Chemical characterization, antioxidant and antimicrobial activities of acai seed (Euterpe oleracea Mart.) extracts containing A- and B-type procyanidins

Acai seed extracts are reported for containing polyphenols with pharmacological properties against inflammation, hypertension, and metabolic syndrome. However, presently, those seeds accumulate as waste, causing environmental problems. Therefore, we aimed to characterize the polyphenol profile of acai seed extracts to investigate its composition and biological effects. Multiple techniques were used for the identification of the extract's metabolites, such as HPLC, mass spectrometry, and mass spectrometry imaging (MALDI-IMS). The extract was majorly composed of B-type and A-type oligomeric procyanidins with a mean degree of polymerization of 11.4 (>3000 Da), formed by catechin and epicatechin as starter and extension subunits, respectively. MALDI-IMS confirmed, for the first time, the presence of A-type procyanidins in the seed's tegument. The extract was not cytotoxic to THP1 (macrophage cell line) and LLC-MK2 (epithelial cell) and, moreover, it efficiently protected macrophages from oxidative stress, which correlated to its high antioxidant capacity, confirmed by DPPH, TEAC and ORAC methods. Additionally, the extract presented antimicrobial activity against gram-positive bacterial strains and Candida albicans. These data indicate the potential use of seed extracts for cosmetic and pharmaceutical formulations.