# In vitro digestion of custard apple pulp: bioaccessibility of phenolic compounds, bioactive amines, and effect on antioxidant potential

## TL;DR

This study shows that custard apple pulp contains bioactive compounds that remain accessible after digestion, though their antioxidant power decreases.

## Contribution

The study provides new insights into the bioaccessibility of phenolics and amines in custard apple pulp using an in vitro digestion model.

## Key findings

- Antioxidant potential decreased by 53% (DPPH) and 29% (ABTS) after digestion.
- Putrescine and spermidine showed bioaccessibility indices of 67% and 46%, respectively.
- Myricetin and rutin were detected only in digested fractions, indicating digestion-related transformations.

## Abstract

Annona squamosa L. (custard apple) is a tropical fruit of the Annonaceae family whose biological effects depend on the presence and gastrointestinal bioaccessibility of bioactive compounds.

To evaluate the bioaccessibility of phenolic compounds and biogenic amines and to assess the effect of in vitro digestion on the antioxidant potential of custard apple pulp (CAP) using the INFOGEST protocol.

CAP was analysed for total phenolic and flavonoid contents and antioxidant potential using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. Individual phenolic compounds and biogenic amines were identified and quantified by chromatographic methods. An in vitro gastrointestinal digestion (INFOGEST) model was applied to determine antioxidant potential after digestion and the bioaccessibility index (BI) of target compounds.

CAP contained 5.51 mg GAE/g total phenolics and 3.39 mg CE/g flavonoids, with antioxidant values of 21.94 µmol TE/g (DPPH) and 29.09 µmol TE/g (ABTS). Four phenolics were detected in undigested CAP: ferulic acid (9.36 µg/g), quercetin (4.84 µg/g), gallic acid (0.57 µg/g), and caffeic acid (0.47 µg/g). Among nine amines analysed, only putrescine (15.78 mg/kg) and spermidine (7.31 mg/kg) were present. After digestion, antioxidant potential decreased by 53 % (DPPH) and 29 % (ABTS). BI values were 58 % for total phenolics and 53 % for flavonoids; putrescine and spermidine showed BI of 67 % and 46 %, respectively. Myricetin and rutin were detected only in digested fractions.

Custard apple pulp contains phenolic compounds, flavonoids, and the biogenic amines putrescine and spermidine that remain bioaccessible after in vitro digestion, despite reductions in antioxidant potential. The detection of myricetin and rutin only in digested fractions indicates digestion-related transformations and interactions between the digestive medium and the CAP matrix. These findings support further investigation of CAP as a source of bioactive compounds for nutraceutical, food, and pharmaceutical applications.

The online version contains supplementary material available at 10.1007/s00394-026-03919-7.