT023, to the CCD 841 cell line. Pine honey (1%) increased RT027 adhesion to the HT-29 cell line. Manuka honey, pine honey, and bee bread at subinhibitory concentrations increased the adhesion of C. difficile. Our research proved that bee products are active against the tested strains of C. difficile.     

In Vitro Activity of Water Extracts of Olive Oil against Planktonic Cells and Biofilm Formation of Arcobacter-like Species

Extra-virgin olive oils contain many bioactive substances that are phenolic compounds. The survival of Arcobacter-like strains in non-buffered (WEOO) and buffered (BEOO) extracts of olive oils were studied. Time kill curves of different strains were measured in the environment of olive oil extracts of different grades. The activity of the extracts was also monitored for biofilm formation using the Christensen method. In vitro results revealed that extra-virgin olive oil extracts exhibited the strongest antimicrobial effects, especially non-buffered extracts, which exhibited strain inhibition after only 5 min of exposure. The weakest inhibitory effects were observed for olive oil extracts. A decrease in biofilm formation was observed in the environment of higher WEOO concentrations, although at lower concentrations of extracts, increased biofilm formation occurred due to stress conditions. The dialdehydic forms of oleuropein derivatives, hydroxytyrosol, and tyrosol were the main compounds detected by HPLC-CoulArray. The results indicate that not all olive oils had a similar bactericidal effect, and that bioactivity primarily depended on the content of certain phenolic compounds.     

Lemon Oils Attenuate the Pathogenicity of Pseudomonas aeruginosa by Quorum Sensing Inhibition

The chemical composition of three Citrus limon oils: lemon essential oil (LEO), lemon terpenes (LT) and lemon essence (LE), and their influence in the virulence factors production and motility (swarming and swimming) of two Pseudomonas aeruginosa strains (ATCC 27853 and a multidrug-resistant HT5) were investigated. The main compound, limonene, was also tested in biological assays. Eighty-four compounds, accounting for a relative peak area of 99.23%, 98.58% and 99.64%, were identified by GC/MS. Limonene (59–60%), γ-terpinene (10–11%) and β-pinene (7–15%) were the main compounds. All lemon oils inhibited specific biofilm production and bacterial metabolic activities into biofilm in a dose-dependent manner (20–65%, in the range of 0.1–4 mg mL⁻¹) of both strains. Besides, all samples inhibited about 50% of the elastase activity at 0.1 mg mL⁻¹. Pyocyanin biosynthesis decreases until 64% (0.1–4 mg mL⁻¹) for both strains. Swarming motility of P. aeruginosa ATCC 27853 was completely inhibited by 2 mg mL⁻¹ of lemon oils. Furthermore, a decrease (29–55%, 0.1–4 mg mL⁻¹) in the synthesis of Quorum sensing (QS) signals was observed. The oils showed higher biological activities than limonene. Hence, their ability to control the biofilm of P. aeruginosa and reduce the production of virulence factors regulated by QS makes lemon oils good candidates to be applied as preservatives in the food processing industry.     

Cytotoxicity of a Lipid-Rich Extract from Native Mexican Avocado Seed (Persea americana var. drymifolia) on Canine Osteosarcoma D-17 Cells and Synergistic Activity with Cytostatic Drugs

Osteosarcoma is the most common malignant bone tumor in both children and dogs. It is an aggressive and metastatic cancer with a poor prognosis for long-term survival. The search for new anti-cancer drugs with fewer side effects has become an essential goal for cancer chemotherapy; in this sense, the bioactive compounds from avocado have proved their efficacy as cytotoxic molecules. The objective of this study was to determine the cytotoxic and antiproliferative effect of a lipid-rich extract (LEAS) from Mexican native avocado seed (Persea americana var. drymifolia) on canine osteosarcoma D-17 cell line. Also, the combined activity with cytostatic drugs was evaluated. LEAS was cytotoxic to D-17 cells in a concentration-dependent manner with an IC₅₀ = 15.5 µg/mL. Besides, LEAS induced caspase-dependent cell apoptosis by the extrinsic and intrinsic pathways. Moreover, LEAS induced a significant loss of mitochondrial membrane potential and increased superoxide anion production and mitochondrial ROS. Also, LEAS induced the arrest of the cell cycle in the G0/G1 phase. Finally, LEAS improved the cytotoxic activity of cisplatin, carboplatin, and in less extension, doxorubicin against the canine osteosarcoma cell line through a synergistic effect. In conclusion, avocado could be a potential source of bioactive molecules in the searching treatments for osteosarcoma.     

Adhesion and Anti-Adhesion Abilities of Potentially Probiotic Lactic Acid Bacteria and Biofilm Eradication of Honeybee (Apis mellifera L.) Pathogens

Lactic acid bacteria (LAB) naturally inhabits the organisms of honeybees and can exhibit adhesive properties that protect these insects against various pathogenic microorganisms. Thus, cell surface (auto-aggregation, co-aggregation, hydrophobicity) and adhesive properties of LAB to two abiotic (polystyrene and glass) and four biotic (collagen, gelatin, mucus, and intestinal Caco-2 cells) surfaces were investigated. Additionally, anti-adhesion activity and the eradication of honeybee pathogen biofilms by LAB metabolites (culture supernatants) were determined. The highest hydrophobicity was demonstrated by Pediococcus pentosaceus 19/1 (63.16%) and auto-aggregation by Lactiplantibacillus plantarum 18/1 (71.91%). All LAB showed a broad spectrum of adhesion to the tested surfaces. The strongest adhesion was noted for glass. The ability to co-aggregate with pathogens was tested for the three most potently adherent LAB strains. All showed various levels of co-aggregation depending on the pathogen. The eradication of mature pathogen biofilms by LAB metabolites appeared to be weaker than their anti-adhesive properties against pathogens. The most potent anti-adhesion activity was observed for L. plantarum 18/1 (98.80%) against Paenibacillus apiarius DSM 5582, while the strongest biofilm eradication was demonstrated by the same LAB strain against Melissococcus plutonius DSM 29964 (19.87%). The adhesive and anti-adhesive activity demonstrated by LAB can contribute to increasing the viability of honeybee colonies and improving the conditions in apiaries.     

Zinc-Chelating Compounds as Inhibitors of Human and Bacterial Zinc Metalloproteases

Inhibition of bacterial virulence is believed to be a new treatment option for bacterial infections. In the present study, we tested dipicolylamine (DPA), tripicolylamine (TPA), tris pyridine ethylene diamine (TPED), pyridine and thiophene derivatives as putative inhibitors of the bacterial virulence factors thermolysin (TLN), pseudolysin (PLN) and aureolysin (ALN) and the human zinc metalloproteases, matrix metalloprotease-9 (MMP-9) and matrix metalloprotease-14 (MMP-14). These compounds have nitrogen or sulfur as putative donor atoms for zinc chelation. In general, the compounds showed stronger inhibition of MMP-14 and PLN than of the other enzymes, with K_i values in the lower μM range. Except for DPA, none of the compounds showed significantly stronger inhibition of the virulence factors than of the human zinc metalloproteases. TPA and Zn230 were the only compounds that inhibited all five zinc metalloproteinases with a K_i value in the lower μM range. The thiophene compounds gave weak or no inhibition. Docking indicated that some of the compounds coordinated zinc by one oxygen atom from a hydroxyl or carbonyl group, or by oxygen atoms both from a hydroxyl group and a carbonyl group, and not by pyridine nitrogen as in DPA and TPA.     

Inhibition of the Quorum Sensing System,Elastase Production and Biofilm Formation in Pseudomonas aeruginosa by Psammaplin A and Bisaprasin

Natural products derived from marine sponges have exhibited bioactivity and, in some cases, serve as potent quorum sensing inhibitory agents that prevent biofilm formation and attenuate virulence factor expression by pathogenic microorganisms. In this study, the inhibitory activity of the psammaplin-type compounds, psammaplin A (1) and bisaprasin (2), isolated from the marine sponge, Aplysinella rhax, are evaluated in quorum sensing inhibitory assays based on the Pseudomonas aeruginosa PAO1 lasB-gfp(ASV) and rhlA-gfp(ASV) biosensor strains. The results indicate that psammaplin A (1) showed moderate inhibition on lasB-gfp expression, but significantly inhibited the QS-gene promoter, rhlA-gfp, with IC₅₀ values at 14.02 μM and 4.99 μM, respectively. In contrast, bisaprasin (2) displayed significant florescence inhibition in both biosensors, PAO1 lasB-gfp and rhlA-gfp, with IC₅₀ values at 3.53 μM and 2.41 μM, respectively. Preliminary analysis suggested the importance of the bromotyrosine and oxime functionalities for QSI activity in these molecules. In addition, psammaplin A and bisaprasin downregulated elastase expression as determined by the standard enzymatic elastase assay, although greater reduction in elastase production was observed with 1 at 50 μM and 100 μM. Furthermore, the study revealed that bisaprasin (2) reduced biofilm formation in P. aeruginosa.     

Nanohybrid of Thymol and 2D Simonkolleite Enhances Inhibition of Bacterial Growth,Biofilm Formation,and Free Radicals

Due to the current concerns against opportunistic pathogens and the challenge of antimicrobial resistance worldwide, alternatives to control pathogen growth are required. In this sense, this work offers a new nanohybrid composed of zinc-layered hydroxide salt (Simonkolleite) and thymol for preventing bacterial growth. Materials were characterized with XRD diffraction, FTIR and UV–Vis spectra, SEM microscopy, and dynamic light scattering. It was confirmed that the Simonkolleite structure was obtained, and thymol was adsorbed on the hydroxide in a web-like manner, with a concentration of 0.863 mg thymol/mg of ZnLHS. Absorption kinetics was described with non-linear models, and a pseudo-second-order equation was the best fit. The antibacterial test was conducted against Escherichia coli O157:H7 and Staphylococcus aureus strains, producing inhibition halos of 21 and 24 mm, respectively, with a 10 mg/mL solution of thymol–ZnLHS. Moreover, biofilm formation of Pseudomonas aeruginosa inhibition was tested, with over 90% inhibition. Nanohybrids exhibited antioxidant activity with ABTS and DPPH evaluations, confirming the presence of the biomolecule in the inorganic matrix. These results can be used to develop a thymol protection vehicle for applications in food, pharmaceutics, odontology, or biomedical industries.     

Physical Properties of Biopolymers Assessed by Optical Tweezers: Analysis of Folding and Refolding of Bacterial Pili

Bacterial adhesion to surfaces mediated by specific adhesion organelles that promote infections, as exemplified by the pili of uropathogenic E. coli, is studied mostly at the level of cell–cell interactions and thereby reflects the averaged behavior of multiple pili. The role of pilus rod structure has therefore only been estimated from the outcome of experiments involving large numbers of organelles at the same time. It has, however, lately become clear that the biomechanical behavior of the pilus shafts play an important, albeit hitherto rather unrecognized, role in the adhesion process. For example, it has been observed that shafts from two different strains, even though they are similar in structure, result in large differences in the ability of the bacteria to adhere to their host tissue. However, in order to identify all properties of pilus structures that are of importance in the adhesion process, the biomechanical properties of pili must be assessed at the single‐molecule level. Due to the low range of forces of these structures, until recently it was not possible to obtain such information. However, with the development of force‐measuring optical tweezers (FMOT) with force resolution in the low piconewton range, it has lately become possible to assess forces mediated by individual pili on single living bacteria in real time. FMOT allows for a more or less detailed mapping of the biomechanical properties of individual pilus shafts, in particular those that are associated with their elongation and contraction under stress. This Mi‐ nireview presents the FMOT technique, the biological model system, and results from assessment of the biomechanical properties of bacterial pili. The information retrieved is also compared with that obtained by atomic force microscopy.     

Inhibition of Bacterial Efflux Pumps by Crude Extracts and Essential Oil from Myristica fragrans Houtt. (Nutmeg) Seeds against Methicillin-Resistant Staphylococcus aureus

Myristicafragrans Houtt. (Nutmeg) is a widely known folk medicine across several parts of Asia, particularly used in antimicrobial treatment. Bacterial resistance involves the expression of efflux pump systems (chromosomal norA and mepA) in methicillin-resistant Staphylococcus aureus (MRSA). Crude extract (CE) and essential oil (EO) obtained from nutmeg were applied as efflux pump inhibitors (EPIs), thereby enhancing the antimicrobial activity of the drugs they were used in. The major substances in CE and EO, which function as EPIs, in a descending order of % peak area include elemicin, myristicin, methoxyeugenol, myristicin, and asarone. Here, we investigated whether the low amount of CE and EO used as EPIs was sufficient to sensitize MRSA killing using the antibiotic ciprofloxacin, which acts as an efflux system. Interestingly, synergy between ciprofloxacin and CE or EO revealed the most significant viability of MRSA, depending on norA and mepA, the latter being responsible for EPI function of EO. Therefore, CE and EO obtained from nutmeg can act as EPIs in combination with substances that act as efflux systems, thereby ensuring that the MRSA strain is susceptible to antibiotic treatment.     

脂肪酶催化乳酸与乙醇合成乳酸乙酯的反应动力学

对脂肪酶催化乳酸与乙醇合成乳酸乙酯反应的动力学进行了研究,根据乒乓机制和双底物抑制的特性建立了反应速率方程.反应时间常数(tR)和扩散时间常数(tD)的计算结果表明,酯化反应速率未受到明显的限制.反应速率方程可以很好地预测实验结果,由非线性拟合得到的动力学参数中,乳酸(A)和乙醇(B)的抑制常数分别为KiA=10.7mmol/L和KiB=275.0mmol/L.这说明乳酸作为短链极性脂肪酸,对酶的失活作用远大于乙醇.乳酸在微液层中聚集并产生了使酶失活的低pH值环境,同时在酯化反应中存在竞争性抑制作用.     

稀土金属盐促进的Mo-Co-K硫化物基催化剂用于合成气选择性制乙醇等低碳混合醇

采用超声法在非水溶剂介质中制备了稀土金属La盐等促进的硫化钼基催化剂,考察了其CO加氢选择性合成乙醇等低碳混合醇的催化性能.在3.0MPa,330℃和H2/CO(体积比)=2.0的反应条件下,La促进的催化剂表现出较Mo-Co-K硫化物基催化剂更高的催化活性,CO转化率和产物中乙醇的分布可分别达到17.2%和53.4%.扫描电镜、透射电镜、X射线衍射和光电子能谱等表征结果表明,稀土金属La盐的加入改善了Mo-Co-K硫化物基催化剂的外观形貌和电子结构,对提高催化活性和乙醇的分布起到重要的作用.