Volatiles, phenolic compounds, antioxidant and antibacterial properties of kohlrabi leaves.

This work presents the volatile compounds and phenolic profile investigation of the leaves of Brassica oleracea L. growing in Tunisia, together with antioxidant and antibacterial properties. Volatile constituents were determined by HS-SPME coupled to GC/MS, and the results showed that α-pinene (31.6%) and limonene (16.9%) were the main volatiles. The phenolic profile was determined by HPLC analysis, the methanol extract revealed the presence of four hydroxycinnamic acids (chlorogenic, ferulic, p-coumaric and sinapic acids), two hydroxybenzoic acids (syringic and gallic acids), and four flavonoids (catechol, catechin hydrate, epigallocatechin and epicatechin 3-O-gallate). The methanol extract showed the best significantly antiradical activity by DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS ((2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) antioxidant assays, with EC₅₀ of 0.32 and 0.45 mg/mL, respectively. For antibacterial activity, the methanol extract inhibits all the tested strains. It can be concluded that kohlrabi leaves are rich in bioactive compounds and are a potential source of natural antioxidants and antibacterials. [ABSTRACT FROM AUTHOR]