Optimization of ultrasonic-assisted extraction of the effective compounds from hops (Humulus lupulus)

The objective of this study was to make optimum use of hops medicinal plant as a flavoring compounds (bitter taste) and extract bioactive compounds. To optimize the extraction efficiency, total phenolic compounds (TPC), bitter taste compounds (α and β acids) and antioxidant activity (inhibition of DPPH free radicals, ferric reducing/antioxidant power) with ultrasound – assisted methods, the Box-Behnken design was used. Sonication exposure time (5, 15 and 25 min), extraction temperature (25, 35 and 45 C) and ultrasound amplitude (20, 60 and 100%) were considered as variables for the extraction of bioactive compounds. The results showed that with increasing the time and intensity of sonication, the extraction efficiency, the amount of bioactive compounds and the antioxidant power of the extract increased; while the extraction rate and antioxidant activity of the extracts decreased with increasing temperature. According to the resulting models, in the optimal conditions of extraction with ultrasound- assisted process (extraction time 12.73 min, extraction temperature 25 C and sonication amplitude 100 %), the extraction efficiency (16.5 %), TPC (75. 1191 mg/100 g), bitter taste compounds (α and β acids 1.01 and 3.09 mg/l respectively) and antioxidant activity (based on DPPH free radical scavenging and reducing power Iron was obtained 40.70% and 409.87 µmol/liter, respectively), higher than the conventional extraction method (maceration, control). Extraction at the optimal point confirmed the obtained results.