Optimisation of the Supercritical Fluid Extraction of Antioxidants from Broccoli Leaves
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Optimisation of the Supercritical Fluid Extraction of Antioxidants from Broccoli Leaves Esther Arnáiz 1 & José Bernal 1 & María Teresa Martín 1 & Juan Carlos Diego 1 & José Luis Bernal 1 & Laura Toribio Recio 1
Received: 1 December 2015 / Accepted: 6 January 2016 # Springer Science+Business Media New York 2016
Abstract This work presents the application of supercritical fluid extraction (SFE), an environmentally friendly methodology, to obtain broccoli leaves extracts with a high antioxidant activity. The following processing variables: pressure, temperature, percentage of ethanol and dynamic extraction time were optimised by means of a central composite design, combined with response surface methodology. The optimised conditions were applied to the extraction of broccoli leaves from different cultivars (Naxos, Nubia, Marathon, Parthenon and Viola). The optimal values of the extraction variables were 150 bars, 35 °C, 20 % ethanol and 10 min of dynamic extraction time. Percentage of ethanol and the combined effect of pressure and time were the factors that affected the extraction the most. The results obtained from different cultivars showed that the Naxos variety provided the extracts with the highest antioxidant activity and total phenolic content; moreover, DPPH (EC 50) values were higher than those previously reported for water extracts. The extracts were recovered in a small quantity of ethanol that could be easily eliminated, obtaining a residue free of contaminants.
Keywords SFE . Broccoli leaves . Antioxidant activity . Total phenolic content . DPPH . ABTS
* Laura Toribio Recio [email protected]
1
I.U. CINQUIMA, Analytical Chemistry Group, University of Valladolid, Paseo de Belén 7, 470, Valladolid, Spain
Introduction Nowadays, there is a great interest to know the antioxidant activity of food and natural products, because numerous studies have shown that the consumption of natural antioxidants is associated with reduced risk of chronic diseases, such as cardiovascular diseases, cancer, diabetes, Alzheimer’s disease, cataracts and age-related functional decline (Krishnaiah et al. 2011; Kelsey et al. 2010). Moreover, natural antioxidants can have different uses such as the following: as dietary supplements, as ingredients in functional foods or in cosmetics as well as to replace synthetic antioxidants. For these reasons, the search for sources of natural antioxidants (plants or microorganisms) have become a topic of increasing concern (Hall 2001; Bandoniene et al. 2000). Brassica-like vegetables, such as kale, cabbage, Brussels sprouts, cauliflower and broccoli are characterised by a high antioxidant activity (Podsędek 2007). Broccoli is a significant source of nutritional antioxidants, as well as biologically active dietary components like glycosides and sulphurcontaining compounds such as glucosinolates (Ares et al. 2014; Moreno et al. 2006). Several papers have studied the antioxidant activity of broccoli; it was ranked as the second between ten common vegetables (Chu et al. 2002) and the sixth bet
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