Variability of the antioxidant properties of Berberis fruits depending on the plant species and conditions of habitat

Abstract

Plant fruits, leaves, stems, and other parts are of high nutritional value, and are the source of physiologically active compounds, which can contribute to the treatment of many diseases caused by oxidative stress. Enrichment of the species spectrum of the fruit plants expands the possibilities of their use in dietary nutrition and human treatment. Unfortunately, the introduction of the new fruit plant species in industrial gardens in the Steppe Dnieper is limited to a large extent by the unfavorable climate. In this regard, the assessment of the possibility of realizing the genetic potential of fruit plants from different geographical areas in the steppe climate acquires both scientific and practical significance. The study was conducted on the basis of the fruit plants collection collection of the Botanical Garden of the DNU including four introduced species and one natural species from the genus Berberis. The anomalous weather conditions during the growing season of 2017 (snowfall in April followed by a drought in June) were accompanied by an earlier stage appearance of leaves, flowering and fruit ripening of all introduced plants, especially the Asian species B. amurensis and B. koreana, compared to the native species B. vulgaris. In accordance with the results obtained, fresh weight of the ripe fruits of Berberis species decreased in the order of B. amurensis > B. vulgaris > B. canadensis > B. koreana > B. x declinata. The highest total phenolics content, determined in the isopropanolic fruit extracts by Folin – Ciocalteau assay, was found in the fresh ripe fruits of B. koreana (1362 ± 66 mg GAE/100 g WW), followed by B. x declinata and B. vulgaris fruits (91% and 77% of the B. koreana phenolics content respectively). The highest total flavonoids content determined using the aluminum chloride method was revealed in the fruits of B. koreana (210 ± 6 mg RE/100 g FW) exceeding the content in fruits of other Berberis species by 1.1–2.1 times, while the lowest value (103 ± 4 mg RE/100 g FW) was found in the fruits of B. amurensis. The total reducing power, determined by RP assay, varied in the range from 5.0 to 9.6 mg AAE/100 g DW, and the highest levels were found in the fruits of B. koreana and B. x declinata (respectively, 9.6 ± 0.6 and 8.6 ± 0.5 mg AE/100 g DW) exceeding the reducing capacity of other Berberis species by 1.7–1.9 times. In the fruits of genus Berberis species strong positive correlation was found between the total reducing power and the total content of phenols (r = 0.87), as well as between the reducing power and the total content of flavonoids (r = 0.84). High correlation coefficients confirm the significant contribution of the Berberis fruit phenolic compounds, including the flavonoids, to the antioxidant capacity. So, the study results showed that fruits of all examined Berberis species can be an easily accessible source of antioxidants, however, the antioxidant capacity of fruits decreased in order of B. koreana > B. x declinata > B. vulgaris > B. amurensis > B. canadensis.