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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 (°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(•) and ABTS(•)(+) 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 °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±0.07) mg/g plant extract. The obtained extract showed a strong ability to scavenge both DPPH(•) 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.
Yingngam et al. (Mon,) studied this question.