# Analysis of Volatile Components in Different _Ophiocordyceps sinensis_ and Insect Host Products
## 1 Introduction  
The Chinese cordyceps, a parasitic _Ophiocordyceps sinensis_ fungus-_Thitarodes/Hepialus_ caterpillar complex endemic only at an elevation of 3000-5000 m in the Tibetan plateau, is a valuable health food and medicinal herb [1]. Modern pharmacological studies indicate that the Chinese cordyceps is good for human circulatory, immune, hematogenic, cardiovascular, respiratory, and glandular systems [2; 3; 4]. Due to the limited distribution, high cost, and over exploitation, the natural Chinese cordyceps is extremely expensive and not satisfactory for market demand [5]. Therefore, artificial cultivation is needed to satisfy the natural resource protection and human comsumption. The artificial cultivation of _O. sinensis_ fruiting bodies on rice media [6] and host caterpillar _Thitarodes_ spp. [7; 8] has been established. Mycelial products of _O. sinensis_ fungus have also been manufactured by fermentation technology [9]. More excitingly, the success of cultivation on a large scale has been achieved recently in China [10; 11]. Several main bioactive compounds were detected in natural and cultured Chinese cordyceps and fermented fungal products, such as nucleosides (adenosine and inosine), carbohydrates (mannitol, trehalose, and polysaccharides), sterols (ergosterol), and sphingolipids, etc. [12; 13; 14; 15]. Some free fatty acids and sterols in natural and cultured Chinese cordyceps were determined by one-step derivatization and GC/MS [16]. From the mycelia of _O. sinensis_ cultured with solid-state media and submerged fermentation, 51 volatile compounds were identified, and there is a great difference in the numbers of compounds in the two mycelia, but phenols, acids, and alkanes were the major classes of compounds, while butylated hydroxytoluene was the most abundant volatile compound in both mycelia [17]. The volatile components in several commercial fermentation products from mycelial strains isolated from natural Chinese cordyceps were also analyzed, and 5,6-Dihydro-6-pentyl-2\(H\)-pyran-2-one (massotia lactone) was discovered as the dominant component in the essential oils of Jinshuibao capsule volatiles, and fatty acids including palmitic acid (C16:0) and linoleic acid (C18:2) were also found to be major volatile compositions of the fermentation products [18]. It seems that products from different cultivation methods may exhibit different volatile components. However, a comprehensive volatile profiling from natural and artificially cultivated Chinese cordyceps is unknown. The Green Analytical Chemistry technique of headspace solid-phase microextraction (HS-SPME) coupled with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC\(\times\)GC-TOFMS) proves to be a sensitive, accurate, efficient, and convenient approach for volatile compounds analysis [19; 20; 21; 22; 23; 24]. HS-SPME can extract chemicals directly from sample headspace for volatile compounds analysis. It is well suitable for volatile sampling by the advantages of ease of automation, solvent-free procedure, high preconcentration capacity, little manipulation of the sample, and high cost-efficiency [19; 20; 21; 24; 25]. GC\(\times\)GC is a powerful technique with high resolution and enhanced sensitivity for separating and analyzing complex samples [19; 20; 21; 24; 25; 26; 27]. In addition, with the strengths in accurate mass measurements and good sensitivity in full-scan acquisition mode of TOFMS, GC\(\times\)GC-TOFMS becomes an increasingly popular analytical technique for characterization of the chemical compositions of biological samples [19; 20; 21; 24; 27]. Recently, the combination of HS-SPME and GC\(\times\)GC-TOFMS has been applied to volatile analysis in many fields [19; 20; 21; 24]. However, there is no report of the simultaneous analysis of volatile components in different _O. sinensis_ and insect hosts-based products by this method. In the present work, HS-SPME and GC\(\times\)GC-QTOFMS were employed to analyze volatile compounds from three categories of samples, including _O.