Ultrasonic Microwave-Assisted Micelle Combined with Fungal Pretreatment of Leaves Significantly Improved the Extraction Efficiency of Total Flavonoids and Gutta-Percha.

A biological pretreatment of leaf biomass was carried out. Above all, the total flavonoids were isolated from leaves by the treatment of alkaline solution of sodium dodecyl benzene sulfonate combined with ultrasonic microwave. The extraction parameters were optimized by central composite design (CCD) software and were displayed as follows: surfactant concentration of 1.5%, microwave power of 700 W, extraction time of 30 min, and liquid-solid ratio of 50 mL/g. The actual yield of total flavonoids was 1.45%. The results of Sudan III color development showed that the cuticle of leaves was completely removed after dilute alkali pretreatment. Then, leaves were fermented by to remove the holocellulose and obtain gutta-percha. The content of cellulose and hemicellulose in leaves obviously decreased after fermentation. The optimum parameters were listed as follows: solid-liquid ratio of 0.06 g/mL, four extraction times, extraction time of 89.72 min, and extraction temperature of 85 °C. The actual yield of gutta-percha was 4.38%. The amount of extraction solvent per unit weight of gutta-percha from untreated leaves was 2.91 mL/mg, while that from leaves treated by was only 0.96 mL/mg. The amount of extraction solvent was grossly reduced, which is beneficial in terms of environmental protection. The characterizations of gutta-percha were verified by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and proton nuclear magnetic resonance (H NMR). This study laid a certain theoretical and experimental basis for the multi-stage extraction of leaves and the utilization of resources.