The objective of this study is to isolate and identify the bioactive compounds that possess antibacterial activities from Melastoma malabathricum stem bark acetone extract (MMSBAE) against Streptococcus mutans. M. malabathricum is widely used in the Southeast Asia to treat many ailments. A total of 12 fractions was purified by vacuum liquid chromatography (VLC) and further analysed by TLC-bioautography to determine antibacterial activities. TLC-bioautography showed that fraction 9 possesses antibacterial activities against S. mutans. Identification of fraction 9 had been done by GCMS and revealed 21 compounds. Some of the compound were important as agent pharmaceutical such as α-amyrin, β-sitosterol, hexadecenoic acid, stearic acid and hexacosanoic acid. Crystal violet and glass surface assay were used to determine anti-biofilm and anti-adherence activity, respectively. The concentrations of fraction 9 that produce 50% reduction in anti-biofilm and anti-adherence activities were 5 mg/mL and 2.50 mg/mL, respectively. Scanning electron microscopy (SEM) was performed to visualize the effect of the fraction 9 on biofilm structure of S. mutans. SEM analysis showed lysed biofilm were found on treated cells. These results indicated that this fraction possesses a powerful anti-cariogenic potential against S. mutans.

Aims: Dental caries is a chronic infectious disease caused by Streptococcus mutans due to its ability to form biofilm. This study aims to assess the antimicrobial efficacy of Melastoma malabathricum leaf extract against S. mutans on the surface of tooth samples as a potential therapy for dental caries. Methodology and results: Extraction of M. malabathricum leaves was done using acetone as the solvent and antibacterial activity of the extracts was determined by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Antibiofilm activity of M. malabathricum extract against S. mutans was determined by comparing the colony count, biofilm formation assay and morphology observation by scanning electron microscope (SEM). The MIC value of extracts was 6.25 mg/mL and MBC value was >25 mg/mL. A decrease in colony count was noted when tooth samples were incubated with M. malabathricum extract for 8 h compared to 4 h incubation. At pH 5, the formation of the colony was the least, medium at pH 8 and maximum at pH 7. A decrease in biofilm formation was observed when tooth samples were incubated with the extract for 8 h. SEM observations showed treatment with the extract caused S. mutans cell membrane to leak leading to cell morphology changes. Conclusion, significance and impact of study: Acetone extract of M. malabathricum leaves showed excellent antibacterial activity against S. mutans. It has bactericidal activity with the ability to inhibit biofilm in dose-dependent manner against S. mutans. The morphological analyses suggested that the extract disrupted the cell membrane of the bacteria.

Aim: This study was to determine the antibacterial activity of Melastoma malabathricum stem bark acetone extract (MMSBAE) against Streptococcus mutans. Methodology and results: Antibacterial activity of the extract was determined by minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), biofilm formation, adherence inhibition, time kill studies and effect on S. mutans membrane integrity. MIC and MBC values of MMSBAE were 1.25 and 5 mg/mL, respectively. Time kill studies showed that reduction of colony forming unit in treated cells is 3 log10 after 10 h of treatment (p < 0.05). The extracts reduced 50% biofilm and adherence activity of S. mutans at 1.88 mg/mL. The effect on S. mutans membrane integrity after exposure to MMSBAE for 90 and 120 min was determined by measuring leakage of cell content at 2 different wavelengths of 260 nm and 280 nm. In leakage assay, the percentage of absorbance (260 nm) in treated cell material showed 57% at 90 min and 60% at 120 min which is higher than negative control (<20%) but less than positive control (100%). The percentage absorbance of treated cell material (280 nm) was 61% at 90 min and 63% at 120 min. Identification of compound in MMSBAE was done by gas chromatography mass spectrometry (GCMS). Ten compounds were identified in the MMSBAE with some of them important in antimicrobial activity such as ethyl ester, undecene, and gamma sitosterol. Conclusion, significance and impact of study: MMSBAE showed excellent bactericidal and antibacterial activities against S. mutans. The antibacterial mode of action of MMSBAE is suggested to be the disruption of the S. mutans membrane structure. The MMSBAE significantly inhibited biofilm and adherence activities of S. mutans in dose dependent manner (p < 0.05). MMSBAE has potential in the development of antibacterial agent with anti-biofilm and anti-adherence activities.

The asymmetric unit of the title complex, [Ni(C14H11FNO)2], contains one-half of the mol­ecule with the NiII cation lying on an inversion centre coordinated by a bidentate Schiff base anion. The cationic NiII center is in a distorted square-planar coordination environment chelated by the imine N and phenolate O donor atoms of the two Schiff base ligands. The N and O donor atoms of the two ligands are mutually trans with Ni—N and Ni—O bond lengths of 1.9242 (10) and 1.8336 (9) Å, respectively. The fluoro­phenyl ring is almost orthogonal to the coordination plane and makes a dihedral angle of 82.98 (7)° with the phenolate ring. In the crystal, mol­ecules are linked into screw chains by weak C—H⋯F hydrogen bonds. Additional C—H⋯π contacts arrange the mol­ecules into sheets parallel to the ac plane.

Objectives: The objectives of the study were to determine antibacterial, anti-adherence, and antibiofilm ctivities of Melastoma malabathricum stem bark acetone extract (MMSBAE) subfraction against Streptococcus mutans. Methods: Fraction 9 (F9) from MMSBAE was subfractionated by thin-layer chromatography (TLC) and analyzed for antibacterial activity against S. mutans by TLC-bioautography. Subfraction 12 (SF12) was isolated from F9 followed by determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values. Results: MIC and MBC values were 10 mg/mL and 160 mg/mL, indicating bacteriostatic property of SF12. Time-kill assay analysis confirmed bacteriostatic property of SF12 against S. mutans. Crystal violet staining and glass surface assays were used to determine anti-adherence and antibiofilm activities. Concentrations produced 50% reduction in anti-adherence and antibiofilm activities were 40 mg/mL and 20 mg/mL, respectively. Scanning electron microscopy was performed to visualize the effect of SF12 on S. mutans biofilm structure. SF12 was found to lyse biofilm formation on treated bacteria indicating powerful anticariogenic potential against S. mutans. Analysis by quantitative real-time polymerase chain reaction revealed SF12 at MIC value downregulated biofilm formation genes such as gbpA, brpA, gtfC, and comDE. Conclusion: SF12 showed bacteriostatic activities against S. mutans by inhibiting adherence and biofilm activities.

Aim:Phyllanthus columnarisMüll.Arg. was found to possess anti-methicillin resistant Staphylococcus aureus(anti-MRSA) activities. This study aimed at isolating, identifying and evaluating the active compounds from the stem bark of Phyllanthus columnarisMüll.Arg. against MRSA. Methodology and results:Stem bark extracts (methanol, acetone and aqueous) of Phyllanthus columnaris were subjected to anti-MRSA screening by disc diffusion method. MIC and MBC tests were carried out to compare the lowest concentration to inhibit and kill the sixteen MRSA tested among the three extracts. TLC bioautography were performed to detect the bioactive compounds. Isolation of the two active compounds was performed by means of preparative TLC. Morphological and ultra-structure alterations of the MRSA treated with bioactive compounds after 24 h were revealed by scanning and transmission electron microscopy.Both methanol and acetone extracts exhibited good anti-MRSA activity with the lowest minimum inhibitory concentration (MIC) value for both extracts were 0.78 mg/mLand the lowest minimum bactericidal concentration (MBC) were 1.56 mg/mL. Bioassay-guided chromatography by bioautography revealed two active anti-MRSA compounds from both tannin-free methanol and acetone extracts and characterized as stigmasterol and lupeol by nuclear magnetic resonance (NMR) spectral data. Scanning and transmission electron microscopy of MRSA treated with stigmasterol and lupeol showed cell wall disruption, release of cytoplasmic com-pounds and decreased in cellular volume. Conclusion,significance and impact of study:Results obtained herein, may suggest that the stem bark of Phyllanthus columnaris possess anti-MRSA and the two of the active compounds isolated were stigmasterol and lupeol. Their anti-MRSA effects up to the morphological and ultra-structure studies were not reported earlier.

Melastoma malabathricum, also known as 'senduduk' in Malaysia, has been used as traditional medicine for diseases such as toothache, dysentery, haemorrhoids and stomachache. Therefore, the objective of this study is to investigate the biological activity of Melastoma malabathricum stem bark extracts (MMSBE) towards Streptococcus mutans. This investigation involved a few methods, which at first is the determination of minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC). Next is by analyzing the time-kill curve, anti-biofilm activity, scanning electron and transmission electron microscopic analyses. Later, next-generation sequencing (NGS) was done to determine differential regulation genes of treated and non-treated S. mutans. Lastly, confirmation of differential regulation genes was done by RT-PCR analysis. As for the results, M. malabathricum stem bark acetone extract (MMSBAE) showed the greatest inhibition concentrations towards S. mutans, followed by M. malabathricum methanol extract (MMSBME). Values of MIC and MBC (MMSBAE) were 1.25 mg/mL and 5 mg/mL. Meanwhile, MIC and MBC values of MMSBME were 5 mg/mL and 40 mg/mL. MMSBAE was chosen to further analyze its anti-bacterial activity against S. mutans. Time kill curve analysis found that MMSBAE possessed bacteriostatic properties against S. mutans. Besides, SEM and TEM analyses revealed that there were some changes to S. mutans cell morphology after treated with MMSBAE while Next gene sequencing analysis revealed significant (p<0.05) gene expression with multiple targets by MMSBAE, which caused inhibition of S. mutans biofilm formation activity.

Development of a green chemistry process for the synthesis of silver nanoparticles has become a focus of interest. This would offer numerous benefits, including ecofriendliness and compatibility for biomedical applications. Here we report the synthesis of silver nanoparticles from the reduction of silver nitrate and an aqueous extract of the lichen Parmotrema praesorediosum as a reductant as well as a stabilizer. The physical appearance of these silver nanoparticles was characterized using ultraviolet-visible spectroscopy, electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction techniques. The results show that silver nanoparticles synthesized using P. praesorediosum have an average particle size of 19 nm with a cubic structure. The antibacterial activity of the synthesized silver nanoparticles was tested against eight micro-organisms using the disk diffusion method. The results reveal that silver nanoparticles synthesized using P. praesorediosum have potential antibacterial activity against Gram-negative bacteria.

New 5-aminopyrazoles2aec were prepared in high yields from the reaction of knowna,a-dicyanoke-tene-N,S-acetals1aec with hydrazine hydrate under reflux in ethanol. These compounds were utilized as intermediates to synthesize pyrazolo[1,5-a]-pyrimidines3aec,4aed,5aec, and6aec, as well as pyrazolo[5,1-c][1,2,4]triazines7aecand8aec, by the reaction of 2-[bis(methylthio)methylene]malononitrile,a,a-dicyanoketene-N,S-acetals1aeb, acetylacetone, acetoacetanilide as well as acetylacetone, and malono-nitrile, respectively. Furthermore, cyclization of 2aec with pentan-2,5-dione yielded the corresponding 5-pyrrolylpyrazoles9aec. Moreover, fusion of 2aec with acetic anhydride resulted in the corresponding1-acetyl-1H-pyrazoles10aec. The antibacterial activity and cytotoxicity against Vero cells of several selected compounds are also reported.