# Analyzing Volatile Compounds of Young and Mature _Docynia delavyi_ Fruit by HS-SPME-GC-MS and rOAV
## 3 Results  
### Volatile Compounds in D. delawayi Fruit with Different Maturities  
The volatile compounds in the samples were measured by HS-SPME-GC-MS. A total of 36 compounds were detected in young fruit (DY), including alkanes (9), an alkene (1), an alcohol (1), aldehydes (8), ketones (6), esters (5), terpenes (5), and a furan (1), while there were 42 compounds in the mature fruit (DM), including alkanes (9), an alkene (1), an alcohol (1), aldehydes (8), ketones (6), esters (9), terpenes (7), and a furan (1) (Figure 1 and Table 1). The DY and DM groups displayed an obviously different number of volatile compounds (Figure 2a). Among the 42 volatile compounds, DM contained unique volatile compounds that included butyl butanoate, butyl hexanoate, hexyl hexanoate, benzyl-carbinyl caproate, cis-\(\alpha\)-bergamotene, and cis-bisabolene. The relative contents of the volatile compounds in DY and DM are shown in Figure 2B. Alkanes mainly originate from the homogeneous decomposition of fatty acid alkoxy radicals [14]. The alkane contents of DY and DM were 0.83% and 0.46%, respectively; however, the alkanes were observed to have a high threshold, which indicated that they hardly affected the flavor of \(D\). _delawayi_ fruit. In addition, the alkene contents in DY and DM were also relatively low (0.04% and 0.15%, respectively), as observed in other Rosaceae fruits [21]. Interestingly, small amounts of 1-octanol and 2-ethylfuran, with green aromas, were detected in both DY and DM. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**NO** & **Classification** & **RT (min)** & **Compound** & **CAS** & **Formula** & **RI A** & \multicolumn{2}{c}{**Relative Content (\%) B**} \\ \cline{6-9}  & & & & & & & **DY** & **DM** \\ \hline C1 & & 11.69 & 4-Methyldecane & 2847-72-5 & C\({}_{11}\)H\  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & **NO** & **Classification** & **RT (min)** & **Compound** & **CAS** & **Formula** & **RI A** & \multicolumn{2}{c}{**Relative Content (\%) [FOOTNOTE:]Footnote : \({}^{\mathrm{A}}\) Retention index. It values were obtained from [[http://www.cfa.com/a/k](http://www.cfa.com/a/k)]([http://www.cfa.com/a/k](http://www.cfa.com/a/k))̃/index.php. Aldehydes are oxidation products of unsaturated fatty acids and a category of volatile compounds commonly found in fruits, such as tomatoes, oranges, and apples [22; 23]. In this study, the number of aldehydes in both DY and DM was 8, while the contents of aldehydes were 1.07% and 2.38%, respectively, among which both DY and DM exhibited the highest (_E_)-2-hexenal contents (0.39% and 1.49%, respectively). The average ketone contents accounted for 11.19% and 6.43% of the volatile compounds identified in DY and DM, respectively. Among them, the levels of 2,6-dimethyl-4-heptanone, 2,3-butanedione and 2-heptanone were highest in both DY and DM, with each exhibiting a green aroma and a sweet fragrance. Figure 1: Heat maps of volatile compounds and their relative contents in _D. delavayi_ fruit of varying maturities. Figure 2: Comparing the volatile compounds in _D. delavayi_ fruit of varying maturities. (**A**) Number of volatile compounds, and (**B**) relative content of volatile compounds. Esters are critical fruit-aroma compounds and are mainly formed by esterifying acids with alcohols [24]. As shown in Figure 2, the number of esters in DY was fewer than that in DM (5 and 9, respectively); however, the total content of esters in DY was higher than that in DM (71.22% and 40.80%, respectively), with relatively high phenethyl acetate and ethyl caprylate contents. Phenethyl acetate is aromatic; its low threshold and high content significantly affect the overall flavor of DY and DM. Terpenes, which are considered to form through the oxidative cleavage of carotenoids, are among the most important groups of volatile compounds and play irreplaceable roles in determining the characteristic aromas of berries as well as essential roles in the phytopharmacological properties (e.g., anti-inflammatory and anticancer) of the fruit [25; 26].