Optimized and validated HPLC method for alpha- and gamma-tocopherol measurement in Laurus nobilis leaves. New data on tocopherol content.

Extraction and chromatographic conditions for measuring tocopherols from Laurus nobilis were optimized. Newly harvested leaves were dried in a microwave oven and crushed; then, alpha- and gamma-tocopherol and tocol, added as internal standard, were directly extracted from portions of ground material with acetone, by probe sonication. After centrifugation and filtration, the acetonic extract was directly analyzed by HPLC using a gradient elution with a Discovery C18 column (25 x 0.46 cm) at 35 degrees C. UV and fluorescence detections were employed simultaneously. Validation parameters of the method for linearity, accuracy, and precision can be considered to be adequate for both detection modes. After validation, a number of samples selected from different geographical areas in the Iberian peninsula were measured, and results compared with those in the literature gave surprisingly high values.