Ultrasound-Assisted Extraction of Bioactive Compounds from Dried Kale

Chong, Kor Li (2022) Ultrasound-Assisted Extraction of Bioactive Compounds from Dried Kale. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Kale (Brassica oleracea var. sabellica) is a deep green leafy vegetable that have sparked intense interest among the community due to its high content of bioactive compounds. However, the effects of the drying process and extraction conditions on the content of bioactive compounds in kale are limited. An efficient extraction method is essential to increase the quantity and quality of the extracted bioactive compounds. This research investigated the effects of temperature (40–80 °C) in drying of kale and ultrasound assisted extraction process condition on the extraction yield, total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity in terms of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP), and anti-inflammatory activity (anti-lipoxygenase activity, anti-LOX) of dried kale extracts. Optimum oven drying temperature was identified at 40 °C with the significantly highest anti-lipoxygenase activity (31.37 ± 1.04%) of UAE-treated dried kale extracts (p < 0.05). Subsequently, the effects of different ultrasonic amplitudes (25–75%) and extraction times (10–30 minutes) were studied on the extraction yield, TPC, TFC, DPPH, FRAP, and anti-LOX of extracts sourced from kale dried at 40 °C. A combination of ultrasonic amplitude at 50% and extraction time of 10 min contributed to the highest yield, DPPH, anti-LOX, and significantly highest TPC (1659.6 ± 29.5 mg GAE/100 g), TFC (2196.1 ± 22.4 QE/100 g) and FRAP (4025.6 ± 29.1 mg FE/ 100 g) with p < 0.05. All the bioactive compounds assays (TPC and TFC) were positively correlated with antioxidant capacities (DPPH and FRAP). By comparing with CE dried kale extracts, UAE dried kale extracts showed the significantly highest total yield, TPC, TFC, DPPH, FRAP and anti-LOX (p < 0.05). Ultrasound shows potential to enhance the bioactive compounds extraction from dried kale and the extracts is possible to be incorporated into food and beverages to increase their bioactivity