Avaliação da toxicidade do extrato bruto das folhas de Hibiscus rosa-sinensis Linn. e do efeito da radiação gama sobre esse extrato

Abstract

Hibiscus rosa-sinensis Linn., plant belonging to the family Malvaceae and popularly known as hibiscus, “mimo-de-vênus” and “hibisco-da-china”, is used in traditional medicine as hair growth promoters, to improve digestion, to stimulate menstrual flow, as well as in the treatment of pain, fatigue and skin diseases. In addition, some studies attribute to it anti-inflammatory, antidiabetic, anthelmintic, and antitumor properties. Similarly to hibiscus, many other plants are used as therapeutic, however, for this it is indispensable that they do not present toxicity or contaminants. Ionizing radiation is a promising option for the decontamination and conservation of plants. Considering the widespread use of the leaves of H. rosa-sinensis to combat pathologies, the aim of this work was to evaluate the safety associated to its use, determining the acute and subacute oral toxicity of the crude extract of the leaves of H. rosa-sinensis (CELH), besides quantifying the secondary metabolites and the antioxidant activity of this extract. Another aim was to verify the effect that ionizing radiation plays in the levels of constituents, activity and toxicity of this plant. For this, part of the CELH was irradiated with gamma radiation of 60Co at a dose of 1 kGy. Crude extract non-irradiated (CELH-NIr) and irradiated (CELH-Ir) were submitted to the same tests: Total polyphenols and flavonoids dosage, identification and quantification of constituents by HPLC-UV, determination of the antioxidant activity in vitro, and evaluation of the acute and subacute toxicity of extract, as recommended by OECD guidelines 423 and 407, respectively. In the acute study, CELH-NIr and CELH-Ir were administered orally in a single dose (2000 mg/kg) to female Wistar rats, followed by minute daily observation of the animals on behavioral changes, signs of toxicity and mortality, for 14 days. At the subacute evaluation, both extracts were administered orally in three doses (100, 200 and 400 mg/kg) for 28 days in different groups of male and female Wistar rats. During the two studies, the animals had their body weight monitored, and at the end of the study, biochemical and hematological parameters were evaluated. The CELH presented expressive antioxidant activity, which was potentiated by gamma radiation. This caused a reduction in the concentration of flavonoids and total polyphenols present in the leaves of H. rosa-sinensis. Through the analysis by HPLC-UV, the compound maslinic acid was identified, which also had its concentration decreased in the CELH-Ir. No behavioral changes or any signs of toxicity were observed in animals treated with CELH. Values of body weight, relative organs weight and hematological parameters were not altered with the treatment. Significant markers of hepatic and renal function also showed no variation, indicating that both CELH-NIr and CELH-Ir are not hepato or nephrotoxic. Slight variations observed in the other biochemical parameters do not follow a dose-response pattern nor do they occur in both sexes, however, it is suggested that further studies are conducted to evaluate the effect of the hibiscus for longer periods and to clarify if the changes are related to the plant. Gamma radiation did not interfere in the absence of toxicity presented by the hibiscus and may be useful to potentiate therapeutic properties of the plant.