LC–MS/MS-based phytochemical profiling and HPLC quantification of Acalypha australis with α-amylase inhibitory assessment

Abstract Acalypha australis has not been thoroughly investigated for its α-amylase inhibitory activity, particularly in studies that integrate bioactivity with quantitative phytochemical profiling. To address this gap, the present study simultaneously evaluated the radical scavenging activity and α-amylase inhibitory activity of A. australis extract (AAE) and contextualized its bioactivity through LC–MS/MS profiling and HPLC-based quantification. AAE exhibited concentration-dependent inhibitory effects, with IC 50 values of 948 µg/mL (ABTS), 708 µg/mL (DPPH), and 23.77 µg/mL (α-amylase). LC-MS/MS analysis tentatively identified 27 compounds, predominantly phenolic acids, flavonoids, and ellagitannins. Six phenolic compounds were quantified through HPLC, with corilagin (2) as the major constituent, while comparatively lower levels of myricetin (6) were detected. Subsequent assays of the isolated constituents revealed that their bioactivities were not uniform, exhibiting distinct response patterns in both ABTS and DPPH radical scavenging systems, as well as in α-amylase inhibition. Although the crude extract exhibited stronger inhibitory activity than the individually tested compounds, this observation may reflect the contribution of multiple constituents, including unidentified components, rather than definitive synergistic interactions. These findings provide a biologically oriented chemical characterization of AAE and support its potential as a moderate in vitro α-amylase inhibitor.