Screening, Toxicity, and Regulation of Herbal Drugs
Wickramasinghe M. Bandaranayake
Summary
Medicinal plants constitute a source of raw materials for both traditional systems
of medicine (e.g. Ayurvedic, Chinese, Unani, Homeopathy, and Siddha) and mod-
ern medicine. Nowadays, plant materials are employed throughout the industrial-
ized and developing world as home remedies, over-the-counter drugs, and ingre-
dients for the pharmaceutical industry. As such, they represent a substantial pro-
portion of the global drug market. Most rural populations, especially in the devel-
oping world, depend on medicinal herbs as their main source of primary health
care. Although most medicinal herbs are not, in their natural state, fit for adminis-
tration, preparations suitable for administration are made according to pharmaco-
peia directions. The therapeutic potential of a herbal drugs depends on its form:
whether parts of a plant, or simple extracts, or isolated active constituents. Herbal
remedies consist of portions of plants or unpurified plant extracts containing sev-
eral constituents, which often work together synergistically.
The herbal drug preparation in its entirety is regarded as the active substance
and the constituents are either of known therapeutic activity or are chemically de-
fined substances or group of substances generally accepted to contribute substan-
tially to the therapeutic activity of the drug. Phytochemical screening involves bo-
tanical identification, extraction with suitable solvents, purification, and character-
ization of the active constituents of pharmaceutical importance. Qualitative chem-
ical examination employing different analytical techniques is conducted to detect
and isolate the active constituent(s). In general, all medicines, whether they are
synthetic or of plant origin, should fulfill the basic requirements of being effica-
cious and safe. Ultimate proof of these can only be achieved by some form of clin-
ical research. A defined and constant composition of the drug is therefore one of
the most important prerequisites for any kind of clinical experiment.
Quality control for the efficacy and safety of herbal products is essential. The
quality control of phytopharmaceuticals may be defined as the status of a drug,
which is determined either by identity, purity, content, and other chemical, physi-
cal or biological properties, or by the manufacturing process. Compared with syn-
25
thetic drugs, the criteria and the approach for herbal drugs are much more com-
plex.
Phytopharmaceuticals are always mixtures of many constituents and are there-
fore very variable and difficult to characterize. The active principle(s) in phytophar-
maceuticals are not always known. The quality criteria for herbal drugs are based
on a clear scientific definition of the raw material. Depending on the type of prep-
aration, sensory properties, physical constants, moisture, ash content, solvent res-
idues, and adulterations have to be checked to prove identity and purity. Microbio-
logical contamination and foreign materials, such as heavy metals, pesticide resi-
dues, aflatoxins, and radioactivity, also need to be tested for. To prove the constant
composition of herbal preparations, appropriate analytical methods have to be ap-
plied and different concepts have to be used in order to establish relevant criteria
for uniformity.
Are there rigorous trials to show that herbal treatments work? With many of
these herbal medicines we do not fully understand how they work. Nor do we al-
ways know which component is pharmacologically active. Even though herbal
remedies may be effective, do their benefits outweigh their risks? In some coun-
tries herbal remedies are sold as food supplements, thus evading safety regula-
tions. Can herbal medicines save money? Not all plant-based medicines are cheap.
Even though global herbal resources have a great potential as natural drugs and
are of great commercial importance, they are very often procured and processed
without any scientific evaluation, and launched onto the market without any man-
datory safety and toxicology studies because there is no effective machinery to reg-
ulate manufacturing practices and quality standards. Although some herbal medi-
cines are efficacious, there is unquestionably a need for more reliable information,
a demand that must be met adequately by doctors, pharmacists, and other health
care professionals.
Policy and regulation in their use, are two of the most sensitive aspects of devel-
oping and using plant-based medicines and health products. At present there is al-
most no policy worth its name to regulate the procurement and sale of medicinal
plants in developing countries. Neither are the products derived from medicinal
plants subject to control.
Stringent quality control should be enforced. Growing evidence of effectiveness
is counterbalanced by inadequate regulation. The present review will address some
of these issues.
Introduction
Since ancient times humanity has depended on the diversity of plant resources for
food, clothing, shelter, and traditional medicine to cure myriads of ailments. Early
humans recognized their dependence on nature in both health and illness. Physi-
cal evidence of the use of herbal remedies has been found from some 60 000 years
ago in a burial site of a Neanderthal man uncovered in 1960 in a cave in northern
26 2 Quality Control, Screening, Toxicity, and Regulation of Herbal Drugs
Iraq [1]. Here, scientists found great quantities of plant pollen, some of which
came from medicinal plants still used today. The first written records detailing the
use of herbs in the treatment of illness are in the form of Mesopotamian clay tab-
let writings and Egyptian papyrus [2]. Led by instinct, taste, and experience, primi-
tive men and women treated illness by using plants, animal parts, and minerals
that were not part of their usual diet. Herbal medicine is the oldest form of health
care known to humanity and has been used in all cultures throughout history.
Primitive people learned by trial and error to distinguish useful plants with benefi-
cial effects from those that were toxic or nonactive, and also which combinations or
processing methods had to be used to gain consistent and optimal results. Even in
ancient cultures, tribal people methodically collected information on herbs and de-
veloped well-defined herbal pharmacopeias. Traditional medicine evolved over
centuries, depending on local flora, culture, and religion [3–5]. Indeed, well into
the twentieth century, much of the pharmacopeia of scientific medicine was de-
rived from the herbal lore of native people. This knowledge of plant-based drugs
developed gradually and was passed on, thus laying the foundation for many sys-
tems of traditional medicine all over the world.
Herbal medicine can broadly be classified into a few basic systems:
Ayurvedic herbalism (derived from the Sanskrit word ayurveda, meaning “the
science of life”), which originated in India more than 5000 years ago and was al-
so practiced in neighboring countries such as Sri Lanka.
Chinese herbalism, which is a part of traditional oriental medicine.
African herbalism.
Western herbalism, which originated from Greece and Rome and then spread to
Europe and North and South America.
Chinese and Ayurvedic herbalism have developed into highly sophisticated sys-
tems of diagnosis and treatment over the centuries. Both have a long and impres-
sive history of effectiveness. Western herbalism today is primarily a system of folk
medicine. A European healing tradition, sometimes called the “wise woman” also
focuses primarily on herbal healing.
Medicinal plants have played a key role in world health. They are distributed
worldwide, but they are most abundant in tropical countries. It is estimated that
about 25% of all modern medicines are directly or indirectly derived from higher
plants [6–23].
By definition, a herb is a plant or a part of a plant valued for its medicinal, aro-
matic, or savoury qualities. Herbs can be viewed as biosynthetic chemical laborato-
ries, producing a number of chemical compounds. Herbal medicine or herbalism
is the use of herbs or herbal products for their therapeutic or medicinal value. They
are also referred to as botanicals, biomedicines, or herbal supplements. Herbal
drugs range from parts of plants to isolated, purified active constituents. They may
come from any part of the plant but are most commonly made from leaves, roots,
bark seeds, and flowers. They are eaten, swallowed, drunk, inhaled, or applied to
the skin [24].
2.1 Introduction 27
Typically, there is no one single herb that is recommended for a given health dis-
order; and there is no one single health disorder linked with just one single herb.
Herbal products often contain a variety of biochemicals found naturally in the
plants and many different biochemicals contribute to a plant’s medicinal benefit.
Chemicals known to have medicinal benefits are referred to as “active ingredients,”
and their presence depends on the plant species, the way the herb is prepared, the
time and season of harvest, the type of soil, etc. Most herbal products contain plant
parts or plant materials in the crude or processed state as active ingredients and cer-
tain excipients, such as solvents, diluents, or preservatives. In most cases, the active
principles responsible for their pharmacological action are unknown.
A herb might be considered a “diluted” drug. To achieve the desired benefit, an
individual must take an adequate amount over a certain length of time. Each herb
is different. While some are safe and effective for specific uses, others are not. The
general perception that herbal drugs are very safe and free from side effects is not
true. Herbs can produce undesirable side effects and can be toxic. A particular
plant part will have many constituents and some of them may well be toxic. How-
ever, it may take more to cause toxicity, because herbs usually are not as potent as
manufactured drugs, and compared with synthetic drugs the adverse effects of
most herbal drugs are relatively infrequent [25–27].
Herbal medicines are very different from well-defined synthetic drugs. For ex-
ample, the availability and quality of the raw materials are frequently problematic;
the active principles are frequently unknown; and standardization, stability, and
quality control are feasible but not easy. In comparison with modern medicine,
herbal medicines cost less, are more often used to treat chronic diseases, and the
occurrence of undesirable side effects seems to be less frequent.
A vast number of plants have medicinal properties; in fact, many pharmaceuti-
cal drugs were originally derived from plants. Ethnopharmacology – the scientific
study of indigenous medicines – is an interdisciplinary science practiced all over
the world. Phytotherapeutic agents or phytomedicines are standardized herbal
preparations that contain, as active ingredients, complex mixtures of plant materi-
als in the crude or processed state. One basic characteristic of phytotherapeutic
agents is the fact that they normally do not possess an immediate or strong phar-
macological action. For this reason, these agents are not suitable for emergency
treatment.
During the past decade, there has been increasing acceptance and public inter-
est in natural therapies in both developing and developed countries. Due to pover-
ty and limited access to modern medicine, about four billion people, 80% of the
world’s population, living in developing countries use herbal medicine as their
source of primary health care [25, 28–30]. In these communities, traditional medi-
cal practice is often viewed as an integral part of their culture.
In the West, people are attracted to herbal therapies for many reasons, the most
important reason being that, like our ancestors, we believe they will help us live
healthier lives. Herbal medicines are often viewed as a balanced and moderate ap-
proach to healing. Individuals who use them as home remedies and over-the-coun-
ter drugs spend billions of dollars on herbal products. As such, they represent a
substantial proportion of the global drug market [16, 19–21, 23, 24, 27, 28, 31–36].
28 2 Quality Control, Screening, Toxicity, and Regulation of Herbal Drugs
This recent resurgence of interest in plant remedies has been spurred on by sev-
eral factors [21, 23, 26, 31]:
The effectiveness of plant medicines.
The preference of consumers for natural therapies, a greater interest in alterna-
tive medicines and a commonly held erroneous belief that herbal products are
superior to manufactured products.
A dissatisfaction with the results from synthetic drugs and the belief that herbal
medicines might be effective in the treatment of certain diseases where conven-
tional therapies and medicines have proven to be inadequate.
The high cost and side effects of most modern drugs.
Improvements in the quality, efficacy, and safety of herbal medicines with the
development of science and technology.
Patients’ belief that their physicians have not properly identified the problem;
hence they feel that herbal remedies are another option.
A movement towards self-medication.
Medicinal plants provide the raw materials for the pharmaceutical industry. In-
deed, about 25% of the prescription drugs dispensed in the United States contain
at least one active ingredient derived from plant material. Many pharmacological
classes of drugs include a natural product prototype. Aspirin, atropine, morphine,
quinine are just a few of the drugs that were originally discovered through the
study of traditional cures and folk knowledge of indigenous people [37]. Herbal
therapies, on the other hand, consist of the chemical components of a plant as they
occur naturally [8]. Some are made from plant extracts, others are synthesized to
mimic a natural plant compound. Pharmaceutical drugs derived from plants are
made by isolating the active chemicals and concentrating them to the medication.
Pharmacognosy is the scientific study of drugs from natural products.
In most countries herbal products are launched into the market without proper
scientific evaluation, and without any mandatory safety and toxicological studies.
There is no effective machinery to regulate manufacturing practices and quality
standards. Consumers can buy herbal products without a prescription and one
might not recognize the potential hazards in an inferior product. A well-defined
and constant composition of the drug is therefore one of the most important pre-
requisites for the production of a quality drug. Given the nature of products of
plant origin, which by definition are never constant and are dependent on and in-
fluenced by many factors, quality control plays a significant role for the industry to
thrive and be successful
Wickramasinghe M. Bandaranayake
Summary
Medicinal plants constitute a source of raw materials for both traditional systems
of medicine (e.g. Ayurvedic, Chinese, Unani, Homeopathy, and Siddha) and mod-
ern medicine. Nowadays, plant materials are employed throughout the industrial-
ized and developing world as home remedies, over-the-counter drugs, and ingre-
dients for the pharmaceutical industry. As such, they represent a substantial pro-
portion of the global drug market. Most rural populations, especially in the devel-
oping world, depend on medicinal herbs as their main source of primary health
care. Although most medicinal herbs are not, in their natural state, fit for adminis-
tration, preparations suitable for administration are made according to pharmaco-
peia directions. The therapeutic potential of a herbal drugs depends on its form:
whether parts of a plant, or simple extracts, or isolated active constituents. Herbal
remedies consist of portions of plants or unpurified plant extracts containing sev-
eral constituents, which often work together synergistically.
The herbal drug preparation in its entirety is regarded as the active substance
and the constituents are either of known therapeutic activity or are chemically de-
fined substances or group of substances generally accepted to contribute substan-
tially to the therapeutic activity of the drug. Phytochemical screening involves bo-
tanical identification, extraction with suitable solvents, purification, and character-
ization of the active constituents of pharmaceutical importance. Qualitative chem-
ical examination employing different analytical techniques is conducted to detect
and isolate the active constituent(s). In general, all medicines, whether they are
synthetic or of plant origin, should fulfill the basic requirements of being effica-
cious and safe. Ultimate proof of these can only be achieved by some form of clin-
ical research. A defined and constant composition of the drug is therefore one of
the most important prerequisites for any kind of clinical experiment.
Quality control for the efficacy and safety of herbal products is essential. The
quality control of phytopharmaceuticals may be defined as the status of a drug,
which is determined either by identity, purity, content, and other chemical, physi-
cal or biological properties, or by the manufacturing process. Compared with syn-
25
thetic drugs, the criteria and the approach for herbal drugs are much more com-
plex.
Phytopharmaceuticals are always mixtures of many constituents and are there-
fore very variable and difficult to characterize. The active principle(s) in phytophar-
maceuticals are not always known. The quality criteria for herbal drugs are based
on a clear scientific definition of the raw material. Depending on the type of prep-
aration, sensory properties, physical constants, moisture, ash content, solvent res-
idues, and adulterations have to be checked to prove identity and purity. Microbio-
logical contamination and foreign materials, such as heavy metals, pesticide resi-
dues, aflatoxins, and radioactivity, also need to be tested for. To prove the constant
composition of herbal preparations, appropriate analytical methods have to be ap-
plied and different concepts have to be used in order to establish relevant criteria
for uniformity.
Are there rigorous trials to show that herbal treatments work? With many of
these herbal medicines we do not fully understand how they work. Nor do we al-
ways know which component is pharmacologically active. Even though herbal
remedies may be effective, do their benefits outweigh their risks? In some coun-
tries herbal remedies are sold as food supplements, thus evading safety regula-
tions. Can herbal medicines save money? Not all plant-based medicines are cheap.
Even though global herbal resources have a great potential as natural drugs and
are of great commercial importance, they are very often procured and processed
without any scientific evaluation, and launched onto the market without any man-
datory safety and toxicology studies because there is no effective machinery to reg-
ulate manufacturing practices and quality standards. Although some herbal medi-
cines are efficacious, there is unquestionably a need for more reliable information,
a demand that must be met adequately by doctors, pharmacists, and other health
care professionals.
Policy and regulation in their use, are two of the most sensitive aspects of devel-
oping and using plant-based medicines and health products. At present there is al-
most no policy worth its name to regulate the procurement and sale of medicinal
plants in developing countries. Neither are the products derived from medicinal
plants subject to control.
Stringent quality control should be enforced. Growing evidence of effectiveness
is counterbalanced by inadequate regulation. The present review will address some
of these issues.
Introduction
Since ancient times humanity has depended on the diversity of plant resources for
food, clothing, shelter, and traditional medicine to cure myriads of ailments. Early
humans recognized their dependence on nature in both health and illness. Physi-
cal evidence of the use of herbal remedies has been found from some 60 000 years
ago in a burial site of a Neanderthal man uncovered in 1960 in a cave in northern
26 2 Quality Control, Screening, Toxicity, and Regulation of Herbal Drugs
Iraq [1]. Here, scientists found great quantities of plant pollen, some of which
came from medicinal plants still used today. The first written records detailing the
use of herbs in the treatment of illness are in the form of Mesopotamian clay tab-
let writings and Egyptian papyrus [2]. Led by instinct, taste, and experience, primi-
tive men and women treated illness by using plants, animal parts, and minerals
that were not part of their usual diet. Herbal medicine is the oldest form of health
care known to humanity and has been used in all cultures throughout history.
Primitive people learned by trial and error to distinguish useful plants with benefi-
cial effects from those that were toxic or nonactive, and also which combinations or
processing methods had to be used to gain consistent and optimal results. Even in
ancient cultures, tribal people methodically collected information on herbs and de-
veloped well-defined herbal pharmacopeias. Traditional medicine evolved over
centuries, depending on local flora, culture, and religion [3–5]. Indeed, well into
the twentieth century, much of the pharmacopeia of scientific medicine was de-
rived from the herbal lore of native people. This knowledge of plant-based drugs
developed gradually and was passed on, thus laying the foundation for many sys-
tems of traditional medicine all over the world.
Herbal medicine can broadly be classified into a few basic systems:
Ayurvedic herbalism (derived from the Sanskrit word ayurveda, meaning “the
science of life”), which originated in India more than 5000 years ago and was al-
so practiced in neighboring countries such as Sri Lanka.
Chinese herbalism, which is a part of traditional oriental medicine.
African herbalism.
Western herbalism, which originated from Greece and Rome and then spread to
Europe and North and South America.
Chinese and Ayurvedic herbalism have developed into highly sophisticated sys-
tems of diagnosis and treatment over the centuries. Both have a long and impres-
sive history of effectiveness. Western herbalism today is primarily a system of folk
medicine. A European healing tradition, sometimes called the “wise woman” also
focuses primarily on herbal healing.
Medicinal plants have played a key role in world health. They are distributed
worldwide, but they are most abundant in tropical countries. It is estimated that
about 25% of all modern medicines are directly or indirectly derived from higher
plants [6–23].
By definition, a herb is a plant or a part of a plant valued for its medicinal, aro-
matic, or savoury qualities. Herbs can be viewed as biosynthetic chemical laborato-
ries, producing a number of chemical compounds. Herbal medicine or herbalism
is the use of herbs or herbal products for their therapeutic or medicinal value. They
are also referred to as botanicals, biomedicines, or herbal supplements. Herbal
drugs range from parts of plants to isolated, purified active constituents. They may
come from any part of the plant but are most commonly made from leaves, roots,
bark seeds, and flowers. They are eaten, swallowed, drunk, inhaled, or applied to
the skin [24].
2.1 Introduction 27
Typically, there is no one single herb that is recommended for a given health dis-
order; and there is no one single health disorder linked with just one single herb.
Herbal products often contain a variety of biochemicals found naturally in the
plants and many different biochemicals contribute to a plant’s medicinal benefit.
Chemicals known to have medicinal benefits are referred to as “active ingredients,”
and their presence depends on the plant species, the way the herb is prepared, the
time and season of harvest, the type of soil, etc. Most herbal products contain plant
parts or plant materials in the crude or processed state as active ingredients and cer-
tain excipients, such as solvents, diluents, or preservatives. In most cases, the active
principles responsible for their pharmacological action are unknown.
A herb might be considered a “diluted” drug. To achieve the desired benefit, an
individual must take an adequate amount over a certain length of time. Each herb
is different. While some are safe and effective for specific uses, others are not. The
general perception that herbal drugs are very safe and free from side effects is not
true. Herbs can produce undesirable side effects and can be toxic. A particular
plant part will have many constituents and some of them may well be toxic. How-
ever, it may take more to cause toxicity, because herbs usually are not as potent as
manufactured drugs, and compared with synthetic drugs the adverse effects of
most herbal drugs are relatively infrequent [25–27].
Herbal medicines are very different from well-defined synthetic drugs. For ex-
ample, the availability and quality of the raw materials are frequently problematic;
the active principles are frequently unknown; and standardization, stability, and
quality control are feasible but not easy. In comparison with modern medicine,
herbal medicines cost less, are more often used to treat chronic diseases, and the
occurrence of undesirable side effects seems to be less frequent.
A vast number of plants have medicinal properties; in fact, many pharmaceuti-
cal drugs were originally derived from plants. Ethnopharmacology – the scientific
study of indigenous medicines – is an interdisciplinary science practiced all over
the world. Phytotherapeutic agents or phytomedicines are standardized herbal
preparations that contain, as active ingredients, complex mixtures of plant materi-
als in the crude or processed state. One basic characteristic of phytotherapeutic
agents is the fact that they normally do not possess an immediate or strong phar-
macological action. For this reason, these agents are not suitable for emergency
treatment.
During the past decade, there has been increasing acceptance and public inter-
est in natural therapies in both developing and developed countries. Due to pover-
ty and limited access to modern medicine, about four billion people, 80% of the
world’s population, living in developing countries use herbal medicine as their
source of primary health care [25, 28–30]. In these communities, traditional medi-
cal practice is often viewed as an integral part of their culture.
In the West, people are attracted to herbal therapies for many reasons, the most
important reason being that, like our ancestors, we believe they will help us live
healthier lives. Herbal medicines are often viewed as a balanced and moderate ap-
proach to healing. Individuals who use them as home remedies and over-the-coun-
ter drugs spend billions of dollars on herbal products. As such, they represent a
substantial proportion of the global drug market [16, 19–21, 23, 24, 27, 28, 31–36].
28 2 Quality Control, Screening, Toxicity, and Regulation of Herbal Drugs
This recent resurgence of interest in plant remedies has been spurred on by sev-
eral factors [21, 23, 26, 31]:
The effectiveness of plant medicines.
The preference of consumers for natural therapies, a greater interest in alterna-
tive medicines and a commonly held erroneous belief that herbal products are
superior to manufactured products.
A dissatisfaction with the results from synthetic drugs and the belief that herbal
medicines might be effective in the treatment of certain diseases where conven-
tional therapies and medicines have proven to be inadequate.
The high cost and side effects of most modern drugs.
Improvements in the quality, efficacy, and safety of herbal medicines with the
development of science and technology.
Patients’ belief that their physicians have not properly identified the problem;
hence they feel that herbal remedies are another option.
A movement towards self-medication.
Medicinal plants provide the raw materials for the pharmaceutical industry. In-
deed, about 25% of the prescription drugs dispensed in the United States contain
at least one active ingredient derived from plant material. Many pharmacological
classes of drugs include a natural product prototype. Aspirin, atropine, morphine,
quinine are just a few of the drugs that were originally discovered through the
study of traditional cures and folk knowledge of indigenous people [37]. Herbal
therapies, on the other hand, consist of the chemical components of a plant as they
occur naturally [8]. Some are made from plant extracts, others are synthesized to
mimic a natural plant compound. Pharmaceutical drugs derived from plants are
made by isolating the active chemicals and concentrating them to the medication.
Pharmacognosy is the scientific study of drugs from natural products.
In most countries herbal products are launched into the market without proper
scientific evaluation, and without any mandatory safety and toxicological studies.
There is no effective machinery to regulate manufacturing practices and quality
standards. Consumers can buy herbal products without a prescription and one
might not recognize the potential hazards in an inferior product. A well-defined
and constant composition of the drug is therefore one of the most important pre-
requisites for the production of a quality drug. Given the nature of products of
plant origin, which by definition are never constant and are dependent on and in-
fluenced by many factors, quality control plays a significant role for the industry to
thrive and be successful
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