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| flowers are rose or white | contorted crownslips in bud |
This family is also famous for the many medicinal and thus toxic
plants. The medicinal substances can be divided in two major groups.
One group is the cardiac-glycosides. These compounds have a digitalis
like action on the heart.
The heart contraction is improved and the volume of pumped blood
is higher, but in over dosage the heart will stop beating.
The other group are the alkaloids. These are nitrogen compounds
made from the building stones of proteins, amino acids or the building
stones of DNA/RNA, purines.
Alkaloids have many different toxic/medicinal actions in bacteria,
fungi and animals and even in other plants.
Nerve cells communicate with other cells by releasing chemicals to
alert the receiving cell that it should alter its activity. These
substances are called neurotransmitters.
An great number of neurotransmitters are variations of amino
acids, just as many alkaloids. These look alikes alkaloids can disturb the
communication between nerve cells in the nervous system and organs in
the body.
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| flowers are rose or white | contorted crownslips in bud |
This plant from Madagascar was introduced in the tropics as an ornamental
plant. Traditional the plant is used to treat malaria, diarrhea and
skin diseases. The tea was used for treatment of diabetes.
There are about 100 alkaloids present in these plants, most
are simple but also complex molecules, build of the simple ones.
These complex compounds like vincristine or vinblastine are used to treat
cancer. Vincristine for example is used (as injection) in
chemotherapy in acute leukemia, Hodgkin’s disease and many other
cancerous diseases.
It needs more than 3 kg of the dried herb to make one injection
with 1 mg vincristine.
These alkaloids prevent the formation of microtubules in the metaphase of cell divisions. So the fast dividing cancer cells are slowned down or even killed, but this has severe side effects on normal cells also.
Some of the simple alkaloids have a antidiabetic action.
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| Holarrhena pubescens | one flower |
This tree has a wide distribution in the old tropics, including
Thailand. The bark (and seeds) are used against amoebic dysentery and
other protozoan diseases.
The seed oil has anthelmintic properties.
The active principle in the bark is the alkaloid connesine.
Connesine is also highly toxic to Trichomonas intestinales and
T. vaginalis.
It can inhibit the grow of insect larva’s.
Seed extracts have antibiotic activity against for example
Pseudomonas and Staphylococcus.
The use of the bark can cause hypotension, so it should be used
carefully
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| Rauvolfia serpentine |
As an ayurvedic medicine in India it is used to cure snakebites, epilepsy and mental diseases like psychoses and epilepsy. Other uses are the uses are: dysentery, stimulating child birth and for uterine contractions.
There are more than 50 alkaloids present, mostly indol alkaloids
like reserpine, derived from tryptophane. This is the raw material
for neurotransmitters that regulate basic functions like blood
pressure and emotional feelings in the mind.
After the introduction of reserpine in 1952 in Western medicine it
changed the treatment reducing blood pressure completely. Reserpine has
a strongly lowering blood pressure effect and at the same time anxiety
releasing action.
It has a depleting action on the neurotransmitter vesicles for a
number of neurotransmitters.
The drug in over dosage gives rise to severe depressions.
The modern anti-depressives are supposed to prevent the
fast removal of these neurotransmitters from the side of action.
Thailand alone exported up to 100 t/year of the dried root powder.
In 1982 the price of powdered roots was 9 US dollar for 1 kg, and
reserpine about 2.5 US dollars per gram.
Now cell-cultures are used to produce basic indol alkaloids, and
enzymes needed for processing the indol like chemicals, but not yet
for the highly complex alkaloids in
In the western world this plant is now scarcely used because of
the difficulty to maintain a safe action of the single substances.
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| Strophanthus gratus | the fragrant flowers |
This is an very showy, good smelling ornamental African plant, also
popular in Thailand, and not because of its interesting pharmaceutical
properties.
The milky juice and the seeds are traditionally used to prepare
poisonous darts in Africa. Small quantities are sufficient, and work
quickly.
The seeds contain a mixture of cardiac-glycosides, with a
mode of action like the well known digitalis cardiac-glycoside. The
main glycoside is g-strophantin or ouabain. ( inhibition of K/Na-pump
in the cardiac cells).
Eating these plants or drinking tea can be very dangerous. You
can get very ill, but the compounds induce vomiting. Most of the times
this vomiting is enough to survive the consumption.
Generally animals like caterpillars that are resistant for these
toxic compounds in their food, can accumulate these compounds in their
body. Predators will die or learn not to eat these toxic animals.
Medicinally ouabain is only clinically used as an injection for
emergencies in congestive heart failure. The action is faster and of
shorter duration than cardiac-glycosides in the genus
It is very easy to inject too much of the drug and together with its
fast action it is than an effective poison (poison darts).
In folk medicine a watery extract is used for treating snake bite.
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| Allamanda cathartica | Thevetia peruviana | Thevetia peruviana | Thevetia peruviana | Asclepias currasavica | dispersing seeds | Nerium oleander |
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| Plumeria | popular ornamentals |
This link offers information about cardiac glycosides.
Wikipedia is sometimes a nice place to refresh and enrich your
knowledge about alkaloids.