Dynamic Changes in Major Active Substances and Volatile Components in Toona sinensis Leaves during Growth

In order to study the dynamic changes of major active substances and volatile components in Toona sinensis at different growth stages, the contents of total flavonoids, total polysaccharides, total saponins and total alkaloids in the leaves of T. sinensis collected from April to October, 2019 were determined by conventional methods, and the volatile compounds by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-ion mobility spectrometry (GC-IMS). Additionally, the volatile components in the leaves of T. sinensis in different growth periods were distinguished by cluster analysis (CA) and principal component analysis (PCA). The results showed that the major active substances in the leaves of T. sinensis exhibited an obvious accumulation tendency during the growth process; the contents of total flavonoids, total polysaccharides and total alkaloids reached the highest levels in October, while the content of total saponins reached the highest level in September. The volatile components changed significantly during the growth period, and 109 and 49 volatile components were identified by GC-MS and GC-IMS, respectively, mainly including terpenes, aldehydes, sulfur-containing compounds and alcohols. Most of the volatile components detected by GC-MS were larger molecules (C₆–C₂₀) at high levels, while most of the volatile components detected by GC-IMS were smaller molecules (C₄–C₁₀) at low levels. The combination of the two techniques can expand the scope of detection of volatile components in T. sinensis leaves. The results of this study can provide a scientific basis for the planting, quality evaluation, and comprehensive development and utilization of T. sinensis.