Multifactorial analysis of temperature, solute-to-solvent ratio, and ultrasound amplitude on the extraction of phenolic and antioxidant compounds from Aloysia citriodora Palau leaves

Ultrasonic-assisted extraction was applied to Aloysia citriodora Palau leaves. To achieve this, a set of extraction parameters—temperature, amplitude, and solute-to-solvent ratio—was evaluated. A 3 3 factorial design was implemented, generating 27 treatments, from which total phenolic content, total flavonoid content, and antioxidant capacity against 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS •+ ), 2,2-diphenyl-1-picrylhydrazyl (DPPH • ), and hydroxyl (OH • ) radicals were assessed. The extract showing the highest free radical scavenging capacity was obtained at 75 °C, a solute-to-solvent ratio of 1:15, and a wave amplitude of 25%. This extract contained 87.74 mg gallic acid equivalent (GAE)/g extract and 76.82 ± 6.21 mg quercetin equivalent (QE)/g extract. Antioxidant capacity was expressed as the half-maximal inhibitory concentration (IC 50 , µg/mL), with values of 9.08 ± 0.08 µg/mL for ABTS •+ , 35.58 ± 0.50 µg/mL for DPPH • , and 0.72 ± 0.007 mg/mL for OH • . The A. citriodora leaf extract demonstrated strong potential for use in the development of new products containing bioactive molecules capable of preventing degenerative diseases.