The link between the phenolic composition and the antioxidant activity in different small berries: A metabolomic approach

Small berries have become an attractive topic of research due to their high content in phenolic compounds and reported antioxidant activity. However, there are currently few reports on the deep characterization of their polyphenol composition. Five kinds of berries (raspberry, blackberry, blueberry, mulberry and black chokeberry) were studied to compare the antioxidant activities and polyphenol compositions of both berry juice and pomace (by-products in processing). Results showed that pomaces were more potent antioxidants than juices, especially those that originated from red raspberry. The polyphenol contents in pomaces ranged from 137 to 222 mg/g, this was higher than juices that ranged from 2.75 to 8.88 mg/g, with mulberry accounting for the highest content. The main compounds in pomaces were phenolic compounds with different relative contents found by UPLC-MS/ MS. A total of 568 compounds were identified, including 238 flavonoids and 131 phenolic acids. PCA, HCA and OPLS-DA analyses were performed to find similarities on the polyphenol and metabolomic profile of the sampled berries. This analysis unveiled that all studied berries presented a significantly different polyphenol profile, on which raspberry and blackberry were the most similar. Results suggested that berry pomaces can be valuable sources of phenolic compounds of which the major components are anthocyanins and phenolic acids, with potential applications as antioxidant food additives, or raw materials for pharmaceuticals, nutraceuticals, and cosmetics.