# Characteristic Volatile Composition of Seven Seaweeds from the Yellow Sea of China
## 2 Results and Discussion
### Network Pharmacology and Potential Biomedical Application of D. Dichotoma  
VOCs in _D. dichotomous_ are characterized by sesquiterpenes and diterpenes. It has been reported that a total of 78 structurally diverse diterpenes have been isolated from \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**No.** & **Aldehydes** & **Molecular Formula** & **Related Fiber** & **Algae** \\ \hline
**2** & 4-Heptenal & C\({}_{7}\)H\({}_{12}\)O & DVB/CAR/PDMS & EP \\
**3** & 3-Cyclohexene-1-carboxaldehyde & C\({}_{8}\)H\({}_{12}\)O & DVB/CAR/PDMS & EP \\ \hline
**7** & \(\beta\)-Cyclocitral & C\({}_{10}\)H\({}_{16}\)O & PDMS & EP, UL \({}^{\text{A}}\), GF, PS, CC, \\  & & & & ST \\ \hline
**8** & (Z)-2-Decneal & C\({}_{10}\)H\({}_{18}\)O & DVB/CAR/PDMS & EP \\ \hline
**9** & Citral & C\({}_{10}\)H\({}_{16}\)O & DVB/CAR/PDMS & EP \\
**11** & 2,4-Decadienal & C\({}_{10}\)H\({}_{16}\)O & PDMS & UL \({}^{\text{A}}\), GF, DD \\ \hline
**12** & (_E_)-4,5-Epoxydec-2-enal & C\({}_{10}\)H\({}_{16}\)O\({}_{2}\) & DVB/CAR/PDMS, & EP \({}^{\text{A}}\), UL \\ \hline
**15** & 2-Undecenal & C\({}_{11}\)H\({}_{20}\)O & DVB/CAR/PDMS & EP \\ \hline
**18** & Tetradecanal & C\({}_{14}\)H\({}_{28}\)O & DVB/CAR/PDMS, & EP \({}^{\text{A}}\), UL, GF, CC, ST \\ \hline
**21** & (_Z_)-11-Hexadecenal & C\({}_{16}\)H\({}_{30}\)O & DVB/CAR/PDMS, & EP \\  & & & & PDMS \\ \hline \hline \end{tabular} \({}^{\text{A}}\) with the highest content.  
\end{table} 
Table 4: Various aldehydes in PCA loading plot, as shown in Figure 3.  
Figure 3: Bi-plot of PCA using aldehydes: (**a**) DVB/CAR/PDMS fiber; (**b**) PDMS fiber. \(D\). _dichotoma_ and exhibit multi-biological properties, such as cytotoxic, antitumor, antiviral, antifouling, antioxidant, antibacterial and antifungal activities [21]. In the present study, a network pharmacology method was performed to verify and discover new bioactivities of \(D\). _dichotoma_. First, the VOCs of \(D\). _dichotoma_ were entered into the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) in the \"chemical name\" search box to obtain relevant targets. The \"compound-target\" relationships are shown in Figure 4, with 31 nodes (1 alga, 10 compounds and 20 targes). Comparing with the average degree score, 6.07, from network topology analysis, six key compounds were disclosed as cedrene, \(\alpha\)-selinene, cubenol, \(\alpha\)-muurolene, \(2\)_A_-decadien and \(\gamma\)-muurolene, of which most are sesquiterpenenes. The first three compounds are cedrene, \(\alpha\)-selinene and cubenol, each of which can act on 10 targets. Next, the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis was used to obtain the potential pathway in which VOCs might play a role. The 10 identified pathways (\(p<0.01\)) are shown in Figure 5: neuroactive ligand-receptor interaction, small cell lung cancer, retrograde endocannabinoid signaling, nicotine addiction, non-small cell lung cancer, GABAergic synapse, morphine addiction, bladder cancer, PI3K-Akt signaling pathway and the calcium signaling pathway. According to the literature, the neuroactive ligand-receptor interaction pathway plays an important role in lung cancer etiology [32]. Considering other pathways such as small cell lung cancer, non-small cell lung cancer, retrograde endocannabinoid signaling and PI3K-Akt signaling, we supposed that \(D\). _dichotoma_ may have certain preventive and therapeutic value in cancer, especially in lung cancer. The non-polar fractions of \(D\). _dichotoma_ exhibit anticancer activity in vitro, including the lung adenocarcinoma cell line (A-549) [33]. Figure 4: Compound–target interaction network of Dictyota dichotomous. In addition, it should be noted that the neuroactive ligand-receptor interaction pathway is the most relevant pathway for VOCs in _D. dichotomous_, with nine target genes involved--CHRM1, CHRM2, CHRM3, CHRNA2, GABRA1, GABRA2, GABRA3, GABRA5 and ADRA1B.