Brazilian Cerrado fruits are source of bioactive substances, above all free and linked phenolic compounds. Xylopia aromatica (Lam.) Mart. (Annonaceae) is a Brazilian Cerrado specie called “pimenta-de-macaco”. The bioactive compounds content in X. aromatica reported in the literature generally refers to extractable polyphenols (EPP) analyzed in aqueous-organic extracts. However, significant amounts of bioactive compounds, usually not considered in chemical studies, remain in extracted residues as non extractable polyphenols (NEPP) that are emerging and ignored fractions of dietary antioxidants that present differential structural and physiological features as compared with well-known extractable polyphenols.
The main objective of this report is to determinate both EPP and NEPP contents (total sum of hydrolyzable polyphenols (HPP) and proanthocyanidins (CT)) and prospecting antioxidant capacity obtained in those different fractions of X. aromatica dried fruits. EPP were obtained in methanol/acetone/water extracts, and NEPP were derived from acidic hydrolysates of extraction residue of dried fruits as described by Pérez-Jimenez and Saura-Calixto (2015). Phenolic compound content was determined using Folin–Ciocalteu colorimetric method (Singleton et al.; 1999) using gallic acid as standard. Extracts and fractions radical scavenging activity was measured by FRAP assay (Rufino et al., 2010).
Among different fractions of the dried fruit analysed in this study, the NEPP contained the highest total phenolic contents (11573.6 mg GAE/100g; 78.9%), expressed by the sum of HPP (5285.2mg GAE/100g; 36.05%) and CT (6288.4mg GAE/100g, 42.89%), that were found to be exceptionally higher than those reported only in extractable fraction studies. EPP extract contained 3088.3mg GAE/100g, totaling 21.06%.
EPP (228.1 μmol Fe++/g; 16.1%), HPP (771.0 μmol Fe++/g; 49.6%) and CT (484.9μmol Fe++/g; 34.3%) antioxidant capacities fractions showed strong positive correlation between antioxidant activity and phenolic contents evaluated by Pearson test (+0.96 for EPP; +0.98 for HPP and +0.92 for CT).