In vitro evaluation of the activity of Cinnamaldehyde as an inhibitor of the biological cycle of Ctenocephalides felis felis.

The objective of this work was to evaluate the in vitro activity of cinnamaldehyde as an inhibitor of the biological cycle of Ctenocephalides felis felis. Tests were carried out with six repetitions containing 10 eggs of C. felis felis together with 0.5g of diet and filter paper discs with area of 23.76 cm2 impregnated with different concentrations of cinnamaldehyde (6; 8; 10; 12; 14; 16; 18; 20; 24 and 28 µg.cm-2) in Petri dishes and incubated in a climate-controlled chamber at 27 ± 1 °C and RH 75 ± 10%, for 30 days. The tests included a placebo group containing the diluent (acetone) and a negative control group, without treatment. At the end of 30 days, the percentage of inhibition of adult emergence/mortality was calculated, as well as the LC50 and LC90. Inhibition of adult emergence greater than 50% was observed from a concentration of 10 µg.cm-2 and 100% inhibition from a concentration of 14 µg.cm-2, obtaining LC50 and LC90 results of 8.75 and 13.57 µg.cm-2, respectively. We concluded that the volatile compound cinnamaldehyde is effective in vitro as an inhibitor of the biological cycle of C. felis felis.

O objetivo deste trabalho foi avaliar a atividade in vitro do cinamaldeído como inibidor do ciclo biológico de Ctenocephalides felis felis. Para realização do teste, seis repetições contendo 10 ovos de C. felis felis juntamente 0,5g de dieta e papel filtro de área 23,76 cm2 impregnado com diferentes concentrações de cinamaldeído (6; 8; 10; 12; 14; 16; 18; 20; 24 e 28 µg/cm2) foram armazenados em placas de petri e incubados em câmara climatizada à 27 ± 1°C e UR 75 ± 10%, por 30 dias. Além disso, o teste contou com um grupo placebo contendo o diluente (acetona) e um grupo controle negativo, sem tratamento. Ao final dos 30 dias, com os dados coletados foram calculados o percentual de inibição de emergência de adultos/mortalidade, como também a CL50 e CL90. Com os resultados, foi observado uma inibição de emergência de adultos superior a 50% a partir da concentração de 10 µg.cm-2 e uma inibição de 100% a partir da concentração 14 µg.cm-2 obtendo como resultados de CL50 e CL90 de 8,75 e 13,57 µg.cm-2, respectivamente. Conclui-se que o composto volátil cinamaldeído tem eficácia in vitro como inibidor do ciclo biológico de C. felis felis.

Larvicidal activity in vitro of essential oils against Cochliomyia hominivorax.

Cochliomyia hominivorax, from the family Calliphoridae, is responsible for causing most myiases in domesticated animals in Brazil. As alternatives to conventional treatments, essential oils (EOs) could possibly be used as natural control of ectoparasites. The aim of this study was to evaluate the in vitro activity of EOs from Salvia sclarea L., Rosmarinus officinalis L., Lavandula hybrida Reverchon, Citrus bergamia Risso, Citrus paradisi L., Juniperus virginiana L., Copaifera reticulata Ducke, Illicium verum Hook f., Pelargonium roseum, Cymbopogon winterianus Jowitt, Cymbopogon flexuosus Steud, Eugenia caryophyllus Spreng, Cinnamomum cassia Presl, Thymus vulgaris L. and Origanum vulgare L. against third-instar larvae of C. hominivorax. To evaluate the mortality rate, filter paper tests were performed at different concentrations and verified after 24 h and 48 h. Essential oils of T. vulgaris, O. vulgare and I. verum induced 100% mortality in the screening test, and their main active components (thymol, carvacrol and anethol, respectively) were also tested alone. In this new test, lethal concentrations (LC50) after 24 h and 48 h, respectively, were 407.1 and 314.2 µg.cm-² for T. vulgaris, 540.9 and 253.8 µg.cm-² for O. vulgare, 314.2 µg.cm-² (after 48 h) for I. verum, 255.6 and 102.3 µg.cm-² for thymol, 970.5 and 931.1 µg.cm-2 for carvacrol and 559.4 µg.cm-2 (after 48 h) for anethol. These results showed the potential of these EOs and their main components for development of ectoparasiticides for veterinary use, especially T. vulgaris EO and thymol.

Antimicrobial Activity of Psidium guajava Aqueous Extract against Sensitive and Resistant Bacterial Strains.

The inappropriate use of antimicrobials, along with environmental conditions, can lead to the emergence of resistant microorganisms. The use of phytopharmaceuticals and herbal medicines has a positive impact and represents a promising alternative. Psidium guajava extracts have been widely reported to have antimicrobial potential; however, studies reporting their activity against resistant bacterial strains are scarce. Because of the emerging resistance, the aim of this study was to analyze the antimicrobial capacity of the aqueous extract of guava leaves against wild-type and resistant bacterial strains. The aqueous extract obtained from the leaves of P. guajava was evaluated by HPLC for the content of total phenolics and tannins, antioxidant activity, and chemical composition. The antimicrobial activity of the extracts was analyzed by the disk diffusion and broth microdilution methods. The results of the chemical analysis of the extracts showed total phenolics content of 17.02 ± 6.87 mg/g of dry extract, total tannin content of 14.09 ± 1.20 mg of tannic acid equivalents/g of dry extract, and moderate antioxidant capacity with an EC50 value of 140 µg/mL. Flavonoids are the major compounds (rutin, hesperidin, and quercetin), followed by phenolic acids. Disk diffusion test results showed the presence of inhibition halos for Gram-positive bacteria (Staphylococcus aureus, sensitive and resistant; Staphylococcus pseudintermedius, sensitive and resistant; and Streptococcus spp., beta-hemolytic), while for Gram-negative bacteria (Escherichia coli, sensitive and resistant), there was no inhibition in the tested concentration range. The Minimal Inhibitory Concentration was 6.8 mg/mL for all Gram-positive strains evaluated. The present study demonstrated the antimicrobial activity of the aqueous extract of P. guajava against sensitive and resistant Gram-positive bacteria. The better antimicrobial activity found in the present study compared with previously reported activity should be highlighted and may be related to the higher concentration of total phenolics present in the tested extract. Moreover, the content of tannins found suggests a species with high quality that produces tannins. These new findings suggest an innovative profile regarding therapeutic resources that can be adopted to combat resistant microbial strains.