PHENOLIC CONTENT AND ANTIOXIDANT CAPACITY DURING STATIC GASTROINTESTINAL DIGESTION OF THE EDIBLE FRACTION OF THE GUABIJÚ FRUIT (Myrcianthes pungens)

Guabiju (Myrcianthes pungens) is a fruit native to Brazil, characterized by dark violet skin and a sweet, slightly astringent taste. Due to its high nutritional value and the diversity of bioactive compounds, the fruit has garnered attention for its antioxidant properties. Digestive process is known to affect the content and bioactivity of numerous dietary bioactive compounds, the objective of this study was to investigate how a simulated static digestion process affects the content of phenolic compounds and the antioxidant capacity of guabiju fruit, a native species that remains underutilized and understudied. A sample of the edible fraction of freeze-dried guabiju fruit (SISGEN: A61B8BE) was used for the simulated gastrointestinal digestion assay following the INFOGEST 2.0 method, using a dialysis membrane to separate the bioaccessible and non-bioaccessible fractions. Following digestion, samples were analyzed using the Folin-Ciocalteu method as a screening for total phenolic content (gallic acid equivalents - GAE), the pH differential method for total monomeric anthocyanins, and the Oxygen Radical Absorbance Capacity (ORAC) to assess the antioxidant capacity (trolox equivalents). The freeze-dried guabiju showed an initial total phenolic content of 0,514±0,00mg GAE/100g. During gastrointestinal digestion, a progressive an increase in total phenolic content from the the oral phase (1.023±0.00mg GAE/100g) to the gastric phase (1.517±0.00mg GAE/100g; p<0.05), but no further changes were observed in the intestinal bioaccessible (1.516±0.01mg GAE/100g), and non-bioaccessible fraction (1.523±0.00 mg GAE/100g) remained statistically equal. Total monomeric anthocyanins in the guabiju powder were 0.038±0.00 mg/100 g of sample. Anthocyanin levels were similar in the oral phase (0.134±0.00 mg/100g) and in the gastric phase (0.017±0.00 mg/100g), but were significantly increased in the intestinal non-bioaccessible fraction (0.024±0,00 mg/100g) and decreased in the bioaccessible fraction (0.001±0.00 mg/100g) compared to the oral phase (p<0.05). Antioxidant capacity did not differ among the oral phase (3,105±870.21 μmol TE/100g of sample), gastric phase (3,209±933.48 μmol TE/100g), and the intestinal non-bioaccessible fraction (3,219±851.29 μmol TE/100g) (p>0.05), demonstrating stability. The bioaccessible fraction had lower antioxidant capacity (1,162±816.13 μmol TE/100g) (p<0.05) that was statistically similar to the antioxidant capacity of freeze-dried guabiju (1,633±70.73 μmol TE/100g). While anthocyanin content was extensively degraded during gastrointestinal digestion, total antioxidant capacity and total phenolic content were more stable. Detailed phenolic compound profiles by HPLC-MS analysis are required to identify phenolic metabolites that are putatively associated to the antioxidant capacity found in the intestinal bioaccessible fraction of guabiju fruits. 

This research was supported by the funding agencies CAPES and FAPERGS.