Phytochemical Profiling and α-Glucosidase and α-Amylase Inhibitory Activities of Underutilised Nanhaia speciosa Aerial Biomass

The aerial parts of Nanhaia speciosa are often discarded despite their potential as a source of bioactive compounds. This study aimed to characterise this underutilised biomass and evaluate its functional properties relevant to carbohydrate digestion. Ultra-high-performance liquid chromatography–quadrupole-Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS), Global Natural Products Social (GNPS) molecular networking, and MS/MS fragmentation analysis tentatively annotated 96 compounds, mainly flavonoids and nitrogen-containing constituents. The extract inhibited α-glucosidase and α-amylase in a concentration-dependent manner, with IC50 values of 9.98 ± 0.02 and 174.83 ± 1.31 μg/mL, respectively, compared with 29.73 ± 0.04 and 39.46 ± 0.19 μg/mL for acarbose. The extract also showed measurable chemical antioxidant capacity. Network pharmacology suggested potential involvement of cAMP-, calcium-, and receptor-associated signalling. Molecular docking prioritised butein as a candidate constituent with favourable predicted interactions with both enzymes, and molecular dynamics simulations supported stable predicted binding. The estimated MM/GBSA binding free energies of butein were −36.68 and −32.03 kcal/mol for α-glucosidase and α-amylase, respectively. These findings indicate that the aerial biomass of N. speciosa is a promising source of phytochemicals with potential carbohydrate-hydrolase inhibitory properties, although the activity of individual constituents requires further experimental validation.