# Analysis of Volatile Components in Different _Ophiocordyceps sinensis_ and Insect Host Products
## 4 Conclusions  
This study presents the volatile metabolite profiles by HS-SPME-GC\(\times\)GC-QTOFMS from _O. sinensis_ fungus and insect host-based products. A total of 120 volatile compounds including 36 alkanes, 25 terpen, 17 aromatic hydrocarbons, 10 ketones, 5 olefines, 5 alcohols, 3 phenols, and 19 other compounds were identified. There are great differences in the volatile compounds among the three categories of _O. sinensis_ fungus, _TInitarodes_ hosts of _O. sinensis_, and the Chinese cordyceps. In general, natural and mature artificial Chinese cordyceps (fungus-insect complexes), fruiting bodies, and fermented products had more volatile compounds than insect larvae, insect pupae, and immature artificial Chinese cordyceps. 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-dimethylundecan (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). Alkanes are the dominant volatile compounds in all products. 2,5,6-trimethyldecane and 2,6,7-trimethyldecane are the major volatile compounds in all products except the larval ones, while 2,2,4,4-tetramethyloctane dominates in the larval products. From the view of the differences in volatile compounds, it seems that the fermented products are not the same as the natural and artificial Chinese cordyceps. Based on the volatile compounds, three classes (_O. sinensis_ fungus, _TInitarodes_ insect, and fungus-insect complexe) were confirmed by partial least squares-discriminant analysis (PLS-DA). Thieno [2,3-c] pyridine, 2,6,11-trimethyldodecane, 2,3,4-trimethyldodecane, 4,7-dimethyllandan, 2,6-dimethylundecane, farnesane, 2,3-dimethyldodecane, and [but-2-en-2-yl] benzene are potential discriminatory compounds. The present results suggested that HS-SPME-GC\(\times\)GC-QTOFMS combined with multivariate data analysis is an ideal method for analyzing and distinguishing different _O. sinensis_ and insect hosts-based products. The information provided in this study is of importance for the further identification of bioactive components and for proposals of possible mechanisms to obtain those bioactive compounds in a different form than the traditional fungus-insect interaction.  
[PERSON] and [PERSON] conceived and designed the experiments; [PERSON] and [PERSON] prepared experimental samples; [PERSON] performed the experiments and analyzed the data; [PERSON] and [PERSON] wrote the manuscript. All the authors reviewed the manuscript. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This study was supported by Guangzhou Science and Technology Projects (201803010087; 201604020030), GDAS Special Project of Science and Technology Development (2018 GDASCX-0107), and Open Project of Guangdong Key Laboratory of Animal Conservation and Resource Utilization (GIABR-KF201703).  
**Acknowledgments:** The authors are grateful to Professor [PERSON] from Guangdong Institute of Analysis, Guangzhou, China for technical support.  
**Conflicts of Interest:** The authors declare no conflict of interest.