Research Center for TCM of Lingnan (Southern China), Jinan University, Guangzhou, P. R. China.
National Engineering Research Center for Modernization of Traditional Chinese Medicine Lingnan Resources Branch, Guangzhou, P. R. China.
PLoS One. 2022 Mar 14;17(3):e0265383. doi: 10.1371/journal.pone.0265383. eCollection 2022.
Astragali Radix (Huangqi) is an important herb medicine that is always processed into pieces for clinical use. Many operations need to be performed before use, among which drying of Astragali Radix (AR) pieces is a key step. Unfortunately, research on its drying mechanism is still limited. Low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) techniques were applied to study the moisture state and distribution during drying. The content of bioactive components and texture changes were measured by HPLC and texture analyzer, respectively. The moisture content of the AR pieces decreased significantly during drying, and the time to reach the drying equilibrium were different at different temperatures. The time when at 70°C, 80°C, and 90°C reach complete drying are 180 min, 150 min and 120 min, respectively. 80°C was determined as the optimum drying temperature, and it was observed that the four flavonoids and astragaloside IV have some thermal stability in AR pieces. When dried at 80°C, although the total water content decreased, the free water content decreased from 99.38% to 15.49%, in contrast to the increase in bound water content from 0.62% to 84.51%. The texture parameters such as hardness changed to some extent, with the hardness rising most significantly from 686.23 g to 2656.67 g. Correlation analysis revealed some connection between moisture content and LF-NMR and texture analyzer parameters, but the springiness did not show a clear correlation with most parameters. This study shows that HPLC, LF-NMR, MRI, and texture analyzers provide a scientific basis for elucidating the drying principles of AR pieces. The method is useful and shows potential for extension and application; therefore, it can be easily extended to other natural herb medicines.
黄芪是一种重要的药用植物，通常加工成片供临床使用。在使用前需要进行许多操作，其中黄芪片的干燥是关键步骤。不幸的是，其干燥机制的研究仍然有限。本研究采用低场核磁共振（LF-NMR）和磁共振成像（MRI）技术研究干燥过程中水分状态和分布的变化。采用高效液相色谱法（HPLC）和质构仪分别测量生物活性成分含量和质地变化。随着干燥的进行，黄芪片中的水分含量显著下降，在不同温度下达到干燥平衡的时间也不同。在 70°C、80°C 和 90°C 下，达到完全干燥的时间分别为 180 min、150 min 和 120 min。因此，80°C 被确定为最佳干燥温度。实验结果表明，黄芪片中的四种黄酮类化合物和黄芪甲苷 IV 具有一定的热稳定性。在 80°C 下干燥时，虽然总水分含量降低，但游离水分含量从 99.38%降至 15.49%，而结合水分含量从 0.62%增加至 84.51%。硬度等质地参数也发生了一定程度的变化，硬度从 686.23 g 上升到 2656.67 g。相关性分析表明，水分含量与 LF-NMR 和质构仪参数之间存在一定的相关性，但弹性与大多数参数没有明显的相关性。该研究表明，HPLC、LF-NMR、MRI 和质构仪为阐明黄芪片干燥原理提供了科学依据。该方法具有一定的实用性和推广应用潜力，因此可以很容易地推广到其他天然草药。
