**3.2** *Chlorophyta*

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

cancer chemoprotective activities [11].

nian corals [18, 19].

arrangement of flagella:

terrestrial environments

**2. Marine biodiversity and chemodiversity**

**3. Systematics and taxonomy of macroalgae**

high boiling and low volatility. The chemical composition of essential oils is principally composed of terpenes derived from the mevalonate and methylerythritol pathways [2]. Monoterpenes and sesquiterpenes are commonly the main contributor group of compounds identified in several essential oils [3]. Moreover, some essential oils contain other chemical classes, such as phenols (derived from shikimic acid pathway); the saturated and unsaturated fatty acids, acting as biosynthetic precursors; alkanes; and, more rarely, nitrogen and sulfur derivatives [4]. The essential oils play an important role in the allelopathic interaction of plants. They are involved in defense and signaling processes [5] and attraction of pollinating insects [6]. They constitute an important raw material source for the pharmaceutical, food, cosmetics, and perfume industries [7]. The essential oils of different plants exhibit a broad spectrum of biological activities. They show antibacterial activities attributed, in some cases, to the presence of phenolic compounds [8]. The literature reports also the excellent antioxidant [9], anti-inflammatory [10], and

More than 70% of the Earth's surface are oceans and seas. It is not surprising to affirm that the marine environment is characterized by an important biodiversity in comparison to terrestrial organisms. In 2010, 230,000 marine species were listed [12]. Consequently, with the increase of biological space (biodiversity), more novel metabolites (high chemodiversity), involved in ecological interactions, are produced in order to ensure easy adaptation of the species [13, 14]. Furthermore, the chemodiversity of the marine ecosystem has no equivalent in terrestrial environment. The large groups of the sea organisms, such as red algae and soft corals, are known to produce a great variety of quite unique secondary metabolites, such as highly halogenated terpenes, definitely due to the high halogen concentration of the sea water, and acetogenins from *Laurencia* (Rhodophyta) [15, 16], toxic polyketide from sponges [17], and prostaglandins from the gorgo-

It was the French botanist Joseph Pitton de Tournefort (1656–1708) who grouped the species into genera and then the Swedish naturalist Carl von Linné (1707–1778), founder of systematics (or taxonomy), who classified the organisms into increasingly large groups: species, genera, families, orders, classes, phylum (or phyla), and kingdoms. Algae, according to Feldmann and Chadefaud [20, 21], are classified into six branches differentiated by the nature of the pigments, the nature and situation of carbohydrate reserves, and the presence or absence, number, and

• Euglenophycophyta: unicellular freshwater algae rich in organic matter

• Chlorophycophyta: green algae; single or multi-cell; marine, freshwater, and

• Chrysophycophyta: most are single-celled; freshwater and sea water

• Pyrrophycophyta: unicellular marine or freshwater algae

**4**

There are estimated to be at least 600 genera with 10,000 species within the green algae [24] recognized inhabiting mostly in the water's surface of the calmer seas. They are characterized by the presence of chloroplasts with two envelope membranes, stacked thylakoids, and chlorophyll a and b. In their fundamental biochemistry (photosynthetic pigments, storage polysaccharides, etc.), the Chlorophyta resemble the higher plants [24].
