Phenolic compounds in blackcurrant (Ribes nigrum L.) leaves relative to leaf position and harvest date Michael Vagiri a,d,⇑ , Sean Conner b , Derek Stewart b,c , Staffan C. Andersson d , Susan Verrall b , Eva Johansson d , Kimmo Rumpunen a a Swedish University of Agricultural Sciences, Department of Plant Breeding, Balsgård, Fjälkestadsvägen 459, SE-291 94 Kristianstad, Sweden b Environmental and Biochemical Science Group, Enhancing Crop Productivity and Utillisation Theme, The James Hutton Institute, Invergowrie, Dundee DD2 5DA, United Kingdom c School of Life Sciences, Heriot-Watt University, Edinburgh, United Kingdom d Swedish University of Agricultural Sciences, Department of Plant Breeding, Box 101, SE-230 53 Alnarp, Sweden article info Article history: Received 3 April 2014 Received in revised form 31 July 2014 Accepted 9 September 2014 Available online 16 September 2014 Keywords: Flavonols Functional food Growth stage HPLC Organic growing Leaf age Phenols Polyphenols Seasonal variation abstract Blackcurrant leaves are an essential source of phenolic compounds and this study investigated their var- iation relative to leaf positions and harvest date. The phenolic content varied between harvest dates, although leaf position on the shoot and interactions also played an important role. The contents of quer- cetin-malonyl-glucoside, kaempferol-malonyl-glucoside isomer and kaempferol-malonyl-glucoside were higher than that of the other identified phenolic compounds, whereas epigallocatechin was the lowest for all investigated leaf positions and harvest dates. The content of several of the compounds was highest in June, while quercetin-glucoside, kaempferol-glucoside and total phenols, increased towards the end of the season. Leaf position influenced the content of myricetin-malonyl-glucoside, myricetin-malonyl-glu- coside isomer, quercetin-malonyl-glucoside and kaempferol-glucoside at the end of the season. Knowl- edge relating to the influence of ontogenetic and harvest time on the content of specific phenolic compounds might contribute in tailoring functional foods or pharmaceutical products using blackcurrant leaves as natural ingredients. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Plants are sustainable sources of bioactive compounds which can be used for different applications, for instance as food addi- tives, functional food ingredients and as nutraceuticals (Martin, Zhang, Tonelli, & Petroni, 2013). During recent years, interest in identifying new possible sources of natural antioxidants and other health promoting compounds has increased. Blackcurrant (Ribes nigrum L.) is a temperate soft fruit crop particularly rich in different antioxidants with health promoting properties (Brennan & Graham, 2009). Recent papers on epidemiological, in vitro and in vivo studies have summarised the positive contribution of black- currants on human health (Gopalan et al., 2012; Karjalainen et al., 2008; Lister, Wilson, Sutton, & Morrison, 2002). The compounds mainly contributing to the antioxidant capacity of blackcurrant are ascorbic acid and phenolic compounds such as flavonoids and phenolic acids (Moyer, Hummer, Finn, Frei, & Wrolstad, 2002; Szajdek & Borowska, 2008). Blackcurrants are normally cultivated for industrial applications with focus on use of the fruits. However, other anatomical parts such as leaves could also potentially be used as a raw material for preparation of extracts for functional foods and the health industry. Traditionally, blackcurrant leaves have been used in European folk medicine for the treatment of rheumatism, arthritis and respiratory problems (Stevic ´ et al., 2010). The culinary uses of leaves include ‘louhisaari’ drink preferably using the young leaves of early summer (Food, 2014; http://www.food.com/recipe/ louhisaari-black-currant-drink-120759). Infusion of blackcurrant leaves to sweetened vodka makes a deep yellowish green beverage with a characteristic sharp flavour and astringent taste (Incredible edibles, 2014; http://www.edible.co.nz/fruits.php?fruitid=22). Recent studies report blackcurrant leaves as an excellent source of total phenols, with content five times higher than what is found in the fruits (Tabart, Kevers, Pincemail, Defraigne, & Dommes, 2006). In addition, the leaves of blackcurrant are now receiving scientific attention due to antioxidant and anti-inflammatory activities reported using in vitro and in vivo models (Declume, http://dx.doi.org/10.1016/j.foodchem.2014.09.041 0308-8146/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Swedish University of Agricultural Sciences, Depart- ment of Plant Breeding, Balsgård, Fjälkestadsvägen 459, SE-291 94 Kristianstad, Sweden. Tel.: +46 44 265838; fax: +46 44 265830. E-mail address: michael.rajeev.vagiri@slu.se (M. Vagiri). Food Chemistry 172 (2015) 135–142 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem