Supercritical CO2 extraction of oregano (Lippia graveolens) phenolic compounds with antioxidant, α-amylase and α-glucosidase inhibitory capacity

Phenolic compounds are recognized for their antioxidant capacity and potential hypoglycemic activity. Thus, there is a need to develop more efficient extraction techniques. Phenolic extracts from Lippia graveolens aerial parts using supercritical CO2 (SC-CO2) extraction were obtained. We aimed to optimize the temperature and pressure conditions to obtain higher total phenolic content (TPC) from L. graveolens. Furthermore, we evaluated the total flavonoid content, antioxidant capacity, and alpha-amylase and alpha-glucosidase inhibition of the optimized supercritical fluid extract (OSFE). The optimal extraction conditions were 35.9 degrees C and 244.6 bar, with a TPC of 354 +/- 8.6 mg GAE/g extract. The OSFE also showed higher TEAC and ORAC values than a conventional methanolic extract (ME); however the yield of the OSFE was lower than the yield of the ME, 5.9% and 25.9%, respectively. Despite that the ME showed 14 flavonoids and one phenolic acid compared to OSFE with 12 flavonoids and two phenolic acids, OSFE presented higher compounds content; both had alpha-glucosidase and alpha-amylase inhibitory activity. The use of SC-CO2 is an environment-friendly alternative to obtain extracts rich in phenolic compounds with beneficial bioactivities for human health.