Effect of Ultrasound-assisted Aqueous Two-phase Extraction on Phenolic Compounds from Nymphaea Pubescens Willd. and its Antioxidant and Antimicrobial Properties

This work aims to study the effect of ultrasound-assisted aqueous two-phase extraction (UAATPE) parameters, including temperature (30, 50, and 70C), time (10, 15, and 20min), and frequency level (12, 24, and 36kHz) on the extract yield and its activity.The experimental results exhibited that total phenolic content (TPC) and total flavonoid content (TFC) had the highest content when using a temperature of 70C for 20min which was 77.24mgGAE/g and 81.08mgQE/g, respectively.Conversely, DPPH radical scavenging activity decreased with increasing temperature.Moreover, the frequency level of 12kHz could improve the TPC yield which was 95.88mgGAE/g.Thus, to evaluate the best extraction conditions, the Fuzzy Analytical Method (FAM) was performed to obtain the overall performance index of each condition.The TPC, TFC, DPPH radical scavenging activity, and Fe2+chelating activity were used as criteria with the weights of 30, 40, 20, and 10%, respectively.The best extraction condition was an extraction temperature of 70C for 20min with an ultrasonic frequency of 12kHz, showing the highest overall performance index of 6.774.The extracts also exhibited antimicrobial activity against Staphylococcus aureus TISTR 746 (MIC 62.5mgGAE) and Escherichia coli TISTR 117 (MIC 1000mgGAE), with both showing MBC as 2000mgGAE/mL.It can be pointed out that UAATPE is an alternative powerful technique for bioactive compound extraction from red water lily.