Optimization of bioactive compounds recovery from thuya solid residues using ultrasound and nonionic surfactants assisted extraction: A response surface methodology study

In this study, we investigated the optimization of recovering bioactive compounds from the solid residues generated during the essential oil extraction of Tetraclinis Articulata (Vahl) Mast. Four independent variables (ethanol concentration, solvent-to material ratio, extraction time and surfactant concentration) using Box-Behnken design (BBD) to enhance the recovery of poly- phenols were studied using surfactant-based ultrasound-assisted extraction. Genapol X-080, Tween 80 and Tween 20 were selected as additives in the water/ethanol solvent system. Genapol X-080 was the most effective surfactant for extracting phenolic compounds and achieving high antioxidant activity, while Tween 80 excelled at extracting flavonoids. In contrast, Tween 20 demonstrated lower effectiveness across all measured parameters. The optimal extraction conditions using Genapol X-080, as predicted by the BBD methodology, were as follows: 75.06% (v/ v) ethanol in water as the extraction solvent, a liquid-to-solid ratio of 30 mL/g, an extraction time of 29.97 min, and a surfactant concentration of 1.78% (v/v). Under the defined optimal parameters, the total polyphenol content was 112.94 +/- 0.41 mg GAE/g, the flavonoid content was 26.27 +/- 0.23 mg QE/g, and the IC50 value was 0.42 +/- 0.03 mg/mL. The extracts show strong antimicrobial activity against S. aureus, L. monocytogenes, and B. subtilis, with L. monocytogenes being the most sensitive, with an inhibition zone of up to 31.74 mm and an MIC as low as 8 mu g/ mL. However, the extracts were ineffective against E. coli and the fungus. This study confirms that the solid residues of Tetraclinis Articulata are a potential exploitable source for the recovery of bioactive phenolic compounds.