Acylated anthocyanins in broccoli sprouts
Introduction
In recent years, increasing attention has been paid to the role of diet in human health associated with a reduced risk of a number of chronic diseases. These beneficial effects have been partially attributed to the compounds which possess antioxidant activity. The major antioxidants of vegetables are vitamins C and E, carotenoids, and phenolic compounds, especially flavonoids (Duthie et al., 2006, Singh et al., 2006).
Variation in the antioxidant contents of Brassica vegetables is caused by many factors: variety, maturity at harvest, growing condition, etc. (de Pascual-Teresa and Sánchez-Ballesta, 2008, Hale et al., 2001, Podsedek, 2007). The studies on phenolic profiles of Brassica vegetables have been focused mainly on broccoli florets. Broccoli is a source of flavonol and hydroxycinnamoyl derivatives (Lin and Harnly, 2009, Podsedek, 2007). Vallejo, García-Viguera, and Tomás-Barberán (2003), reported that quercetin and kaempferol 3-O-sophoroside-7-O-glucoside were the main flavonol glycosides, and the other minor glucosides were isoquercitrin, kaempferol 3-O-glucoside and kaempferol 3-O-diglucoside. The predominant hydroxycinnamoyl acids have been identified as 1-sinapoyl-2-feruloylgentiobiose, 1,2-diferuloylgentiobiose, 1,2,2′-trisinapoylgentiobiose, and neochlorogenic acid. In addition, 1,2′-disinapoyl-2-feruloylgentiobiose and 1-sinapoyl-2,2’-diferuloylgentiobiose, isomeric forms of 1,2,2’-trisinapoylgentiobiose and 1,2,2’-triferuloylgentiobiose, and chlorogenic acids are also present in broccoli (Vallejo, Tomás-Barberán, & Ferreres, 2004). Polyglycosylated and polyglycosylated/acylated flavonoids are common in the Brassicaceae, and there is considerable data on Brassica (Llorach, Gil-Izquierdo, Ferreres, & Tomás-Barberán, 2003). However, the acylated anthocyanins, as far as we are aware, have not been previously reported in edible sprouts of broccoli.
Broccoli, belongs to the Brassica genus and is a nutritious vegetable and a good source of vitamins A and C, potassium, folic acid, riboflavin (vitamin B2) and iron. It is high in fibre and low in calorie content and contains important antioxidant phytochemicals like, polyphenols, β-carotene and α-tocopherol, indoles and isothiocyanates (which have been shown to act as anticarcinogens by inhibition of the phase I enzymes and induction of the phase II enzymes) (Podsedek, 2007, Singh et al., 2006).
Edible sprouts are novel nutritive and phytonutrient-rich plant-derived foods, good source of flavonoids and other polyphenols, that are produced without adding extensive product development or new equipments or costly marketing efforts. On the other hand, there is an increasing awareness that multiple genetic and environmental factors affect production and accumulation of bioactive components (in the food) for the improvement of health (Moreno, Carvajal, López-Berenguer, & García-Viguera, 2006). Due to the increased consumption of sprouts there needs to be optimisation for quality, palatability and bioactivity.
Within the coloured flavonoids, anthocyanins are the most important group of plant pigments, also considered as multifunctional components of food due to their antioxidant activity and other beneficial biological properties (Drabent et al., 1999, Sadilova et al., 2006). Nevertheless, in certain fruits and vegetables, anthocyanins exist in smaller amounts and only some of them exist in such an amount that they can determine the proper colour. For example, in Brassica oleracea L. extracts, from 8 to 15 anthocyanins were found, which exist as 5-glucosindes and 3,5-glucosides with different anthocyanidins as chromophoric groups (Drabent et al., 1999).
The chemical structure of the anthocyanin determines the stability, colour intensity and potential biological activity. For example, acylation of the anthocyanin molecule improves its stability through intramolecular and/or intermolecular copigmentation, and self-association reactions. Therefore, sources of acylated anthocyanins may provide the desirable stability for food applications (de Pascual-Teresa and Sánchez-Ballesta, 2008, Giusti and Wrolstad, 2003). On the other hand, acylated anthocyanin extracts inhibited α-amylase action, indicating that acylated anthocyanins would have a potential function in suppressing the increase in postprandial glucose levels from starch (Matsui et al., 2001a), of interest in the development of a physiologically functional food (Matsui et al., 2001b). The increased stability of these pigments together with their added value due to potential beneficial effects opens a new window of opportunity for their use in a variety of food applications (Giusti & Wrolstad, 2003).
The anthocyanins that have been isolated from the Cruciferae (Brassicaceae) family have unusually complex structures with one or more cinnamic acids. From the chemotaxonomical point of view, two typical anthocyanidin glycoside types have been known in this family, such as anthocyanidin 3-O-sophoroside-5-O-glucosides and 3-O-sambubioside-5-O-glucosides (Honda et al., 2005). The genus Brassica and Raphanus have characteristic varieties containing acylated anthocyanidin 3-O-sophoroside-5-O-glucoside (Suzuki et al., 1997, Tatsuzawa et al., 2006).
Therefore, the aim of this work was to characterise the anthocyanin composition of edible sprouts of broccoli not described to this date using HPLC/PAD/ESI-MSn and also discussing the genotypical influence on the phytochemical composition of these sprouts with respect to their anthocyanin profile and contents.
Section snippets
Material and sprouting conditions
Commercial broccoli and certified seeds of ‘Marathon’ and ‘Nubia’ were obtained from Ramiro Arnedo SA (Murcia, Spain). The ‘Viola’ seeds correspond to Early Purple Sprouting Broccoli were purchased at Thompson&Morgan UK Ltd. (Poplar Lake, Ipswich, Suffolk, UK) and the broccoli seeds from the sprouting-variety, were provided by the company “Intersemillas” (Poligono Ind. Loriguilla, Valencia, Spain). Seeds were pre-hydrated and aerated in a 0.5% NaClO solution for 2 h as in Pérez-Balibrea, Moreno,
Anthocyanin characterisation
Molecular ions (m/z) of common anthocyanins and typical acylating groups are presented in Table 2. The extracts, with a complex anthocyanin profile that shows different acylating patterns with only one anthocyanidin group, were evaluated. Depending on the HPLC conditions and the complexity of the anthocyanin profile, the length of the experimental run may range from several minutes to up to an hour. Usually, for practical reasons, the approach is to develop a systematic methodology that could
Conclusions
There is increasing recognition of the nutritional value of the sprouts of various vegetables, beans, and crops (Moreno, Pérez-Balibrea, et al., 2006, Pérez-Balibrea et al., 2008, Watanabe, 2007). The consumption of broccoli sprouts is limited in Europe; even though it is recognised as a healthy food in America and Asia. This study indicates that broccoli sprouts could exert health benefits due to an abundance of phytochemicals such as flavonoids, with considerable potential for functional
Acknowledgements
The authors wish to thank the Fundación Seneca-Regional Agency for Science and Technology for the financial support of this work (Project ref. n# 05588/PI/07). Part of this work was also funded by M.I.C.I.N.N. (PETRI Project PET2006_0305) and CSIC I3 Programme (Project 200870I070).
The author Perez-Balibrea is funded by a grant from Murcia Regional Regional Agency for Science and Technology ‘Seneca Foundation’.
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