Ultrasound-assisted extraction of phenolic compounds from Cratoxylum formosum ssp formosum leaves using central composite design and evaluation of its protective ability against H2O2-induced cell death

Objective: To optimize the processing parameters for phenolic compounds extracted from Cratoxylum formosum ssp. formosum leaves using an ultrasound-assisted extraction and to evaluate its protective ability against H2O2-induced cell death. Methods: The influence of three independent variables including ethanol concentration (%), extraction temperature (degrees C) and extraction time (min) on the extraction yield of phenolic compounds were optimized using a central composite design-based response surface methodology. The obtained extract was assessed for its antioxidant activity by DPPH center dot and ABTS(center dot+) methods. Cellular protective ability against H2O2-induced cell death was evaluated on HEK293 cells using the MTT assay. Results: The optimal conditions to achieve maximal yields of phenolic compounds were ethanol concentration of 50.33% (v/v), temperature of 65 degrees C, and extractiontion time of 15 min. The yield of phenolic compounds was (40.00 +/- 1.00) mg gallic acid equivalent/g dry powder which matched well with the values predicted from the proposed model. These conditions resulted in a higher efficiency concerning the extraction of phenolics compared to a conventional heat reflux extraction by providing shorter extraction time and reduced energy consumption. 5-O -caffeoylquinic acid identified by high performance liquid chromatography-diode array detector -electron spin ionization-mass spectrometry was the major compound in the obtained extract [(41.66 +/- 0.071 mg/g plant extract]. The obtained extract showed a strong ability to scavenge both DPPH center dot. and ABTS free radicals and exhibited additionally good ability to protect HEK293 cells death against oxidative stress. Conclusions: These results indicate the suitability of ultrasound-assisted extraction for the extraction of phenolic compounds from Cratoxylum formosum ssp. formosum leaves. This phenolic-enriched extract can be used as valuable antioxidant source for health benefits.