Phytochemical Profile and Biological Activities of Allium longistylum Sprouts

Allium longistylum is a relatively understudied species whose phytochemical composition and biological activities remain largely unexplored. In this study, the first true leaf (FTL) and the second true leaf (STL) of A. longistylum were compared with respect to phenolic composition, antioxidant capacity, antimicrobial activity, and quorum-sensing (QS) inhibition. Total phenolic content (TPC) and total flavonoid content (TFC) were determined spectrophotometrically, while antioxidant activity was evaluated using ABTS and DPPH radical scavenging assays. Antimicrobial and anti-QS activities were assessed against Staphylococcus aureus, Acinetobacter baumannii, and Chromobacterium violaceum. STL exhibited significantly higher TPC and TFC than FTL, consistent with its stronger radical scavenging activity. Both extracts showed moderate antimicrobial activity and reduced violacein production in C. violaceum, indicating interference with QS. UPLC-Q-Orbitrap-ESI-MS/MS profiling tentatively identified several phenolic acids and flavonoid derivatives. HPLC analysis confirmed the presence of selected phenolic compounds, although several prominent peaks in the chromatograms remained unidentified. Many of the compounds detected by UPLC-Q-Orbitrap-ESI-MS/MS and HPLC have previously been reported to exhibit antioxidant, antimicrobial, and anti-QS activities; their presence may therefore contribute to the bioactivities observed in both extracts. However, their contribution to the observed effects remains speculative and requires further validation through targeted isolation and bioactivity testing. The results suggest that A. longistylum is a promising source of phenolic compounds with antioxidant and antimicrobial properties.