Ageing behaviour and analytical characterization of the Jatobá resin collected from Hymenaea stigonocarpa Mart.

Abstract

This paper reports the results of an analytical study to characterize the trunk resin collected from the Hymenaea stigonocarpa Mart. species from the region of Minas Gerais (Brazil), popularly known as Jatobá resin. Hymenaea resins are reported to have been used in artistic applications such as protective varnishes in polychromed sculptures and paintings. Therefore, the identification of the main chemical changes that take place in the resin when it is prepared as a thin film exposed to atmospheric effects have been considered herein. Changes due to the degradation effect of light have been studied on a series of specimens prepared as a thin films and subjected to accelerated UV light ageing. The results based on GC–MS, THM–Py–GC–MS analyses, and on-line trimethylsilylation Py–GC–MS using hexamethyldislylazane as a derivatization reagent, have been compared. The study shows that eperuic acid and its Δ7 and Δ8 isomers, together with copalic acid, are the major components of the studied resin. Other compounds such as kolavenic acid, iso-ozic acid and epi-pinifolic acid are also present in this resin as minor components. This composition differs from those of resins obtained from other species of the Hymenaea genus growing in this Amazonian region. UV light ageing of the Jatobá resin prepared as a thin film results in the appearance of a new isomer of eperuic acid. Some changes in the relative content of the major components present in the resin have also been observed after ageing.