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ETHNOPHARMACOLOGICAL RELEVANCE: Propolis is a bee product widely used in folk medicine due to its numerous pharmacological properties. However, samples from different regions can differ in chemical composition, effectiveness, and side effects. Despite the widespread use of Brazilian red propolis, which is an isoflavone-rich variety, its toxicity has not been carefully studied. AIMS OF THE STUDY: To assess the acute and sub-acute toxicity of the hydroethanolic extract of red propolis (HERP) administered orally to rats. MATERIALS AND METHODS: HERP for the acute (300mg/kg) and sub-acute (10, 100 and 200mg/kg) toxicity studies was administered orally to rats according to OECD Guidelines 420 and 407, respectively. Clinical signs were identified, and hematological and biochemical analyses were performed. Water and food uptake as well as body and organ weights of animals were recorded. RESULTS AND CONCLUSIONS: The acute study revealed no lethal effects at 300mg/kg of HERP, but toxic signs were observed, as HERP had an LD50 of more than 300mg/kg, indicating a warning. The most toxic signals in sub-acute studies were observed in males at a dose of 200mg/kg HERP. These results suggest estrogen-like activity, possibly from the isoflavones in HERP.

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The biological activity of extracts from the leaves, bark and roots of Muellera frutescens, an Amazonian ichtyotoxic plant, were evaluated to find new environmentally safe insecticides. The n-hexane extracts of bark, leaf, and root showed a strong toxic activity against Aedes aegypti mosquito larvae. Bioguided fractionation of the bark extract led to the isolation of seven isoflavonoids (12a-hydroxyelliptone, elliptone, (-)-variabilin, rotenone, rotenolone, tephrosin and deguelin). Rotenone and deguelin are responsible for the larvicidal activity of the plant. M frutescens leaves contain up to 0.6%, w/w, deguelin. These results justify the traditional ichtyotoxic use of M frutescens. The leaves contain a relatively high proportion of deguelin and, therefore, can be considered as a renewable source of this environmentally friendly insecticidal isoflavonoid.

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Ipriflavone (7-isopropoxy-isoflavone) is a semisynthetic isoflavone derivative from daidzein and prescribed to prevent and treat osteoporosis in postmenopausal women. In the present study, ipriflavone was investigated with regard to their cytotoxic and mutagenic effects using the micronucleus assay (MN) in vivo on cells of bone marrow and peripheral blood of Swiss albino mice and the micronucleus test with the cytokinesis-blocked micronucleus assay (CBMN assay) on human peripheral blood lymphocytes. The studies were performed in mice with three dosages of the drug, 1.71, 8.57 and 42.85 mg/kg bw in single oral exposure, and for two dosages, 5 and 10 µg/mL in the CBMN assay. Ipriflavone, in the dosages tested, did not differ from controls neither in the induction of MN nor induced cytotoxicity to cells in the in vivo test. However, in the CBMN assay, the concentration of 10 µg/mL induced a statistically significant increase in MN formation and decreased cell proliferation, demonstrating to be mutagenic and cytotoxic at this concentration.

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A ipriflavona possui efeito inibitório sobre o citocromo p450 e sobre a proliferação do DNA, interferindo na síntese de hormônios estereoidianos, e consequente interferência no transporte e desenvolvimento pré-implantacional e na implantação do blastocisto. Consumidos em altas doses pode acarretar abortamentos e malformações. Para verificar a embriotoxicidade da ipriflavona durante as fases de transporte tubário e implantação do blastocisto de ratas, ratas Wistar prenhes foram tratadas duas vezes ao dia com 1mL de suspensão aquosa de ipriflavona, nas doses de 0 (C), 300 (T1), 1500 (T2) e 3000 (T3) mg/kg/dose, durante os oito primeiros dias de prenhez com eutanásia no 14o dia. Indícios de toxicidade foram avaliados por análises hematimétricas, bioquímicas e comportamentais. Foram contados fetos vivos, mortos e reabsorvidos (inicial e tardiamente). Os animais não apresentaram sinais clínicos de toxicidade. Índice de implantação e perdas pré-embrionária sofreram interferência do uso da ipriflavona. Dados apontam para um efeito estrogênico da ipriflavona, observados na interferência da implantação do blastocisto de ratas Wistar.

Ipriflavone has inhibitory effect on the cytochrome p450 and the proliferation of DNA, interfering with hormone synthesis estereoidianos, and consequent interference with the transport and preimplantation development and implantation of the blastocyst. Consumed in high doses can cause miscarriages and malformations. To verify the embryotoxicity of ipriflavone during the phases of tubal transport and implantation of the blastocyst in rats, Wistar rats were treated twice daily with 1 mL of aqueous suspension of ipriflavone at doses of 0 (C), 300 (T1), 1500 (T2) and 3000 (T3) mg / kg / dose during the first eight days of pregnancy with euthanasia on day 14. Signs of toxicity were characterized by hematological, biochemical and behavioral. Live fetuses were counted, dead and resorbed (early and late). The animals showed no clinical signs of toxicity. Index pre-implantation embryo and losses suffered interference from the use of ipriflavone. Data point to an estrogenic effect of ipriflavone, due to interference in blastocyst implantation in Wistar rats.

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