All about plant extraction

PLANT EXTRACTION

AN ACTIVITY BASED ON RIGOROUS STANDARDS

Dedicated to extracting active principles from plants. However, the term "extract" is often improperly used, since not all separation processes enable obtaining a plant extract.

An alliance of science and tradition

Ancient origins.

The origin of extracting active principles from plants is lost in the night of time. Humans learned very early about plant benefits and developed the first techniques to obtain what we now call an "extract". These first extracts were obtained mainly from water-based processes or alcohol fermentation using procedures such as infusion, maceration, decoction or distillation.

The simplicity of these first procedures, as well as the tools, materials and ways of heating, required experience and know-how rather than science.

Even today, in spite of precise automation, more adequate equipment, advances in process engineering and analysis, as well as new extraction technologies such as high pressure, microwaves or ultrasound, the notion of plant extraction expertise still rests on the proper association between the mastery of current technology and tradition.

What is a plant extract?

A plant extract must, by definition, be obtained from a solid-liquid extraction.

Solid-liquid extraction is defined as an operation to separate elements contained in a solid body by solubilization with a solvent, and it may be followed by purification.

The extract is contained in the solvent. If the solvent is an edible solvent, it is not necessary to dissociate it from the extract. If the solvent is not an edible solvent, separation allows obtaining a dry extract.

What are the quality criteria?

Selection of raw materials, choice of solvent, process utilization and equipment performance are determining factors. These multiple parameters must be professionally combined. Only their proper combination allows obtaining high-quality plant extracts.

The oldest and largest floral reserve

Over 200,000 plant species have now been identified, but only one percent of existing plants have been studied scientifically.

A passing fad for some, an alternative medicine for others, phytotherapy is the oldest form of medical treatment. For centuries, humans have searched out the secrets of plants.

This began around 3000 B.C. In the sixth century B.C., Hippocrates used plants as a remedy. The first book on medical treatments using plants was written at the time of the crusades and monks cultivated medicinal gardens.

Phytotherapy today

Phytotherapy in the twentieth century combines tradition and technology to provide greater guarantees.

Phytotherapy is the result of thousands of years of experience and is now scientifically supported.

Backed by clinical and pharmacological studies, the success of current phytotherapy results from improved knowledge of plants and a qualitative selection of the varieties used.

Progress in extraction methods leads to improved conservation of plant integrity.

New plant properties have been discovered. Methods of administration have been multiplied and modernized (tablets, capsules, etc.) to meet new consumer demands.

DEFINITION OF PLANT EXTRACTS

The definition of plant extracts is vague for some. Simple powders made from crushed plants are often commercially known as "extracts," undoubtedly because of the fact that water is removed from the plants through a drying process.

Thus, before we can talk about extracts, we need to recall the technical definition of extraction.

A box indicates the extraction procedures using raw plant materials. These processes obtain a liquid from a solid origin, in contrast to purification processes that always need a solubilization step.

Except for the case of pressing, where ingredients of liquid origin are extracted, an extract is obtained only from a solid-liquid extraction, which may be followed by purification.

The contact phase corresponds to the mass transfer step. The first phase of separation cannot be dissociated from the contact phase because it enables separating the used solid from the enriched solvent, usually by simple filtration. At this stage, the extract is contained in the solvent.

If the solvent is edible, it is not necessary to proceed to a second separation that removes the solvent and leaves a dry extract. The example of coffee, probably the most-consumed extract in Europe, illustrates this process.

Coffee (the raw material) is put in contact with water in a percolator at a certain temperature and for a certain length of time. The first separation is done with a paper filter, which enables drinking the coffee directly. If we do another separation, we obtain instant coffee.

 There is no other way to carry out a solid-liquid extraction. However, it is often possible to:

Combine these processes with each other or with other procedures such as distillation, steam distillation, rectification, etc.

Use different solvents successively or mixed together.

Assist the extraction process with high pressure (supercritical CO2), microwaves, ultrasounds, etc.

The combination of these parameters gives rise to an almost limitless number of different extracts. This is especially true since intrinsic extraction parameters such as temperature, pressure, pH, or duration, as well as the nature and type of solvent, solvent ratio, type of equipment or stirring, must also be controlled.

And we mustn't forget raw materials, probably the most important factor and the most difficult to master. Extractors must guarantee constant product quality even though the quality of the plant to be extracted can vary according to weather conditions, cultural practices or geographic origin, even though the plant variety is the same. Simple operations like grinding can considerably modify extraction results and, in particular, extraction specificity.

The extract obtained from solid-liquid extraction as defined below is thus a highly technical product which nonetheless relies on the traditional know-how specific to each industry. The table below lists some of the names of traditional extracts by implementation procedure and industry. We can see that an identical extraction process does not always have the same name.

There are also a number of technical and commercial names on the market related to biological properties (diuretic extract), composition (extract titered in polyphenols), solvents used (hydroalcoholic extract), botanical origin (ginkgo extract) or to a combination (hydroalcoholic ginkgo extract, for instance).

In conclusion, the number and variety of parameters used in plant extraction make it impossible to model them fully even today. Although an increasing amount of scientific knowledge in domains as diverse as botany, analysis or process engineering is required for proper extraction, it is based above all on a keen appreciation of balance between ingredients and processes.