# Seasonal Variability of Volatilome from _Dictyota dichotoma_
## 2 Results and Discussion
### Variations of Headspace Volatilome of Fresh D. dichotomous
The major cadinence-type sesquiterpenes in May were: epicubenol (11.79% (I); 2.56% (II)), \(\delta\)-cadinene (6.43% (I); 3.45% (II)), \(\alpha\)-amorphene (3.40% (I); 2.51% (II)), and epi-bicyclosesquiphellandrene (2.85% (I); 2.28% (II)). Minor cadinane-type sesquiterpenes (Tables 1 and 2) were: \(\gamma\)-cadinene, (_E_)-cadina-1,4-diene, \(\tau\)-cadinol, \(\alpha\)-copaene, \(\alpha\)-cubebene, \(\beta\)-cubebene, \(\gamma\)-cuncumene, \(\gamma\)-muvolene, \(\alpha\)-calacorene, \(\tau\)-cadinol and cubenol. The major selinate-type sesquiterpenes, also abundant in May, were germacrene D (6.11% (I); 14.39% (II)) and germacrene C (3.30% (I); 4.59% (II)), followed by \(\gamma\)-selinene, found periodically up to 1.94% (I) or 0.77% (II). Among aromadendrane-type sesquiterpenes, \(\beta\)-gurjunene (5.10-cycloamodendrane sesquiterpene) was found in May with 5.73% (I) or 3.92% (II). \(\alpha\)-Humulene (\(\alpha\)-carophyllene), as carophyllene-type sesquiterpene, was present in May with 5.85% (I) or 3.86% (II). Among other sesquiterpenes, gleenol was present up to 1.14% (I) or 0.65% (II). Among C\({}_{13}\)-norisoprenoids, the most abundant was \(\beta\)-ionone (up to 2.45% (I) or 1.84% (II) in May), followed by \(\beta\)-cyclocitral. There is a partial similarity with our previous research [14] on fresh _D. dichtota_ HS collected in the Adriatic Sea, but from another location. Namely, predominant sesquiterpene was germacrene D (28.3%) followed by cadinene-type sesquiterpenes: \(\delta\)-cadinene \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline  & & & \multicolumn{2}{c}{**May**} & \multicolumn{2}{c}{**June**} & \multicolumn{2}{c}{**July**} & \multicolumn{2}{c}{**August**} & \multicolumn{2}{c}{**September**} \\ \cline{3-13}
**No.** & **Compound** & **RI** & **Fr** & **Dr** & **Fr** & **Dr** & **Fr** & **Dr** & **Fr** & **Dr** & **Fr** & **Dr** \\ \cline{3-13}  & & & & & & & & & & & & & \\ \hline \multicolumn{13}{c}{**Area (\%)**} \\ \hline
67 & (_E_)-Cadina-1,4-diene & 1537 & 0.89 & - & 0.20 & - & 0.16 & - & 0.17 & - & 0.37 & - \\
68 & \(\alpha\)-Calacorene & 1552 & 0.19 & - & 0.05 & - & 0.07 & - & - & - & - & - \\
69 & Dactylol & 1557 & 15.38 & - & 0.11 & - & 0.04 & - & 0.04 & - & 0.05 & - \\
70 & Germacrene-4-ol & 1578 & 0.34 & - & 0.20 & - & 0.04 & - & 0.06 & - & 0.06 & - \\
71 & Gleenol & 1589 & 0.58 & 0.26 & 0.65 & - & 0.24 & 0.18 & 0.27 & - & - & - \\
72 & Headacene \({}^{\rm a}\) & 1600 & - & - & 0.08 & - & 0.08 & - & 0.21 & - & 0.13 & - & 0.07 \\
73 & Epicubenol & 1616 & 2.56 & - & 0.30 & - & 0.09 & - & 0.22 & - & 0.22 & - \\
74 & r-Cadinol & 1630 & 0.22 & - & 0.10 & - & - & - & - & - & - \\
75 & Cubenol & 1647 & 0.21 & - & 0.18 & - & 0.09 & - & 2.18 & - & 0.10 & - \\
76 & Heptadecene \({}^{\rm a}\) & 1700 & 0.14 & 0.14 & 0.91 & 0.13 & 0.86 & 0.21 & 1.89 & 0.37 & 2.35 & 0.22 \\
77 & Pentadecan \({}^{\rm a}\) & 1718 & 0.12 & - & 0.41 & - & 0.43 & - & 0.87 & - & 1.36 & - \\
78 & Isopendydictyl A & 2127 & 0.34 & - & 0.71 & - & 0.31 & - & 0.57 & - & - & - \\ \hline \end{tabular}  
*–identification confirmed by standard compound; other compounds were tentatively identified; GC-MS analyses were performed on HP-5 MS capillary column (30 m \(\times\) 0.25 mm, 0.25 \(\mu\)m film thickness, Agilent Technologies, Palo Alto, Santa Clara, CA, USA).  
\end{table} 
Table 2: _Cont._(8.3%), \(\gamma\)-cadinene (3.4%), \(\beta\)-cadinene (2.8%) and _trans_-cadina-1_A_-diene (1.2%). Additionally, \(\beta\)-bourbonene was identified with (5.1%) and \(\alpha\)-copaene with a lower percentage. Compared to the VOCs results of this alga from the Yellow Sea of China [15], a lower number of sesquiterpenes were found with predominant germacrene D (34.83% with DVB/CAR/PDMS fibre; 62.00% with PDMS fibre), together with minor ones such as \(\delta\)-cadinene, \(\gamma\)-muurolene and \(\beta\)-bourbonene and cubenol (up to 4.70%).