Ultrasound-assisted extraction of phenolic compounds from apple peel

This study investigated the extraction of phenolic compounds from apple peel by ultrasound-assisted extraction (15, 30 and 45 min) and conventional extraction (15, 30, 45, 60, 75 and 90 min). The antioxidant capacity (DPPH), total phenolic content, total flavonoid content, and individual phenolic compounds of apple peel extracts were determined. HPLC analysis indicated that apple peel extracts had chlorogenic acid, rutin, catechin, epicatechin, procyanidin B1, procyanidin B2 and procyanidin C1. In the conventional method, the total phenolic content, total flavonoid content and antioxidant activity of apple peel extract in 90 min of conventional extraction was found as 1848.50 ±0.40 mg GAE/kg, 571.01 ±2.88 mgKA/kg and 9.70±0.00 mmol Trolox eq./g, respectively. In 45 min of the ultrasound-assisted extraction, total phenolic content, total flavonoid content and antioxidant activity of extracts were determined as 2021.83±65.69 mg GAE/kg, 532.66 ±2.43 mgKA/kg and 11.73 ±0.08 mmol Trolox eq./g respectively. The application of ultrasound-assisted extraction markedly decreased extraction time and improved the extraction efficiency compared with the conventional method.