the use of biological assays to evaluate botanicals - Drug ...

514 Jerry L. McLaughlin, Lingling L. Rogers, and Jon E. Anderson
chemists has been simply to isolate, charac- include diverse and unknown mechanisms as
terize, and publish a plethora of novel botani- well as new chemical entities. In addition, in
cally-derived chemical substances without such specific bioassays the same extracts
regard to bioactivities. To achieve applied have to be analyzed many times, over and
meaning and significance, today’s work in over again, before detecting activities. It
natural product chemistry must incorporate would seem more logical to prescreen with
bioassays. Extracts must be screened for bio- general bioassays, throw out the negatives,
logical activity, the “active” extracts selected, and then employ specific bioassays on the
fractionations directed with bioassays, and actives. Unfortunately, this is not the trend
the bioactive compounds identified and then today within the major pharmaceutical com-
exploited. panies. The molecular pharmacologists have
This is the salvation of the natural product assured themselves of continued employchemist,
and such work must be performed ment as each new specific bioassay that they
with all useful bioactive botanicals if these devise must be employed to retest their firm’s
products are to be accepted and incorporated entire library of substances. Irrespective of
into legitimate, long-term, health practices. whether general or specific bioassays are fa-
Three readily available technologies must be vored, the use of all bioassays must be pro-
combined:
moted, and this promotion is the purpose
of this paper. The four bioassays which are
1. Separation techniques (chromatography), described below are easily adapted as “bench
2. Structural elucidation methods (spectrom- top” procedures for use in natural product
eters and X-ray crystallography), and chemistry. They are inexpensive, rapid, and
3. Simple bioassays.
Today’s natural product chemists are very
technologically simple, requiring little technical
training.
familiar with the first two, but, generally,
they ignore the third. It is the hope of the
authors of this paper that talents can cease
being wasted on the myriad of inactive natu-
Brine Shrimp Lethality:
A Rapid General Bioassay
for Bioactive Compounds
ral metabolites and can become increasingly Bioactive compounds are almost always
devoted to the identification of bioactive bo- toxic in high doses. Pharmacology is simply
tanical products. The health use of heteroge- toxicology at a lower dose, and toxicology
neous standardized botanical products will is simply pharmacology at a higher dose.
become generally acceptable in the United Thus, in vivo lethality in a simple zoologic
States only after their bioactive components organism can be used as a convenient monihave
been identified. Standardization of the tor for screening and fractionation in the dis-
products by biological assays will then gencovery and monitoring of bioactive natural
erate reproducible benefits and the resulting products. The eggs of brine shrimp, Artemia
consumer confidence.
salina (Leach), are readily available in pet
A rush to very specific, in vitro, robotic, shops at low cost and remain viable for years
mechanism-based bioassays has occurred in in the dry state. Upon being placed in sea
recent years. Receptor binding, enzyme in- water, the eggs hatch within 48 hours to pro-
hibition, affinity columns, DNA nicking, tuvide large numbers of larvae (nauplii) for
bulin inhibition, and so forth usually mimic experimental use.
the effects of some previously known com- Brine shrimp nauplii have been used prepound
having a specific mechanism of ac- viously in a number of bioassay systems, but
tion. Researchers must be cautious, however, the authors have developed a method where-
with mechanism-based assays. The field of by natural product extracts, fractions, or pure
vision of such specific microscopes is very compounds are tested at initial concentra-
narrow; they must be assured that the scope tions of 10, 100, and 1000 ppm (or mcg/
of their bioassays can be wide enough to
ml) in vials containing 5 ml of brine and