ANTITHYROID EFFECTS IN-VIVO AND IN-VITRO OF BABASSU AND MANDIOCA - A STAPLE FOOD IN GOITER AREAS OF BRAZIL

Babassu (Orbignya phalerata), a palm-tree coconut fruit, mixed with ma ndioca (Manihot utilissima) is the staple food of people living in the endemic goiter area of Maranhao in Brazil, where goiter prevalence am ong schoolchildren was still 38% in 1986 despite an adequate iodine in take in most of the population. Therefore, the question arose as to wh ether or not the ingestion of babassu alone or mixed with mandioca con tributed to the persistence of endemic goiter in this area of Brazil. In this investigation we examined the potential antithyroid effects of babassu and mandioca by means of in vivo studies in Sprague-Dawley ra ts, in vitro studies in porcine thyroid slices and using a purified po rcine thyroid peroxidase (TPO) system. Samples of various edible parts of babassu and mandioca flour were homogenized and extracted in goitr ogen-free water (GFW) for in vivo experiments, and in methanol (100 g/ l), GFW or 0.06 mol/l phosphate buffer (pH 7.0) for in vitro experimen ts. The edible parts of babassu produced significant in vive antithyro id effects (p < 0.05-< 0.001) in rats on a high iodine intake (141 mu g I- day(-1) rat(-1)), as well as distinct and reproducible antithyroi d and anti-TPO activities in both in vitro systems, their action being similar to that of the thionamide-like antithyroid drugs propylthiour acil and methimazole. The antithyroid action of aqueous extracts of ma ndioca flour in vive and in thyroid slices in vitro was also evident b y significant (p < 0.01-< 0.001) and pronounced inhibition of the iodi de organification process; however, in contrast to babassu, methanol a nd aqueous extracts of mandioca flour caused little inhibition in vitr o in the TPO system. Little or no effect was produced by babassu or ma ndioca on thyroid iodide transport by thyroid slices or in vive in the rat, indicating that neither thiocyanate nor perchlorate-like compoun ds are responsible for their antithyroid effects. Results of this stud y provide direct experimental evidence, both in vive and in vitro, of antithyroid effects of babassu and mandioca, supporting the hypothesis that this staple food is responsible, at least in part, for the persi stence of goiter in the iodine-supplemented endemic region of Maranhao in Brazil.