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AIM: This paper reports on the antimycobacterial activity of the oleoresins and extracts obtained from Copaifera spp. MATERIALS & METHODS: The minimum inhibitory concentration (MIC) and fractional inhibitory concentration index techniques helped to evaluate the effect of these oleoresins and extracts against six strains of mycobacteria that cause tuberculosis. RESULTS & CONCLUSION: Among the assayed oleoresins and plant extracts, the Copaifera langsdorffii, Copaifera duckei, Copaifera reticulata and Copaifera trapezifolia oleoresins provided the lowest MIC values against some of the tested strains. The combination of Copaifera spp. samples with isoniazid did not evidence any synergistic action. Some Copaifera spp. oleoresins may represent a future source for the discovery of new antimycobacterial drugs due to their low MIC values.

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The search for new, effective and safe antimicrobial compounds from plant sources has continued to play an important role in the maintenance of human health since ancient times. Such compounds can be used to help to eradicate microorganisms from the root canal system, preventing/healing periapical diseases. Mikania glomerata (Spreng.), commonly known as "guaco," is a native climbing plant from Brazil that displays a wide range of pharmacological properties. Many of its activities have been attributed to its phytochemical composition, which is mainly composed of diterpenes, such as ent-kaurenoic acid (KA). The present study evaluated the potential activity of an ent-kaurenoic-rich (KA) extract from Mikania glomerata (i.e. Mikania glomerata extract/MGE) and its major compound KA against bacteria that can cause endodontic infections. Time-kill assays were conducted and the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), anti-biofilm activity, and synergistic antimicrobial activity of MGE and KA were determined. The MGE exhibited MIC and MBC values, which ranged from 6.25 to 100 µg/mL and 12.5 to 200 µg/mL respectively. The MIC and MBC results obtained for the KA, ranged from 3.12 to 100 µg/mL and 3.12 to 200 µg/mL respectively. Time-kill and anti-biofilm activity assays conducted for KA at concentrations between 3.12 and 12.5 µg/mL exhibited bactericidal activity between 6 and 72 h of incubation and 50% inhibition of biofilm formation for Porphyromonas gingivalis (clinical isolate), Propionibacterium acnes (ATCC 6919), Prevotella nigrescens (ATCC 33563), P. melaninogenica (ATCC 25845), Aggregatibacter actinomycetemcomitans (ATCC 43717). For synergistic antimicrobial activity, KA combined with chlorhexidine dichlorohydrate (CHD) had an additive effect with increased efficacy against P. gingivalis (clinical isolate) compared to CHD alone. It was concluded that M. glomerata extract and its major compound ent-kaurenoic acid (KA) showed in vitro antibacterial activity, the latter being a potential biofilm inhibitory agent. They may play important roles in the search for novel sources of agents that can act against bacteria present in endodontic infections.

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Many studies have reported that medicinal plant extracts can inhibit oral pathogen growth or adhesion to surfaces and therefore reduce dental caries formation. The addition of these extracts to oral products like mouthwashes and dentifrices is considered an important strategy in caries control. In this sense, we have developed a Mikania glomerata extract with high ent-kaurenoic acid content (KAMg). So, this work describes the preparation of such extract and the development of a validated HPLC-DAD method to determine its ent-kaurenoic acid (KA) content. Herein it is also described the KAMg in vitro antibacterial evaluation against several cariogenic bacteria in comparison with KA and the investigation of further aspects of the KAMg activity. Toxicological aspects of the developed extract were evaluated by assessing its cytotoxicity and genotoxicity. KA and a KA-rich extract like KAMg showed to inhibit the growth of microorganisms responsible for dental caries at relatively low MIC (Minimum inhibitory concentration) values, albeit not as low as the MIC value obtained for chlorhexidine digluconate (CHD), the golden anticariogenic standard approved by the American Dental Association Council on Dental Therapeutics. However, KAMg was more effective to inhibit the formation of a Streptococcus mutans biofilm with four times lower MICB50 (minimum inhibitory concentration that reduces 50% of the biofilm) value as compared with CHD. Taking into account all these data and considering the absence of genotoxic and cytotoxic activity under the tested conditions, it is suggested that KAMg is a natural product to be considered as active ingredient in oral care products.

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Endodontic infections have a polymicrobial nature, but anaerobic bacteria prevail among the infectious microbes. Considering that it is easy to eliminate planktonic bacteria, biofilm-forming bacteria still challenge clinicians during the fight against endodontic diseases. The chemical constituents of the oleoresin of Pinus elliottii, a plant belonging to the family Pinaceae, stand out in the search for biologically active compounds based on natural products with potential application in the treatment of endodontic infections. Indeed, plant oleoresins are an abundant natural source of diterpenes that display significant and well-defined biological activities as well as potential antimicrobial action. In this context, this study aimed to (1) evaluate the in vitro antibacterial activity of the oleoresin, fractions, and subfractions of P. elliottii as well as the action of dehydroabietic acid against 11 anaerobic bacteria that cause endodontic infection in both their planktonic and biofilm forms and (2) assess the in vitro antibiofilm activity of dehydroabietic acid against the same group of bacteria. The broth microdilution technique helped to determine the minimum inhibitory concentration (MIC) of the oleoresin and fractions. This same technique aided determination of the MIC values of nine subfractions of Fraction 1, the most active fraction. The MIC, minimum bactericidal concentration, and antibiofilm activity of dehydroabietic acid against the tested anaerobic bacteria were also examined. The oleoresin and fractions, especially fraction PE1, afforded promising MIC values, which ranged from 0.4 to 50 µg/mL. Concerning the nine evaluated subfractions, PE1.3 and PE1.4 furnished the most noteworthy MIC values, between 6.2 and 100 µg/mL. Dehydroabietic acid displayed antibacterial activity, with MIC values lying from 6.2 to 50 µg/mL, as well as bactericidal effect for all the investigated bacteria, except for Prevotella nigrescens. Assessment of the antibiofilm activity revealed significant results--MICB50 lay between 7.8 and 62.5 µg/mL, and dehydroabietic acid prevented all the evaluated bacteria from forming a biofilm. Hence, the chemical constituents of P. elliottii are promising biomolecules to develop novel therapeutic strategies to fight against endodontic infections.

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Bixin is a carotenoid found in the seeds of Bixa orellana L., a plant native to tropical America that is used in the food industry. The aim of this study was to investigate the effect of bixin on DNA damage and pre-neoplastic lesions induced by 1,2-dimethylhydrazine (DMH) in the liver and colon of Wistar rats. The animals received bixin at daily doses of 0.1, 1.0 and 10mg/kg body weight (bw) by gavage. For the assessment of DNA damage in hepatocytes and colon cells with the comet assay, the administration of bixin was for 7 days. The animals received a single subcutaneous injection of 25mg/kg bw of DMH, and were euthanized 4h later. For the evaluation of the frequency of aberrant crypt foci (ACF), the animals were treated with the different doses of bixin for 4 weeks. Four doses of 40mg/kg bw DMH, two doses in the first week and two doses in the second week, were administered and euthanasia occurred at 4 weeks after the beginning of treatment. Bixin reduced the frequency of DNA damage in hepatocytes at the highest two doses tested (1.0 and 10mg/kg bw). On the other hand, no differences in the frequency of DNA damage in colon cells were observed between animals treated with bixin plus DMH and those treated with DMH alone. In addition, the frequency of ACF did not differ significantly between the group treated with bixin plus DMH and the DMH group. The results suggest that bixin does not suppress the formation of ACF, indicating the absence of a protective effect against colon carcinogenesis.

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