Effect of extraction conditions on total phenolic content and antioxidant capacity of bagasse Mexican oregano

Mexican oregano (Lippia graveolens Kunth) is one of the most important species worldwide due to its human health benefit properties and high economic value. Oregano leaves are primarily used for essential oil extraction, generating substantial agro-industrial waste known as bagasse (OB). It has been reported that OB still contains several bioactive compounds with high antioxidant activity. This study aimed to evaluate the extraction conditions to recover phenolic compounds and assess their antioxidant capacity in OB extracts obtained through ultrasound. A 3k Box-Behnken design was employed to explore the effects of temperature, mass/volume ratio, and [EtOH]. Total phenolic content and antioxidant capacity against DPPH· and ABTS·+ radicals were determined. The increase in temperature and m/v ratio promoted the extraction of phenolic compounds, with strong correlations to antioxidant activity by DPPH· (0.81) and ABTS·+ (0.82) assays. A quadratic effect by [EtOH] was observed, with a maximum value of 50% ethanol. The highest value of total phenolic content (35.66 mgGAE/gdm), and antioxidant capacity against DPPH· (100.94 mgTE/gdm) and ABTS (93.02 mgTE/gdm) radicals were achieved in treatment 13 (0.02 mg/mL, 50% EtOH, and 90°C). The OB is a potential source of bioactive compounds with potential applications in functional food development.