Fractionation of Phenolic Compounds from Hickory By-Products Using Solid Phase Extraction-Sonication: Chemical Composition, Antioxidant and Antimicrobial Activity

Hickory is an abundant source of phenolic compounds that exhibit a diverse range of bioactivities. In this study, phenolic compounds were extracted and purified from hickory green husk (HG), hickory nutshell (HN), and hickory seed coat (HS) using solid-phase extraction and ultrasonication (SPE-US). The effects of the SPE-US treatment on the structure and properties of the phenolic compounds were then investigated, including their composition, antioxidant activity, and antimicrobial activity. The dominant phenolic substances in the different extracts after SPE-US treatment were: ellagic acid and trans ferulic acid (HS); ellagic acid and sinapic acid (HN); and rutin (HG). The HS-SPE-US1 extract exhibited the highest total polyphenol content (416 ± 11 mg GAE/g DW), total flavonoid content (47.51 ± 0.68 mg RE/g DW), Fe3+ reduction ability (74.2 ± 1.0 mmol Fe2+/g DW), radical (DPPH and ABTS) scavenging ability, and antimicrobial activity against Staphylococcus aureus.