Effects of nine-steam-nine-bask processing on the bioactive compounds content, bioaccessibility, and antioxidant capacity of Polygonatum cyrtonema Hua
Xiling Wang, Yanan Cheng, Bing Zheng, Yi Chen, Jianhua Xie, Xiaobo Hu, Xiaoting Qin, Jiajun Song, Yue Qiu, Qiang Yu
Abstract
The traditional ‘nine-steam-nine-bask’ method of Polygonatum cyrtonema Hua (PCH) has been controversial due to nine-cycle requirement. This study employed in vitro digestion to investigate changes in bioactive substances, bioaccessibility, and antioxidant activity of PCH at different steam-bask times. It revealed the correlation between bioactive substances and antioxidant activity in PCH, and validated the ‘nine-steam-nine-bask’ process’s efficacy. In undigested samples, total phenol content (TPC), reducing sugar content (RSC), and DPPH and ABTS activities increased with more cycles, peaking in the nine-cycle sample at 7.627 mg GAE/g DW, 465.333 mg GE/g DW, 17.698, and 36.986 μmol VCE/g DW. Similar trends were observed throughout digestion. Total sugar (755.96 mg GE/g DW) and total saponin content (1.35 mg DE/g DW) plateaued during gastrointestinal digestion. Correlation analysis further revealed close relationships between bioactive substances and antioxidant activity. Multivariate statistical analysis confirmed that nine cycles maximized the distinction between steam-bask and non-steam-bask PCH.