Introduction
The word "pharmacognosy" derives from the
Greek words pharmakon (drug),
and gnosis
or knowledge.
The term pharmacognosy was used for the first time by the Austrian physician
Schmidt in 1811. Originally - during the 19th century and the beginning of the
20th century - "pharmacognosy" was used to define the branch of
medicine or
commodity sciences ("Warenkunde" in German) which dealt with
drugs in their
crude, or unprepared, form.
Crude drugs are the dried, unprepared material of plant, animal or mineral
origin, used for medicine. The study of pharmakognosie was first
developed in German-speaking areas of Europe. The term drogenkunde
("science of crude drugs") is also used synonymously.
Although most pharmacognostic studies focus on plants and medicines derived
from plants, other types of organisms are also regarded as pharmacognostically
interesting, in particular, various types of microbes (bacteria, fungi, etc.),
and, recently, various marine organisms.
Ethnopharmacology
When studying the effectiveness of herbal medicines and other nature-derived
remedies, the information of the traditional uses of certain extracts of even
extract combinations plays a key role. The lack of studies proving the use of
herbs in traditional care is especially an issue in the United States where the
use of herbal medicine has fallen out of use since the Second World War and was
considered suspect since the
Flexner Report of 1910 led to the closing of the eclectic medical schools
where botanical medicine was exclusively practiced. This is further complicated
by most herbal studies in the latter part of the 20th Century having been
published in languages other than English such as German, Dutch, Chinese,
Japanese, Korean and Farsi. As it may be more difficult to review foreign
language publications, many of these publications have undergone been
incorporated into the US Food and Drug Administration's "FDA"
determinations of drug safety. In 1994 the US Congress passed the
Dietary Supplement Health and Education Act (DSHEA), regulating labeling and
sales of herbs and other supplements. Most of the 2000 US companies making
herbal or natural products[2]
choose to market their products as
food supplements that do not require substantial testing.
Issues in Phytotherapy
The part of pharmacognosy focusing on use of crude extracts or semi-pure
mixtures originating from nature, namely phytotherapy, is probably the best
known and also the most debated area in pharmacognosy. Although phytotherapy is
sometimes connected to
alternative medicine, when critically conducted, it may be considered the
scientific study on the effects and clinical use of herbal medicines.
Constituents and Drug Synergyism
One characteristic of crude drug material is that constituents may have an
opposite, moderating or enhancing effect. Hence, the final effect of any crude
drug material will be a product of the interactions between the constituents and
the effect of each constituent on its own. To effectively study the existence
and affect of such interactions, scientific studies must examine the affect that
multiple constituents, given concurrently, have on the system. Herbalists assert
that as phytopharmaceuticals rely upon
synergy for their activities, plants with high levels of active constituents
like
ginsenosides or
hypericin
may not correlate with the strength of the herbs. In
phytopharmaceutical or
herbal medicine, the therapeutic effects of herbs cannot be determined
unless its active ingredient or
cofactors are identified or the herb is adminsistered as a whole. One way
manufacturers have attempted to indicate strength is to engage in
standardization to a
marker
compound. Companies use different markers, or different levels of the same
markers, or different methods of testing for marker compounds. Many herbalists
believe that the active ingredient in a plant is the plant itself.[3]
Herb and Drug Interactions
The Sloan Kettering Memorial Cancer Center stated, in a review of a Juice
product, which had been marketed as preventing cancer, that antioxidants could
theoretically interfere with chemotherapy.[4]
A recent review of the effect of antioxidants on chemotherapy, however, found no
evidence for any deleterious effects of antioxidants on chemotherapy.[5]
A study of herb drug interactions indicated that the vast majority of drug
interactions occurred in four classes of drugs, the chief class being blood
thinners, but also including
protease inhibitors,
cardiac glycosides and certain antibiotics like
cyclosporin.Cyclosporin is not an antibiotic it is an immuno-suppressant[6]
[7]
Natural products chemistry
Most bioactive compounds of natural origin are secondary metabolites, i.e.
species-specific chemical agents that can be grouped into various categories A typical protocol to isolate a pure chemical
agent from natural origin is bioassay-guided fractionation, meaning step-by-step
separation of extracted components based on differences in their physicochemical
properties, and assessing the biological activity, followed by next round of
separation and assaying. Typically, such work is initiated after a given crude
drug formulation (typically prepared by solvent extraction of the natural
material) is deemed "active" in a particular in vitro assay. If the
end-goal of the work at hand is to identify which one(s) of the scores or
hundreds of compounds are responsible for the observed in vitro activity,
the path to that end is fairly straightforward: 1. fractionate the crude
extract, e.g. by solvent partitioning or chromatography. 2. test the fractions
thereby generated with in vitro assay. 3. repeat steps 1) and 2) until
pure, active compounds are obtained. 4. determine structure(s) of active
compound(s), typically by using spectroscopic methods.
Loss of Biodiversity
Farnsworth for example, has found that 25% of all prescriptions dispensed
from community pharmacies in the United States from l959 to l980 contained
active ingredients extracted from higher plants. A much higher percentage is
found in the developing world. As many as 80% of all people living in developing
countries, or roughly two thirds of the world's population, rely almost
exclusively on traditional medicines using natural substances, mostly derived
from plants.
Sustainable Sources of Plant and Animal Drugs
As species face loss of habitat or overharvesting, there have been new issues
to deal with in sourcing crude drugs. These include changes to the herb from
farming practices, substitution of species or other plants altogether,
adulteration and cross-pollination issues. For instance, ginseng which is field
farmed may have significant problems with fungus, making contamination with
fungicides an issue. This may be remedied with woods grown programs, but they
are insufficient to produce enough ginseng to meet demand. The wildcrafted
echinacea, black cohosh and American ginseng often rely upon old growth root,
often in excess of 50 years of age and it is not clear that younger stock will
have the same pharmaceutical effect.[16]
Black cohosh may be adulterated with the related Chinese actea species, which is
not the same. Ginseng may be replaced by ginseniodes from Jiaogulan which has
been stated to have a different effect than the full panax root.[17]
The problem may be exacerbated by the growth of pills and capsules as the
preferred method of ingesting medication as they are cheaper and more available
than traditional, individually tailored prescriptions of raw medicinals but the
contents are harder to track. Seahorses are a case in point: Seahorses once had
to be of a certain size and quality before they were accepted by practitioners
and consumers. But declining availability of the preferred large, pale and
smooth seahorses has been offset by the shift towards prepackaged medicines,
which make it possible for TCM merchants to sell previously unused juvenile,
spiny and dark-coloured animals. Today almost a third of the seahorses sold in
China are prepackaged.
[18]
The farming of plant or animal species, used for medicinal purposes has
caused difficulties. Rob Parry Jones and Amanda Vincent write:
- One solution is to farm medicinal animals and plants. Chinese
officials have promoted this as a way of guaranteeing supplies as well
as protecting endangered species. And there have been some
successes�notably with plant species, such as American ginseng�which is
used as a general tonic and for chronic coughs. Red deer, too, have for
centuries been farmed for their antlers, which are used to treat
impotence and general fatigue. But growing your own is not a universal
panacea. Some plants grow so slowly that cultivation in not economically
viable. Animals such as musk deer may be difficult to farm, and so
generate little profit.
Seahorses are difficult to feed and plagued by disease in captivity.
Other species cannot be cultivated at all. Even when it works, farming
usually fails to match the scale of demand. Overall, cultivated TCM
plants in China supply less than 20 per cent of the required 1.6 million
tonnes per annum. Similarly, China's demand for animal products such as
musk and pangolin scales far exceeds supply from captive-bred sources.
- Farming alone can never resolve conservation concerns, as government
authorities and those who use Chinese medicine realise. For a start,
consumers often prefer ingredients taken from the wild, believing them
to be more potent. This is reflected in the price, with wild oriental
ginseng fetching up to 32 times as much as cultivated plants. Then there
are welfare concerns. Bear farming in
China is
particularly controversial. Around 7600 captive bears have their bile
"milked" through tubes inserted into their gall bladders. The World
Society for the Protection of Animals states that bear farming is
surrounded by "appalling levels of cruelty and neglect"
[19]. Chinese officials state that 10 000 wild bears would
need to be killed each year to produce as much bile, making bear farming
the more desirable option. The World society for the Protection of
Animals, however, states that "it is commonly believed in China that the
bile from a wild bear is the most potent, and so farming bears for their
bile cannot replace the demand for the product extracted from wild
animals".
- One alternative to farming involves replacing medical ingredients
from threatened species with manufactured chemical compounds. In
general, this sort of substitution is difficult to achieve because the
active ingredient is often not known. In addition, most TCM users
believe that TCM compounds may act synergistically so several
ingredients may interact to give the required effect. Thus TCM users
often people prefer the wild source.
Tauro ursodeoxycholic acid, the active ingredient of
bear bile, can be synthesised and is used by some Western doctors to
treat gallstones, but many TCM consumers reject it as being inferior to
the natural substance from wild animals.[20]
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