ABSTRACT
SUMMARY Aims: This study investigated the bioactivity of the crude leaf extract (CLE) and fractions hexane (HX) and ethyl acetate (EtOAc) from Talinum paniculatum alone and in association with fluconazole (FLC) against reference strain and clinical isolates of FLC-resistant Candida albicans. Furthermore, the antioxidant capability, chemical composition of this plant, and the effect's underlying mechanisms were evaluated. Methods: The antifungal activity was evaluated using checkerboard assay to establish the minimum inhibitory (MIC) and minimum microbicidal concen trations (MMC). During FLC and plant products challenges, the reactive oxygen species (ROS) generation (hydroxyl radicals [HO●]) were detected in C. albicans cells using the membrane-permeable fluorescent probes APF and HPF. High-performance liquid chromatography (HPLC) profile, quantitative analysis of antioxidant compounds, and free radical scavenging activity (DPPH assay) tests were performed. Results: The CLE and fractions presented outstanding antifungal activity and selectivity against C. albicans cells but had no synergistic effect's with FLC. The MIC values for CLE and its fractions against C. albicans reference strain were in the order of HX (31.25 µg ml-1) < EtOAc (62.5 μg ml-1) < CLE (500 μg ml-1), and against FLC-resistant C. albicans HX (125 μg ml-1) = EtOAc < CLE (500 μg ml-1). CLE and its fractions had more potent antifungal activities than FLC against the clinical isolates. Moreover, fungicidal effect's for these plant products were demonstrated against FLC-resistant C. albicans, which further conirmed an antifungal potential. Conversely, during association, plant products were shown to cause an increase in FLC MIC anywhere from 2- to 16-fold. FLC exposure led to an increase in the steady-state levels of ROS (HO●) in C. albicans cells. Next, we found that the increases in FLC MICs were owing to action of antioxidants containing-CLE and its fractions in preventing FLC-induced ROS-mediated growth inhibition of C. albicans. Conclusion: T. paniculatum can be a source of bioactive compounds with antifungal potential. However, because of the common use of its edible leaf, caution is advised during therapy with FLC (since it can decrease FLC susceptibility).
RESUMEN Objetivos: este estudio investigó la bioactividad del extracto de hoja en bruto (EHB) y las fracciones hexano (HX) y acetato de etilo (AcOEt) de Talinum paniculatum solo y en asociación con fluconazol (FLC) contra cepas de referencia y aislados clínicos de Candida albicans resistente a FLC. Además, evaluó la capacidad antioxidante, la composición química de esta planta y los mecanismos subyacentes del efecto fungicida. Métodos: la actividad antifúngica se evaluó mediante microdilución en caldo para establecer las concentraciones inhibitorias mínimas (CIM) y microbicidas mínimas (CMM). Durante el tratamiento con FLC y productos vegetales se detectó la generación de especies reactivas de oxígeno (ERO) (radicales hidroxilo [HO●]) en células de C. albicans utilizando las sondas fluorescentes permeables a la membrana APF y HPF. El perfil de cromatografía líquida de alta resolución (CLAR), el análisis cuantitativo de compuestos antioxidantes y el ensayo DPPH fueron evaluados. Resultados: el EHB y las fracciones presentaron una excelente actividad antifúngica y selectividad contra las células de C. albicans, pero no tuvieron efectos sinérgicos con FLC. Los valores de CIM para EHB y sus fracciones contra la cepa referencia de C. albicans fueron del orden de: HX (31,25 μg ml-1) < AcOEt (62,5 μg ml-1) < EHB (500 μg ml-1), y contra C. albicans resistente a FLC: HX (125 μg ml-1)= AcOEt < EHB (500 µg ml-1). EHB y sus fracciones fueron más potentes antifúngicos que FLC contra los aislados clínicos. Además, estos productos vegetales tienen efectos fungicidas contra C. albicans resistentes a FLC, esto conirmó el potencial antifúngico. Por el contrario, durante la asociación se demostró que los productos vegetales causan un aumento en la CIM de FLC de 2 a 16 veces. La exposición a FLC aumentó los niveles de ERO (HO●) en las células de C. albicans. Los aumentos en las CIM de FLC se debieron a la acción de los antioxidantes presentes en EHB y sus fracciones para prevenir la inhibición del crecimiento mediada por ERO inducida por FLC en C. albicans. Conclusión: T. paniculatum puede ser una fuente de compuestos bioactivos con potencial antifúngico. Sin embargo, debido al uso común de su hoja comestible, se recomienda usarla con precaución durante la terapia con FLC (ya que puede disminuir la susceptibilidad a FLC).
ABSTRACT
SUMMARY In this study, the bioactivity of Talinum paniculatum was evaluated, a plant widely used in folk medicine. The extract from the T. paniculatum leaves (LE) was obtained by percolation with ethanol-water and then subjecting it to liquid-liquid partitions, yielding hexane (HX), ethyl acetate (EtOAc), butanol (BuOH), and aqueous (Aq) fractions. Screening for antimicrobial activity of the LE and its fractions was evaluated in vitro through broth microdilution method, against thirteen pathogenic and non-pathogenic microorganisms, and the antimycobacterial activity was performed through agar diffusion assay. The cytotoxic concentrations (CC90) for LE, HX, and EtOAc were obtained on BHK-21 cells by using MTT reduction assay. The LE showed activity against Serratia marcescens and Staphylococcus aureus, with Minimum Inhibitory Concentration (MIC) values of 250 and 500 µg/mL, respectively. Furthermore, HX demonstrated outstanding activity against Micrococcus luteus and Candida albicans with a MIC of 31.2 µg/mL in both cases. The MIC for EtOAc also was 31.2 µg/mL against Escherichia coli. Conversely, BuOH and Aq were inactive against all tested microorganisms and LE proved inactive against Mycobacterium tuberculosisand Mycobacterium bovisas well. Campesterol, stigmasterol, and sitosterol were the proposed structures as main compounds present in the EF and HX/EtOAc fractions, evidenced by mass spectrometry. Therefore, LE, HX, and EtOAc from T. paniculatumshowed potential as possible sources of antimicrobial compounds, mainly HX, for presenting low toxicity on BHK-21 cells with excellent Selectivity Index (SI = CC90/MIC) of 17.72 against C. albicans.
RESUMO Neste estudo foi avaliada a bioatividade de Talinum paniculatum, planta amplamente utilizada na medicina popular. O extrato das folhas (EF) de T. paniculatum foi obtido por percolação com etanol-água e, em seguida, submetido à partição líquido-líquido, obtendo-se as frações hexânica (HX), acetato-etílica (AcOEt), butanólica (BuOH) e aquosa (Aq). A triagem para a atividade antimicrobiana do EF e de suas frações foram avaliadas in vitro através do método de microdiluição em caldo contra treze micro-organismos patogênicos e não-patogênicos e, a atividade antimicobacteriana, foi avaliada através do teste de difusão em ágar. As concentrações citotóxicas (CC90) do EF e das frações HX e AcOEt foram obtidas sobre células da linhagem BHK-21 através do ensaio de redução do MTT. O EF mostrou atividade contra Serratia marcescens e Staphylococcus aureus, com valores de concentração inibitória mínima (CIM) de 250 e 500 µg/mL, respectivamente. Além disso, HX demonstrou excelente atividade contra Micrococcus luteus e Candida albicans com uma CIM de 31,2 µg/mL, em ambos os casos. Contra Escherichia coli, a CIM para AcOEt foi também de 31,2 µg/mL. Por outro lado, as frações BuOH e Aq foram inativas contra todos os micro-organismos testados, assim como o EF contra Mycobacterium tuberculosis e Mycobacterium bovis. Campesterol, estigmasterol e sitosterol foram as estruturas propostas como principais compostos presentes no EF e nas frações HX e AcOEt, evidenciadas através de espectrometria de massas. Portanto, o extrato da folha e as frações HX e AcOEt provenientes de T. paniculatum apresentaram potencial como possíveis fontes de compostos antimicrobianos, HX principalmente, por ter apresentado uma baixa toxicidade sobre células BHK-21 com um bom índice de seletividade (IS = CC90/MIC) de 17,72 contra C. albicans.