The artificial technical processes that determine the "removal of" water, therefore the slowing down or blocking of the hydrolysis reactions, are LYOPHILIZATION and DRYING.
Drying is the most used method because it is simpler and handed down by the phytotherapeutic tradition, and its history, as the only means to avoid drug alteration processes.
Both methods limit the processes of drug degradation, or block them but not irreversibly. The removal of the water deprives the enzyme of the element necessary to determine the hydrolysis reactions, but not the disappearance of the enzyme itself. If after drying, the drug is not properly stored in an environment poor in humidity and is exposed to possible sources of water, the drug slowly undergoes degradation processes, always at the expense of the hydrolytic enzymes. If the drug is properly stored, however, the action of the hydrolytic enzymes is extremely slowed down, therefore the drug it is more likely to last over time. Therefore, freeze-drying and drying are processes that determine a temporary and non-irreversible block of the degradation or aging of the drug.
ARTIFICIAL FACTORS TO REMOVE WATER FROM DRUGS.
DRYING: there are different drying methods.
Drying on racks: this is the simplest method. By trellis we mean one or a group of frames, about 1m by 2m in size, made of wood with a metal or jute grate; these frames are generally arranged on different planes, at a distance of 15-20 cm from each other to allow for correct and correct ventilation; or they can simply be arranged in an airy room. The preventive evaluation of the size of the drug is very important, because the characteristics of the trellis are chosen on the basis of this; in the case of the leaves it is possible to use very simple trellis structures, even on several levels, while for the drying of rather large fragments of drugs, which require a "drying on racks in order to be preserved, only one plane or a single floor. Drying normally takes place, except for exceptions, in the shade, under canopies or inside open and ventilated rooms.
Drying on racks, therefore, is an extremely simple, ancient and economical method; however, there are limitations.The drying time, first of all, is directly proportional to the humidity present in the air; the more humid the air, the greater the time required for drying. Consequently, if the time of removal of the water increases, the hydrolytic enzymes have the possibility of increasing their action, degrading the drug both in a morphological and phytochemical way.
For what has been said, drying on racks can be carried out for drugs that do not contain large quantities of water, such as roots, trunks, rhizomes or in any case woody plant parts; the exploitation of racks to dry leaves and flower heads is also subject to location and climate in which they are dried, which must preferably be hot / dry.
On the one hand, drying on racks has considerable economic advantages, but on the other hand has the major drawback of being too tied to climatic trends and the type of drug. For example, if unexpected climatic conditions occur (the temperature suddenly drops, the humidity increases), there is the possibility that all the raw material will be ruined.
Drying on racks is carried out under roofs, with some exceptions, because solar radiation can cause photoreactive phenomena; sunlight, in fact, catalyzes photooxidation reactions that begin when the drug is exposed directly to the sun. These phenomena determine two main elements of damage: due to the active ingredients and to the pigments of the plant.
At the time of drying, the pigments are now disorganized, because they have lost their ability to perform a receptor function, to convey chlorophyll, etc .; however, even after the source has been collected, they do not lose their sensitivity to light. Therefore, the pigments however, they can absorb light radiations and, once they reach certain energies, lose the stability of their orbitals and, in fact, change their characteristics.
Altering the natural peculiarities of the pigments means modifying the morphological and macroscopic aspects of the drug, which are very important for its characterization and for making it fall within the official validity parameters.
Finally, there are some drugs for which drying on racks in the sunlight is foreseen, since the phenomena of photo - oxidation are favorable to a better medicinal quality.
Other articles on "Drying, drying on racks"
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