# Analysis of Volatile Components in Different _Ophiocordyceps sinensis_ and Insect Host Products
## 2 Results and Discussion
### Identification of Volatile Components  
Component identification was achieved by matching the QTOFMS spectral with a commercial mass spectral library (NIST 17), with a minimum match factor of 800. The current quantitative method was consistent with similarly reported references [25; 26], and the qualitative data of volatile components in different analyzed products (Table 1) with their peak area percentages are presented in Table 2. A total of 120 volatile compounds were detected in all samples with various concentration levels. A total of 107, 101, 71, 70, 89, 89, 113, 103, 105, 107, 102, 99, 40, 45, 82, and 69 compounds (Figure 2A) were identified in the products of W, A, A0, A1, A2, A3, FB, FC20d, FC40d, FC60d, FC80d, FC100d, Tx-LU, Tx-LI, Tx-PU, and Tx-PI (Table 1), accounting for 95.70%, 88.14%, 91.96%, 89.50%, 90.59%, 90.73%, 93.42%, 91.08%, 89.84%, 87.04%, 91.54%, 91.45%, 87.10%, 90.15%, 87.63%, and 91.81% of the total peaks areas, respectively. The identified compounds included 36 alkanes, 25 terpenes, 17 aromatic hydrocarbons, 10 ketones, 5 olefines, 5 alcohols, 3 phenols, and 19 other compounds. The volatile compound amounts showed great variation in different samples and ranged from 40 compounds in Tx-LU to 113 compounds in FB. In general, natural and mature artificial Chinese codyceps (fungus-insect complexes), fruiting bodies, and fermented products had more volatile compounds than insect larvae, insect pupae and immature artificial Chinese codyceps. Figure 1: Comparison of an expanded region of the 1D GC (**A**) and the same region from GC \(\times\) GC (**B**) chromatograms of volatile components from a quality control sample. Compounds identification: (1) 2,5,9-trimethyldecane; (2) 2,2,4,4-tetramethylcane; (3) p-limonene; (4) o-cymene; (5) 2,4-dimethyl-2,3-heptadien-5-yne; (6) 3-octene-2-one; (7) 2,3-dihydropyran-6-one. Twenty-four volatile compounds were identified in all the 16 samples, including 4-carene (C10), 3-carene (C18), 2,2,4,4-tetramethyloctane (24), 2-propyltoluene (C29), 2,4,6-trimethyldecane (C31), 2,6-dimethyl-6-trifluoroacetoxyoctane (C34), linalool (C41), 2-nonen-1-ol (C42), 6-ethyl-2-methyloctane (C44), (+)-\(\alpha\)-terpineol (C61), 2,6-dimethylundecane (C65), 2,8-dimethylundecane (C68), 4-methyldodecane (C73), 4,7-dimethyllandan (C75), 2,3-dimethylundecane (C76), 2,4-dimethyldodecane (C77), 2,6,11-trimethyldodecane(C78), 4,6-dimethyldodecane (C84), 2,3,5,8-tetramethyldecane (C86), farnesane (C94), tetradecane (C97), seychellene (C108), 2,6-di-tert-butyl-4-methyl-p-quinol (C109), and hexadecane (C118). The mutual volatile compounds accounted for 40.19%, 41.24%, 51.44%, 48.59%, 50.58%, 41.86%, 38.44%, 48.04%, 48.31%, 47.03%, 44.37%, 48.49%, 64.94%, 68.73%, 49.13%, and 40.87% of the total volatile compounds in W, A, A0, A1, A2, A3, FB, FC20d, FC40d, FC60d, FC80d, FC100d, Tx-LU, Tx-LI, Tx-PU, and Tx-PI, respectively. With the method of simultaneous distillation-extraction (SDE) and GC-MS, 17 and 42 volatile compounds were identified in the mycelia of _O. sinensis_ from solid-state media and submerged fermentation, respectively [17]; in Bailing capsule and Zhiling capsule, the commercial fermentation products of _O. sinensis_ mycelia, 39 and 56 volatile compounds were identified, respectively [18]. While by the technique of HS-SPME combined with GC\(\times\)GC-QTOFMS in this study, 99-107 volatile compounds were identified from the fermentation cultures of _O. sinensis_ mycelia, indicating the superior sensitivity and resolution of the present method.