Autenticação de óleo resina de copaíba por Ressonância Magnética Nuclear

Abstract

Copaiba oil is a resin oil extracted from the trunk of trees of species of the genus Copaifera. This oil has several pharmacological activities, such as anti-inflammatory, antibacterial, and antifungal. Because of these properties, this oil has been used natives and the traditional population to cure or alleviate illnesses, such as inflammation and wounds, through oral or topical use. However, these pharmacological benefits, associated with low production, make copaiba oil a high value-added Amazonian bioproduct. Consequently, adulteration with soybean oil is common and increases profitability. However, this practice harms the consumer who purchases an adulterated product. Commonly, the authentication of this product is done by gas chromatography, which in addition to high analytical cost, is not efficient in detecting adulteration with vegetable oil. Because of this, the search for simple, fast, cheap, and reliable methods to identify adulterants in this oil is necessary. Thus, NMR support by chemometric tools (PCA and PLSR) was used to solve this problem. Four major constituents were identified by GC-MS: -caryophyllene (22.9 to 68.7%), - copaene (1.5 to 24.2%), germacrene D (1.2 to 16.4%), and -humulene (3.5 to 15.7%) in all samples. Caryophyllene oxide (0.2 to 16.0%), drimenol (5.1 to 20.3%), and juniper camphor (2.0 to 12.1%) were identified, mainly in samples with higher viscosity. The use of high-resolution NMR allowed adulteration with soybean oil to be identified. The commercial samples’ adulterant contents were estimated by ERETIC2 and PLSR and varied between 3.2 to 96%. These two quantitative approaches are in good agreement with each other. The authentication of copaiba oil by TD-NMR was limited due to high chemical variability and high variation in viscosity. Therefore, the use of high-resolution NMR was more effective and allowed to identify and quantify adulteration with soybean oil in commercial samples of copaiba, regardless of chemical variability. Therefore, this methodology is quite satisfactory for the authentication of samples of copaiba resin oil.