Optimized microwave-assisted extraction of phenolic compounds from Scirpus holoschoenus and its antipseudomonal efficacy, alone or in combination with Thymus fontanesii essential oil and lactic acid

Phenols extracted from Scirpus holoschoenus rhizomes, alone or in combination with other substances, have interesting antipseudomonal properties. Maximum extraction efficiency was achieved by using parametric optimization methods. In this study, the microwaveassisted extraction of phenolic compounds from S. holoschoenus L. rhizome was performed with the help of Response Surface Methodology, and the optimal parameters were found to be 56% acetone, 69 s time and 600W for power, with a TPC value of 30.70 +/- 1.22 mg GAE/g dry weight (dw). The ethyl acetate fraction (EA) of the optimized extract was tested in combination with diluted essential oil of T. fontanesii (EOd) and lactic acid (LA) on Pseudomonas aeruginosa. Mixture design indicated that at 7 degrees C, the 75% EOd, 25% EA and 0% LA mixture gave the largest diameter inhibition zone (63 +/- 2 mm). A mixture of 83.7% EOd and 16.28% EA was the most effective at 37 degrees C (24.16 +/- 1.04 mm). (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.