The artificial technical processes that determine the removal of water, hence the slowing down or blocking of hydrolysis reactions, are LILOPHILIZATION and ESSICATION.
Drying is the most used method because it is simpler and handed down from the phytotherapeutic tradition, and from its history, as the only means to avoid drug alteration processes.
Both methods limit drug degradation processes, 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 in a subsequent time the drying, the drug is not properly stored in an environment poor in humidity and is exposed to possible sources of water, the drug is slowly experiencing degradation processes, always at the expense of hydrolytic enzymes. If the drug is properly preserved, on the other hand, the action of hydrolytic enzymes is extremely slowed down, so the drug is more likely to last over time. Therefore, freeze-drying and drying are processes that determine a temporary and non-irreversible blockage of the degradation or aging of the drug.
ARTIFICIAL WATER REMOVAL FACTORS FROM DRUGS.
DRYING: there are different drying methods.
Drying on racks : this is the simplest method. For trellis means one or a set of frames, about 1m by 2m in size, made of wood with a metal or jute grating; these frames are generally arranged on different planes, at a distance of 15-20 cm from each other to allow correct and correct ventilation; or they can simply be arranged in a ventilated room. The preventive evaluation of the size of the drug is very important, because on the basis of it the characteristics of the trellis are chosen; in the case of the leaves it is possible to use very simple lattice structures, even on several floors, while for the drying of rather large drug fragments, which need drying on racks in order to be preserved, only one floor or one is used single flatbed. Drying normally takes place, with certain exceptions, in the shade, under canopies or in open and ventilated rooms.
Therefore, drying on racks is an extremely simple, ancient and economic method; however, limitations are not lacking. The drying time, first of all, is directly proportional to the humidity present in the air; the more the air is humid and the longer the time required for drying. Reflexively, if the water removal time increases, the hydrolytic enzymes have the possibility of increasing their action, degrading the drug both morphologically and phytochemically.
According to the above, drying on racks can be carried out for drugs that do not contain high amounts of water, such as roots, trunks, rhizomes or parts of woody plants; furthermore, the exploitation of racks for drying leaves and flower heads depends on the location and climate in which they are dried, which should preferably be hot / dry.
Drying on racks has on one hand considerable economic advantages, but on the other hand it presents the big drawback of being too tied to climatic trends and to the type of drug. If, for example, unforeseen climatic conditions occur (the temperature suddenly drops, humidity increases), there is the possibility that the whole raw material will be ruined.
Drying on racks is carried out under canopies, with the exception of exceptions, because solar radiation can determine photoreactive phenomena; in fact, sunlight catalyzes photooxidation reactions that begin when the drug is exposed directly to the sun. These phenomena determine two main elements of damage: against the active principles and against the plant's pigments.
At the time of drying the pigments are now disorganized, because they have lost their ability to perform receptorial function, to convey chlorophyll, etc .; however, even after the source is harvested, they do not lose their sensitivity to light. Therefore, pigments can still absorb light radiations and, once certain energies are reached, lose the stability of their orbitals and, in fact, modify their characteristics.
Altering the natural peculiarities of pigments means modifying the morphological and macroscopic aspects of the drug, which are very important for its characterization and to make it fit into the official validity parameters.
Finally, there are some drugs for which drying on racks is expected in the light of the sun, since the phenomena of photo-oxidation are favorable to a better officinal quality.
