# GC- and UHPLC-MS Profiles as a Tool to Valorize the Red Alga Asparagopsis armata+
## 3 Results and Discussion
### GC-MS of Lipophilic Extract

Table 4: Tentative identified compounds on dichloromethane extract (extract A) from dried _A. armata_ by GC-MS. The results in Table 4, graphically summarized in Figure 4, clearly show the predominance, in this lipophilic extract, of halogenated compounds (54.8%), being 40.6% dibromine mono-unsaturated alcohols and 14.2% mono-bromine and mono-chloride compounds. The most abundant compound in the extract (1,4-dibromobutenol, Rt 15.5 min) belongs to this class (68.8% of the total halogenated compounds and 37.8% of the total identified compounds). The presence of one or more halogen atoms, chlorine, or bromine, in the chemical structure of several of the identified compounds is assumed, with a high degree of certainty, from the characteristic isotopic pattern of each chemical element. The bromine exists as two isotopes in approximately equal amounts of atomic mass 79 and 81, while chlorine has 2 isotopes of atomic mass 35 and 37 in a ratio of approximately 3:1. In the case of the most abundant compound, at Rt 15.5 min, the presence of 2 bromine atoms is deduced from the peak corresponding to molecular ion [M]\({}^{\star\star}\) at _m_/_z_ 300/302/304 (a very weak signal) in the ratio of 1:2:1. The mass spectrum of this compound also shows the base peak at _m_/_z_ 75, corresponding to [HOSi(CH\({}_{3}\))\({}_{2}\)]\({}^{+}\), and the second most intense peak at _m_/_z_ 285/287/289 (also in a 1:2:1 ratio), corresponding to [M-15]\({}^{+}\) (loss of a methyl group from the TMS ether moiety). These signals support the hypothesis that the compound at Rt 15.5 min is a silylated primary alcohol [33], with two bromine atoms as substituents. Thus, it can be deduced that the compound in the extract will have a molecular mass of 230 corresponding to the chemical formula C\({}_{4}\)H\({}_{6}\)OBr\({}_{2}\), suggesting the presence of a double bond in the basic structure of dibromo butanol. The greatest diagnostic value is the fragments with _m_/_z_ at 131/133 and 137/139. The presence of these peaks, with identical intensity in each pair, shows that the fragmentation of the molecule gives rise to fragments containing one bromine atom each, being a strong indication of bromine atoms on different carbons. The peak at _m_/_z_ 131/133 will correspond to the fragment [C\({}_{4}\)H\({}_{4}\)Br]\({}^{+}\), resulting from loss of HBr by the molecular ion, following a 8-chain loss, indicating that the bromine atoms are found in the carbons 1 and 4. The peak at _m_/_z_ 137/139 could result from loss of a methyl from the silyloxyl group, followed by bonding of the resulting siliconium ion to the terminal bromine atom, and a final rearrangement [33] to originate the fragment [BrSi(CH\({}_{3}\))\({}_{2}\)]\({}^{+}\). Comparing the mass spectrum of 1,4-dibromobuten-1-ol (15.5 min) with that exhibited by the compound at 23.7 min, it is concluded that both are dibrominated mono-unsaturated alcohols with molecular formula C\({}_{4}\)H\({}_{6}\)OBr\({}_{2}\), which mean they are isomers. They have a very similar fragmentation pattern [M-CH\({}_{3}\)]\({}^{+}\) at _m_/_z_ 285/287/289, [BrSi(CH\({}_{3}\))\({}_{2}\)]\({}^{+}\) at _m_/_z_ 137/139, and the base peak at _m_/_z_ 73 ([Si(CH\({}_{3}\)))\({}_{3}\)]\({}^{+}\), being the last one ubiquitous to the spectra of TMS derivatives. The most significant differences are the absence of signals at _m_/_z_ 131/133 and  
Figure 4: Graphical presentation of the percentage of each class of compounds dichloromethane extract of _A. armata._  
the presence of the peak at _m/z_ 197/199/201 corresponding to the fragment [C\({}_{3}\)H\({}_{3}\)Br\({}_{2}\)]\({}^{+}\), resulting from an \(\alpha\)-cleavage with retention of the 2 bromine atoms and the double bond on the cation. These fragments suggest that the difference between the compounds at 15.5 and 23.7 min is the position of the bromo substituents. These two compounds are the only di-halogenated compounds identified in the extract and correspond to 166.2 mg/100 g of dry algae (40.6% of identified compounds).