Ryozo Yamaguchi

Antibacterial property of isoflavonoids isolated from Erythrina variegata against cariogenic oral bacteria

The antibacterial property of 7 compounds, isolated from Erythrina variegata (Leguminosae) by repeated silica gel column chromatography, against cariogenic oral bacteria was investigated. Extensive spectroscopic study revealed that all were isoflavonoids. Among them, 3,9-dihydroxy-2,10-di(gamma,gamma-dimethylallyl)-6a,11a-dehydropterocarpan (erycristagallin) showed the highest antibacterial activity against mutans streptococci, other oral streptococci, Actinomyces and Lactobacillus species with a minimum inhibitory concentration (MIC) range of 1.56-6.25 microg/ml, followed by 3,6a-dihydroxy-9-methoxy-2,10-di(gamma,gamma-dimethylallyl)pterocarpan (erystagallinA) and 9-hydroxy-3-methoxy-2-gamma,gamma-dimethylallylpterocarpan (orientanol B) (MIC range: 3.13-12.5 microg/ml). The antibacterial effect of erycristagallin to mutans streptococci was based on a bactericidal action. Erycristagallin (6.25 microg/ml: MIC) completely inhibited incorporation of radio-labelled thymidine into Streptococcus mutans cells. Incorporation of radio-labelled glucose into bacterial cells was also strongly inhibited at MIC, and 1/2 MIC of the compound reduced the incorporation approximately by half. The findings indicate that erycristagallin has a potential as potent phytochemical agent for prevention of dental caries by inhibiting the growth of cariogenic bacteria and by interfering with incorporation of glucose responsible for production of organic acids.

Antibacterial properties of a new isoflavonoid from Erythrina poeppigiana against methicillin-resistant Staphylococcus aureus

A new isoflavonoid, together with four known isoflavonoids, was isolated from the roots of Erythrina poeppigiana. The chemical structure was determined by extensive spectroscopic studies, and then its antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) was investigated. The new isoflavonoid was identified as 3,9-dihyroxy-10-gamma,gamma-dimethylallyl-6a,11a-dehydropterocarpan (compound 1). Compound 1 inhibited bacterial growth most potently of the five isolates, and had a minimum inhibitory concentration (MIC) of 125 microg/ml against thirteen MRSA strains. Inhibitory activity was based on bactericidal action and viable cell number reduced by approximately 1/10,000 after 4 h incubation with compound 1. Despite intense bactericidal action against MRSA, compound 1 never resulted in leakage of 260 nm-absorbing substances from bacterial cells. Compound 1 (12.5 microg/ml) completely inhibited incorporation of radio-labeled thymidine, uridine and leucine into MRSA cells. Although glucose incorporation was also markedly inhibited by the compound, the amount of glucose incorporated by bacterial cells increased gradually with incubation time. These findings suggest that compound 1 exhibits anti-MRSA activity by interfering with incorporation of metabolites and nutrients into bacterial cells or by affecting the nucleic acids of MRSA cells. Furthermore, this new compound could be a potent phytotherapeutic agent for treating MRSA infections.

Different antibacterial actions of isoflavones isolated from Erythrina poeppigiana against methicillin-resistant Staphylococcus aureus

Aims:  To screen six isoflavones isolated from Erythrina poeppigiana (Leguminosae) for their antibacterial activity against methicillin‐resistant Staphylococcus aureus (MRSA).

Erythrina poeppigiana-derived phytochemical exhibiting antimicrobial activity against Candida albicans and methicillin-resistant Staphylococcus aureus.

Aims: To screen five phytochemicals isolated from Erythrina poeppigiana (Leguminosae) for antimicrobial activity against both Candida albicans and methicillin‐resistant Staphylococcus aureus (MRSA).

Evaluation of co-aggregation among Streptococcus mitis, Fusobacterium nucleatum and Porphyromonas gingivalis

Aims: To develop a semi‐quantitative method for evaluating co‐aggregation reactions among three bacterial species, and to examine the influence of Fusobacterium nucleatum on the adherence of Porphyromonas gingivalis.

Antibacterial Constituents from the Roots of Erythrina herbacea against Methicillin-resistant Staphylococcus aureus

Two new compounds, erybacin A (1) and erybacin B (2), together with 10 known compounds (3- 12), were isolated from the roots of Erythrina herbacea. Their structures were established on the basis of spectroscopic analyses. Erybacin A is a rare, naturally occurring 1-hydroxy-1,3-diphenylpropan-2-one derivative. The isolated compounds were evaluated for their antibacterial activity against 13 strains of methicillin-resistant Staphylococcus aureus (MRSA). The new compound 2 showed a potent bactericidal activity against MRSA.

Quantitative analysis of S. mutans and S. sobrinus cultivated independently and adhered to polished orthodontic composite resins

In Orthodontics, fixed appliances placed in the oral cavity are colonized by microorganisms. Objective The purpose of this study was to quantitatively determine the independent bacterial colonization of S. mutans and S. sobrinus in orthodontic composite resins. Material and methods Seven orthodontic composite adhesives for bonding brackets were selected and classified into 14 groups; (GIm, GIs) Enlight, (GIIm, GIIs) Grengloo, (GIIIm, GIIIs) Kurasper F, (GIVm, GIVs) BeautyOrtho Bond, (GVm, GVs) Transbond CC, (GVIm, GVIs) Turbo Bond II, (GVIIm, GVIIs) Blugloo. 60 blocks of 4x4x1 mm of each orthodontic composite resin were made (total 420 blocks), and gently polished with sand-paper and ultrasonically cleaned. S. mutans and S. sobrinus were independently cultivated. For the quantitative analysis, a radioactive marker was used to codify the bacteria (3H) adhered to the surface of the materials. The blocks were submerged in a solution with microorganisms previously radiolabeled and separated (210 blocks for S. mutans and 210 blocks for S. sobrinus) for 2 hours at 37ºC. Next, the blocks were placed in a combustion system, to capture the residues and measure the radiation. The statistical analysis was calculated with the ANOVA test (Sheffè post-hoc). Results Significant differences of bacterial adhesion were found amongst the groups. In the GIm and GIs the significant lowest scores for both microorganisms were shown; in contrast, the values of GVII for both bacteria were significantly the highest. Conclusions This study showed that the orthodontic composite resin evaluated in the GIm and GIs, obtained the lowest adherence of S. mutans and S. sobrinus, which may reduce the enamel demineralization and the risk of white spot lesion formation.

Two new isoflavanones from Erythrina costaricensis

Two new isoflavanones, 5,3′-dihydroxy-4′-methoxy-5′-(3-methyl-1,3-butadienyl)-2″,2″-dimethylpyrano[5,6:6,7]isoflavanone (1) and 5,3′-dihydroxy-5′-(3-hydroxy-3-methyl-1-butenyl)-4′-methoxy-2″,2″-dimethylpyrano[5,6:6,7]isoflavanone (2), together with two known isoflavonoids, cristacarpin, and euchrenone b10, were isolated from the stems of Erythrina costaricensis. Their structures were established on the basis of spectroscopic evidence. These new compounds are rare isoflavanones, possessing both a 2,2-dimethylpyran substituent and a prenyl analog. The antibacterial activities of 1 and 2 against the methicillin-resistant Staphylococcus aureus were examined.

Adherence of Streptococcus mutans to orthodontic band cements

BACKGROUND The aim of this study was to quantitatively determine the adherence of Streptococcus mutans to orthodontic band cements. METHODS Two hundred and ten blocks of seven different band cements for orthodontic prescription were made using a Teflon mould (4 × 4 × 1 mm). The obtained blocks were slightly polished and cleansed ultrasonically. Certified S. mutans ATCC 25175 were cultured with conventional methods for growth in Petri dishes and trypticase soy broth. Quantitative analysis was carried out with radioactive markers to codify the bacteria ((3) H). Subsequently, a combustion system was used to capture the residues, the radioactivity of the samples was measured, and the values recorded in disintegrations per minute (dpm). One-way analysis of variance (ANOVA) with a Scheffé test for multiple comparisons was realized with a significance level of ≤0.05. RESULTS Significant differences were found among different band cement materials (p < 0.001). Two band cement materials showed statistically lower values than the others (Transbond Plus Band Cem and Ketac Cem). In contrast, GC Fuji Ortho Band presented the highest adherence of S. mutans. CONCLUSIONS Among the cements evaluated, Transbond Plus Band Cem and Ketac Cem showed lower adherence of S. mutans.

A method for evaluating the cariogenicity of oral bacteria using radio-labelled synthetic hydroxyapatite

R. YAMAGUCHI, M. SATO, H. TSUCHIYA, K. YAMAMOTO, Y. DOI AND F. IWAKU. 1996. Radioactive hydroxyapatite was synthesized using 45Ca to evaluate the cariogenicity of oral streptococci. Discs prepared from it were suspended in media containing sucrose, then inoculated with Streptococcus mutans or Streptococcus sanguis. The radioactivity in the supernatant fluid was measured at specified time intervals. Released 45Ca in the supernatant fluids markedly increased in both species during the experimental period, while Strep, mutans showed much higher decalcification than Strep, sanguis. The present method would be useful for semi‐quantitative evaluation of bacterial decalcification ability.