Most plant drug undergoes a period of storage before they are finally used by industries to prepare pharmaceutical and medicinal product. During this period many undesirable changes may occur in the crude drugs if they are not properly stored and preserved against reabsorption of moisture, oxidation, excessive heat or humidity, direct sunlight, growth or moulds and bacteria and infestation by insects and rodents, Proper storage and preservation of crude plant drugs are thus very important factors in maintaining a high degree of quality in them. All efforts towards proper storage should be geared to protect the drugs from all the above deteriorating factors and agents.
Storehouses of crude drugs should be well built with steel, concrete or brick. They should be unheated and rodent proof. In order to protect the stored drugs from excessive light and heat, undesirable oxidation and re-absorption of moisture, the storehouses should be cool, dark, and well ventilated with dry air. Usual containers of crude drugs include cardboard boxes wooden cased, sacks and paper bags, Drugs in these containers reabsorbed, wooden cases, sacks and paper bags. Drugs in these containers reabsorb up to 12 percent of moisture and become so-called air-dry’. Most drugs maintain their good quality in their air-dry condition, if protected from other deteriorating agents. But drug like Digitalis and Cannabis lose a considerable part of their activity when they become air dry. They should therefore be kept in sealed containers with a dehydrating agent. Volatile and fixed oils are liable to oxidation. They should also be stored in sealed, we 11-filled containers or any air in the container should be replaced by an inert gas.
Air dry drugs are liable to attack by insects, mites, fungi and bacteria. Drugs that are particularly susceptible to attacks by these agents include Ginger, Belladonna root, Nutmeg, Coriander, Stramonium, Rhubarb, Aconite and Ergot.
Insect pests of stored plant drugs include members of the orders Lepidoptera, Coleoptera and Arachnida. Lepidoptera includes the moths and butterflies, which in their larval stage attack most root and rhizome drugs. The weevils and beetles with attack many different drugs and spices belong to the order Coleoptera. The Arachnids include the mites, which commonly attack Cantharides, Ergot and Linseed.
Attack by beetles, moths and mites may be prevented by storing drug in airtight containers and in a dry cool atmosphere, Attacks on stored drug by insects, fungi and bacteria can also be effectively prevented by exposing the drugs periodically to a temperature of 60 to 65°C. This method is also very effective in exterminating the insects and the microorganisms from the infested drug samples. Fumigation of storehouses with methyl bromide, ethylene oxide and other similar toxic gases and vapours effectively destroy insects and microorganisms and controls their further growth in stored drug. Chloroform and carbon tetrachloride have also been found to be useful in controlling insect pests in stored plant drugs.
Drugs susceptible to re-absorption of moisture, insect and microbial attacks should not be stored in wooden boxes or paper bags or carton boxes. Tin cans, covered metal bins and amber glass containers are most suitable for storing drugs which are easily oxidised or adversely affected by light and moisture. Since elevated temperatures accelerate all chemical reactions, storehouses for drugs should be as cool as possible. Drugs like enzymes, vaccines, toxins and toxoids should be stored in deep freezers at a temperature of O to 4°C and in some cases even below 0°C.
