Unveiling purple Capsicum frutescens Chili: First report on metabolomic composition, antioxidant capacity, and synergistic enzyme inhibition

Abstract

Purple chili ( Capsicum frutescens ) has gained attention due to its distinctive coloration, which serves not only culinary purposes but also as food decoration. However, the metabolomic profile and bioactivities of purple chili in C. frutescens remain inadequately characterized, with existing literature predominantly focusing on purple chili varieties of C. annuum . This study aimed to analyze the phytochemical composition and preliminary in vitro bioactivities of purple chili extract through antioxidant potential assessment, inhibition of target enzymes implicated in non-communicable diseases, and evaluation of synergistic effects with synthetic drugs. Using LC-ESI-MS/MS, the predominant phenolic compounds identified were fisetin (62.4%), rutin (32.5%), and naringenin (5.1%). Capsaicinoids detected by HPLC included capsaicin (49.8%), dihydrocapsaicin (40.5%), and nordihydrocapsaicin (9.7%). Non-targeted metabolomic analysis via HPLC-qTOF-MS revealed chlorogenic acid as the predominant compound, with lower rutin content and no detection of fisetin or naringenin, highlighting method-dependent variations in metabolite profiling. In vitro bioactivity assessment demonstrated DPPH radical scavenging, FRAP, and ORAC antioxidant activities of 23.78, 71.96, and 607.63 µmol TE/g DW, respectively. The extract also exhibited strong inhibitory activity against α-glucosidase and β-site amyloid precursor protein cleaving enzyme 1 (BACE-1), enzymes involved in type 2 diabetes and Alzheimer's disease, respectively. Notably, synergistic interactions were observed between the extract and the pharmaceuticals acarbose and donepezil, suggesting potential for therapeutic enhancement at reduced drug doses through combination treatment. These results represent the first comprehensive metabolomic and preliminary in vitro bioactivity characterization of purple chili in C. frutescens , establishing a foundation for its potential development as a functional food ingredient.