Extracts from subendemic Italian plants with traditional digestive uses: phytochemical and bioactivity modulation during in vitro simulated gastrointestinal digestion

This study investigates the impact of simulated gastrointestinal digestion on the phytochemical stability and bioactivity of hydroalcoholic extracts from two subendemic edible plants traditionally used for disorders related to the digestive tract, Ptilostemon casabonae (L.) Greuter from Sardinia and Achillea erba-rotta subsp. moschata (Wulfen) I. Richardson from the Alpine area. While both species are rich in phenolic metabolites and widely used in folk medicine, their digestive fate and post-digestion bioactivity remain largely unexplored. The hydroalcoholic extracts were subjected to the standardized INFOGEST 2.0 in vitro digestion model. Characterization by HPLC-PDA-MS/MS, antioxidant capacity (ABTS and DPPH assays) and α-glucosidase inhibitory activity were evaluated before and after digestion. Gastrointestinal digestion induced pronounced remodelling of the phenolic profile, with caffeoylquinic and dicaffeoylquinic acids undergoing isomerization and partial degradation. In contrast, flavonoids showed comparatively higher stability across digestive phases. Although both extracts exhibited reduced total phenolic content and intestinal bioaccessibility, A. erba-rotta subsp. moschata showed higher overall bioaccessibility than P. casabonae. A general decline in antioxidant capacity was observed after gastric digestion, with partial modulation in the intestinal phase depending on the extract. Notably, α-glucosidase inhibitory activity was preserved after digestion in P. casabonae, whereas a significant reduction was observed for A. erba-rotta subsp. moschata. Overall, this study highlights the importance of thoroughly investigating these lesser-known edible plants by applying the digestion protocol to determine the stability of their extracts, which could affect their biological performance.