Antioxidant and antiproliferative properties of strawberry tree tissues

Abstract

Strawberry tree (Arbutus unedo) belongs to the Ericaceae family and is endemic to the Mediterranean area. Its fruits are edible and its fruits and leaves are used in folk medicine for diverse purposes. Previous studies have shown that the fruits are rich in flavonoids, responsible for their antioxidant properties and compounds isolated from the entire plant were promising in cancer chemopreventive therapy. Strawberry tree fruits and leaves extracts enriched in polyphenols, but devoid of organic acids, carotenoids and sugars, were prepared by solid phase extraction (SPE) and tested for their antioxidant activities and their ability to inhibit metalloproteinases: attributes that could be related with initiation and proliferation of cancer cells. After fractionation by SPE, the apparent polyphenol yield was reduced for both leaf and fruit samples by the elimination of vitamins and organic acids, but the antioxidant and metalloproteinases inhibitory activities were potentiated. The antioxidant activity and the MMP-9 inhibitory activity of the polyphenol-enriched fractions of A. unedo tissues were similar or higher than those of blackberry and green tea, which have been recognized in the literature as highly effective. The phenolic profile of the fruit was dominated by gallic acid and quercetin derivatives with smaller amounts of proanthocyanidins and anthocyanins. The phenolic profile of the leaves was also dominated by gallic acid derivatives, flavonol derivatives and some tannins but lacked anthocyanins. The fractions obtained from both strawberry tree tissues seem to be quite promising as antioxidants and antiproliferative agents. Further cell-based assays are underway to study these possible outcomes.