Hi, solars-ga:
The word "artemicide" is an unusual one, and it took a trip to the
library for me to figure it out.
As mikewa-ga comments below, LC50 means "lethal concentration" for an
expected 50% of sample. [The difference between this and LD50 or
"lethal dose" for 50% of sample we shall return to momentarily.]
Taken together with the suffix "-cide" (which means killing), we
should be pretty confident that artemicide has to do with killing
something. But what???
[Brine shrimp -- Wikipedia]
http://en.wikipedia.org/wiki/Brine_shrimp
"Brine shrimp (Artemia) are a primitive type of aquatic crustacean.
They are more closely related to zooplankton than to true shrimp and
are found worldwide in saltwater, though not in oceans. Artemia is a
well known genus as one variety, the Artemia salina, has been sold as
novelty gifts, most commonly under the marketing name Sea Monkeys."
Yes, artemicide in this context means a substance that kills brine
shrimp (or sea monkeys, if you prefer to think of it that way!). Not
the sort thing I would have known, until I follow the trail from your
link above to a bound copy of Dr. James A. Duke's book:
[Handbook of Biologically Active Phytochemicals and Their Activities]
James A. Duke, Ph.D. (botany); CRC Press, 1992
Initially I was frustrated by this slim volume, because it has little
more than what is said on the Web site. Less in fact, if you consider
that the entry for narcotine in the book version does not list
"artemicide" as one of its activities. However many of the other
compounds, eg. stigmasterol and beta-sitosterol, are shown there to
have such activity. References are given for these last two to LC50
values in this paper:
[Bioactive Constituents of Melodorum Fruticosum]
J. H. Jung, S. Pummangura, C. Chaichantipyuth, C. Patarapanich, and J.
L. McLaughlin; Phytochemistry v.29(5), 1990, pp. 1667-1670; Pergamon
Press
"Abstract - The bark of Melodorum fruticosum was examined for
bioactive constituents. Fractionation and isolation were guided by
the brind shrimp lethality bioassay, leading to the isolation of
several bioactive constituents which were identified as dichamantin,
pinocembrin, polycarpol, benzylbenzoate, and stimasterol/sitosterol.
Further bioassays (cytotoxicities, antitumour and plant growth
regulating) were performed with these agents."
...
"The brine shrimp bioassay and the inhibition of crown gall tumours on
potato discs are convenient supplements to cell culture and the more
expensive antitumour assays, sparing the need for higher animals or
their serum."
The figure quoted by Dr. Duke in his book for
stigmasterol/beta-sitosterol LC50 (110ppm) is the same given in Table
2. "Bioassay results for isolated compounds" in under the first
experimental column "Brine shrimp LC50 ppm":
"It is interesting that the stimasterol and sitosterol mixture (1:1)
was toxic to brine shrimp (LC50 110ppm) and showed marginal activity
in the human tumour cell lines."
* * * * * * * * * * * * * *
Finally the use of LC50 versus LD50 signifies the difference between
exposure to a pervasive hazard versus exposure to a discrete amount.
Here the brine shrimp are placed in a solution of known concentration;
the dose given each would not be known as precisely as the
concentration.
regards, mathtalk-ga |
Clarification of Answer by
mathtalk-ga
on
21 Nov 2004 09:49 PST
I think it would be more accurate to say that killing brine shrimp
(artemicide) is considered a general screen for bioactive compounds
and not specific to potential "cancer killing" agents.
The word cytotoxicity literally means "cell poisoning":
[Cytotoxicity -- Dictionary.com]
http://dictionary.reference.com/search?q=cytotoxicity&r=67
One might expect a good cancer therapy to kill cancer cells
efficiently, while doing little or no harm to normal cells. A fairly
recent PubMed article:
[A comparison between two brine shrimp assays
to detect in vitro cytotoxicity in marine natural products]
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=130034
connects these roles, but says this:
"The brine shrimp lethality assay is considered a useful tool for
preliminary assessment of toxicity. It has also been suggested for
screening pharmacological activities in plant extracts. However, we
think that it is necessary to evaluate the suitability of the brine
shrimp methods before they are used as a general bio-assay to test
natural marine products for pharmacological activity."
This brief article is also interesting for its citations of earlier
works on brine shrimp assays, including this 1956 paper:
[Artemia salina as a test organism for a bioassay]
Michael AS, Thompson CG, Abramovitz M.; Science (1956)123:464
regards, mathtalk-ga
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