Chemical constituents and biological activities of Albizia myriophylla wood

Context: Albizia myriophylla Benth (Leguminosae) is a medicinal plant widely used in Thailand and other Asian countries as a folk medicine remedy for many ailments.

Objective: The objective of this study is to investigate the chemical compositions, antibacterial activity, and cytotoxicity of A. myriophylla wood.

Materials and methods: The structure identification of the isolated compounds was established using spectroscopic methods. In vitro antibacterial activity against Streptococcus mutans, Staphylococcus aureus, and Bacillus cereus and the cytotoxicity against KB cells of extracts and compounds from A. myriophylla were performed using broth microdilution and resazurin microplate assays, respectively. The lupinifolin content in A. myriophylla extracts was quantified by high-performance liquid chromatography.

Results: A rare flavan-3,4-diol (1) together with eight known compounds (2–9) were isolated from the wood of A. myriophylla. Compounds 4–9 exhibited anti-S. mutans activity, of which lupinifolin (5) was the most potent with an MIC value of 0.98?µg/mL, followed by its dihydroxy derivative 4 with an MIC value of 62.5?µg/mL. Compounds 4 and 5 also displayed marked antibacterial activity against B. cereus and S. aureus (MIC value 15.63–125?µg/mL) and showed strong cytotoxic activity against KB cells (IC₅₀ value 4.95–12.55?µg/mL). The lupinifolin contents in ethanol extracts from two different collections of this plant originating from central and southern Thailand were 93.85 and 0.04?mg/g, respectively.

Conclusion: This is the first report of compounds 1–4 from A. myriophylla. Compounds 4 and 5 showed potent antibacterial and cytotoxic activities compared with other isolates. The anti-S. mutans activity of A. myriophylla extracts seems to be related to the lupinifolin content.     

Isopanduratin A from Kaempferia pandurata as an active antibacterial agent against cariogenic Streptococcus mutans

An antibacterial compound active against Streptococcus mutans was isolated from Kaempferia pandurata and identified as isopanduratin A using 1H NMR, 13C NMR and EI-MS. The minimum inhibitory concentration (MIC) of isopanduratin A was 4 mg/l which was much lower than that of some other natural anticariogenic agents such as sanguinarine (12 mg/l), green tea extract and carvacrol (125 mg/l), thymol (250 mg/l) and isoeugenol and eucalyptol (500 mg/l). The bactericidal test showed that isopanduratin A completely inactivated S. mutans at 20 mg/l in 1 min. Significant inhibitory activity of isopanduratin A was also observed against S. sobrinus, S. sanguinis and S. salivarius with an MIC of 4 mg/l. Damage to the cell membrane and cell wall of S. mutans by isopanduratin A was shown using transmission electron microscopy (TEM). These results suggest that isopanduratin A could be employed as a potential antibacterial agent for preventing dental caries.     

The antibacterial component from Cinnamomi Cortex against a cariogenic bacteriumStreptococcus mutans OMZ 176

The methanol extract of Cinnamomi Cortex showed antibacterial action against cariogenic bacterium,Streptococcus mutans OMZ 176. The active principle of the extract was identified to betrans-cinnamaldehyde, which was bactericidal in the minimal inhibitory concentration (MIC) of 100 μg/ml againt the strain. From the results of antibacterial activity of cinnamaldehyde and its derivatives, the acrolein group in the cinnamal-dehyde was elucidated to be an essential element for the activity.     

Rational design of peptides with enhanced antimicrobial and anti‐biofilm activities against cariogenic bacterium Streptococcus mutans

Streptococcus mutans (S. mutans) is known to be a leading cariogenic pathogen in the oral cavity. Antimicrobial peptides possess excellent properties to combat such pathogens. In this study, we compared the antimicrobial activity of novel linear reutericin 6‐ and/or gassericin A‐inspired peptides and identified LR‐10 as the leading peptide. Antibacterial assays demonstrate that LR‐10 is more active against S. mutans (3.3 μM) than many peptide‐based agents without resistance selection, capable of killing many oral pathogens, and tolerant of physiological conditions. LR‐10 also presented a faster killing rate than chlorhexidine and erythromycin, and appeared to display selective activity against S. mutans within 10 s. S. mutans is usually encased in plaque biofilms. Biofilm inhibitory assays indicated that LR‐10 had excellent inhibitory effect on the biofilm formation of S. mutans and biofilm‐encased cells in vitro at low concentrations (6.5 μM). Consistent with most peptides, LR‐10 kills S. mutans mainly by disrupting the cell membranes. Notably, both hemolytic activity assays and cytotoxicity tests indicated that LR‐10 could keep biocompatible at the effective concentrations. Hence, LR‐10 could be a good candidate for clinical treatment of dental caries.     

Synergistic effect of lysozyme on bactericidal activity of magnolol and honokiol against a cariogenic bacterium,Streptococcus mutans OMZ 176

A combination of magnolol or honokiol with lysozyme isolated from the egg white of the Korean Ogol fowl (Korean natural monument No. 265) exhibited synergistic effect of bactericidal activity against a typical cariogenic bacterium,Streptococcus mutans OMZ 176. The synergistic ratio increased with time dependence.     

Synthesis and evaluation of oxazaborolidines for antibacterial activity against Streptococcus mutans

Several representative oxazaborolidines have been synthesized and evaluated against S. mutans for antibacterial activity. This is the first reported antibacterial activity of this class of compounds. The minimal inhibitory concentration values ranged from 0.53 to 6.75 mM.     

Comparative evaluation of in-vitro effects of Brazilian green propolis and Baccharis dracunculifolia extracts on cariogenic factors of Streptococcus mutans

Streptococcus mutans triggers dental caries establishment by two major factors: synthesis of organic acids, which demineralize dental enamel, and synthesis of glucans, which mediate the attachment of bacteria to the tooth surface. Propolis is a natural product that may prevent dental caries. Baccharis dracunculifolia DC (Asteraceae), a native plant from Brazil, is the most important botanical origin for the production of green propolis (Brazilian propolis) by honeybees. However, whether B. dracunculifolia (Bd) has an anticariogenic effect, like green propolis, remains unknown. Herein, we have made a comparative evaluation of the effects of extracts from green propolis and Bd on the glucan synthesis and acidogenic potential of S. mutans. The inhibitory effects of the extracts on bacterial acid production were evaluated through the potentiometric measurement of pH from bacterial suspensions treated with serial concentrations of both extracts. Besides presenting close inhibitory values at the same concentration range, Bd leaf rinse and green propolis extracts had similar IC(50) values (0.41 and 0.34 mg/ml, respectively). Both extracts produced a bacteriostatic effect on S. mutans cultures at a concentration of 0.40 mg/ml. Estimated inhibitory values of green propolis and Bd leaf rinse extracts on the synthesis of insoluble glucans (IC(50)=12.9 and 25.0 microg/ml, respectively) and soluble glucans (IC(50)=50.4 and 49.1 microg/ml, respectively) were not significantly different from each other at p<0.05. The results demonstrate that Bd leaf rinse and green propolis extracts have similar inhibitory effects on the S. mutans cariogenic factors evaluated herein, and allowed us to suggest that Bd leaves may be a potential source for pharmaceutical products employed for this purpose.     

Antibacterial effect of parabens against planktonic and biofilm Streptococcus sobrinus.

Tooth decay is an infectious disease caused by bacteria immobilized on the tooth surfaces. Eradication of these bacteria, for example Streptococcus sobrinus (S. sobrinus), from the oral cavity is essential in the prevention and treatment of tooth decay. We have tested the antimicrobial effect of several paraben derivatives such as methyl (MP), ethyl (EP), propyl (PP) and butyl (BP) against immobilized and planktonic S. sobrinus. The antibacterial effect was as follows: MP>EP>PP=BP on immobilized bacteria and MP>EP=PP>BP on planktonic bacteria. An antibacterial synergistic effect was found between several combinations of parabens on immobilized and planktonic S. sobrinus. Our results indicate that parabens are potential antibacterial agents against immobilized or planktonic bacteria found in the oral cavity.     

Synthesis and antibacterial activities of 4-hydroxy-o-phenylphenol and 3,6-diallyl-4-hydroxy-o-phenylphenol against a cariogenic bacteriumStreptococcus mutans OMZ 176

For the purpose of survey of the antibacterial activity against a cariogenic bacterium Streptococcus mutans OMZ 176 with the introduction of hydroxyl and allyl groups to o-phenylphenol (Fig. 2, 1), 4-hydroxy-o-phenylphenol (2), and 3,6-diallyl-4-hydroxy-o-phenylphenol (4) were synthesized, successively. The synthesized compounds, 2 and 4 showed more potent antibacterial activity than the starting material, 1. The hydroxyl group was supposed to the essential element for the antibacterial activity and the introduction of allyl group to phenolic ring to be another element to increase the activity.     

In vitro antibacterial activity of the peptide PsVP-10 against Streptococcus mutans and Streptococcus sobrinus with and without glycocalyx

The antibacterial activity of the peptide PsVP-10 obtained from Pseudomonas sp. R10 against Streptococcus mutans and Streptococcus sobrinus was investigated. One hundred and twenty strains of S. mutans and 120 strains of S. sobrinus with and without glycocalyx were isolated from saliva samples in trypticase-yeast-cysteine-sucrose-bacitracin (TYCSB) agar. Bacterial identification was made by polymerase chain reaction. Glycocalyx production was observed in modified TYCSB agar and confirmed with a modified version of the microplate adherence assay. The minimum inhibitory concentration (MIC) of PsVP-10 bacteriocin was determined by means of the agar dilution method, and the time of bacterial death was calculated by means of colony-forming unit counts. The MIC of the bacteriocin PsVP-10 for both bacterial species with and without glycocalyx was < 2 mg/L and the time of bacterial death was less than 240 s for all the studied bacterial strains. Thus, bacteriocin PsVP-10 could be an interesting possibility to combat these cariogenic bacterial species.     

In vitro antimicrobial activity of a chitooligosaccharide mixture against Actinobacillus actinomycetemcomitans and Streptococcus mutans.

The purpose of this study was to evaluate the in vitro antibacterial activity of a chitooligosaccharide mixture (MW 2000–30 000 Da) with a deacetylation degree of 91.5% against two representative oral pathogens, Actinobacillus actinomycetemcomitans and Streptococcus mutans. A 0.1% concentration of the chitooligosaccharides (derived from the exoskeletons of marine crustaceans) was used to estimate antibacterial activity. Approximately 2 log colony forming units (CFU)/ml of A. actinomycetemcomitans were inactivated by 0.1% chitosan after 30 min, while 120 min exposure inactivated about 4.5 log CFU/ml of this organism. In contrast, the level of inactivation against S. mutans was less than 0.5 log CFU/ml after an exposure of up to 120 min. Electron microscopy showed that the exposure of A. actinomycetemcomitans to the chitooligosaccharides resulted in the disruption of cell membranes and that it could be considered for the treatment of periodontal diseases associated with A. actinomycetemcomitans.     

Antibacterial Activity of Xanthones from Guttiferaeous Plants against Methicillin-resistant Staphylococcus aureus

Extracts of Garcinia mangostana (Guttiferae) showing inhibitory effects against the growth of S. aureus NIHJ 209p were fractionated according to guidance obtained from bioassay and some of the components with activity against methicillin-resistant Staphylococcus aureus (MRSA) were characterized. One active isolate, α-mangostin, a xanthone derivative, had a minimum inhibitory concentration (MIC) of 1.57?12.5 μg mL^?1. Other related xanthones were also examined to determine their anti-MRSA activity. Rubraxanthone, which was isolated from Garcinia dioica and has a structure similar to that of α-mangostin, had the highest activity against staphylococcal strains (MIC = 0.31?1.25 μg mL^?1), an activity which was greater than that of the antibiotic vancomycin (3.13?6.25 μg mL^?1). The inhibitory effect against strains of MRSA of two of the compounds when used in conjunction with other antibiotics was also studied. The anti-MRSA activity of α-mangostin was clearly increased by the presence of vancomycin; this behaviour was not observed for rubraxanthone. The strong in-vitro antibacterial activity of xanthone derivatives against both methicillin-resistant and methicillin-sensitive Staphylococcus aureus suggests the compounds might find wide pharmaceutical use.     

Antibacterial activity of ciprofloxacin against fresh clinical isolates from superficial suppurative foci

The minimum inhibitory concentrations (MICs) of 5 drugs (ciprofloxacin (CPFX), and 4 drugs used as standard) were determined to investigate antibacterial potencies of CPFX against bacterial strains isolated in 1989 from superficial suppurative foci. The clinical isolates tested included 375 strains from 11 aerobic bacterial species, and 50 strains from 2 anerobic bacterial genera (group) for a total of 425 isolates. Interpreting MIC level distributions of these drugs as the expression of antibacterial potencies, the results are as follows. 1. When activities of new-quinolone antibiotics were tested, we found that, CPFX expressed far superior antibacterial potency to ofloxacin (OFLX) and norfloxacin (NFLX) against coagulase-negative staphylococci, Enterococcus faecalis, Enterococcus faecium, Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Proteus mirabilis, Proteus vulgaris, Morganella morganii, Pseudomonas aeruginosa and Peptostreptococcus spp., although the activity of CPFX against Bacteroides fragilis group was weaker than that of OFLX, and CPFX had similar activity against Staphylococcus aureus to OFLX. 2. In comparison to beta-lactam antibiotics, CPFX was inferior to amoxicillin (AMPC) against E. faecalis and inferior to AMPC and cefaclor (CCL) against Peptostreptococcus spp. Against all other bacterial species, however, CPFX expressed superior antibacterial potency to AMPC and CCL. 3. Scattered findings of low sensitivity or resistance to CPFX were observed among the S. aureus, E. faecalis, E. faecium, P. vulgaris, M. morganii, P. aeruginosa and B. fragilis (group) species, but with an exception of E. faecium, the incidence of resistance strains was low.     

Antibacterial activity of fosfomycin against the causative bacteria isolated from bacterial enteritis

The in vitro antibacterial activities of fosfomycin (FOM) and 3 fluoroquinolones against Salmonella spp., pathogenic Escherichia coli, Campylobacter spp. and Shigella spp. were investigated. The activity upon the environmental condition in the inflammation was compared with standard condition in vitro. On standard condition, the MIC90 of tosfloxacin (TFLX), norfloxacin (NFLX) and levofloxacin (LVFX) against E. coli (77 strains), Shigella spp. (50) and Salmonella spp. (41) were < or = 0.025-0.10, 0.10, and 0.05 microgram/ml, respectively. The MIC90 of FOM against those organisms was 0.39-1.56 micrograms/ml. The MIC90 of TFLX, NFLX, LVFX against Campylobacter spp. were 6.25, 100 and 3.13 micrograms/ml, respectively. The MIC90 of FOM was 50 micrograms/ml. The activity of FOM was unaffected by pH and in anaerobic condition. On the other hand, the activity of NFLX was decreased in low pH and in anaerobic condition. In the presence of horse blood and addition of Na+, the activities of both agents were unaffected. These results suggested that FOM is equally active with or superior to fluoroquinolone in the intestinal infection treatment.     

Antibacterial activities of ofloxacin against recent isolates from patients with community-acquired infections

In order to survey antibacterial activities of ofloxacin (OFLX) against 1,440 bacterial strains isolated from patients with community-acquired infections in 1987 and 1990, minimum inhibitory concentrations (MICs) of the drug as well as those of other new quinolones and oral cephems were determined. The following conclusions were reached. 1. Comparison of the MIC distribution for strains isolated in 1987 with those in 1990 suggested a tendency toward an increase in the frequency of OFLX-resistant isolates with the passage of time of Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Citrobacter spp., Klebsiella ssp., Enterobacter spp., Proteus vulgaris, Morganella morganii, Providencia spp., and Acinetobacter calcoaceticus. Most common elevations of MIC values against these bacteria were observed in MIC80 and MIC90 values, while no significant alteration was observed in MIC50 values. However, MIC50's of OFLX against Serratia marcescens and Pseudomonas aeruginosa were relatively high for strains isolated in both 1987 and 1990. Most of the OFLX-resistant strains of S. aureus seemed to be methicillin-resistant (MRSA). Furthermore, MIC80 of OFLX against coagulase-negative staphylococci was high in strains isolated in both 1987 and 1990. 2. Susceptibility of Streptococcus spp. was evaluated only in strains isolated in 1990. The results were comparable to those reported by others in the early 1980s. 3. Bacteria which showed no or infrequent emergence of OFLX-resistant strains even in 1990 were Proteus mirabilis, Haemophilus influenzae, Neisseria gonorrhoeae, Campylobacter spp. and Peptostreptococcus spp. 4. Recently isolated strains from patients with community-acquired infections showed a tendency toward an increase of the frequency of OFLX-resistant strains among many bacteria. However, the bacteria which contained high percentages of OFLX-resistant strains except for MRSA were so-called less-virulent bacteria, and in the other bacteria elevations of MIC values were only observed in MIC80 and MIC90. These results suggested that OFLX preserved a potent antibacterial activity against bacteria which were major causative pathogens in community-acquired infections.     

Mutant prevention concentrations of garenoxacin against Streptococcus pneumoniae isolates from otorhinolaryngological infections

The minimum inhibitory concentrations (MICs) and the mutant prevention concentrations (MPCs) of garenoxacin (GRNX), were compared to those of levofloxacin (LVFX), and moxifloxacin (MFLX) against 78 Streptococcus pneumoniae isolates from otorhinolaryngological infections in Japan during the period January 2007 to June 2007. The MIC and MPC for 90% of the isolates (MIC90 and MPC90) of GRNX were 0.06 and 0.12 microg/mL, respectively, and were the lower values than LVFX and MFLX MIC90s and MPC90s. The ratios of MPC/MIC of GRNX were the lower values than those of LVFX and MFLX.