Chemical Composition and Biological Activity

**3**

**Chapter 1**

**Abstract**

*Mohamed El Hattab*

activities of volatile products.

**1. Introduction**

Algae Essential Oils: Chemistry,

Ecology, and Biological Activities

This chapter focuses on the essential oils and volatile fractions of seaweed. It includes an introduction to the essentials and volatile fractions and the main chemical classes found. This part is completed by a presentation of the fundamental aspects of biodiversity and the chemodiversity of the marine environment followed by the taxonomy and systematics of marine macroalgae. The heart of this chapter concerns the chemistry of volatile products extracted from marine algae. It reports the specificities of the marine natural products chemistry in comparison to that of terrestrial organisms. The description of volatile compounds in seaweed is divided into two parts, the first reports the common compounds identified in main volatile fractions and the second cover the specific volatile components. These include C11 hydrocarbons, sulfur compounds, and halogenated hydrocarbons. These latter are playing a very important role in communication and chemical defense. The last part includes aspects of chemical ecology and biological

**Keywords:** essential oils, marine algae, C11 hydrocarbons, sulfur compounds,

The origin of the distillation methods is an invention attributed to the Arab alchemists and to the Persian scientist Avicenna (980–1037) with the establishment of the steam distillation process. Avicenna invented a setup to prepare essential oils and aromatic waters. Essential oils, sometimes called quintessence, are a very complex mixture of volatile compounds produced by the secondary metabolism in various plant organs (flowers, fruits, seeds, leaves, etc.) and algae. According to ISO and AFNOR standards, essential oils are defined as volatile composition obtained from raw materials by steam distillation and/or by cold expression from citrus peels (known as essences) [1]. The definition of an essential oil excludes other volatile fractions obtained by steam distillation and/or hydrodistillation from the crude extract resulted from solvent extraction, supercritical fluid extraction, solventand water-free microwave extraction, ultrasound-accelerated solvent extraction, solid-phase microextraction, and headspace extraction. The chemical composition of essential oils and volatile fraction could be quite similar. Moreover, it should be pointed out the clear difference between the physical and chemical properties of essential oils and fixed or fatty oils. The fixed oils contain mainly triglycerides, esters composed of three saturated fatty acids linked to glycerol, characterized by

halogenated sesquiterpenes, chemical ecology, biological activities
