Bioaccessibility of phenolic compounds and antioxidant capacity in beluntas leaves (Pluchea indica) with in vitro assay

Pluchea indica (L.) Less (beluntas) is a wild plant widely consumed in Indonesia, either fresh or after steaming. This study aimed to determine the effect of steaming and whole leaf consumption on antioxidant capacity, total phenolics, and flavonoids of beluntas leaves, both before and after simulated gastrointestinal digestion. Prior to digestion, steaming increased antioxidant capacity by two to threefold, with ABTS values rising from 19.36 ± 0.77 to 42.61 ± 0.07 mg TE/g (dry basis). During digestion, antioxidant capacity and TPC decreased in the gastric phase but increased in the intestinal phase for both FBL and SBL. The ABTS radical cation scavenging activity of SBL was 27.18 ± 0.19 mg TE/g (dry basis) in the gastric phase and increased approximately threefold in the intestinal phase to 61.16 ± 1.61 mg TE/g (dry basis). FBL exhibited significantly lower antioxidant activity than steamed leaves in both gastric (29.79 ± 0.21 mg TE/g, dry basis) and intestinal phases (38.58 ± 0.31 mg TE/g, dry basis). UHPLC-HRMS showed that phenolic compounds detected in negative ionization mode predominated before digestion, but their relative abundance decreased after simulated digestion. The bioaccessibility index post-intestinal (BI-PI) of antioxidant capacity in both fresh and steamed beluntas leaves exceeded 100%. These results indicate that the consumption of whole beluntas leaves can retain antioxidant compounds during digestion. This may be related to the protective role of the leaf matrix, where cell wall structures act as a physical barrier and facilitate the gradual release of bioactive compounds during intestinal digestion.