## 3 Results
### Thermal Desorption-Gas Chromatography-Mass Spectrometry of the Melanin from Ochroconis lascauxensis  
Due to the compositional similarity of the three melanins and the abundance of pyrolysis products from different types of materials, we selected the melanin of _Ochroconis lascauxensis_ as a model for further analyses. A pyrogram of the bulk melanin revealed an abundance of lipid-, polysaccharide-, and protein-derived compounds as denoted in Figure 1A, which can mask the presence and identification of other structural (aromatic) components. To circumvent this problem, we used a second analytical approach: a double shot pyrolysis involving thermal desorption at 300 \({}^{\circ}\)C followed by a pyrolysis at 500 \({}^{\circ}\)C. The first thermal step is considered to produce a thermal desorption of lipid compounds, a pyrolysis of polysaccharides and a mild pyrolysis of proteins. \begin{table}
\begin{tabular}{c c c c} \hline
**Peak** & **Compound** & **Peak** & **Compound** \\ \hline
56 & \(n\)-Hexadecene & 116 & Antihaergostan-5,7,9,16,22-pentene \\
57 & \(n\)-Hexadecane & 117 & Hexadecanoic acid hexadecyl ester \\
58 & Fluorene & 118 & Ergosta-4,6,8(14),22-tetraen-3-one \\
59 & \(n\)-Heptadecene & 119 & Stigmasta-3,5-dien-7-one \\
60 & \(n\)-Heptadecane & 120 & Hexadecanoic acid octadecyl ester \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._A third analytical approach involved 6\(N\) HCl hydrolysis of the melanins. Acid hydrolysis with constant-boiling at 110 \({}^{\circ}\)C for 24 h has been widely accepted as a standard method for removal of proteinaceous materials and carbohydrates [23], which absence could evidence other (aromatic) structural units masked by the high amount of pyrolysis products. Figure 2A shows the chromatograms of the thermal desorption at 300 \({}^{\circ}\)C of the untreated _O. lascauxensis_ melanin. Figure 2B depicts the acid hydrolyzed melanin subjected to the same protocol. A list with desorption products at 300 \({}^{\circ}\)C of the melanin of _O. lascauxensis_ is shown in Table 2. \begin{table}
\begin{tabular}{c c c c} \hline
**Peak** & **Compound** & **Peak** & **Compound** \\ \hline
1 & Chloromethane & 58 & Dodecanoic acid \\
2 & Sulfur dioxide & 59 & _n_-Nonylbenzene \\
3 & Hexanal & 60 & _n_-Hexadecene \\
4 & Benzene & 61 & _n_-Hexadecene \\
5 & Dimethyldisulfide & 62 & Diethylphalate \\
6 & Toluene & 63 & Methylthiobenzeneothiazzo \\
7 & Butanoic acid & 64 & Benzophenone \\
8 & Pyridine & 65 & Phenylhexanoic acid \\
9 & Furfural & 66 & Tridecanoic acid \\
10 & Maleic anhydride & 67 & _n_-Decylbenzene \\
11 & Pentanoic acid & 68 & Heptadecatriene \\
12 & _n_-Propylbenzene & 69 & Heptadecadiene \\
13 & Benzaldehyde & 70 & _n_-Heptadecene \\
14 & Hexanoic acid & 71 & Phenyloctanone \\
15 & Anhydrodeoxypentenulose & 72 & 2-Pentadecanone \\
16 & Phenol & 73 & Methyladecylbenzene \\
17 & _n_-Butylbenzene & 74 & Diketodipyrrole \\ \hline \end{tabular}
\end{table} 
Table 2: Pyrolysis products obtained in the pyrolysis at 300 \({}^{\circ}\)C of the untreated and acid hydrolyzed _Ochroconis lascauxensis_ melanin. Figure 2: Untreated and acid hydrolyzed _Ochroconis lascauxensis_ melanin pyrolyzed at 300 \({}^{\circ}\)C. Peaks refer to Table 2.  
The untreated melanin is characterized by the presence of huge peaks corresponding to fatty acids: hexadecanoic (peak 87), octadecaenoic (peak 98), octadecenoic (peak 99), and octadecanoic (peak 100) acids. Of minor intensity were the peaks of tetradecanoic acid (76) and the methyl esters of hexadecanoic (85), octadecadienoic (93), octadecenoic (94), and octadecanoic (95) acids. Fatty acid derivatives were the \(\gamma\)-lactone of hydroxyhexadecanoic (peak 97) and \(\delta\)-lactone of hydroxyoctadecanoic (peak 106) acids and hexadecanoic acid dodecyl ester (peak 111). Tetadecylfuran (peak 84) was also relevant.