*4.2.2 Sulfur compounds in the genus* Dictyopteris

The organic sulfur compounds are widespread in terrestrial and marine plants [104]. Due to the relatively high sulfate concentration in seawater, and the particularly high sulfide concentration in anoxic environments, it was expected that many sulfides would occur in the marine environment [104]. They are reported in few taxa and act as chemical defenses against herbivores [105]. As part of this single group, some *Dictyopteris* species (*Phaeophyceae, Dictyotales*) are acknowledged to produce considerable amounts of sulfur-containing compounds (**Figure 5**); many of them were found in *D. polypodioides* [106]. Among the first seaweeds discovered to produce organic sulfur compounds were the Hawaiian brown algae

**13**

*Algae Essential Oils: Chemistry, Ecology, and Biological Activities*

metabolites seem to be restricted to the *Dictyopteris* genus.

*4.2.3 Halogenated terpenes from red algae* (Rhodophyta)

*D. plagiogramma* and *D. australis* [107]. Eight compounds containing a C11 unit attached to a sulfur atom with oxygen substituent at C-3 have been isolated and characterized [47]; most of these compounds appear to be biosynthetically related to C11 hydrocarbon pheromones and may originate from oxidative degradation of highly unsaturated eicosanoids (arachidonic acid) via oxygenated intermediates. The 1-undecen-3-ol, present in essential oils from *Dictyopteris* spp., may represent the common precursor to both classes of C11 compounds [95, 107]. The C11 sulfur

As noted previously, the halogenated compounds are common in the marine environment. They are formed among diverse species such as bacteria, sponges,

Rhodophyta class possesses a privileged biosynthetic pathway for organohalogen compounds. A huge number of organohalogens have been isolated from most genera of Rhodophyta [108, 109]. The genus *Laurencia* is the most prolific source of sesquiterpenes among all marine macroalgae, most notably, the halogenated sesquiterpenes belonging to a variety of chemical skeletons including chamigrane, bisabolane, laurane, snyderane, and brasilane along with some rearranged derivatives [110, 111]. Inquisitively, bromine is the most occurring halogen in marine natural products, despite that its concentration in seawater is lower than that of chlorine. To the best of our knowledge, the isolation of halogenated monoterpenes is limited to three families of marine red algae, the *Plocamiaceae* and *Rhizophyllidaceae* [112, 113], and *Ceramiaceae* [114]. The chemical structure of Rhodophyta monoterpenes is characterized by multiple halogen substitutions (chlorine and bromine) and by uncommon carbon cycle structures in the case of cyclic compounds. All halogenated acyclic seaweed monoterpenes appear to be derived from the halogenation of myrcene or ocimene [114]. As indicated in the rich bibliography dedicated to this purpose [45, 113, 115–117], the almost majority of halogenated terpenoids (monoterpenes, sesquiterpenes, and diterpenes) described in red algae are isolated from crude solvent extracts. Monoterpenes, even halogenated, are characterized by high volatility; they are the main constituents of essential oils and volatile fractions. The selective supercritical fluid extraction, by adjusting time and pressure, of Santa Cruz *P. cartilagineum* [118] has allowed the

molluscs, algae, and several marine worms. Among all marine algae, the

isolation of eight halogenated monoterpenes (81–87) (**Figure 6**).

chemical composition of essential oils and volatile fraction of red algae.

The first brominated sesquiterpene (**Figure 8**) ketone spirolaurenone (96), chamigrane skeleton, was described in the essential oil of *L. glandulifera* (Japan) in 1970 [123], followed by the 10-Bromo-7-chamigren-2-one (97) in the same species [124]. The preintricatol (98), found in *L. gracilis* [125], seem to be the precursor of halogenated sesquiterpenes of chamigrene type. The Puertitols A (99) and B (100) were isolated from *L. obtusa* [126] as well as the metabolites (101) and (102) from *L. caespitosa* [127]. An important halosesquiterpene characteristic of the family

The same species collected along the central coast of Chile [119] conduct to the isolation of eight monoterpenes (88–95), four of which are based on the 1-(2-chlororovinyl)-2,4,5-trichloro-1,5-dimethylcyclohexane skeleton (**Figure 7**). As in the genus *Plocamium*, the chemical study of the genera *Portieria* [120], *Ochtodes* [121], and *Microcladia* [114, 122] has led to the isolation of over 100 of acyclic, cyclic, and tetrahydrofuran halogenated monoterpenes. A large number of halogenated sesquiterpenes, more than monoterpenes, were described in red algae especially in the genus *Laurencia* (Ceramiales). Although the sesquiterpenes are also volatile compounds, we describe in this paragraph only the ones reported in the

*DOI: http://dx.doi.org/10.5772/intechopen.91672*

**Figure 5.** *Sulfur compounds of the genus* Dictyopteris*.*

*Algae Essential Oils: Chemistry, Ecology, and Biological Activities DOI: http://dx.doi.org/10.5772/intechopen.91672*

*Essential Oils - Bioactive Compounds, New Perspectives and Applications*

not have a determined biological function [94].

*4.2.2 Sulfur compounds in the genus* Dictyopteris

However, it has been verified that the biological activity is associated with a single constituent which may not be the major product. These by-products sometimes play a role of modulator of response of the gametes, and in general, they do

The organic sulfur compounds are widespread in terrestrial and marine plants [104]. Due to the relatively high sulfate concentration in seawater, and the particularly high sulfide concentration in anoxic environments, it was expected that many sulfides would occur in the marine environment [104]. They are reported in few taxa and act as chemical defenses against herbivores [105]. As part of this single group, some *Dictyopteris* species (*Phaeophyceae, Dictyotales*) are acknowledged to produce considerable amounts of sulfur-containing compounds (**Figure 5**); many of them were found in *D. polypodioides* [106]. Among the first seaweeds discovered to produce organic sulfur compounds were the Hawaiian brown algae

**12**

**Figure 5.**

*Sulfur compounds of the genus* Dictyopteris*.*

*D. plagiogramma* and *D. australis* [107]. Eight compounds containing a C11 unit attached to a sulfur atom with oxygen substituent at C-3 have been isolated and characterized [47]; most of these compounds appear to be biosynthetically related to C11 hydrocarbon pheromones and may originate from oxidative degradation of highly unsaturated eicosanoids (arachidonic acid) via oxygenated intermediates. The 1-undecen-3-ol, present in essential oils from *Dictyopteris* spp., may represent the common precursor to both classes of C11 compounds [95, 107]. The C11 sulfur metabolites seem to be restricted to the *Dictyopteris* genus.

#### *4.2.3 Halogenated terpenes from red algae* (Rhodophyta)

As noted previously, the halogenated compounds are common in the marine environment. They are formed among diverse species such as bacteria, sponges, molluscs, algae, and several marine worms. Among all marine algae, the Rhodophyta class possesses a privileged biosynthetic pathway for organohalogen compounds. A huge number of organohalogens have been isolated from most genera of Rhodophyta [108, 109]. The genus *Laurencia* is the most prolific source of sesquiterpenes among all marine macroalgae, most notably, the halogenated sesquiterpenes belonging to a variety of chemical skeletons including chamigrane, bisabolane, laurane, snyderane, and brasilane along with some rearranged derivatives [110, 111]. Inquisitively, bromine is the most occurring halogen in marine natural products, despite that its concentration in seawater is lower than that of chlorine. To the best of our knowledge, the isolation of halogenated monoterpenes is limited to three families of marine red algae, the *Plocamiaceae* and *Rhizophyllidaceae* [112, 113], and *Ceramiaceae* [114]. The chemical structure of Rhodophyta monoterpenes is characterized by multiple halogen substitutions (chlorine and bromine) and by uncommon carbon cycle structures in the case of cyclic compounds. All halogenated acyclic seaweed monoterpenes appear to be derived from the halogenation of myrcene or ocimene [114]. As indicated in the rich bibliography dedicated to this purpose [45, 113, 115–117], the almost majority of halogenated terpenoids (monoterpenes, sesquiterpenes, and diterpenes) described in red algae are isolated from crude solvent extracts. Monoterpenes, even halogenated, are characterized by high volatility; they are the main constituents of essential oils and volatile fractions. The selective supercritical fluid extraction, by adjusting time and pressure, of Santa Cruz *P. cartilagineum* [118] has allowed the isolation of eight halogenated monoterpenes (81–87) (**Figure 6**).

The same species collected along the central coast of Chile [119] conduct to the isolation of eight monoterpenes (88–95), four of which are based on the 1-(2-chlororovinyl)-2,4,5-trichloro-1,5-dimethylcyclohexane skeleton (**Figure 7**). As in the genus *Plocamium*, the chemical study of the genera *Portieria* [120], *Ochtodes* [121], and *Microcladia* [114, 122] has led to the isolation of over 100 of acyclic, cyclic, and tetrahydrofuran halogenated monoterpenes. A large number of halogenated sesquiterpenes, more than monoterpenes, were described in red algae especially in the genus *Laurencia* (Ceramiales). Although the sesquiterpenes are also volatile compounds, we describe in this paragraph only the ones reported in the chemical composition of essential oils and volatile fraction of red algae.

The first brominated sesquiterpene (**Figure 8**) ketone spirolaurenone (96), chamigrane skeleton, was described in the essential oil of *L. glandulifera* (Japan) in 1970 [123], followed by the 10-Bromo-7-chamigren-2-one (97) in the same species [124]. The preintricatol (98), found in *L. gracilis* [125], seem to be the precursor of halogenated sesquiterpenes of chamigrene type. The Puertitols A (99) and B (100) were isolated from *L. obtusa* [126] as well as the metabolites (101) and (102) from *L. caespitosa* [127]. An important halosesquiterpene characteristic of the family

**Figure 6.** *Monoterpenes isolated Santa Cruz* Plocamium cartilagineum*.*

**Figure 7.**

*Monoterpenes isolated from* Plocamium cartilagineum *(Chile).*

Rhodomelaceae is elatol (103); it is isolated from *L. elata* [128] and from several other species of *Laurencia* [129]. An exhaustive literature review has described the chemical structure data and biological activities of the halogenated sesquiterpenes of red algae [130, 131].
