Adulteration of Herbal Drugs
Direct or intentional adulteration of drugs usually includes practices in which a
herbal drug is substituted partially or fully with other inferior products. Due to
morphological resemblance to the authentic herb, many different inferior com-
mercial varieties are used as adulterants. These may or may not have any chemical
or therapeutic potential. Substitution by “exhausted” drugs entails adulteration of
the plant material with the same plant material devoid of the active constituents.
This practice is most common in the case of volatile oil-containing materials,
where the dried exhausted material resembles the original drug but is free of the
40 2 Quality Control, Screening, Toxicity, and Regulation of Herbal Drugs
essential oils. Foreign matter such as other parts of the same plant with no active
ingredients, sand and stones, manufactured artifacts, and synthetic inferior princi-
ples are used as substitutes [29].
The practice of intentional adulteration is mainly encouraged by traders who are
reluctant to pay premium prices for herbs of superior quality, and hence are in-
clined to purchase only the cheaper products. This encourages producers and trad-
ers to sell herbs of inferior quality. Rarity of a herbal product is another factor that
influences adulteration. Sometimes sale of inferior products may be unintention-
al. In the absence of proper means of evaluation, an authentic drug partially or ful-
ly devoid of the active ingredients may enter the market. Factors such as geograph-
ical sources, growing conditions, processing, and storage are all factors that influ-
ence the quality of the drug. Deterioration may contribute to indirect adulteration,
and crude drugs are often prone to deterioration, especially during storage, leading
to the loss of the active ingredients, production of metabolites with no activity and,
in extreme cases, the production of toxic metabolites. Physical factors such as air
(oxygen), humidity, light, and temperature can bring about deterioration directly or
indirectly [88]. These factors, alone or in combination, can lead to the development
of organisms such as molds, mites, and bacteria. Oxidation of the constituents of a
drug can be brought about by oxygen in the air, causing some products, such as es-
sential oils, to resinify or to become rancid. Moisture or humidity and elevated
temperatures can accelerate enzymatic activities, leading to changes in the physi-
cal appearance and decomposition of the herb.
Dried herbs are particularly prone to contamination with spores of bacteria and
fungi present in the air. Bacterial growth is usually accompanied by the growth of
molds, whose presence is evidenced by changes in appearance, break down of the
plant material, and smell. Mites, nematode worms, insects/moths, and beetles can
also destroy herbal drugs during storage.
Control measures to protect against deterioration include the use of airtight con-
tainers made of materials that will not interact physically or chemically with the
material being stored. Storage in ventilated, cool, dry areas and periodic spraying
of the stored area with insecticides will help to prevent the spread of infestation.
Sterilization of crude drugs is achieved by treatment of bulk consignments with
ethylene oxide, and methyl bromide under controlled conditions and complying
with acceptable limits for toxic residues [29, 47, 88]. World markets from time to
time experience wild fluctuations in the price of herbals. One reason for this is in-
discriminate harvesting which leads to the extinction of natural populations – still
the only source of bioresources. This in turn encourages producers to replace the
required herb with other supplements.
Direct or intentional adulteration of drugs usually includes practices in which a
herbal drug is substituted partially or fully with other inferior products. Due to
morphological resemblance to the authentic herb, many different inferior com-
mercial varieties are used as adulterants. These may or may not have any chemical
or therapeutic potential. Substitution by “exhausted” drugs entails adulteration of
the plant material with the same plant material devoid of the active constituents.
This practice is most common in the case of volatile oil-containing materials,
where the dried exhausted material resembles the original drug but is free of the
40 2 Quality Control, Screening, Toxicity, and Regulation of Herbal Drugs
essential oils. Foreign matter such as other parts of the same plant with no active
ingredients, sand and stones, manufactured artifacts, and synthetic inferior princi-
ples are used as substitutes [29].
The practice of intentional adulteration is mainly encouraged by traders who are
reluctant to pay premium prices for herbs of superior quality, and hence are in-
clined to purchase only the cheaper products. This encourages producers and trad-
ers to sell herbs of inferior quality. Rarity of a herbal product is another factor that
influences adulteration. Sometimes sale of inferior products may be unintention-
al. In the absence of proper means of evaluation, an authentic drug partially or ful-
ly devoid of the active ingredients may enter the market. Factors such as geograph-
ical sources, growing conditions, processing, and storage are all factors that influ-
ence the quality of the drug. Deterioration may contribute to indirect adulteration,
and crude drugs are often prone to deterioration, especially during storage, leading
to the loss of the active ingredients, production of metabolites with no activity and,
in extreme cases, the production of toxic metabolites. Physical factors such as air
(oxygen), humidity, light, and temperature can bring about deterioration directly or
indirectly [88]. These factors, alone or in combination, can lead to the development
of organisms such as molds, mites, and bacteria. Oxidation of the constituents of a
drug can be brought about by oxygen in the air, causing some products, such as es-
sential oils, to resinify or to become rancid. Moisture or humidity and elevated
temperatures can accelerate enzymatic activities, leading to changes in the physi-
cal appearance and decomposition of the herb.
Dried herbs are particularly prone to contamination with spores of bacteria and
fungi present in the air. Bacterial growth is usually accompanied by the growth of
molds, whose presence is evidenced by changes in appearance, break down of the
plant material, and smell. Mites, nematode worms, insects/moths, and beetles can
also destroy herbal drugs during storage.
Control measures to protect against deterioration include the use of airtight con-
tainers made of materials that will not interact physically or chemically with the
material being stored. Storage in ventilated, cool, dry areas and periodic spraying
of the stored area with insecticides will help to prevent the spread of infestation.
Sterilization of crude drugs is achieved by treatment of bulk consignments with
ethylene oxide, and methyl bromide under controlled conditions and complying
with acceptable limits for toxic residues [29, 47, 88]. World markets from time to
time experience wild fluctuations in the price of herbals. One reason for this is in-
discriminate harvesting which leads to the extinction of natural populations – still
the only source of bioresources. This in turn encourages producers to replace the
required herb with other supplements.
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