Tocopherol measurement in edible products of vegetable origin

Since natural antioxidants present increasing interest for food industry due to their beneficial effect on health, new potential sources have been screened among edible aromatic plants and a microalgae, Spirulina platensis. The determination was performed after optimising a previously validated method, because important differences have been found among values described in literature for tocopherol content in products of vegetable origin. Values obtained ranged from 3.42 mg α-tocopherol/100 g of dill to 132.2 mg/100 g of fresh bay and from 0.14 mg γ-tocopherol/100 g of spearmint to 3.45 mg/100 g of parsley. In all cases results were calculated from fresh leaves. Preliminary experiments were developed with bay (Laurus nobilis) plant to devise the supercritical fluid extraction of tocopherols, generating environmentally friendly processes to selectively extract fractions enriched with antioxidant compounds while removing fractions corresponding to essential oils, that is, those that correspond to the characteristic aroma of the plants. Another striking result has been the tocopherol content in the microalgae, 1.3 mg α-tocopherol/100 g of dried commercial spirulina, which do not justify the supposed source of antioxidant vitamins. Results suggest the need of more reliable determinations of tocopherols in vegetable sources to be included in databases.