In this research work, the effect of different concentrations of copper, iron, lead, zinc and nickel ions on the tendency for gum formation in gasohol fuel is investigated. For that purpose, a gasohol sample has been doped with these five metals ions at concentration levels of 0.25, 1.0, 2.0 and 3.0 μg ml − 1. Washed gum content tests have been carried out using ASTM D 381 on samples stored for 7, 14, and 28 days. The results show that gum formation is strongly affected by Cu and Fe, with a much weaker effect from Ni and Zn, and an almost negligible effect from Pb. A variance analysis (ANOVA) of the experimental results shows that an increase in metal concentration strongly increases the rate of gum formation for all metal ions investigated, particularly Cu and Fe, while an increase in storage time has only a much weaker effect, being negligible for Zn.

RESUMO:Este trabalho descreve o isolamento e caracterização de alguns metabólitos presentes nos caules de Davilla rugosa (Dilleniaceae), conhecida vulgarmente como cipó-caboclo e utilizada pela população na medicina tradicional brasileira para diversas enfermidades. O extrato hidrometanólico foi particionado entre hexano, clorofórmio e acetato de etila. Da fase hexânica foram obtidos a friedelina, sitostenona e ácido betulínico. Da fase clorofórmica foram isolados através de técnicas cromatográfi cas o ácido betulínico e a narigenina. Enquanto que do extrato acetato de etila foram obtidos dois outros fl avonóides, quercetina e 4'-O-metil taxifolina. As substâncias tiveram suas estruturas elucidadas através da análise de dados no UV e de RMN.Unitermos: Davilla rugosa, Dilleniaceae, ácido betulínico, fl avonóides.ABSTRACT: "Phytochemical study of Davilla rugosa: fl avonoids and terpenoids". This work describes the fi rst chemical study of the Brazilian medicinal plant Davilla rugosa (Dilleniaceae) popularly known as "cipó-caboclo". The hydromethanolic extract of the stems was partitioned between hexane, CHCl 3 and EtOAc. Chromagraphic methods of fractions resulted in isolation of friedelin, sitostenone, betulinic acid, narigenin, quercetin and 4'-O-methyl taxifolin. The compounds were identifi ed by spectrometric data analyses.