## 3 Isolation and Biodiversity of Monoterpenes from Macroalgae
### Monoterpenes Isolated from Different Macroalgae Species
[17] first reported -CHCl\({}_{2}\) moiety at C-1 position of three new ocimeene-type polyhalogenated monoterpenes, Doralides A-C (**52**-**54**), as well as three known compounds (**55**-**57**) from _Plocamium corallorhiza_ ([PERSON]) [PERSON] [PERSON] collected from the coast of South Africa. [PERSON] et al. [18] observed that _P. corallorhiza_ contained unusual moieties attached to monoterpene skeleton. They isolated four new unstable halogenated monoterpene aldehydes (**58**-**61**) which were not detected in the algae collected from the west coast of South Africa, but they were present in the macroalgae from the southeastern coast. According to the similar structure to known compounds, such as plocoralide B, they suggested that the compounds (**58**-**61**) were degradation products formed during the isolation. The aldehyde group at C-1 is usually characteristic to terrestrial monoterpenes but they were first to report this functional group in marine halogenated monoterpenes. [PERSON] et al. [64] described the isolation and characterization of two novel monoterpenes, halogenated cyclohexanone derivatives, plaxenone A and plaxenone B (**62**, **63**) from _Plocamium maxillosum_ ([PERSON]) [PERSON]. A recent study on _Plocamium angustum_ ([PERSON]) [PERSON] and [PERSON] from New Zealand revealed the presence of new polyhalogenated monoterpene with tetrahydropyran ring, costatone C (**64**), isolated from this species for the first time [65], while costatone A (**65**) [66] and costatone B (**66**) [67] were isolated earlier from different _Plocamium costatum_ ([PERSON]) [PERSON] and [PERSON] samples collected in South Australia. Several monoterpenes are very unstable and during their isolation degradation can occur. During the last few years, a new hyphenated technique, high-performance liquid chromatography-nuclear magnetic resonance (HPLC-NMR), has been employed for obtaining the chemical profile of the genus _Plocamium_. This technique is non-destructive and all of the isolated compounds are fully recovered. [PERSON] and [PERSON] [68] successfully used this technique to obtain phytochemical profile of _Plocamium metensii_ ([PERSON] [PERSON] which represents the first application of this technique on marine algae. While they obtained the mixture of compounds and isolated other compounds besides monoterpenes, [PERSON] et al. [69] used this technique to obtain and identify two pure monoterpene compounds. First, they obtained an already known compound, plocamenone (**67**), from _Plocamium angustum_ and then they identified its unstable double bond isomer isoplocamenone (**68**) and concluded that this is a very valuable method for the analysis of unstable compounds. On the other hand, [PERSON] et al. [67] used the HPLC-UV-MS-SPE-NMR technique for determination of halogenated monoterpenes from _P. costatum_ and _P. hamatum_. This technique is relatively new and it combines traditional and hyphenated chromatographic techniques which employs solid-phase extraction (SPE) as an interface between traditional chromatography, ultraviolet spectroscopy (UV), liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR). It has the advantage over HPLC-NMR technique because the analytes trapped on SPE cartridge are eluted with minimal volumes of solvent directly into NMR flow-probe. The results indicated new halogenated monoterpenes including the compounds (**66**, **69**-**75**), and two known halogenated monoterpenes (**76**) and (**77**). The compound (**70**) was isolated as the mixture with compound (**71**) at the ratio of 2:1. These two compounds showed similar \({}^{1}\)H NMR spectrum with only very slight differences in their chemical shifts (\(\Delta\delta_{\rm H}\) 0.1), indicating that these two compounds are stereoisomers. However, their absolute configuration was unassigned. Similar as genus _Plocamium_, genus _Portieria_ showed differentiation of monoterpene content depending on the collection location, as was shown by [PERSON] et al.