| Popis: |
Ginkgolic acids are unwanted constituents in standard Ginkgo biloba leaves extracts. Thus, for the quality control of ginkgo extracts, it is important to establish an effective degradation method, with high catalytic efficiency and safety, to remove ginkgolic acids. Laccases are oxidases with potential for application in elimination of hazardous phenolic compounds. In this study, single-factor and orthogonal experiments were used to optimize extraction of ginkgolic acid from G. biloba sarcotestae. The results showed that ethanol was the best solvent, with the highest extraction rate for ginkgolic acid at 85% ethanol. On this basis, we measured ethanol volume fraction, extraction time, temperature and solid-liquid ratio using an orthogonal experiment. By using absorbance of 310 nm as standard, the optimal extraction conditions were 85% ethanol with, solid-liquid ratio of 1:14 at 40°C for 12 h. These conditions gave a ginkgolic acid yield of 73.1 mg·g−1. Subsequently, recombinant laccase was used to degrade the ginkgolic acid in several laccase/mediator systems, of which LacC was the best. At 50°C, pH 4.5, enzyme concentration of 0.01 U·mL−1, 0.5 mmol·L−1 mediator ABTS and reaction time of 3 h, the degradation rate of ginkgolic acid reached 100%. These results lay the foundation for research on and application of biological enzymes for detoxification of G. biloba extracts. |
