A continuous process based on the combination of ultrasounds and/or microwaves pretreatments followed by enzymatic hydrolysis and simultaneous extraction (EHSE) has been proposed to recover genipin from Eucommia ulmoides bark. At first, in the pretreatment step, the mixture of 1.0 g dried bark powder and 10 mL deionized water were irradiated by microwave under 500 W for 10 min. Then, in hydrolysis step, the optimal conditions were as follows: 0.5 mg/mL of cellulase concentration, 4.0 pH of enzyme solution, 24 h of incubation time and 40 °C of incubation temperature. After incubation, 10 mL ethanol was added to extract genipin for 30 min by ultrasound. After EHSE treatment, the yield of genipin could reach 1.71 μmol/g. Moreover, scanning electron micrographs illustrated that severe structural disruption of plant was obtained by EHSE. The results indicated that the EHSE method provided a good alternative for the preparation of genipin from Eucommia ulmoides bark as well as other herbs.
Keywords: Eucommia ulmoides bark; enzymatic hydrolysis and simultaneous extraction; genipin; ultrasound/microwave irradiation pretreatment.