In Vitro Inhibition of Digestive Enzymes by Leaf Metabolites from Neurolaena lobata (L.) R. Br. ex Cass. (Asteraceae).

Digestive enzymes such as pancreatic lipase (PL), α-glucosidase (AG), and α-amylase (AA) play key roles in the hydrolysis of dietary lipids and carbohydrates and are therefore relevant biochemical targets for evaluating compounds with potential to modulate postprandial metabolic responses. Neurolaena lobata (L.) R. Br. ex Cass. (Asteraceae) is a neotropical medicinal species traditionally used for several health-related conditions, including metabolic complaints. This study evaluated the in vitro inhibitory activity of the hydroalcoholic extract, selected VLC fractions, and isolated metabolites from N. lobata leaves against PL, AG, and AA. Enzyme inhibition screening of the extract and VLC fractions was used to select fractions for phytochemical investigation, affording six known metabolites: the sesquiterpene lactones neurolenin B (C1) and lobatin A (C2), the benzoic acid derivatives p-hydroxybenzoic acid (C3) and 3,4-dihydroxybenzoic acid (C4), and the flavonoids 6-hydroxykaempferol 3,7-dimethyl ether (C5) and quercetagetin 3,7-dimethyl ether (C6). The hydroalcoholic extract and the MeOAc and iPrOH fractions inhibited PL, AG, and AA. Among the isolated compounds, C1, C2, C5 and C6 inhibited PL and AG, with IC50 values ranging from 134 to 615 µM and from 170 to 639 µM, respectively, whereas all compounds showed weak AA inhibition. Exploratory kinetic analysis yielded apparent inhibition profiles mainly consistent with competitive behavior; C6 showed an apparent profile consistent with noncompetitive inhibition against AG under the assay conditions used. These findings expand the phytochemical and in vitro bioactivity profile of N. lobata and provide preliminary evidence of digestive enzyme modulation in isolated enzyme systems, without establishing therapeutic efficacy.