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The aim of this study was carry out a phytochemical characterization of Operculina hamiltonii and to assess its antiparasitic potential against Trypanosoma cruzi, Leishmania brasiliensis and Leishmania infantum and also its cytotoxic activity. The infusion of this plant was selected on the basis of its popular use. A lyophilized infusion was analyzed by HPLC-DAD methodology. The anti-epimastigote and antipromastigote activity and cytotoxic activity were determined in vitro assay using a concentration range of 62.5–1000 μg/mL. The HPLC results showed the presence of quercetin and chlorogenic acid as the major compounds. The infusion exhibited significant leishmanicidal activity with IC50 of 236.93 μg/mL for Leishmania braziliensis and 342.90 μg/mL for L. infantum. This study showed trypanocidal activity with IC50 10.61 μg/mL, however, demonstrated significant cytotoxicity at concentrations equal to or greater than 250 μg/mL with IC50 47.62 μg/mL. Our results suggest that, due to the cytotoxic activity of this natural product, new assays should be performed to investigate this effect, mainly to evaluate O. hamiltonii for possible anticancer activity.

Introduction The survival and spreading of resistant bacterial strains has boosted research which focusses on discovering new antimicrobial agents derived from plant species. Several studies have demonstrated that substances present in plant extracts can modify the activity of antibiotics, increasing their efficacy. Species of the genus Psidium have been popularly used to treat bacterial infections. However, their modulatory effect on antibiotic activity remains to be elucidated. The aim of this study was to evaluate the modulatory effect of the hydroalcoholic extracts obtained from the leaves of Psidium guajava L. and Psidium brownianum Mart ex DC on bacterial proliferation, both separately and in combination with antibiotics. Methods The assays were performed using the microdilution method. The minimum inhibitory concentration (MIC) of the extracts and drugs were determined against standard and clinical isolates of Escherichia coli , Pseudomonas aeruginosa and Staphylococcus aureus . To verify the potentiation of the antibiotic activity, the MIC of the antibiotics were determined alone and in association with the extracts. Results The extracts of P. guajava and P. brownianum did not present clinically significant activity against the Gram negative bacteria evaluated, with MIC values against S. aureus of 256 and 512 μg/mL, respectively. However, when combined at sub-inhibitory concentrations with antibiotics, both extracts presented significantly synergistic effects. Conclusions Our results demonstrated the effectiveness of P. guajava and P. brownianum on modulating bacterial growth, suggesting that these natural products might be used in drug development in association with antibiotics, reducing bacterial resistance and thus, improving the treatment of bacterial infections.

Medicinal plants are often the only therapeutic resource for many communities and ethnic groups. Cordia verbenacea DC., "Erva-baleeira," is one of the species of plants currently used to produce a phytotherapeutic product extracted from its leaves. The present study aimed to establish its chemical profile, antibacterial activity and resistance-modulating potential. The C. verbenacea extracts were prepared from fresh leaves using solvents as methanol and hexane. Ethyl Acetate was used for the preparation of the fraction. Phytochemical screening was carried out using HPLC-DAD for determination and quantification of the secondary metabolites present in the fractions. Antibacterial and resistance-modulation assays were performed to determine minimum inhibitory concentration (MIC) using a microdilution assay. The data were subjected to statistical analysis with two-way ANOVA and Bonferroni posttests. Results of phytochemical prospecting and HPLC analysis of the fractions were in agreement with the literature. The natural products presented moderate antibacterial activity when considering the clinical relevance of a MIC of 256 μg/mL against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, and 512 μg/mL against P. aeruginosa. However, when the fractions were combined with antibiotics we observed a synergic effect, as natural products enhanced the antibacterial effect of aminoglycosides, significantly decreasing the MIC of antibiotics at 12.5%-98.4%. We believe that the data obtained from phytochemical analysis and from antibacterial and resistance modulation assays of C. verbenacea extracts new can open perspectives in the search for new alternatives for the treatment of bacterial infections and stimulate the renewed use of antibiotics with reduced effectiveness due to resistance.

Introduction “Erva-baleeira,” Cordia verbenacea DC. (Boraginaceae), is one of the species of plants currently exploited for the purpose of producing a phytotherapeutic product, which is extracted from the leaves. Methods Extracts of C. verbenacea were prepared from fresh leaves, and chloroform fractions were obtained from the different extracts for evaluation. Phytochemical screening was performed and the phytochemicals were quantified by HPLC-DAD. The microdilution assay was used to determine antibiotic and aminoglycoside-modifying activities (2.4–2500 μg/mL), and the results were analyzed using two-way ANOVA and Bonferroni post-test. Results Phytochemical screening and HPLC analysis of the fractions were in agreement with the literature, which describes the presence of several tannins and flavonoids in C. verbenacea leaves. The fractions showed moderate antibacterial activity when considering clinical relevance with a MIC of 128 μg/mL against a resistant strain of Staphylococcus aureus and 512 μg/mL against a resistant strain of Pseudomonas aeruginosa. However, when they were combined with antibiotics, synergism was observed, significantly lowering the MIC of the antibiotics by 12.5 (P Conclusions Our results indicated that the fractions of C. verbenacea, when combined with an antibiotic, demonstrated significant synergistic activity. Due the extensive use and sale of products derived from C. verbenacea may exert pressure on the populations of this species. The development of management plans for rational and sustainable use of the species and more studies with emphasis on the use of such fractions in the treatment of other diseases are necessary.

Introduction Developing resistance to antimicrobial agents is increasingly observed for many microorganisms is increasingly becoming a problem worldwide. The aim of the present work was to evaluate the antibacterial and antibiotic-modifying activity of essential oils of Ocimum gratissimum and Plectranthus amboinicus (Lamiaceae), alone and combined. Methods Standard and multiresistant bacterial strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were utilized, and antibiotics of the aminoglycoside class were tested, using the microdilution technique. Results The antibacterial effect of the O. gratissimum L. and P. amboinicus L. oils alone and combined have a minimum inhibitory concentration (MIC) ≥ 1024 μg/mL, except against E. coli ATCC10536, which showed a MIC = 128 μg/mL and against S. aureus ATCC25923 with MIC = 512 μg/mL. The drug-modifying effect of the essential oil of O. gratissimum L. resulted in an antagonism, reducing the effect of antibiotics, against all bacterial strains assayed. However, the essential oil of P. amboinicus L. showed a synergistic effect, potentiating the antibiotic activity of these drugs against the bacterial strains assayed. When the mixture of the O. gratissimum and P. amboinicus oils was combined with the antibiotic, a synergistic effect was observed. Conclusions The data obtained are promising, but further studies are needed to isolate the active compounds and to conduct pharmacological tests in vivo, making it possible to develop new therapeutic alternatives for the treatment of diseases caused by multiresistant microorganisms.