The effects of extraction method on the measured tocopherol level and antioxidant activity of L. nobilis vegetative organs

Tocopherol contents of Tunisian Laurus nobilis vegetative organs were screened for antioxidant activity. Tocopherol isomers extracted by probe sonication and micro-scale saponification were analysed by reversed-phase high performance liquid chromatography (RP-HPLC) with UV detection to determine the optimum extraction method. Total phenolic, flavonoid and proanthocyanidin contents were determined spectrophotometrically. Significant variations in the amounts of α-, γ- and δ-tocopherols were observed with the two different extraction methods as well as with different plant parts. Leaf extract contained the highest amount of α-tocopherol (139 mg/100 g fresh weight), but root extract contained the highest content of flavonoids (11.12 mg catechin equivalents (CE)/g dry weight or DW), total phenolics (55.45 ± 2.9 mg GAE/g DW) and condensed tannins (9.76 ± 0.1 mg CE/g DW). Acetonic extract of laurel leaf exhibited the highest antioxidant activity response to lipid peroxidation in the β-carotene-linoleic acid system, which may have been due to the high content of α-tocopherol. These findings suggest that laurel leaf may be a source of natural α-tocopherol and that it may be increasingly important for human consumption, as well as for the agro-food, cosmetic and pharmaceutical industries.