# Characteristic Aroma Compound in Cinnamon Bark Extract Using Soybean Oil and/or Water
## 3 Results and Discussion  
### Changes in the Relative Concentrations of Volatile Compounds in the Water Extract  
Table 1 shows changes in the relative content of volatile compounds in the water extract of cinnamon bark. A total of 26 volatile compounds were identified, including 7 aldehydes, 4 alkenes, 7 alcohols, 2 ethers, 3 ketones, and 3 esters. Aldehydes accounted for more than 90% of the total volatile compound content, which was consistent with a previous finding of cinnamon essential oil [1]. Cinnamaldehyde was the most abundant compound in aldehydes, followed by benzaldehyde. With the increased stewing time, the relative content of furfural and cinnamaldehyde decreased significantly, whereas the contents of hexanal, nonanal, benzaldehyde, benzenreponal, and \(p\)-anisaldehyde increased significantly. The decrease in the total aldehyde content was attributed to the decrease in the cinnamaldehyde content, which accounted for more than 90% of the total aldehyde content (Table 1). A previous study has reported that increasing extraction intensity can significantly increase the relative content of aroma compounds in the water extract of spices [30]. Therefore, the increase in the relative content of the five aldehydes noted above can be attributed to the extension of extraction time. The decreased relative content of furfural and cinnamaldehyde may be related with their antioxidant properties. It has previously been demonstrated that furfural and cinnamaldehyde have the ability to scavenge free radicals [31; 32], and  
heating is a vigorous oxidation process. An antioxidant can react with free radicals to generate a variety of products, resulting in a decrease in its relative content. For example, \(\alpha\)-tocopherol can react with peroxynitrite to form tocopherylquinone, and it can also react with peroxyl radicals to generate epoxytocopherolquinone. In addition, two \(\alpha\)-tocopherol can react to producetocopherol dimers via a radical coupling reaction [33]. Therefore, the decrease in the relative content of furfural and cinnamaldehyde could be due to the structural transformation in the process of scavenging free radicals.  
Among alkenes, the levels of camphene, D-limonene, and cyclootetetraene increased with the increased heating time, which was attributed to the improved extraction efficiency [30]. In addition, the 4-methoxystyrene content decreased, which may be due to the substance's catalytic activity [34].  
The relative content of eucalypt and linalool increased with the increased heating time, whereas the relative content of 1-octen-3-ol, isopulegol, and \(\alpha\)-terpineol decreased significantly. Isopulegol and \(\alpha\)-terpineol share the general structure of monoterpenoids, which have a remarkable ability to scavenge free radicals [35]. [PERSON] and [PERSON] [36] reported that 1-octen-3-ol showed potent antioxidative activities. As a result, the antioxidant properties of 1-octen-3-ol, isopulegol, and \(\alpha\)-terpineol caused a decrease in their relative content, as did the decrease in furfural and cinnamaldehyde.  
With the increased heating time, the relative content of anthelo increased significantly, but the relative content of all ketones and esters decreased significantly, except ethyl cinnamate. The lower levels of these compounds may be related to their vapor pressure (Table 1), as compounds with high vapor pressure tend to migrate into the air phase during heating, resulting in a decrease in their concentrations in the cinnamon extract.