Analytical characterization of purified mimosa (Acacia mearnsii) industrial tannin extract: Single and sequential fractionation

Mimosa (Black wattle) tannin extract is one of the few industrially available natural sources of polyphenols. Even if its composition is rather known, limited attempts for its purification were done until now. A Soxhlet extraction, using various solvents, with single and sequential processes was performed, and the separated fractions were analytically investigated. Yield, molecular mass, phenolic and condensed tannin contents, antioxidant activity and FT-IR spectroscopy have shown that the ethyl acetate fraction strongly contains antioxidants and low molecular mass tannins (also hydrolyzable), while the alcoholic fractions contain purified flavonoids with higher molecular mass; the final residues resulted enriched in carbohydrates and ashes. Sequential extractions optimize the class of compounds extracted according to the specific application. Conforming to statistical analysis, significant correlations have been observed between phenolic content and the antioxidant activity, as well as between molecular masses and ashes content.