*3.6. Volatile Compounds*

Forty volatile constituents were identified as shown in Table 5. The typical analytical ion current (AIC) chromatogram is shown in Figure S2. The chemical composition of volatiles was found in agreemen<sup>t</sup> with previous reports [43]. The main volatile compounds identified were nonanal (18.829%, **13**), β-pinene (12.179%, **14**), 1-octen-3-ol (12.129%, **15**), neryl alcohol (10.135%, **16**), α-pinene (8.046%, **17**), 6-methyl-3,5-heptadiene-2-one (6.803%, **18**), *p*-cymen-9-ol (3.108%, **19**), and sylvestrene (3.022 %, **20**) (Figure S3). It is important to note that the content of the compounds differed from a previous study carried out on the volatile compounds in propolis samples from Yucatan (México). In that sample, hexadecanoic acid (10.9%) and trans-verbenol (7.0%) were the predominant compounds [44].


**Table 5.** Volatile components from Mexican propolis GUA-4.

a: Retention time; b: Retention index; c: Mass spectrum.
