**6.2. Waxes**

Waxes are lipoidal matter constituting mainly from long aliphatic chains that may contain one or more functional groups. They may contain hydroxyl groups as in the case of primary and secondary long-chain alcohols that are frequently present in the form of esters. Others contain unsaturated bonds, aromatic systems, amide, ketonic, aldehydic or carboxylic functional groups. On the other hand, synthetic waxes constitute of long-chain hydrocarbons (alkanes or paraffins) that lack functional groups. They are similar to the fixed oils and fats since they are esters of fatty acids, but with the difference that the alcohol is not glycerin. The seeds of *Simmondsia chinensis* yield the liquid wax, jojoba wax, which consists of straight chain esters of fatty acids and alcohols [42]. Jojoba wax has anti-inflammatory, anti-aging and wound healing activities, and hence it can be utilized in several skin conditions. Jojoba wax has also been used in topical medications to enhance drug absorption. In addition, it is used in skin care products and in cosmetics such as sunscreens and moisturizers [43].

### **6.3. Essential oils**

Essential oils are volatile aromatic complex mixtures of relatively low molecular weight compounds. Although they may contain up to 60 components, yet they are characterized by the presence of two or three major components at fairly high concentrations (20–70%) compared to other components present in trace amounts. For example, *Origanum compactum* essential oil contains carvacrol (30%) and thymol (27%) as major components. Linalol is the major component of *Coriandrum sativum* essential oil reaching up to 68%. Other examples are *Artemisia herba-alba* essential oil which contains α- and β-thuyone (57%) and camphor (24%) as major constituent, *Cinnamomum camphora* essential oil with 1,8-cineole (50%) as major constituent and finally *Mentha piperita* essential oil with menthol (59%) and menthone (19%) being the major constituent. Generally, these major components determine the biological properties of the essential oils [44]. They have many and important medical uses such as antiseptic, antimicrobial, analgesic, sedative, anti-inflammatory, spasmolytic and locally anesthesic remedies. They are also used as fragrances in embalmment and in food preservation [45].

surfaces or skin. Here, they produce a coating of "slime" that soothes and protects exposed or irritated surfaces of the gastrointestinal tract. They are used extensively in the management of inflammatory digestive disorders, especially when there is ulceration. Their relative indigest-

Plants Secondary Metabolites: The Key Drivers of the Pharmacological Actions of Medicinal Plants

http://dx.doi.org/10.5772/intechopen.76139

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According to the abovementioned data, there are several classes of secondary plant metabolites that are responsible for the biological activities of herbal medicines. Eventually, secondary plant metabolites exert their action on molecular targets that differ from one case to the other. These targets may be enzymes, mediators, transcription factors or even nucleic acids. The use of herbal medicines should be based on comprehensive phytochemical studies for the determination of the chemical constituents of the herbs involved. Hence the knowledge of the resultant pharmacological and toxicological effects can be deduced, as well as the possible synergistic or antagonistic effects due to the use of multiple component herbal formulae. For this reason, the isolation and structural elucidation of secondary plant metabolites, though ancient, is still a huge and fast growing approach, and the techniques used for separation and

Pharmacognosy Department, Pharmaceutical Science Division, National Research Center,

[1] Seigler DS.Plant Secondary Metabolism. New York: Springer Science: Business Media; 1995. ISBN: 978-1-4613-7228-8; ISBN: 978-1-4615-4913-0 (eBook). DOI: 10.1007/978-1-4615-4913-0

[2] Jones ME, Kossel A. A biographical sketch. Yale Journal of Biology and Medicine.

[3] Bourgaud F, Gravot A, Milesi S, Gontier E. Production of plant secondary metabolites:

[4] Bennets HW, Underwood EJ, Shier FL. A specific breeding problem of sheep in subterranean clover pastures in Western Australia. Australian Veterinary Journal. 1946;**22**(1):2-12

[5] Goławska S, Sprawka I, Łukasik I, Goławski A. Are naringenin and quercetin useful chemicals in pest-management strategies? Journal of Pest Science. 2014;**87**(1):173-180

ibility and hydrophilic properties have important influences on bowel behavior [47].

**8. Conclusion**

**Author details**

Giza, Egypt

**References**

1953;**26**(1):80-97

analysis are advancing continuously.

Rehab A. Hussein\* and Amira A. El-Anssary

\*Address all correspondence to: rehaba.husein@yahoo.com

A historical perspective. Plant Science. 2001;**161**:839-851
