Effect of harvesting year and elderberry cultivar on the chemical composition and potential bioactivity: A three-year study

Highlights

• Composition and bioactivity of Portuguese elderberry cultivars were studied.

• Sabugueiro, Sabugueira and Bastardeira cultivars were studied in three years.

• Harvesting year had a stronger effect on composition than cultivars.

• Bastardeira was richer in anthocyanins, total soluble solids and antioxidants.

• Sabugueiro was richer in total free sugars.

Abstract

Sambucus nigra is one of the richest sources of anthocyanins and other polyphenols being used industrially as a source of antioxidants, colorants, and bioactives. Although cultivars can influence elderberry composition, no study has addressed the effect of harvesting year on elderberries composition and bioactivity. The composition of the main Portuguese cultivars, “Sabugueiro”, “Sabugueira” and “Bastardeira”, were evaluated during three consecutive years. Harvesting year had a stronger influence on the chemical composition than cultivars, including total sugars, anthocyanins, and phenolic compounds, being related to the different climatic conditions, especially water status. “Bastardeira” was the best cultivar concerning total soluble solids, anthocyanins, polyphenols, and antioxidant activity, but containing a lower total free sugar content compared to “Sabugueiro”. The results obtained in this study provide novel information from a nutritional perspective and for breeding programs aiming to select cultivars with enhanced levels of health-promoting compounds or for other industrial applications of elderberries.

Introduction

At present, food and pharmaceutical industries have a growing demand for valuable natural sources of antioxidants, colorants, and health-promoting substances. Among common fruits and vegetables, elderberry (Sambucus nigra) is one of the richest sources of anthocyanins, flavonols, and other polyphenols, which contribute to its high antioxidant capacity (Seabra et al., 2010, Thole et al., 2006) and coloring capacity which is one of the primary factors for its commercial use. Due to the high abundance of phytochemicals, elderberry berries are used to treat various illnesses like constipation, viral infections, and upper respiratory infections, such as colds, flu, catarrh, being also used as diuretic and to alleviate pain (Duymuş et al., 2014, Krüger et al., 2015, Salvador et al., 2015). Elderberry fruits extracts also demonstrated beneficial effects against degenerative diseases (cardiovascular and inflammatory diseases), cancer and diabetes, presenting antioxidant and anti-inflammatory activities, immune-stimulating, chemopreventive and atheroprotective effects (Duymuş et al., 2014, Fazio et al., 2013, Mikulic-Petkovsek et al., 2016, Özgen et al., 2010, Schmitzer et al., 2010). Nevertheless, elderberries also contain sambunigrin, a toxic cyanogenic glycoside, but its levels are decreased during thermal processing (Senica, Stampar, Veberic, & Mikulic-Petkovsek, 2016). Also, elderberry fruits contain the allergenic protein Sam n1 that triggers type I allergy (Förster-Waldl et al., 2003, Jiménez et al., 2017).

It is well known that the composition of fruits depends on many factors. The plant metabolism and the synthesis of secondary metabolites are the results of several intrinsic factors, such as genetic factors that characterize the cultivars as well as the season of flowering and ripening, and the degree of fruit ripeness. On the other hand, extrinsic factors play also an important role in the fruit composition like the edaphoclimatic conditions (environmental and climatic conditions) that include exposure to different levels of radiation and wind, temperature, water availability, soil composition, and other agronomic factors. However, a combination of these intrinsic and extrinsic factors can be observed in the same cultivar in different years, and consequently, the fruits can present different chemical profiles in each season (Salvador et al., 2015, Sidor and Gramza-Michałowska, 2015). Although some studies have pointed out the effect of cultivar on the chemical composition of elderberries (Lee and Finn, 2007, Mikulic-Petkovsek et al., 2016, Mikulic-Petkovsek et al., 2015, Mikulic-Petkovsek et al., 2012, Salvador et al., 2015, Veberic et al., 2009), as far as we know no study has addressed the effect of harvesting year, and the climatic conditions of each year, on the chemical composition and bioactivity of elderberries.

In Portugal, elderberries plantation is almost exclusively located at Varosa Valley (Northern Portugal). The plantation of elderberries has increased significantly in the last decades, due to implementation of National and European programs combined with the excellent edaphoclimatic conditions in this region. At present, in Varosa Valley, about 1500–2000 tons of elderberries are produced annually which are almost totally exported as refrigerated berries to other European countries (Neto, 2007, Salvador et al., 2015, Silva et al., 2017). The main elderberry cultivars cultivated in this region are “Bastardeira”, “Sabugueira” and “Sabugueiro”. There is little information on the chemical composition of these Portuguese cultivars. The few existing studies were only focused on elderberry by-products. Seabra et al. (2010), reported the use of elderberries pomace to obtain extracts rich in anthocyanins. Silva et al. (2017) evaluated the potential use of elderberries branches to extract polyphenols, mainly anthocyanins. Regarding the fruit, the chemical composition of the lipophilic extracts from these three cultivars was similar and has been described by Salvador et al. (2015). Ursolic and oleanolic acids were the main components. Therefore, the purpose of this work was to study the effect of cultivar, “Bastardeira”, “Sabugueira” and “Sabugueiro”, and harvesting year in the phenolic profile, sugar content, organic acids content and antioxidant activity of elderberries.