Since crude drugs consist of various plant and animal parts and their products, they occur in a variety of morphological forms depending on the nature of their sources. These natural forms undergo further changes when they are prepared for commercial market. Various crude plant drugs are brought to the commercial market in the following common forms:
Entire form, i.e., in their whole condition without bringing about any spectacular change in their natural gross morphology. This form is common in cases of seeds and fruits, but also olccurs in cases of some flowers, leaves and roots and rhizomes.
Cut, sliced or broken form, i.e., the drug may be cut into small pieces or sliced into thinner portions or broken into pieces in order to facilitate drying and also to economise space for storage. These forms are found in case of fleshy rhizomes, tubers, woods and barks.
Matted or pressed form, i.e., they may be more or less matted together as in lose bunches or bales or may be pressed together by hydraulic pressure into hard compact bales which give the drug a stiff pressed appearance. The dried, sun-bleached Chondrus or Irish moss represents a typical matted form and pressed form is common in baled leaves.
Powdered form, i.e., the plant part is reduced by milling into a coarse or fine powder. This is the most common form of occurrence of most drugs as it is the most convenient form as far as handling and economy of space in storage are concerned.
Peeled form, i.e., the outer part of the bark (i.e., the periderm) may be removed from the plant part. Many roots (e.g., Althea), ‘ rhizomes (e.g., Ginger) and barks (e.g., Ceylon cinnamon) occur in the market in the peeled form.
When crude drugs of natural origin occur in the entire form their morphological and sensory characters, like shape, texture, external markings, fracture, colour, odour and taste, are of immense significance in their identification. These features are characteristic of a number of drugs. Brief descriptions of these characters of various plant parts are given in the chapter on organized drugs.
When drugs occur in powdered form they possess very few macroscopic morphological features of identification other than some sensory characters like colour, odour and taste. These sensory characters are briefly described below.
The colour of a drug constitutes an important character for its identification and refers to the particular hue expressed by the drug whether entire, sectioned or powdered, normally under ordinary light. Official monographs specify colours for different drugs using a hue name,· with or without a modifier to describe the rclativc degree of strength of the hue.
Crude drugs may possess almost all types of colours and shades of colours. However, the following generalisation can be applied to indicate the normal colours of various plant parts in powdered form.
Powders of leaves and herbs generally acquire a green to light green to brownish green colour depending on the type of the leaf and the method employed for drying it.
Powdered roots and rhizomes usually posses a cream to light brown to brown colour depending on the amount of bark and starch present in the sample.
Barks in powdered form normally exhibit a brown to deep brown colour due to the presence of large quantities of cork, resin and oil.
Woods appears off-white to cream to brown in their powdered form depending on whether the drug is obtained from depending on whether the drug is obtained from the sap wood or the heart wood and the type of depositions on their walls or their inclusions.
In describing the colour of a drug, therefore, one must be specific in using the modifier to the orginal hue name of the colour.
Odour is a particular sensation, perceived by the nose, produce by the volatile constituents of many drugs. The intensity of the odour depends on the amount of volatile constituents the drug possesses. Odours arc characteristic of individual drugs as they vary from each other in quality as well as intensity. Some possess distinct odours, which may be pleasant or unpleasant; others possess indistinct odours, and still others may not possess any odour. Odours are generally described in comparative terms being compared with other substances in nature. The terms commonly used for describing odours include: (a) aromatic, when the plant part possesses a pleasing sweet scent; (b) spicy, when a drug produces a similar odour to that characteristic smell of spices; (c) alliaceous, a disagreeable odour similar to that of Onion: (d) camphoraceous, a strong unpleasant odour similar to or same as that of Camphor; (c) balsamic, the characteristic smell of aldehydes as produced by balsams, and (f) characteristic, hen the smell is very distinct hut when cannot be correlated to or compare with any natural substance as the others. Odour is an important parameter for distinguishing or even identifying many crude drugs of natural origin.
Taste is the particular sensation excited by certain substances when they are brought into contact with the tongue and moistened with the saliva. Proper taste of a substance is perceivable only when that substance or its constituents are
soluble or partially soluble in the mouth fluid. Tastes of various drugs are often very useful in their identification and evaluation. Where applicable monographs of crude drugs include an item titled odour and taste. Tastes of various crude drugs may be described as follows:
Insipid or tasteless, hen a substance, being insoluble in the saliva, does not produce any sensation to the tongue.
True tastes, when the substance produces a distinct sensation to the tongue, being highly soluble in the saliva. True tastes can be acidic (sour), saline (salty), saccharine (sweet) and bitter (a very unpleasant repulsive taste).
Odorous tastes, where the taste is influenced or dominated by the characteristic odour or the substance. The taste of this type is perceived as the characteristic odour and is described by the same term, such as aromatic, balsamic, spicy, alliaceous, camphoraceous, etc.
Sensual tastes, such as mucilaginous (a soft slimy feeling), oily (a bland smooth feeling), astringent (a puckering or contracting feeling), pungent (a warm biting sensation), acrid (an unpleasant irritating sensation) and nauseous (a taste which excites vomiting).