Postharvest UV-B irradiation improves the accumulation of flavonoid and biosynthetic gene expressions in Scutellaria baicalensis root

摘要

To examine the effects of postharvest UV-B radiation on the accumulation of flavonoid in Scutellaria baicalensis root and the underlying mechanism, the quantitative analysis of the flavonoid contents (baicalin, wogonoside, scutellarin, baicalein and wogonin) was performed using HPLC. The expressions of key enzyme genes PAL, 4CL, CHS, CHI, UBGAT and GUS in the biosynthesis of flavonoid were examined using RT-PCR. The value of flavonoids, especially baicalin, wogonoside and wogonin, displayed a time-dependent increase, and the content of baicalin in the control reached 80.7 mg/g at 12 h during drying process. The content of baicalin in UV-B treatment was increased significantly by 69.67% ( p 0.05) and 51.32% ( p 0.05) respectively compared with control at 12 h (109.14 mg/g) and 24 h (97.35 mg/g) and reach the maximum value at 24 h. The key enzymes exhibited different expression patterns during the postharvest drying process. The mRNA levels of key enzyme genes CHS, CHI, GUS and PAL in the control were observed to be stimulated, reaching peak levels at 12 h, and their maximum value reached 3-, 3-, 4-, 5- and 4-fold of that at 0 h respectively. While they exhibited an even more increase in UV-B irradiation treatment compared to the control. Appropriate water deficit in dehydration could significantly promote the levels of flavonoids in S. baicalensis roots and suitable concentration of UV-B treatment is an effective approach for promoting the content of flavonoids during the postharvest drying process.