Evaluation of radioprotective activity of flavonoid isolated from Conocarpus erectus Linneus (Combretaceae) in human lymphocytes irradiated in vitro

Mangrove plants have important bioactive substances, which present radioprotective effect. An important specie is Conocarpus erectus L. (Combretaceae), which has in its biochemical composition flavonoids, a group of secondary metabolites of the class of polyphenols that have antioxidant properties. Until the late nineteenth century, the action of these compounds was seen as irrelevant because the radiation damage was not well known. The ionizing radiation interacts with the cell and can cause damage to the DNA, causing changes that can lead to cell death. Radioactivity and ionizing radiation are part of the environment, but it is not perceived naturally by the sense organs of human beings, differing from visible light and heat. This study (in vitro) isolated the major flavonoid from the aqueous extract of C. erectus leaves (EAFCe), also investigated the cytotoxic activity and explored radioprotective action in human lymphocytes exposed to gamma radiation. Initially, the collection of the vegetal material was carried out in the mangrove of the municipality of Itamaracá / PE (district of Vila Velha). EAFCe was prepared by infusion in distilled water (400 for 30 min), lyophilized and stored at room temperature. The phytochemical profile of EAFCe was performed by High Performance Liquid Chromatography (HPLC) by qualitative tests under an analytical system. In the purification and isolation of the CFFCe flavonoid, the HPLC was used under preparative system, monitored by Ultra Violet (UV) and mass spectrometry. For evaluation of cytotoxicity and micronucleus analysis, human peripheral blood mononuclear cells were obtained from 4 mL of blood of 4 volunteers. The analysis of the cytotoxic activity of flavonoid isolated from EAFCe at concentrations of 1, 10, 50 and 100 μ / mL was performed by the MTT test (3- (4,5-dimethylthiazol- 2yl) -2,5-diphenyl bromide tetrazoline), previously counting viable cells by Tripan Blue. The potential radioprotective effect of flavonoid isolated from EAFCe at concentrations of 1 and 0.5 μ / mL was determined by microscopic analysis of human lymphocytes (in vitro) exposed to the dose of 3 gray (Gy) of gamma rays from a radiation source of cobalt-60 (Gammacell 220 Excel) with high dose rate (2,181 kGy/h). Micronuclei were counted in a total of 300 cells from each group (irradiated and control). Statistical analysis of the radioprotective effect was performed using the Pearson chi-square statistical test with a value of ≤0.05. The phytochemical profile of EAFCe showed the presence of flavonoids. In the cytotoxicity analysis, 98% of the human lymphocytes did not present cell death after the treatment with the flavonoid isolated from the EAFCe, showing a statistically significant result in the ideal concentration of 1μ / L. The occurrence of flavonoids in plants is diffused through magnetic resonance and ¹³C analyzes. In this work, NMR studies of various signals are reported by complete assignment of proton and carbon by detailed spectral analysis. The results of the potential radioprotective effect showed that the presence of micronuclei in irradiated and non-irradiated lymphocytes treated with the flavonoid isolated from EAFCe at the concentration of 1.0 μ / mL ( ≤0.05) was 5.7% and 2.7%, respectively, and these percentages were compared to the other groups (control, doxorubicin and other compound concentrations). From the results of this research, the flavonoid isolated from the aqueous extract of C. erectus L. (Combretaceae), at a concentration of 1.0 μ / mL, may be a therapeutic medium as a natural radioprotector, not demonstrating cellular toxicity, and may be used in the areas of medicine and pharmacy. (author)