PHYTOCHEMICAL PROFILING AND PRELIMINARY CHARACTERIZATION OF LUPEOL-RELATED COMPOUNDS FROM IRAQI ERUCA SATIVA MILL. AERIAL PARTS WITH 2,2-DIPHENYL-1-PICRYLHYDRAZYL RADICAL SCAVENGING ACTIVITY

Objective: In this study, the phytochemical profile of Iraqi Eruca sativa Mill. aerial parts was investigated with a view to identify and characterize a lupeol-related compound from the n-hexane fraction and to evaluate the antioxidant activity of the obtained solvent fractions and isolated compound. Methods: The aerial parts of E. sativa were extracted and then fractionated with different polarities of solvents. 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (RSA) of the n-hexane, ethyl acetate fractions, and the isolated compound L1 was evaluated. The phytochemical constituents of the n-hexane fraction were preliminarily examined by gas chromatography-mass spectrometry (GC–MS) by comparison of mass spectral data with NIST/Wiley library profiles and characteristic fragmentation patterns. Preliminary characterization of the isolated compound L1 was done by thin-layer chromatography, high-performance liquid chromatography, ultraviolet–visible spectroscopy, Fourier-transform infrared spectroscopy, and mass spectrometric analysis. Results: The n-hexane fraction was analyzed by GC–MS, and several phytoconstituents were revealed with lupeol assigned tentatively on the basis of spectral matching, retention behavior, and characteristic fragmentation pattern. The isolated compound L1 exhibited similar chromatographic and spectroscopic features to the authentic lupeol standard, confirming its initial identification as lupeol. The DPPH assay revealed concentration-dependent scavenging activity of the radicals by the tested samples. The IC50 values for ascorbic acid, ethyl acetate fraction, n-hexane fraction, and isolated compound L1 were 38.8 μg/mL, 44.6 μg/mL, 68.6 μg/mL, and 105 μg/mL, respectively. Conclusion: This study is the first evidence of the presence of lupeol in Iraqi E. sativa aerial parts and shows the differences in antioxidant activity between the investigated samples. The better activity of the ethyl acetate fraction shows the effect of solvent polarity on the extraction of antioxidant components of the plant material. Detailed quantitative phytochemical analysis and advanced structural confirmation including nuclear magnetic resonance studies are required for full establishment of the identity of the isolated compound and the constituents responsible for the observed antioxidant activity.