Index
- The chemical constituents of herbal drugs
- Intrinsic variability factors
- Environmental variability factors
- Variability factors dependent on the preparation process
- Standardization of extracts
- Control and quality
- Conclusions
- Insights
Questions and answers
The chemical constituents of herbal drugs
Plants are an important resource for human life , as evidenced by their numerous fields of application. Many are used in the health field , such as officinal or medicinal plants , to treat pathologies or improve the state of well-being, however it is necessary to keep in mind that plants are not born with the specific intent of treating humans. Only the great experience of the tradition of use, supported in some cases by modern scientific evidence, has led man to select some plant species useful for health.
The variety of phytochemicalspresent in the plant kingdom has evolved to allow plants to communicate, defend and survive in different ecosystems. In most cases, the physiological function of these molecules is not known; however, some of these act as deterrents against herbivorous animals or as a lure for pollination vectors. Herbal preparations consist of extracts, extremely complex mixtures of different molecules. This complexity often favors the biological activities of interest but, on the other hand, makes it more difficult to understand the molecular mechanisms underlying an effect and therefore the study and identification of new molecules with pharmacological activity.
The set of chemical constituents that contribute, with different roles, to the biological activity of a plant extract and those that can favor the activities of the active ingredients, is called phytocomplex .
Whatever the use of a phytocomplex , both in the medical and health fields, it is therefore essential to identify its chemical composition .
The factors that influence the presence of these molecules, including the active ingredients contained in drugs, that is the part of the plant containing the active ingredients, are numerous; these can be divided between intrinsic factors , linked to the genetic heritage of the plant itself, and extrinsic factors, such as environmental and conservation variables.
Intrinsic variability factors
Among the factors responsible for the variations of chemical constituents in a plant we find the genetic characteristics and the stage of development (age) of the plant organism . In a given population, there may be individuals with genetic variations such as to manifest a different content of active ingredients .
These differences, found in the wild or promoted through cross breeding procedures, are used to select high-yielding individuals for cultivation purposes.
In order to guarantee a good yield , a medicinal plant must be harvested at the maximum content of active ingredients, a period that is called balsamic time. In general, the balsamic time corresponds to the end of the growth period of a plant, especially for annual or biennial plants.
In perennials the content of active ingredients grows usually with increasing age , but there are some exceptions, such as cinchona bark ( Cinchona calisaya L. ).
Environmental variability factors
Even environmental factors are able to influence the content of chemical constituents in a drug. The light is an essential factor both for the sustenance of the plant and for the synthesis of secondary metabolites, in fact plants grown in a little sunny setting often contain a lower content of active ingredients. Factors such as temperature , altitude and soil composition (presence of salts, humidity and pH) can change the production of secondary metabolites, because they alter the optimal growth conditions.
Finally, also the interaction with other plant organismspresent in the same habitat can influence the content of active ingredients of a certain species, this occurs thanks to the action of substances known as plant hormones. Furthermore, some plants produce and release molecules capable of inhibiting the growth and development of competing plants, through a phenomenon called allelopathy .
Variability factors dependent on the preparation process
A poor preservation of herbal drugs may be responsible for a deterioration of active ingredients , but also due to a bacterial or fungal contamination. From the moment a drug is collected, a decay process begins which involves changes in the organoleptic characteristics (smell, taste, color, etc.) and an alteration or loss of its chemical constituents. These variations are caused by spontaneous reactions due to chemical or physical factors , or reactions mediated by enzymes . The degrading enzymes that most influence drug preparation processes are: oxidase, peroxidase, hydrolase and isomerase .
The most used techniques in order toto minimize the alterations are: protection from sources of light and heat , drying , freezing , lyophilization (or also called cryodrying, is based on freezing and sublimation) and some methods (e.g. stabilization) aimed at reducing those enzymes involved in decay, up to the sterilization of drugs. L ‘ water provides an environment suitable for the operation of the enzymes, as well as a breeding ground for the proliferation of bacteria and mold, so the drugs are generally brought to the state of dehydration.
L ‘ drying results in an only temporary blockage of the enzymatic activity, which can resume after rehydration, while stabilization, a procedure carried out through ethanol vapors over 100 ° C, followed by drying, irreversibly inactivates the enzymes. Unfortunately, not all drugs can be subjected to high temperatures, due to the thermal instability of the active ingredients they contain.
Finally, before being sold, a drug must undergo an adequate decontamination procedure to break down the microbial load and bring it within the limits of acceptability set by the Pharmacopoeia . The decontamination can be practiced using various techniques: irradiation (by gamma rays, X-rays, electron beams), fumigation, heat (dry or steam) orhigh pressure treatment .
The choice of the best method is also based on the lower loss of bioactive molecules .
Main extraction techniques
A plant, before being used in the health field, in most cases undergoes an extraction process , through a series of more or less complex interventions, with the aim of recovering from the plant matrix the active ingredients necessary to exercise the biological activity sought.
If it is intuitive to imagine that the active ingredients can be concentrated in a specific part of the plant , such as leaves, tissues and roots, it is less known that starting from the same matrix it is possible, with different extraction techniques, to recover different molecules and therefore to have biological activities different from those expected.
The extraction process is a step that requires a detailed analysis of the best conditions , potentially different for each drug used, and must be carried out in such a way as to ensure decontamination without altering the chemical composition of the drug or leaving toxic residues.
Below is a list of the main extractive preparations in the vegetable field.
Preparations from fresh plant material
- Juices : products obtained by pressing ;
- Mother tinctures : liquid preparations obtained by maceration in ethyl alcohol;
- Essential oils : mixtures of volatile substances obtained by steam distillation , pressure or extraction with organic solvents or supercritical fluids.
Preparations from dry plant material
- Powders : obtained by crushing or shredding ;
- Infusions : made in water, previously brought to boiling temperature ;
- Decoctions : performed by boiling pulverized drugs ;
- Tinctures : liquid preparations obtained with alcohol generally through maceration or percolation ;
- Extracts with solvents : made with the use of different types of solvents, they are divided into fluids , soft or dry, depending on the degree of final evaporation of the solvent used.
Standardization of extracts
Each molecule endowed with a biological activity needs to reach a certain concentration to exert its effect.
The standardization is a requirement of the extract, which according to quantitative chemical analysis, determine the appropriate content of one or more active compounds in the batch analyzed in order to ensure their effectiveness. Standardization allows to reduce variability and to obtain comparable preparations by composition. Fundamental to this process is to define and correctly identify the botanical species to be used , as well as the spontaneous or cultivated origin.
Once the correct drying method has been chosen, the preparation method must be selected, together with the relevant suitable solvent, the concentration of the active ingredients is determined (titration).
If molecules with recognized biological activity are present inside the drug, these molecules must be used for quantification, often expressed in terms of minimum content. However, if the active constituents of a preparation are not known, one or more molecules must be selected as markers , for analytical purposes of quality control, even if in this case no information on the biological activity of the preparation can be attributed.
When the entire phytocomplex has an activity, it is not enough to define the concentration of a single molecule, but it is necessary to have a picture of the different components.
The application of these analyzes allows the realization of preparations with a relatively constant composition and, therefore, with a reproducible biological effect .
Control and quality
The quality control of plant preparations is the set of processes aimed at evaluating the botanical, phytochemical and pharmaco-toxicological characteristics of a product , in comparison with the standard reference values. The presence of adequate levels of active ingredients, as discussed in the previous paragraph, guarantees efficacy, but purity measurements provide information on the safety of use.
Quality controls must be performed on both the starting material and the finished product.
As a reference for the quality control may be employed various sources such as: the monographs of the Pharmacopoeia , the monographs EMA or ESCOP monographs, which contain the description of the drug and the tests necessary for correct identification.
From a regulatory point of view, herbal drugs do not have to comply with standardization values, but must meet purity requirements , in particular the absence of contaminants, such as pesticides, heavy metals or microbes .
In some cases the drug may fail to meet quality requirements due to adulterations , i.e. intentional or unintentional modifications , which in the first case often occur for profit reasons.
The sophistication of a drug can come about by adding inferior or exhausted material(already used in other extractions) or through the use of other materials , such as inert or waste materials. The addition of conventional drugs (such as anorectics) to herbal drugs is certainly very serious in order to produce a relevant pharmacological action. This situation is often responsible for the main adverse effects on consumers.
The adulteration unintentional , such as errors of identification or preparation , occur due to lack of means of evaluation, an example is the non-compliance of the balsamic time .
The identification of the plant material requires the presence of expert personnel, able to know the botanical aspects of the plant species in question and their chemical characteristics.
Finally, conservation also plays a decisive role in the quality of a product, as if badly managed, it can lead to the development of bacterial or fungal contamination with the consequent possible production of toxins .
Conclusions
The challenges of producing a safe and effective vegetable preparation are many.
From these aspects it emerges much more clearly why it is wrong to consider a priori every natural product as “safe” . The correct identification, the choice of the extraction method, the standardization and the right conservation are all fundamental and essential elements for the realization of quality vegetable preparations. These aspects require great skills and economic investments for manufacturing companies, but these efforts must be recognized by consumers , not only to repay the most serious companies , butto avoid coming across ineffective products , or worse, dangerous for human health.
Insights
Book: Pharmacognosy and phytotherapy: pharmacological bases and application aspects.
Authors: Mazzanti G, Dell’Agli M, Izzo A.
Publisher: Piccin
Year: 2020 (in publication)
Book: Phytotherapy: rational use of plant drugs
Authors: Capasso F, Grandolini G, Izzo A.
Publisher: Springer
Year: 2006
Book : Pharmacognosy, botany, chemistry and pharmacology of medicinal plants
Authors: Capasso F.
Publisher: Springer
Year: 2011
Questions and answers
WHAT ARE THE MAIN ASPECTS THAT INFLUENCE THE QUALITY OF A VEGETABLE PREPARATION?
The preparation of quality vegetable products is based on the respect of different phases. First, the plant material must be correctly identified and follow validated extraction procedures . The presence of the active ingredients and the absence of contaminants must be conducted with appropriate analytical evaluations. Finally, proper storage must be performed in all steps before and after processing.
WHAT IS STANDARDIZATION?
The standardization is an indispensable characteristic to realize preparations, improving health and identifies the minimum content of one or more active ingredients within a extract / final product. It is used to guarantee the effectiveness of a product. This value can only be obtained through analytical investigations carried out by the preparatory company.
WHAT SAFETY ASPECTS MUST BE EVALUATED IN A PLANT PREPARATION?
To be considered safe, after the correct identification of the drug, a plant preparation must be subjected to tests to exclude the presence of contaminants , such as pesticides, heavy metals or biological agents such as bacteria and fungi. In addition, the drug must be adequately controlled , in order to verify the correspondence with the standards described in the various monographs available.
WHAT IS THE PHYTOCOMPLEX?
The phytocomplex is the set of chemical constituents that contribute, with different roles, to the biological activity of a plant extract and is made up of the molecules defined as active ingredients , together with all the other components that can favor their activity. The content of the molecules is influenced by genetic and environmental factors to which the plant of origin is subjected. To make preparations for health purposes it is essential to quantify the active ingredients contained therein
