In Vitro Antibacterial Activity and Mode of Action of Piper betle Extracts against Soft Rot Disease-Causing Bacteria.

Soft rot disease affects a range of crops in the field and also during transit and storage, resulting in significant yield losses and negative economic impacts. This study evaluated the in vitro antibacterial activities and mode of action of Piper betle extracts against the soft rot disease-causing bacteria, Erwinia caratovora subsp. caratovora (ECC). Dried leaves of P. betle were extracted with water, ethanol, and hexane solvents and evaluated for their antibacterial activity. The results showed the highest antibacterial activity against ECC in the ethanol extract, followed by hexane and water extracts with minimum inhibitory concentration (MIC) 1.562, 6.25, and more than 12.50 mg/mL, respectively. The time-kill assay indicated a bactericidal mode of action. ECC growth was destroyed within 6 and 8 hours after treatment with the ethanol extract at 4-fold MIC and 2-fold MIC, respectively. The ethanol extract of P. betle showed promising activity against ECC, with the potential for further development as a novel alternative treatment to control phytobacteria.

Photocatalytic Degradation Mechanism of the Pharmaceutical Agent Salbutamol Using the Mn-Doped TiO2 Nanoparticles Under Visible Light Irradiation.

In the present work, the photocatalytic degradation of salbutamol [2-(tert-butylamino)-1-(4-hydroxyl-3-hydroxymethylphenyl)ethanol] under visible irradiation using Mn-doped TiO2 is investigated. The Mn-doped TiO2 nanoparticles were synthesized by the sol-gel method with ratios of 0.1, 0.2, and 0.3%. Significant characteristics, including the rutile/anatase phases ratio, specific surface area, and band gap energy, were due to the amount of Mn doping; the narrowest band gap energy of 2.80 eV was observed in 0.2% Mn-doped TiO2 with specific surface areas of 89.36 m2/g and 10.87/89.13 of rutile/anatase phases. The investigation involved salbutamol photocatalytic degradation, a kinetic study, and the identification of intermediate compounds. The results indicated that 0.2% Mn-doped TiO2 obtained the best salbutamol removal of 95% under an irradiation time of 180 min. Salbutamol slowly degraded to the intermediate compounds in the first 60 min (k = 0.0088 1/min), and these intermediate compounds were dramatically mineralized to small hydrocarbon fragments and carbon dioxide in the later irradiation times (k = 0.0179 1/min). According to the high-performance liquid chromatography-mass spectrometry (HPLC-MS) results, possible degradation pathways of salbutamol were proposed: 2-(tert-butylamino)-1-(3,4-dihydroxyphenyl)ethanone, 2-(tert-butylamino)-ethanol, and 2-(tert-butylamino)-1-(4-hydroxyl-3-hydroxymethylphenyl)ethanone were initially formed and then transformed to 2-(methylamino)-1-(3,4-dihydroxyphenyl)ethanone, 2-(tert-butylamino)-acetic acid, hydroquinone, and 1-(4-hydroxylphenyl)ethanol, respectively. The mineralization of all intermediate compounds was verified by 90% chemical oxygen demand (COD) reduction, and the effluent contained a relatively low COD concentration of 7.8 mg/L.

Ultrasonic-Assisted Extraction of Phenolic Compounds, Flavonoids, and Antioxidants from Dill (Anethum graveolens L.).

This study evaluated the effect of ultrasonic-assisted extraction (UAE) on the isolation of phenolic compounds, flavonoids, and antioxidants from dill. UAE improved the extraction yields of total phenolic compounds and total flavonoid content as well as increased the antioxidant activities of all dill extracts. The optimum UAE condition to obtain highest total phenolic compounds, total flavonoid content, and antioxidant activities was 50% ethanol for 30 min giving 135.88 ± 3.23 mg gallic acid equivalent/g extract and 229.53 ± 4.97 mg rutin equivalent/g extract, respectively. Lowest IC50 values against 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals were 0.034 ± 0.00 mg/mL and 0.12 ± 0.00 mg/mL, respectively. Results indicated the capability of UAE in extracting biologically active compounds from dill as a prospective functional material.

Anti-Methicillin-Resistant Staphylococcus aureus Activities of Artocarpus lakoocha Roxb Extract and Its Mode of Action.

Antibacterial activities and mode of action of Artocarpus lakoocha Roxb extracts against methicillin-resistant Staphylococcus aureus (MRSA) were evaluated, with its biological properties including antioxidant activity and total phenolic content also measured. Heartwoods of A. lakoocha Roxb were extracted by solvents including water, ethanol, acetonitrile, ethyl acetate, isopropanol, and hexane. Results showed that antibacterial activity against MRSA, antioxidant activity, and total phenolic content were highest in the acetonitrile extract. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were 312.5 and 625.0 µg/mL, respectively. Time-killing evaluation indicated a bactericidal mode of action with IC50 values against ABTS and DPPH radicals of 2.37 ± 0.09 and 32.10 ± 0.74 mg/mL, respectively, and total phenolic content 455.29 ± 18.35 mg GAE/g extract. Results suggested that acetonitrile extract of A. lakoocha Roxb had good potential activity against MRSA, with promise for further development as a novel alternative drug.

Enhanced Photocatalytic and Photokilling Activities of Cu-Doped TiO2 Nanoparticles.

In this work, metal-doped titanium dioxide (TiO2) was synthesised with the aim of improving photocatalytic degradation and antimicrobial activities; TiO2 was doped with copper (Cu) ranging from 0.1 to 1.0 wt%. The physical and chemical properties of the Cu-doped TiO2 nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), the Brunauer-Emmett-Teller method (BET) and diffuse reflection spectroscopy (DRS). The results revealed that the anatase phase of TiO2 was maintained well in all the Cu-doped TiO2 samples. No significant difference in the particle sizes or the specific surface areas was caused by increasing Cu doping. However, the band gap decreased continuously from 3.20 eV for undoped TiO2 to 3.12 eV for 1.0 wt.% Cu-doped TiO2. In addition, the 0.1 wt.% Cu-doped TiO2 displayed a much greater photocatalytic degradation of methylene blue (MB) and excellent antibacterial ability for Escherichia coli (E. coli) compared to undoped TiO2. On the other hand, the high Cu doping levels had negative impacts on the surface charge of nanoparticles and charge transfer for OH• generation, resulting in decreasing MB degradation and E. coli photokilling for 1.0 wt.% Cu-doped TiO2.

Novel Strategy for the Development of Antibacterial TiO2 Thin Film onto Polymer Substrate at Room Temperature.

This work demonstrates a novel method to deposit an antibacterial TiO2 thin film on a polymer substrate at room temperature. A combination of sol-gel and photon assistance was used in the experiment in order to avoid any thermal processes of thin film crystallization. The morphological photograph of samples indicated that the TiO2 thin film was perfectly coated on the PVC substrate without any cracks or pinholes. Chemical analysis by EDS and XPS reported that the thin film consisted of titanium (Ti), oxygen (O), and carbon (C). The Raman spectrum proved that the thin film was the anatase phase of TiO2 and, furthermore, that it was contaminated with carbon remaining from the photon assistance process. In addition, the optical band gap of the thin film was 3.35 eV, suggesting that the photocatalytic activity of TiO2 should occur under UV-A radiation. The bacteria viability assay was examined using E. coli and S. typhimurium as indicator strains under UV-A irradiation (365 nm) at different times. The data from OD and CFU count revealed that >97% of bacteria were killed after 60 min of irradiation, and the bacteria were completely killed at 120 min for E. coli and 180 min for S. typhimurium.

Multiple mutations in the aglycone binding pocket to convert the substrate specificity of dalcochinase to linamarase.

Dalcochinase from Dalbergia cochinchinensis Pierre and linamarase from Manihot esculenta Crantz are ß-glucosidases which share 47% sequence identity, but show distinct substrate specificities in hydrolysis and transglucosylation. Previously, three amino acid residues of dalcochinase, namely I185, N189 and V255, were identified as being important for determining substrate specificity. In this study, kinetic analysis of the ensuing double and triple mutants of dalcochinase showed that only those containing the 185A mutation could appreciably hydrolyze linamarin as well as transfer glucose to 2-methyl-2-propanol. So, the space provided by the I185A mutation appeared to be a prerequisite for accommodation of the aglycone moiety containing three substituents at the carbinol carbon. However, quantitative analysis of the energy parameters revealed mostly antagonistic interactions between these mutations. In addition, the N189F mutant showed a potential for use in enzymatic synthesis of alkyl glucosides via transglucosylation and reverse hydrolysis reactions. Thus, substitution of only 2-3 key residues in the aglycone binding pocket of dalcochinase could convert its specificities to that of linamarase, as well as to be suitable for any chosen hydrolytic or synthetic applications.

Mutational analysis in the glycone binding pocket of Dalbergia cochinchinensis ß-glucosidase to increase catalytic efficiency toward mannosides.

Dalcochinase and Abg are glycoside hydrolase family 1 ß-glucosidases from Dalbergia cochinchinensis Pierre and Agrobacterium sp., respectively, with 35% sequence identity. However, Abg shows much higher catalytic efficiencies toward a broad range of glycone substrates than dalcochinase does, possibly due to the difference in amino acid residues around their glycone binding pockets. Site-directed mutagenesis was used to replace the amino acid residues of dalcochinase with the corresponding residues of Abg, generating three single mutants, F196H, S251V, and M369E, as well as the corresponding three double mutants and one triple mutant. Among these, the F196H mutant showed increases in catalytic efficiency toward almost all glycoside substrates tested, with the most improved catalytic efficiency being a 3-fold increase for hydrolysis of p-nitrophenyl ß-D-mannoside, suggesting a preferred polar residue at this position and consistent with the presence of histidine at this position in two other GH1 glycosidases from barley and rice that prefer ß-mannosides. In addition, the M369E mutation resulted in a small increase in catalytic efficiency for cleavage of p-nitrophenyl ß-D-galactoside. By contrast, the multiple mutants were up to 8-fold less efficient than the recombinant wild-type dalcochinase, and displayed primarily antagonistic interactions between these residues. Thus, differences in catalytic efficiency between dalcochinase and Abg are therefore not primarily due to differences in the residues that directly contact the substrate, but derive largely from contributions from more remote residues and the overall architecture of the active site.