LC-MS-MS and GC-MS analyses of biologically active extracts and fractions from Tunisian Juniperus phoenice leaves

Despite some studies related to Juniperus phoenicea L. (Cupressaceae), phytochemical and biological investigations of this plant remain unexplored.

This work is the first report dealing with the identification and characterization of volatile components and flavonoids in hexane and methanol extracts from J. phoenicea leaves Materials and methods: Antioxidant activity of hexane, and methanol extracts from J. phoenicea leaves were determined by DPPH-radical scavenging assay. α-Amylase inhibitory activity was evaluated by enzyme inhibition using in vitro assay (each extract was dissolved in DMSO to give concentrations of 50, 100 and 200 mg/mL). The chemical composition of fractions (Fr1-Fr3) from methanol extract was determined by high-performance liquid chromatography coupled with mass spectroscopy (HPLC-MS) analysis.

The hexane extract was analyzed by GC-MS technique which allowed the identification of 32 compounds. The main constituents were α-humulene (16.9%), pentadecane (10.2%) and α-cubebene (9.7%). Fraction Fr 2 exhibited a strong DPPH radical-scavenging activity (IC₅₀=20.1 μg/mL) compared to that of BHT as well as the highest α-amylase inhibitory activity (IC₅₀=28.4 μg/mL). Three flavonoids were identified in these fractions using HPLC-MS analysis: Quercetin 3-O-glucoside, isoscutellarein 7-O-pentoside and quercetin 3-O-pentoside. In addition, the more active fraction (Fr 2) was purified with semi-preparative HPLC affording one pure compound (amentoflavone) using ¹H NMR analysis. This compound exhibited powerful DPPH radical-scavenging (IC₅₀=14.1 μg/mL) and α-amylase inhibition (IC₅₀=20.4 μg/mL) effects.

This study provides scientific support to some medicinal uses of J. phoenicea found in North Africa.