Abstract
A biological pretreatment of Eucommia ulmoides leaf biomass was carried out. Above all, the total flavonoids were isolated from Eucommia ulmoides 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 Eucommia ulmoides leaves was completely removed after dilute alkali pretreatment. Then, Eucommia ulmoides leaves were fermented by Trichoderma viride to remove the holocellulose and obtain gutta-percha. The content of cellulose and hemicellulose in Eucommia ulmoides leaves obviously decreased after Trichoderma viride 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 Eucommia ulmoides leaves was 2.91 mL/mg, while that from leaves treated by Trichoderma viride 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 (1H NMR). This study laid a certain theoretical and experimental basis for the multi-stage extraction of Eucommia ulmoides leaves and the utilization of Eucommia ulmoides resources.
Highlights
Eucommia ulmoides, a member of Eucommia ulmoides family, is a large woody plant that mainly grows in China [1]
The increase of surfactant content could increase the solubility of total flavonoids in the system solution
The results showed that the pretreatment of Eucommia ulmoides leaves by surfactant SDBS combined with Trichoderma viride was a favorable method for the extraction of gutta-percha
Summary
A member of Eucommia ulmoides family, is a large woody plant that mainly grows in China [1]. Eucommia ulmoides bark and leaves contain a variety of active components such as flavonoids, lignans, polysaccharides, and volatile oil. It harbors a special biomaterial, Eucommia ulmoides gum [2]. This gum is called balata or gutta-percha, a rubber with a molecular structure of trans-1,4-polyisoprene (Figure 1). The gutta-percha is an isomer of natural rubber (cis-1,4-polyisoprene) [3]. In addition to high flexibility (known as the general character of natural rubber), gutta-percha has shown excellent plasticity. Eucommia ulmoides is a deciduous tree that produces a large number of fallen leaves every year. The development of effective components of Eucommia ulmoides leaves instead of Eucommia ulmoides bark is advantageous to the sustainable and healthy development of Eucommia ulmoides resources [7]
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