The addition of silver-zinc zeolite to acrylic resins yields antimicrobial activity, but may affect negatively the mechanical properties, depending on the percentage of zeolite.

Seven pimarane type-diterpenes re-isolated from Viguiera arenaria Baker and two semi-synthetic pimarane derivatives were evaluated in vitro against the following main microorganisms responsible for dental caries: Streptococcus salivarius, S. sobrinus, S. mutans, S. mitis, S. sanguinis and Lactobacillus casei. The compounds ent-pimara-8(14),15-dien-19-oic acid (PA); ent-8(14),15-pimaradien-3b-ol; ent-15-pimarene-8b,19-diol; ent-8(14),15-pimaradien-3b-acetoxy and the sodium salt derivative of PA were the most active compounds, displaying MIC values ranging from 2 to 8 μg∙mL-1. Thus, this class of compounds seems promising as a class of new effective anticariogenic agents. Furthermore, our results also allow us to conclude that minor structural differences among these diterpenes significantly influence their antimicrobial activity, bringing new perspectives to the discovery of new natural compounds that could be employed in the development of oral care products.

In the present work, the anticariogenic activities of nine labdane type-diterpenes and four sesquiterpenes were investigated. Among these metabolites, (-)-copalic acid (CA) was the most active compound displaying MIC values very promising (ranging from 2.0 to 6.0 µg/mL) against the main microorganisms responsible for dental caries: Streptococcus salivarius, S. sobrinus, S. mutans, S. mitis, S. sanguinis and Lactobacillus casei. Time kill assays performed with CA against the primary causative agent (S. mutans) revealed that, in the first 12 h, this compound only inhibits the growth of the inoculum (bacteriostatic effect). However, its bactericidal effect is clearly noted thereafter (between 12 and 24 h). Also, CA did not show a synergistic effect when combined with the anticariogenic gold standard (chlorhexidine, CHD) in the checkerboard assays against S. mutans. In conclusion, the results points out CA as an important metabolite in the search for new effective anticariogenic agents.

The antimicrobial activity of four labdane-type diterpenes isolated from the oleoresin of Copaifera langsdorffii as well as of two commercially available diterpenes (sclareol and manool) was investigated against a representative panel of microorganisms responsible for periodontitis. Among all the evaluated compounds, (−)-copalic acid (CA) was the most active, displaying a very promising MIC value (3.1 µg mL−1; 10.2 µM) against the key pathogen (Porphyromonas gingivalis) involved in this infectious disease. Moreover, CA did not exhibit cytotoxicity when tested in human fibroblasts. Time-kill curve assays performed with CA against P. gingivalis revealed that this compound only inhibited the growth of the inoculums in the first 12 h (bacteriostatic effect). However, its bactericidal effect was clearly noted thereafter (between 12 and 24 h). It was also possible to verify an additive effect when CA and chlorhexidine dihydrochloride (CHD, positive control) were associated at their MBC values. The time curve profile resulting from this combination showed that this association needed only six hours for the bactericidal effect to be noted. In summary, CA has shown to be an important metabolite for the control of periodontal diseases. Moreover, the use of standardized extracts based on copaiba oleoresin with high CA contents can be an important strategy in the development of novel oral care products.

The in vitro inhibitory activity of crude EtOH/H2O extracts from the leaves and stems of Rosmarinus officinalis L. was evaluated against the following microorganisms responsible for initiating dental caries: Streptococcus mutans, S. salivarius, S. sobrinus, S. mitis, S. sanguinis, and Enterococcus faecalis. Minimum inhibitory concentrations (MIC) were determined with the broth microdilution method. The bioassay-guided fractionation of the leaf extract, which displayed the higher antibacterial activity than the stem extract, led to the identification of carnosic acid (2) and carnosol (3) as the major compounds in the fraction displaying the highest activity, as identified by HPLC analysis. Rosmarinic acid (1), detected in another fraction, did not display any activity against the selected microorganisms. HPLC Analysis revealed the presence of low amounts of ursolic acid (4) and oleanolic acid (5) in the obtained fractions. The results suggest that the antimicrobial activity of the extract from the leaves of R. officinalis may be ascribed mainly to the action of 2 and 3.

Recebido em 3/1/07; aceito em 25/9/07; publicado na web em 2/4/08 COMPARATIVE STUDY OF SCREENING TECHNIQUES FOR ANTIBACTERIAL ACTIVITY EVALUATION OF PLANT CRUDE EXTRACTS AND PURE COMPOUNDS. In this work, the effectiveness of four screening techniques (three techniques of the diffusion method and one microdilution broth method) were compared. Evaluated were the ethanolic and dichloromethanic extracts of Miconia rubiginosa (Melastomataceae) against six standard bacteria (ATCC). The results showed statistical disagreement among the three diffusion techniques. Among the diffusion techniques, the well technique displayed the best result. However the microdilution broth method demonstrated to be the most adequate method to evaluate the antibacterial activity of plant crude extracts and pure compounds when compared to the other methodologies.Keywords: antimicrobial activity; screening methods; plant extracts. INTRODUÇÃOAtualmente existem diversas técnicas de screening para definir se o extrato de uma determinada planta possui atividade antimicrobiana, desde as mais simples, que podem ser realizadas rotineiramente, até as mais sofisticadas, que muitas vezes se tornam indisponíveis em alguns laboratórios. Apesar disso, há poucos estudos que relatam qual o melhor método de screening a ser utilizado de acordo com o tipo de extrato a ser testado, mesmo no que se refere às técni-cas mais simples. Por vezes, relatos de resultados em diferentes artigos publicados com uma mesma planta são apresentados de maneira distinta em relação à atividade antimicrobiana, às vezes até mesmo discrepantes, mesmo naqueles em que foram utilizadas as mesmas condições de experimento (ex: solvente utilizado para extração, temperatura, tempo de incubação e microrganismos indicadores), embora as técnicas ou modificações empregadas nos méto-dos de screening para avaliar a atividade antimicrobiana por diferentes autores não tenham sido as mesmas. 1 Os dois métodos mais comumente utilizados para o screening de extratos de plantas com potencial antibacteriano são o de difusão em ágar e de diluição em caldo. O método de difusão em ágar pode ser realizado através das técnicas do disco, do poço ou template. 2-4 Diversas modificações já foram realizadas nas metodologias de screening a fim de se obter resultados mais confiáveis, uma vez que alguns fatores, tais como composição do meio de cultura, microrganismos testados, método de extração, pH e solubilidade das amostras no meio de cultura, podem alterar os resultados, sendo difícil, portanto, padronizar um procedimento. 1 Quando se utiliza o método de difusão vários fatores podem se tornar fontes de erros, tais como composição do meio de cultura, preparação incorreta do meio de cultura, espessura do meio de cultura, densidade do inóculo incorreta, uso de swab com excesso de caldo para inoculação das placas, temperatura e tempo de incubação inadequados, interações entre o antimicrobiano e o meio de cultura, utilização errada da atmosfera de CO 2 quando necessária, leitura prematura, erro na medida das zonas ...

Two kaurane diterpenes, ent-kaur-16(17)-en-19- , respectively. Our results show that KA has potential to be used as a prototype for the discovery of new effective anti-infection agents against microorganisms responsible for caries and periodontal diseases. Moreover, these results allow to conclude that minor structural differences among these diterpenes significantly influence their antimicrobial activity, bringing new perspectives to studies on the structure-activity relationship of this type of metabolites with respect to caries and periodontal diseases.

The antimicrobial activity of Syzygium cumini leaves extract, known as "jambolão", was evaluated. The crude hydroalcoholic extract was active against Candida krusei (inhibition zone of 14.7 ± 0.3 mm and MIC = 70 µg/ mL), and against multi-resistant strains of Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus.