Simple and rapid procedures for the extraction of bioactive compounds from Guayule leaves

Solid liquid extraction (SLE) and ultrasound-assisted extraction (UAE) using food grade solvents were applied to Guayule leaves in order to obtain phenolic compound-rich extracts. The influence of solvent composition and time were evaluated for both techniques reaching the highest phenolic content with UAE using water and 25% aqueous ethanol (27.0 ± 0.2 and 22 ± 2 mg gallic acid equivalents/g dried leaves, respectively) and with SLE using water and 50% aqueous ethanol (16 ± 1 and 17 ± 1 mg/g, respectively). Antioxidant and antiradical activities of the selected extracts were evaluated by means of spectrophotometric procedures. In addition HPLC-ESI-QTOF-MS was used to characterize the bioactive compounds in the richest extracts. A variety of phenolic compounds, mainly phenolic acids and flavonoids, were identified for the first time in Guayule leaves. This study indicates that conventional extraction techniques, such as SLE and UAE, represent a powerful tool for the fast isolation of antioxidant compounds from Guayule.