Determination of Adulteration in Evening Primrose Oil Capsules by ¹H NMR Analysis and Chemometric Techniques

The consumption of dietary supplements has grown exponentially over the last few years, among which the oil obtained from evening primrose seeds stands out for containing a high level of polyunsaturated fatty acids, especially γ-linolenic fatty acid, which helps to reduce effects of menopause, premenstrual tension, and among other benefits. This work presents a study of the lipid quality of the eight main brands of evening primrose oil capsules on the national market, evaluated using ¹H nuclear magnetic resonance spectroscopy together with chemometric analysis techniques (principal component analysis and multiple linear regression). Therefore, among the commercially acquired samples, only two had a lipid profile close to the reference evening primrose oil, the others had scores ranging from 17.9 to 25.8, making them unsuitable for consumption. This was possible based on the identification of markers in the ¹H spectra with potential for study and application in determining the lipid quality of other encapsulated vegetable oils.