Background: This study investigates the antimicrobial and antioxidant potential of thymoquinone (TQ) rich Nigella sativa L. seed oil (NSO) extracted using supercritical carbon dioxide extraction (SCFE-CO2). 
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Methods: N. sativa seeds were ground, sieved (Mesh No. 24) and subjected to SCFE using CO2&nbsp;at extraction conditions 40oC, 20 MPa and 0.71 x 10-3 m particle size. The extracted oil was characterized for thymoquinone (TQ) content using GC-MS/MS and microstructural differences between raw and defatted seeds post-extraction using Scanning Electron Microscopy (SEM) analysis at 1 KX magnification. Antibacterial efficacy was assessed against five pathogenic strains (Listeria monocytogenes ATCC 13932, Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 25922, Vibrio parahaemolyticus ATCC 17802 and Pseudomonas aeruginosa ATCC 9027) using the disc diffusion method, while antioxidant activity was evaluated using the DPPH radical scavenging assay. 
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Result: The extracted oil yielded 18.8% (w/w) with a TQ content of 3.62%. The microstructural matrix of defatted seeds confirmed the effective extraction of oil and its bioactives, showing a lesser oil fraction residue. Zones of inhibition (mm) at 100 &micro;L and 200 &micro;L for Listeria monocytogenes were 13&plusmn;0.09 and 15.3&plusmn;0.05; for Staphylococcus aureus, 10&plusmn;0.20 and 13.3&plusmn;0.06; for Escherichia coli, 12&plusmn;0.15 and 16.6&plusmn;0.12; for Vibrio parahaemolyticus, 10&plusmn;0.32 and 15&plusmn;0.08; for Pseudomonas aeruginosa, 14&plusmn;0.10 and 18.2&plusmn;0.07. NSO exhibited strong antioxidant activity, with 96.76% radical scavenging activity (RSA).

Assessment of Antimicrobial and Antioxidant Efficacy of SCFE-CO2 Extracted Nigella sativa L. Seed Oil

Assessment of Antimicrobial and Antioxidant Efficacy of SCFE-CO₂ Extracted Nigella sativa L. Seed Oil