HISTORICAL DIMENSION
OCH 3 OCH3
OCH3
O CH3
OCH3 OCH3
CH3O
OCH3
+ +
N
O OH
N
O
H
CH3
OH
OCH3 CH3
CH3 CH3O
H
+
N
N N
N
N O
CH3 CH3
Br O
H CH3
CH3HO H
H CH3
H O
N
N N
N
N O
O HCH3
HO H
H CH3
H O
(Continued)
THE PLANT AND ANIMAL KINGDOMS AS SOURCES OF DRUGS66
8
Drug
Dextromethorphan
Structure Template molecule, structure
Morphine
Plant source and traditional use Papaver somniferum
Analgesic, soporific from Mediterranean region
Clinical use of drug Cough suppressant Analgesic
Pethidine
Etoposide Podophyllotoxin Podophyllum peltatum
Used as purgative and wart treatment by native North Americans
Anticancer
Metformin Galegine Galega officinalis
Used to treat diabetes in Europe
Antidiabetic in type 2 diabetes
Table 8.2 Some important drugs developed from molecules found in traditional medicinal plants. (Cont’d)
O O
O
O
OCH3 OCH3 CH3O
OH
H2N HN
HN N
H CH3 CH3
H2N HN
N
H CH3 CH3 O
O O
H H3C
OH O
O O
O O
CH3O OH
OCH3 HO
NCH3 O
C2H5O HO
H
NCH3
HO
H
NCH3 HO
O
TRADITIONAL PLANT MEDICINES AS A SOURCE OF NEW DRUGS67
8
Neostigmine Physostigmine Physostigma venenosum Treatment of
myasthenia gravis
Rivastigmine Ordeal poison from West
Africa
Treatment of early symptoms of Alzheimer’s disease
Sodium cromoglycate
Khellin Ammi visnaga
Treatment of bronchial complaints in Egypt
Antiasthmatic
Verapamil Papaverine Papaver somniferum
Analgesic, soporific from Mediterranean region
Angina and anticardiac arrhythmia
O O
OCH3
CH3
O OCH3
N
OCH3 OCH3 CH3O
CH3OO
CH3 H3C
CH3 CN
N
OCH3 OCH3 CH3O
CH3O O
O O
−OOC O
O
COO−
O OH
2Na+ O
O N CH3
CH3
N CH3
CH3 CH3 +
O N CH3
CH3 N CH3 CH3
O CH3
N N O
CH3 N O H
CH3 CH3 H CH3
8
their macronutritional properties. Attention has also been focused on the ways in which the role of a substance can change through time or as it is transferred from one culture to another. Thus, coffee was thought of as primarily medicinal when it was first introduced into northwest Europe in the seventeenth century, but quite rapidly became a beverage. It is also of interest that cultural restraints might mini- mize abuse of a substance in its indigenous context but that, when these restraints are removed as the plant begins to be used in another part of the world or society, it becomes a problem to that society.
An example of this situation is seen with the abuse of kava-kava in Australia by aboriginal peoples, who do not have the framework of ritualistic use of these roots in the Pacific islands of Fiji and Tonga, where it originates.
Several recent surveys have shown that using ethnopharmacology as a basis of selecting species for screening results in a significant increase in the ‘hit rate’ for the discovery of novel active compounds
compared with random collection of samples. It should be noted that several ‘classical’ drugs stated to have derived from ethnopharmaco- logical investigations, e.g. several shown in Table 8.1, arise from plants known as poisons rather than those with a more ‘gentle’ action, which comprise the bulk of many herbal medicine species. The latter group often relies on a mixture of compounds with a mixture of activities, where synergism and polyvalence might be occurring, and where the isolation of one ‘active constituent’ is much less likely.
With a very large number of living organisms still awaiting sci- entific investigation (about 90% of the estimated 250,000 species of flowering plants, probably the most studied part of the biosphere), ethnopharmacology appears to offer a reasonable selective strategy to be considered in deciding which organisms to study. An interesting overview of some ethnopharmacologically based molecules and the problems involved in their gaining regulatory status was published recently (T. W. Corson and C. M. Crews, Cell, 2007, 130: 769–774).
Herbal ‘medicine’ and botanical source Current use Geographical source Traditional use (if different) African prune bark Pygeum africanum To reduce benign prostatic
hyperplasia
Central African highlands Ashwagandha Withania somniferum
roots
To enhance memory, general tonic
India ‘Rasayana’ general tonic
Black cohosh Cimicifuga racemosa roots
Depression associated with menstrual cycle and menopause
North America Arthritis, neuralgia, menstruation disorders
Cat’s claw Uncaria tomentosa.
U. guianensis roots, stem bark, leaves
Rheumatism Amazon area of South
America
Antirheumatic and to treat infections and tumours Dan shen, Chinese sage Salvia
miltiorrhiza roots
Cardiovascular and cerebrovascular disease including ischaemic stroke
China Cardiovascular diseases and
cognitive decline Devil’s claw Harpagophytum procumbens
fruit
Rheumatism South-west Africa (Kalahari desert)
Purgative and for treating ulcers and boils
Dong quai Angelica sinensis root Menopausal symptoms China Irregular menstruation, blood deficiency
Echinacea Echinacea angustifolia, E. purpurea, E. pallida roots and aerial parts
Common cold and other respiratory infections
North America Anti-infective and to treat snakebite
Eleutherococcus, Siberian ginseng Eleutherococcus senticosus roots
Relief of fatigue, general health Siberia To help cope with stress Ginkgo Ginkgo biloba leaves To reduce CNS effects of
ageing
China For bronchitis
Ginseng Panax ginseng root Relief of fatigue, general health China, Korea Golden seal Hydrastis canadensis roots Catarrh, appetite and digestion
stimulant
North America Gastrointestinal and skin disorders Gotu Kola, hydrocotyle Centella asiatica
herb
Wound healing and skin conditions
India Rheumatism and skin conditions
Guarana Paullinia cupana seed kernels Tonic Northern Amazon forest Stimulant drink
Hoodia Hoodia gordonii stems Obesity Southern Africa Used to prevent hunger
Karela Momordica charantia Antidiabetic India and Southeast Asia
Kava Piper methysticum roots Anxiolytic and tranquillizer Tonga, Fiji Social drink to aid relaxation, treatment for skin conditions Lapacho, Pau d’Arco Tabebuia
avelladanae (and other Tabebuia spp.) inner bark
Stimulation of immune system to prevent infections
Tropical South America General tonic
Maca Lepidium meyenii tuber hypocotyl Erectile dysfunction, menopausal symptoms
High Andes of South America
Aphrodisiac Saw palmetto Serenoa repens fruits To reduce benign prostatic
hyperplasia
South-east USA
Table 8.3 Ethnopharmacological origins (other then Europe) of some common herbal ‘medicines’.
TRADITIONAL PLANT MEDICINES AS A SOURCE OF NEW DRUGS 69
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TRADITIONAL PLANT MEDICINES AS A SOURCE OF NEW DRUGS