The tocopherol content of different legume crops

The health promoting properties of fruits and vegetables are strongly related to the presence of bioactive phytochemicals. Tocopherols attract a lot of interest, since they act as antioxidants by trapping radical intermediates, reducing the risk of chronic diseases, such as cardiovascular diseases and cancer. Tocopherols (T) can exist in four different regioisomers: alfa-T, beta-T, gamma-T, and delta-T, which differ for the methylation pattern of the phenolic ring. The isomers have different activities: alfa-T affects health aspects, while gamma-T has a relevant role in protecting the fatty acids in the seed. In this work, seeds from the main legume crops, i.e. soybean, lupin, chickpea, lentil, bean, pea, and broad bean, were analysed. Finally, a close investigation was performed on white lupin: eight cultivars were sowed in two different pedo-climatic areas and during two agricultural years, in order to highlight the differences in the tocopherol content due to genotypic and pedoclimatic parameters. The seeds were dehulled and ground, the oil was extracted in a Soxhlet apparatus with hexane for 3 h, then analysed by a HPLC equipped with a fluorimetric detector, using a Lichrosorb Si60 column and n-hexane:isopropanol (99:1, v/v) as eluent. The amounts of tocopherols were calculated by comparing their peak areas with the calibration curves. Gamma-T is the most abundant isomer in all samples, whereas beta-T has never been detected. In general, alfa-T and delta-T are very sensitive to each specific sample, for example alfa-T is absent in common beans, whereas delta-T is absent in narrow-leaf lupin. In soybeans, the total tocopherol content is about 14 mg/100 g, in Albanian peas it falls in the range between 10 and 14 mg/100 g, in Italian peas and broad beans is about 6 mg/100 g, in Italian common beans is about 3 mg/100 g, and in chickpeas is about 11 mg/100 g. The contents of the three lupin species are the following (average values): pearl-lupin 10.2 mg/100 g, white lupin 9.7 mg/100 g, and narrow-leaf lupin 8.6 mg/100 g, respectively. Large differences have been observed in the tocopherol contents of the white lupin cultivars.