The factors which must be considered in relation to drug deterioration are
Humidity, temperature, light and the presence of oxygen; when
these conditions are suitable, living organisms (bacteria, moulds, mites
and insects) will rapidly multiply, using the drug as a source of food.
Drugs affected in this way are excluded by national pharmacopoeias.
Primary factors
As indicated air-dry drugs contain about 10–12% of
moisture, and in some instances (e.g. digitalis) this may be sufficient to
activate enzymes present in the leaves and bring about decomposition
of the glycosides. Other drugs, such as powdered squill, which contain
mucilage quickly absorb moisture and become a sticky mass. The con-
tainerized shipment of drugs which is now common practice can lead to
spoilage due to excessive condensation of moisture on the inner metal
walls. It is a particular problem with cargoes in transit from humid moist
climates to temperate regions. An increase in temperature, in combina-
tion with moisture, may accelerate enzyme activity; a large temperature
rise will obviously lead to a loss of volatile constituents (e.g. essential
oils from dried plant material) and in the case of absorbent cotton-wool
cause a reorientation of the small amount of fatty material present lead-
ing to non-absorbency or lower absorbency. Direct sunlight can cause
decomposition of certain constituents (e.g. vitamins in cod-liver oil) as
well as producing a bleaching of leaves and flowers. Oxygen assists in
the resinification of volatile oils and in the rancidification of fixed oils.
Mould and bacterial attack
The moulds found in deteriorating drugs are usually the same as those
associated with poorly stored food products. Species of Rhizopus, Mucor,
Penicillium and Eurotium are common. Their presence is indicated by
a mass of hyphae which bind the particles of drug and by a characteris-
tic smell. Deterioration of drugs is only one aspect of the importance of
moulds in pharmacognosy.Bacterial attack of crude
drugs is less obvious unless chromogenic species are involved or effects
produced such as dustiness in cotton-wool by attack on the fibres. Although
not a cause of deterioration, certain pathogenic bacteria such as salmonel-
lae and Escherichia coli are tested for in some crude drugs taken internally
(digitalis, sterculia, tragacanth, gelatin). Also, as plant materials which
have been dried under normal conditions contain viable bacteria and mould
spores in variable amounts, the pharmacopoeias set limits for the total via-
ble aerobic count per gram of drug.
Coleoptera or beetles
Beetles are insects and constitute the largest order of the animal kingdom,
comprising some 250000 species, of which about 600 have been found
associated with stored food products or drugs. Not all of these utilize the
stored product itself but may be found in the wood of packing-cases or liv-
ing predaciously. Beetles have a body which is divided into head, thorax and
abdomen. To the lower side of the thorax are attached three pairs of legs,
while the upper surface usually bears two membranous hind-wings which
are folded beneath horny elytra (forewings). They show complete meta-
morphosis of egg, larval, pupal and adult stages, and those which constitute
pests in stored products cause damage both as adults and as larvae. Among
the characters which distinguish the larvae of most species which attack
foodstuffs and vegetable drugs are the well-developed biting mouth-parts
and a head which is darker in colour than the rest of the body...