design of sonotrode ultrasound-assisted extraction of phenolic compounds from psidium guajava l. leaves

Psidium guajava l. has gained a special attention as health plant due to the presence of phenolic compounds. box-behnken design (bbd) has been applied for the extraction of target compounds from guava leaves via sonotrode ultrasound-assisted extraction (uae). different extraction times (5, 30, and 55 min), ratios of ethanol/water (50, 75, and 100% (v/v)), and ultrasound (us) power (80, 240, and 400 w) were tested to find their effect on the sum of phenolic compound (spc), flavonols and flavan-3-ols via hplc-esi-qqq-ms, and antioxidant activity (dpph and teac assays). the best process conditions were as follows: 40 min, 60% ethanol/water (v/v), and 200 w. established method has been used to extract phenolic compounds in two guava leaves varieties (pyrifera and pomifera). pyrifera var. showed greater values of the spc via hplc-esi-qqq-ms (49.7 mg/g leaf dry weight (d.w.)), flavonols (12.51 mg/g d.w.), flavan-3-ols (7.20 mg/g d.w.), individual phenolic compounds, and antioxidant activity (8970 ± 5 and 465 ± 6 μmol trolox/g leaf d.w, respectively) than pomifera var. conventional extraction showed lower amounts of phenolic compounds (7.81 ± 0.03 and 4.64 ± 0.01 mg/g leaf d.w. for flavonols and flavan-3ols, respectively) in comparison to the ultrasound-assisted ones.