Plant derived additives: Why is it important to classify them?

Essential oils

According to some website definitions, an essential oil is “a concentrated hydrophobic liquid from plants, containing volatile chemical compounds that are easily evaporable at normal temperatures.” The term “essential” is not used in the same sense as when talking about an amino acid or an essential fatty acid (necessary for animals). It is used in the sense that it contains the essence of a plant’s fragrances. Interestingly, when analyzing the chemical composition of these, they are neither oils nor fatty acids, as they only have a hydrophobic quality. Some common examples of essential oils used in animal feed are: orange peel, oregano, thyme, rosemary, and cinnamon oil.

The most common active compounds of such oils are thymol, carvacrol, cinnamaldehyde or limonene. Some commercial products are enriched or formulated with synthetically manufactured active compounds (rather than naturally extracted) to ensure product composition quality. Most of them are all marketed as essential oils.

Functional oils

Functional oils are those that have properties beyond their energy value (Bess et a., 2012). These activities vary depending on the type of oil. These include, but are not limited to, antioxidant, antimicrobial and/or anti-inflammatory properties.

All essential oils are functional oils, but not all functional oils are essential oils, as many functional oils are not volatile or fragranced.

Examples of this are castor oil, cashew peel oil and medium-chain fatty acids, which are hydrophobic compounds, but are not volatile and do not contain a fragrance. Therefore, they cannot be classified as essential oils. Functional oils may or may not be chemical oils. For example, castor oil and medium-chain fatty acids are triglycerides or fatty acids while cashew peel oil is a mixture of alkylphenols and their polymers. This highlights the wide variety of chemical compounds that are present within these products.

Botanical or phytogenic products

Botanicals orphytogenic products are synonymous and refer to the whole or processed parts of a plant, such as the roots, leaves or bark (Díaz-Sánchez et al., 2015). The terms “botanical” or “phytogenic compound” would also include all functional oils and as explained above, all essential oils would also be included within the group of functional oils.

Figure 1. Illustration of terminology used to describe essential oils, functional oils, and botanical or phytogenic products.

Botanical or phytogenic products also include non-hydrophobic compounds such as fructooligosaccharides (also derived from plants). This example shows the great variety of substances within this group, both from a chemical standpoint and in regards to their mechanism of action.

The importance of using the right terminology

Using the right term to describe a product goes beyond using good scientific terminology. As it represents the first step in making the right decision regarding which product is the most appropriate. Phytogenic compounds are very different and their activities also vary greatly. No one would venture into choosing an antibiotic by chance to prevent or treat any disease. A good professional will decide upon an antibiotic, based on the type of compound (for example, a beta-lactam, a macrolide or an ionophore) that is considered the most suitable to treat the pathology under consideration. This same logic should apply to phytogenic compounds. For example, thymol and carvacrol (present in oregano) are different from cardol and cardanol (present in cashew peel oil) and are all different from sanguinarine (present in the Macleaya cordata plant).

Figure 2. Comparison of the chemical structure of three phytogenic products.

Conclusion

It is very important that consumers demand that suppliers of this type of products offer clear information regarding their composition, and activity. As well as requesting quality controls that validate the use of such products, like it is done with any other “conventional” food additive. This must be the base of a proper and efficient use for these alternative products. Which hold great potential, and will probably become a long lasting asset within the feed additive market.

Source: Abstract taken and modified modified from “Correcta clasificación de los aditivos extraídos de plantas.”