Eperua oleifera Ducke (Fabaceae) Oilresin Chemical Composition and the Isolation of a Natural Diterpenic Acid Methyl Ester.

Eperua oleifera Ducke, commonly known as "copaíba-jacaré," produces oilresins traditionally used in folk medicine for wound healing and as antifungal and antibacterial agents, similar to those of Copaifera species. However, its chemical composition remains poorly characterized. This study investigated the oilresin of E. oleifera collected in the Brazilian Amazon region. After derivatization, the sample was analyzed by GC-MS, with data compared to literature, mass spectral libraries, and standards previously isolated. In addition, neutral and acidic fractions were separated using ion-exchange open-column chromatography with silica modified with KOH-impregnated silica as the stationary phase. Twelve diterpenes were identified, including nine carboxylic acids and three alcohols. Hardwickiic acid and copalic acid were the major components, fully characterized by NMR. The most abundant compound in the neutral fraction was isolated and identified by HRMS and NMR as the methyl ester of hardwickiic acid-a compound not previously reported in oilresins. The application of GC-MS enabled the identification of diterpenes based on known fragmentation patterns. In addition, the direct infusion experiment detected a methyl ester that, to our knowledge, has not been previously reported in oilresins.