Rodrigo Cassio Sola Veneziani

Antimicrobial activity of terpenoids from Copaifera langsdorffii Desf. against cariogenic bacteria

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. Copyright

Pimarane-type Diterpenes: Antimicrobial Activity against Oral Pathogens

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.

Antimicrobial evaluation of diterpenes from Copaifera langsdorffii oleoresin against periodontal anaerobic bacteria.

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.

Schistosomicidal Activity of the Essential Oil of Ageratum conyzoides L. (Asteraceae) against Adult Schistosoma mansoni Worms

The in vitro schistosomicidal effects of the essential oil of Ageratum conyzoides L. (Ac-EO) against adult worms of Schistosoma mansoni is reported in this paper. Concerning this activity, Ac-EO was considered to be active, but less effective than the positive control (praziquantel, PZQ) in terms of separation of coupled pairs, mortality, decrease in motor activity, and tegumental alterations. However, Ac-EO caused an interesting dose-dependent reduction in the number of eggs of S. mansoni. Precocene I (74.30%) and (E)-caryophyllene (14.23%) were identified as the two major constituents of Ac-EO. These compounds were tested individually and were found to be much less effective than Ac-EO and PZQ. A mixture of the two major compounds in a ratio similar to that found in the Ac-EO was also less effective than Ac-EO, thus revealing that there are no synergistic effects between these components. These results suggest that the essential oil of A. conyzoides is very promising for the development of new schistosomicidal agents.

Antimicrobial ent-pimarane diterpenes from Viguiera arenaria against Gram-positive bacteria

The dichloromethane crude extract from the roots of Viguiera arenaria (VaDRE) has been employed in an antimicrobial screening against several bacteria responsible for human pathologies. The main diterpenes isolated from this extract, as well as two semi-synthetic pimarane derivatives, were also investigated for the pathogens that were significantly inhibited by the extract (MIC values lower than 100 microg mL(-1)). The VaDRE extract was significantly active only against Gram-positive microorganisms. The compounds ent-pimara-8(14),15-dien-19-oic acid (PA); PA sodium salt; ent-8(14),15-pimaradien-3beta-ol; ent-15-pimarene-8 beta,19-diol; and ent-8(14),15-pimaradien-3beta-acetoxy displayed the highest antibacterial activities (MIC values lower than 10 microg mL(-1) for most pathogens). In conclusion, our results suggest that pimaranes are an important class of natural products for further investigations in the search of new antibacterial agents.

Antimicrobial Activity of Kaurane Diterpenes against Oral Pathogens

Two kaurane diterpenes, ent-kaur-16(17)-en-19-oic acid (KA) and 15-β-isovaleryloxy-entkaur- 16(17)-en-19-oic acid (KA-Ival), isolated from Aspilia foliacea, and the methyl ester derivative of KA (KA-Me) were evaluated against oral pathogens. KA was the most active compound, with MIC values of 10 μg mL-1 against the following microorganisms: Streptococcus sobrinus, Streptococcus mutans, Streptococcus mitis, Streptococcus sanguinis, and Lactobacillus casei. However, KA did not show significant activity against Streptococcus salivarius and Enterococcus faecalis, with MIC values equal to 100 and 200 μg mL-1, 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.

Antimicrobial Activity of Diterpenes from Viguiera arenaria against Endodontic Bacteria

Six pimarane-type diterpenes isolated from Viguiera arenaria Baker and two semi-synthetic derivatives were evaluated in vitro against a panel of representative microorganisms responsible for dental root canal infections. The microdilution method was used for the determination of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Porphyromonas gingivalis, Prevotella nigrescens, Prevotella intermedia, Prevotella buccae, Fusobacterium nucleatum, Bacteroides fragilis, Actinomyces naeslundii, Actinomyces viscosus, Peptostreptococcus micros, Enterococcus faecalis and Aggregatibacter actinomycetemcomitans. The compounds ent-pimara-8(14),15-dien-19-oic acid, its sodium salt and ent-8(14),15-pimaradien-3β-ol were the most active, displaying MIC values ranging from 1 to 10 μg mL-1. The 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 chemicals for use as a complement to instrumental endodontic procedures.

Chemical Composition and in vitro Schistosomicidal Activity of the Essential Oil of Plectranthus neochilus Grown in Southeast Brazil

The chemical composition and the in vitro schistosomicidal effects of the essential oil of Plectranthus neochilus (PN‐EO) grown in Southeast Brazil was studied. β‐Caryophyllene (1; 28.23%), α‐thujene (2; 12.22%), α‐pinene (3; 12.63%), β‐pinene (4; 6.19%), germacrene D (5; 5.36%), and caryophyllene oxide (6; 5.37%) were the major essential oil constituents. This chemical composition differed from that previously reported for specimens harvested in Africa. Concerning the in vitro schistosomicidal activity against adult Schistosoma mansoni worms, PN‐EO was considered to be active, but less effective than the positive control praziquantel (PZQ) in terms of separation of coupled pairs, mortality, decrease in the motor activity, and tegumental alterations. However, PN‐EO caused an interesting dose‐dependent reduction in the number and the percentage of developed S. mansoni eggs. These results suggest that PN‐EO might be very promising for the development of new schistosomicidal agents.

Antileishmanial Activity of the Hydroalcoholic Extract of Miconia langsdorffii, Isolated Compounds, and Semi-Synthetic Derivatives

The in vitro activity of the crude hydroalcoholic extract of the aerial parts of Miconia langsdorffii Cogn. was evaluated against the promastigote forms of L. amazonensis, the causative agent of cutaneous leishmaniasis in humans. The bioassay-guided fractionation of this extract led to identification of the triterpenes ursolic acid and oleanolic acid as the major compounds in the fraction that displayed the highest activity. Several ursolic acid semi-synthetic derivatives were prepared, to find out whether more active compounds could be obtained. Among these ursolic acid-derived substances, the C-28 methyl ester derivative exhibited the best antileishmanial activity.

Differences in secondary metabolites from leaf extracts of Mikania glomerata Sprengel obtained by micropropagation and cuttings

GC analysis of the dichloromethane extracts obtained from cultivated specimens of Mikania glomerata Sprengel possibilited to verify that cuttings technique led to production of kaurenoic acid and coumarin while the same results have not been observed by propagation process using in vitro techniques.