Chemical composition, antibacterial and antioxidant activities of oils obtained by different extraction methods from Lepidium sativum L. seeds

The oils obtained from plants by different extraction methods and their constituents are known to possess a vast range of pharmacological and biological activities. The essential oils (EOs) extracted by different methods viz. Clevenger type apparatus (CTA), modified simple distillation (MSD), and simultaneous distillation extraction (SDE) and fatty acid (FA) compositions of the petroleum ether Soxhlet extracted oil (PESO) of Lepidium sativum L. seeds were determined by GC-MS. Several differences were observed in the compositions of the EOs together with their concentrations. Fifty three components representing about 96.85 % of the total constituents were detected in the EO isolated by CTA. 1-Isocyano-2-methylbenzene (71.63 %) and benzaldehyde (11.21 %) were the most predominant components. About 98.53 % of the oil extracted by SDE exhibited a wide range of compounds with 1-isocyano-2-methylbenzene (36.18 %), benzyl isothiocyanate (8.71 %), and benzaldehyde (2.96 %) as the major constituents. In addition, 48 compounds representing about 97.29 % of the oil constituents were identified from the oil obtained by MSD. The chemical profile of this oil was dominated by fatty acids (47.31 %), of which linoleic acid represented the highest amount (12.81 %). 1-Isocyano-2-methylbenzene, identified as a dominant compound in oils extracted by CTA and SDE was also the predominant compound of this oil, but its concentration was low (27.84 %). Forty-six FAs, contributing about 98.47 % of the oil were also identified from PESO. The major constituents were palmitic (27.39 %), α-linolenic (14.18 %), stearic (9.94 %), arachidic (9.43 %), linoleic (6.91 %), oleic (4.76 %), gondoic (4.07 %), and behenic (3.16 %) acids. Moreover, the oils were assessed for their bactericidal activity against two Gram negative (Klebsiella pneumoniae and Escherichia coli) and two Gram positive (Staphylococcus aureus and Bacillus cereus) bacteria by the disc diffusion method. DPPH and H₂O₂ methods were also employed to determine their antioxidant properties. Except PESO, all oils demonstrated appreciable activity against the selected bacterial strains. The EO extracted by SDE displayed higher antibacterial activity against all the investigated bacteria, except S. aureus at 1 mg/mL concentration. In addition, this oil exhibited more significant antioxidant activity in both DPPH (IC₅₀ value, 15.69 ± 0.72 mg/mL) and H₂O₂ (IC₅₀ value, 19.18 ± 0.60 mg/mL) assays. To conclude, the investigated oils of L. sativum seeds proved to be a rich source of bioactive secondary metabolites and SDE is the efficient and effective method of EO extraction to identify many of these compounds. Moreover, the method is better in terms of oil extraction yield/efficiency, antioxidant, and antibacterial activities.