Cubé Resin Insecticide: Identification and Biological Activity of 29 Rotenoid Constituents

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Abstract
Cubé resin, the root extract from Lonchocarpus utilis and urucu, is an important insecticide, acaricide, and piscicide. The four major active ingredients are rotenone, deguelin, rotenolone, and tephrosin, totaling 77 wt %. As a commercial pesticide, the minor constituents are also of chemical interest and toxicological relevance. This study identifies 25 minor rotenoids in cubé resin “brittle” of which 12 are new compounds, the most unusual being 7‘-chloro-5‘-hydroxy-4‘,5‘-dihydrodeguelin (the first chlororotenoid from a plant extract) and four isomers of 4‘,5‘-dihydro-4‘,5‘-dihydroxytephrosin. Several of the minor rotenoids may be decomposition products from free radical processes during sample preparation, extraction with trichloroethylene, and processing the resin. Assays of the 29 rotenoids as inhibitors of NADH:ubiquinone oxidoreductase activity (primary target for toxicity) and phorbol ester-induced ornithine decarboxylase activity (indicator of cancer chemopreventive action) and for cytotoxicity establish similar structure−activity relationships in each system and the importance of the overall molecular conformation and the E-ring substituents. Keywords: Cubé resin; cytotoxicity; insecticide; NADH:ubiquinone oxidoreductase; ornithine decarboxylase; piscicide; rotenoid; rotenone