A review on scale-up approaches for ultrasound-assisted extraction of natural products

The extraction of bioactive compounds from natural sources is a topic of great interest. In this sense, ultrasound-assisted extraction (UAE) has emerged as a promising technology for fast and efficient extraction of natural products without high organic solvent consumption. However, most studies on UAE are focused on laboratory scale. In order for this technology to be suitable for industrial applications, more pilot studies need to be developed and discussed. In this sense, this review aimed to address scale-up applications of UAE of natural products developed from 2019 to the first semester of 2024. Applications involving hydrodynamic cavitation were not included in this review. Key parameters related to ultrasound were addressed, such as reactor configuration, process type (batch or continuous), frequency, and others. Furthermore, the major challenges associated with the upscaling of UAE, as well as current trends and future perspectives were discussed. It was observed that flow cells were the main reactor type used in scale-up UAE of natural products and that flow-through was the main operation mode. The use of these devices enabled processing of higher sample volumes, possibly due to more homogeneous energy distribution in the reactor. Hence, further enhancements in this area should be expected. Furthermore, phenolic compounds were the main targets of extraction and low frequencies (<100 kHz) were used. However, a challenge remains regarding the lack of essential information in several publications, which makes comparison between studies difficult, as well as their reproduction. Nevertheless, scale-up UAE of natural products is a promising research area.