Effects of different postharvest drying processes on flavonoid content and enzymatic activity of Styphnolobium japonicum (L.) Schott flowers for industrial and medicinal use
Ya-Feng Zuo,
Xin-Qiu Liu,
Xiang-Song Meng,
Meng-Hu Wang,
Jian Tang,
Ting-Ting Hu,
Wen-Jian Wang,
Wei Zhang,
De-Ling Wu
Affiliations
Ya-Feng Zuo
School of Chinese Medicine, Bozhou University, Bozhou 236800, China; Key Laboratory of Chinese Medicine Materials Research of Anhui Higher Education Institutes, Bozhou University, Bozhou 236800, China; Corresponding author. School of Chinese Medicine, Bozhou University, Bozhou 236800, China.
Xin-Qiu Liu
Department of Pharmacy, Bozhou Hospital of Traditional Chinese Medicine, Bozhou 236800, China
Xiang-Song Meng
School of Chinese Medicine, Bozhou University, Bozhou 236800, China; Key Laboratory of Chinese Medicine Materials Research of Anhui Higher Education Institutes, Bozhou University, Bozhou 236800, China; Corresponding author.
Meng-Hu Wang
School of Chinese Medicine, Bozhou University, Bozhou 236800, China; Key Laboratory of Chinese Medicine Materials Research of Anhui Higher Education Institutes, Bozhou University, Bozhou 236800, China
Jian Tang
School of Chinese Medicine, Bozhou University, Bozhou 236800, China; Key Laboratory of Chinese Medicine Materials Research of Anhui Higher Education Institutes, Bozhou University, Bozhou 236800, China
Ting-Ting Hu
School of Chinese Medicine, Bozhou University, Bozhou 236800, China; Key Laboratory of Chinese Medicine Materials Research of Anhui Higher Education Institutes, Bozhou University, Bozhou 236800, China
Wen-Jian Wang
School of Chinese Medicine, Bozhou University, Bozhou 236800, China; Key Laboratory of Chinese Medicine Materials Research of Anhui Higher Education Institutes, Bozhou University, Bozhou 236800, China
Wei Zhang
School of Pharmacy, Anhui University of Chinese Medicine, Hefei 230012, China
De-Ling Wu
School of Pharmacy, Anhui University of Chinese Medicine, Hefei 230012, China; Corresponding author.
Traditionally, fresh S. japonicum flowers (SJF) and S. japonicum flowers buds (SJFB) are dried prior to further processing and use. Here, we investigated the ways in which drying techniques, including sun drying (SD), steam drying (STD), microwave drying (MD), hot air drying (HAD, 40 °C, 60 °C, 80 °C, 100 °C), and freeze drying (FD), alter the flavonoid composition of freshly-harvested SJF and SJFB. The flavonoid content of dried samples was determined by Ultra High Performance Liquid Chromatography-Diode Array Detector (UPLC-DAD). Overall, different drying techniques had significantly different effects on the RU content, ranging from 10.63 % (HAD-80 °C) to 34.13 % (HAD-100 °C) in SJF and from 18.91 % (HAD-100 °C) to 29.16 % (HAD-40 °C) and 30.53 % (SD) in SJFB. To clarify the mechanism by which drying affects the RU content of S. japonicum flowers, we studied the activity of a rutin-hydrolyzing enzyme (RHE) isolated from SJF and SJFB using multiple separation and assay methods. According to the Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) results, the apparent molecular weight of the purified RHE was approximately 38 kDa. According to UPLC-DAD, RHE catalyzes the production of quercetin (QU) from rutin (RU), but not from other flavonoid glycosides. Drying fresh SJF and SJFB at low and high temperatures can inhibit RHE activity and prevent RU hydrolysis. Therefore, subjecting freshly-harvest SJF to HAD-100 °C, and freshly-harvest SJFB to SD or HAD-40 °C, can greatly increase the RU content. In particular, HAD is viable for large-scale application due to its simplicity and industrial feasibility.
