Avaliação fitoquímica e atividade antioxidante, antileucêmica e imunomoduladora de Xanthosoma sagittifolium (L.) Schott

Abstract

The increasing incidence of chronic diseases and cancer has been related to poor diet, high level of stress, sedentary lifestyle and aging. In this sense, functional foods and nutraceuticals have been improving health quality and life expectance. In Brazil, the Xanthosoma sagittifolium species, known as taioba, presents many nutrients, however it is not widely used. The aim of this work was to study the antioxidant, antileukemic and/or immunomodulators in vitro effects of the hydroethanolic extract of Xanthosoma sagittifolium leaves (HEXs-L) and fractions, and the phytochemical aspects of active samples. The antioxidant action was measured by colorimetric methods and ROS detection by fluorescent probe DCFH-DA. Cytotoxicity was assessed by MTT assay on leukemic cell lines (K562 and Jurkat), solid tumors (MCF-7, A549, PC3) and non-tumor cells (macrophage line RAW 264.7, NIH-3T3 fibroblasts and murine splenocytes). The apoptosis (annexin V staining), cell cycle (propide iodide staining) and nitric oxide production (Griess reaction) were also evaluated, as well as lymphocytes subpopulation (specific fluorescent antibodies) and p21 protein expression, by flow cytometry. The mRNA levels of Bax and cyclin A were analyzed by qPCR. The HEXs-L and its hexanic (HexF), diclorometanic (DCMF), ethyl acetate (EtAcF) and aqueous (AqF) fractions were analyzed by high-performance liquid chromatography, gas chromatography mass spectrometry and/or electrospray ionization/mass spectrometry. The HEXs-L and AcETF showed high DPPH neutralization (63.8% and 70.5%, respectively, at 1 mg/mL), while the HEXs-L, EtAcF and AqF reduced lipid peroxidation (55.8%, 61.8% and 57.2%, respectively) and all samples were able to chelate ferrous ions (>90% at 1 mg/ml). Only HEXs-L reduced intracellular ROS levels in RAW 264.7 cells (77.8%, 50 μg/ml) without causing cytotoxicity. The HEXs-L (IC50 = 95.5 μg/mL) and HexF (IC50 = 118 μg/mL) showed low activity, and higher with DCMF (IC50=63.1 μg/mL). Both HEXs-L and DCMF inhibited Jurkat cell proliferation, reducing cells in S and G2/M phases, and increasing in sub- G1 (85.9% and 56%, respectively), indicating cell death association. These effects occurred with both reduced cyclin A mRNA level (FHex and palmitic acid) or increased one (DCMF). Otherwise, the p21 protein expression was increased approximately five fold after incubation with HEXs-L, HexF and DCMF, beyond AP, which may be related to apoptosis induction (increased Annexin-V+ cells). The mRNA level of Bax was not changed by treatment with HEXs-L, HexF or AP, and it was reduced by DCMF. HEXs-L, HexF and DCMF inhibited NO production (26.5%, 40.8% and 43.5%, respectively), TNF-α (40%, 22.5% and 26.4%, respectively), IL-10 (27.5%, 34.9% and 58.4%, respectively) and IL-1β (51.8%, 57.4% and 42.5%, respectively) by macrophages RAW 264.7. In addition, the EFXs increase both the percentage of total T CD8+ (46%) and T CD8+CD69+ (active) (48%) lymphocytes. The HEXs-L, EtAcF and AqF showed diglucoside apigenin (flavone) as major compounds, while HexF and DCMF showed palmitic acid, which must be contributing to the observed effects. Highlighting, neither HEXs-L nor their fractions were toxic to non-tumor cells. Taioba leaves can be considered an important source of compounds with immunomodulatory, antioxidant and antileukemia action, potentially beneficial to health maintenance and disease prevention