Effect of Psidium cattleianum leaf extract on Streptococcus mutans viability, protein expression and acid production

Plants naturally produce secondary metabolites that can be used as antimicrobials. The aim of this study was to assess the effects of Psidium cattleianum leaf extract on Streptococcus mutans. The extract (100%) was obtained by decoction of 100 g of leaves in 600 ml of deionized water. To assess killing, S. mutans biofilms were treated with water (negative control) or various extract dilutions [100, 50, 25% (v/v) in water] for 5 or 60 min. To evaluate the effect on protein expression, biofilms were exposed to water or 1.6% (v/v) extract for 120 min, proteins were extracted and submitted to 2-dimensional difference gel electrophoresis. Differentially expressed proteins were identified by mass spectrometry. The effect of 1.6% (v/v) extract on acid production was determined by pH measurements and compared to a water control. Viability was similar after 5 min of treatment with the 100% extract or 60 min with the 50% extract (about 0.03% survival). There were no differences in viability between the biofilms exposed to the 25 or 50% extract after 60 min of treatment (about 0.02% survival). Treatment with the 1.6% extract significantly changed protein expression. The abundance of 24 spots was decreased compared to water (p < 0.05). The extract significantly inhibited acid production (p < 0.05). It is concluded that P. cattleianum leaf extract kills S. mutans grown in biofilms when applied at high concentrations. At low concentrations it inhibits S. mutans acid production and reduces the expression of proteins involved in general metabolism, glycolysis and lactic acid production

Supplementary Material for: Systematic Screening of Plant Extracts from the Brazilian Pantanal with Antimicrobial Activity against Bacteria with Cariogenic Relevance

This study proposes a bioprospection methodology regarding the antimicrobial potential of plant extracts against bacteria with cariogenic relevance. Sixty extracts were obtained from ten plants - (1) <i>Jatropha weddelliana</i>, (2) <i>Attalea phalerata</i>, (3) <i>Buchenavia tomentosa</i>, (4) <i>Croton doctoris</i>, (5) <i>Mouriri elliptica</i>, (6) <i>Mascagnia benthamiana</i>, (7) <i>Senna aculeata</i>, (8) <i>Unonopsis guatterioides</i>, (9) <i>Allagoptera leucocalyx</i> and (10) <i>Bactris glaucescens</i> - using different extraction methods - (A) 70° ethanol 72 h/25°C, (B) water 5 min/100°C, (C) water 1 h/55°C, (D) water 72 h/25°C, (E) hexane 72 h/25°C and (F) 90° ethanol 72 h/25°C. The plants were screened for antibacterial activity at 50 mg/ml using the agar well diffusion test against <i>Actinomyces naeslundii</i> ATCC 19039, <i>Lactobacillus acidophilus</i> ATCC 4356, <i>Streptococcus gordonii</i> ATCC 10558, <i>Streptococcus mutans</i> ATCC 35688, <i>Streptococcus sanguinis</i> ATCC 10556, <i>Streptococcus sobrinus</i> ATCC 33478 and <i>Streptococcus mitis</i> ATCC 9811. The active extracts were tested to determine their minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), cytotoxicity and chemical characterization. Forty-seven extracts (78%) were active against at least one microorganism. Extract 4A demonstrated the lowest MIC and MBC for all microorganisms except <i>S. gordonii</i> and the extract at MIC concentration was non-cytotoxic. The concentrated extracts were slightly cytotoxic. Electrospray ionization with tandem mass spectrometry analyses demonstrated that the extract constituents coincided with the mass of the terpenoids and phenolics. Overall, the best results were obtained for extraction methods A, B and C. The present work proved the antimicrobial activity of several plants. Particularly, extracts from <i>C. doctoris</i> were the most active against bacteria involved in dental caries disease