Optimization of ultrasound- and enzymatic-assisted extractions of polyphenols from dried red onion peels and evaluation of their antioxidant activities.

There is a recognized need for exploring new natural antioxidants that have high antioxidant potential. Thus, the aim of this study was to optimize the extraction process of onion peels using ultrasound- and enzymatic-assisted extractions (UAE and EAE) methods to utilize the optimal extracts as natural antioxidants. Box-Behnken Design (BBD) was implemented to reach the optimal extracts with the highest simultaneous content of total phenolic content (TPC) and total flavonoid content (TFC). The optimal UAE and EAE extracts were subjected to High Performance Liquid Chromatography (HPLC) analysis to identify their chemical profile. The antioxidant activities of optimal extracts obtained by UAE and EAE were evaluated in vitro using DPPH and FRAP assays and their abilities to increase the oxidative stability of sunflower oil were studied using Rancimat test. The optimal conditions for UAE were 34.02 W, 26.87 mL/g solid, and 45.43 min, meanwhile they were 30.00 mL/g solid, 45.43 min at enzyme concentration of 0.52% for EAE method. DPPH and FRAP assays results revealed that EAE optimal extract show superior antioxidant activity over UAE optimal extract. The protection factor of optimal EAE extract against sunflower oil oxidation was close to that of butylated hydroxytoluene (BHT).

Extraction of essential oil from methyl cinnamate basil (Ocimum canum Sims) with high yield in a short time using enzyme pretreatment.

This research was carried out to evaluate the effect of viscozyme pre-treatment followed by hydrodistillation (E-HD) on extraction yield, extraction time and quality of methyl cinnamate basil (O. canum) oil. The viscozyme, as a multienzyme acting on cell wall, was used at different concentrations (0.5% and 1%, v/w) for 30, 60 and 90 min at 50 °C and pH 5 before hydrodistillation (HD). Oxygenated monoterpenes/monoterpene hydrocarbons ratio was used as a quality index for the obtained essential oil. Enzymatic pretreatment at 1% enzyme concentration for 90 min followed by HD increased yield of essential oil by 44.5% with high quality index and decreased HD time from 180 to 30 min. Thirty-nine volatile compounds, comprising > 99% of the essential oil were identified and quantified by Gas Chromatography Mass Spectrum (GC-MS). The major components of essential oil were (E)-methyl cinnamate, camphor, trans-ß-caryophyllene and 1,8-cineole. Results confirm the effectiveness of the enzyme pretreatment, which enhance extraction of O. canum essential oil in a short time, with a high quality.