Seed oil extraction from red prickly pear using hexane and supercritical CO2: assessment of phenolic compound composition, antioxidant and antibacterial activities

BACKGROUND: Investigating Opuntia species for their seed oil content is of much importance owing to their potential use for food and in cosmetic applications. These oils have an important content in unsaturated fatty acids as well as antioxidant compounds (e.g. polyphenols, vitamin E), which have been associated with the prevention of some chronic diseases. Moreover, Opuntia stricta oils possess important antimicrobial activities. For instance, the main focus of this study was to compare the effectiveness of conventional (hexane extraction) and novel (supercritical (SC)‐CO₂) extraction methods for the recovery of oil and phenolic compounds from O. stricta seeds. The oil yield of both extracts was then compared and the polyphenol content and composition of both extracts were determined by liquid chromatography–high‐resolution mass spectrometry. Additionally, antioxidant (DPPH assay) and antimicrobial activities (disc diffusion method) of O. stricta seed oils were determined. RESULTS: The oil yield (based on Soxhlet's method) of O. stricta seeds was determined using SC‐CO₂ (49.9 ± 2.2%), and hexane (49.0 ± 1.5%). Although obtaining similar oil extraction yields using the two methods, the extracted oil using SC‐CO₂ was more enriched in polyphenols (172.2 ± 11.9 µg gallic acid equivalents (GAE) g⁻¹ oil) than that extracted using hexane (76.0 ± 6.9 µg GAE g⁻¹ of oil). Polyphenol profiles showed that the SC‐CO₂ process led to the yield of more compounds (45) than that using hexane extraction (11). Moreover, the antioxidant and antimicrobial activities of SC‐CO₂ extract showed a high percentage of inhibition. CONCLUSION: SC‐CO₂ extraction of O. stricta seed oil led to extraction of oil with a similar yield to that with hexane extraction, but with higher polyphenol content. The extract containing polyphenols exhibited high antioxidant and antibacterial properties, demonstrating their great potential as feedstock for high‐oil quality. © 2016 Society of Chemical Industry