Antioxidant properties of methanolic extracts obtained from blackberries and elderberry

Berry fruits are exceptionally rich sources of sugars, organic acids andpolyphenols and present an interestlng nutritional alternative. A large andgrowing body of evidence has convingly established the anticancer potentialof singly purified constituent found in berry fruits. These include phenolics, such as anthocyanins, flavonoids, proanthocyanidins, hydrolyzable tannins and other flavonoid-related molecules. Considering the important anti-inflammatory and anticancer properties of these classes of compounds, we found of interest to investigate the antioxidant properties of blackberries (Rubus spp.) and elderberry (Sambucus nigra) extracts. We correlated the total polyphenol (Folin-Ciocalteau’s method) and anthocyanin content with the antioxidant capacity evaluated by FRAP (Ferric reducing antioxidant power) and ABTS (2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) methods in fruits collected from plants wildly grown in the Southern Italy (Rubus procerus and Sambucus nigra), or from cultivated blackberries (Rubus fruticosus). A good correlation was measured between antioxidant activity and phenolic content (r > 0.5). Moreover, two different models were employed to characterize antioxidant power of berry methanolic extract. We isolated plasma and erythrocytes from healthy volunteer donors. Plasma was added with hypochlorite (HCLO), a well-known biological oxidant inducing chloramine formation. The presence of Rubus and Sambucus extract reduced chlorination, protecting plasma from HCIO damage. This effect was strongly correlated with total potyphenol content (r = 0.93). Alternatively, we employed the erythrocyte plasma membrane redox system (PMRS), which transfers electrons from intracellular donor to extracellular accettors , enabling the cells to counteract oxidative processes. Applying this method, we measured the ability of Rubus and Sambucus extracts to donate electrons to extracellular electron acceptors through the PMRS system. Also, in this case, the effect was correlated with total polyphenol concentration (r2 = 0.98). We hypothesized that the measured antioxidant effect in blood components of berry methanolic extracts could be attributed to their different anthocyanin concentration and supposedly to their different composition.