Berry Leaves: An Alternative Source of Bioactive Natural Products of Nutritional and Medicinal Value

Abstract

Berry fruits are recognized, worldwide, as "superfoods" due to the high content of bioactive natural products and the health benefits deriving from their consumption. Berry leaves are byproducts of berry cultivation; their traditional therapeutic use against several diseases, such as the common cold, inflammation, diabetes, and ocular dysfunction, has been almost forgotten nowadays. Nevertheless, the scientific interest regarding the leaf composition and beneficial properties grows, documenting that berry leaves may be considered an alternative source of bioactives. The main bioactive compounds in berry leaves are similar as in berry fruits, i.e., phenolic acids and esters, flavonols, anthocyanins, and procyanidins. The leaves are one of the richest sources of chlorogenic acid. In various studies, these secondary metabolites have demonstrated antioxidant, anti-inflammatory, cardioprotective, and neuroprotective properties. This review focuses on the phytochemical composition of the leaves of the commonest berry species, i.e., blackcurrant, blackberry, raspberry, bilberry, blueberry, cranberry, and lingonberry leaves, and presents their traditional medicinal uses and their biological activities in vitro and in vivo.

Keywords: Ribes; Rubus; Vaccinium; analysis; chlorogenic acid; polyphenols; traditional use.

Figure 1

The phenolic composition of the commonest berries. Chokeberries (Aronia mitschurinii) contain the highest concentration of bioactive compounds, mainly anthocyanins and proanthocyanins. Bilberry (Vaccinium myrtillus) is rich in anthocyanins, as well as wild blueberry (Vaccinium corymbosum), which also contains notable amount of phenolic acids. Lowbush blueberry (Vaccinium angustifolium) and the American cranberry (Vaccinium macrocarpon) are sources of proanthocyanidins. The berries of the genus Rubus, i.e., raspberry (Rubus idaeus), cloudberry (Rubus chamaemorus), and blackberry (Rubus fruticosus) contain all the principle bioactive compounds that we meet in berries, and especially ellagitannins. Gooseberry (Ribes uva-crispa) and red currant (Rubus rubrum), on the other hand, contain mainly phenolic acids and only traces of the other compounds.

Figure 2

Structures of the most common phenolic acids and acid derivatives of berry leaves.

Figure 3

Structures of the main flavonoid aglycons and terpenes of berry leaves.