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Also known as
the graviola, the soursop has achieved recent popularity as a cancer treatment
in various alternative medicine journals.
The soursop,
Annona muricata, belongs to the Annonaceae family, along with the paw paw,
Asimina triloba. Initially grown for its delicious fruit, it has recently been
promoted as an antic cancer treatment.
Health and
alternative medicine publications continually refer to research work carried
out at Purdue University under the leadership of Dr. Jerry McLaughlin, and
claim that McLaughlin and his co-workers have isolated a group of chemicals
from the soursop that selectively target the tumour cells of drug resistant
cancers.
The Truth Behind the Anti-Cancer Claims
Mclaughlin
has, in fact, carried out National Cancer Institute funded research on both the
soursop and the paw paw since 1976. He has also discovered a group of chemicals
known as the annonaceous acetogenins that do indeed appear to destroy tumour
cells in breast, ovarian, pancreatic, liver and lung cancers. These chemicals,
derivatives of long chain fatty acids, have also been shown to display
pesticidal properties.
Despite these
tests occurring in vitro only (that is, in the lab but not on actual cancer
patients), McLaughlin’s results are encouraging. The acetogenins appear to act
by inhibiting an important electron transport pathway in the production of ATP
in the mitochondria of tumour cells, with the result that these cells are
depleted of the energy they require to grow and multiply.
Moreover, it
is the tumour cells that seem to be targeted and not normal somatic cells, as
Purdue scientists discovered in tests on six human cell lines. Apparently, a
special glycoprotein pump present in tumour cells that is capable of resisting
the effects of anti cancer drugs is destroyed by acetogenins.
The Limited Effectiveness of the Soursop as a
Cancer Treatment
Mclaughlin’s
best results, however, have been with the paw paw, rather than the soursop. Two
acetogenins, Bullatacin and Bullatalicin, found only in the paw paw, have
proved to be much more potent than other chemicals in this family of compounds.
The Purdue
team has discovered that these two molecules have double ring structures, as
opposed to the less effective compounds with single or triple rings. Tests
carried out by the pharmaceutical company, Pfizer, have also confirmed the
effectiveness of Bullatacin in killing tumour cells.
As a
consequence, while the 30 or so acetogenins in the soursop do have the capacity
to destroy cancer cells, they are much less effective than those found in the
paw paw. Furthermore, because extracting acetogenins from the soursop is not
rigorously controlled, there is no guarantee that the concentration of this
compound in the ground leaves, seeds and twigs of the plant is consistent.
Paw paw
preparations, on the other hand, appear to be more stringently monitored. Paw
paw twig extract, endorsed by McLaughlin, is available in capsule form from the
company ‘Nature’s Sunshine’. Given the higher potency of paw paw acetogenins,
coupled with its more sophisticated production techniques, it would seem that
cancer patients seeking alternative treatments should choose this over any
soursop products on the market.
Why Haven’t Acetogenin Treatments Been Approved by
the F.D.A?
It must be
noted that none of these acetogenin preparations have yet to be approved by the
FDA as cancer treatments. According to the alternative medicine magazine, ‘Truth
on Medicine’, large pharmaceutical companies, which could afford clinical
trials, are not interested in acetogenins because they are natural compounds
that cannot be synthesised.
As a result,
they cannot be patented and are therefore not a profitable proposition. Mclaughlin
himself adds that because the acetogenins have multiple forms (or isomers), it
would be too difficult a task for these companies to process an average of
around 256 possible isomers per molecule. With a range of up to 50 different
acetogenins, McLaughlin believes this would be ‘simply too complex for modern
studies’.
Can Acetogenins be Synthesised?
The accuracy
of McLaughlin’s statement can perhaps be questioned in the light of studies by
the University of Minnesota in 1993 and the Scripps Research Institute in 2000
that have in fact managed to synthesise isomers of Bullatacin, one of the most
potent acetogenins. Whether this is enough for pharmaceutical companies to work
with and patent is another question.
Nevertheless,
the fact that independent studies continually show the tumour suppressing
qualities of the acetogenins suggests a degree of truth in the claims made
about the Annonaceae family. In the light of McLaughlin’s work, however,
further research on the paw-paw rather than the soursop would appear to hold
more promise.
References
Avedissian
et.al, 2000, ‘Total Synthesis of Asimicin and Bullatacin’, The Scripps Research
Institute, technion.ac.il
Cancer active,
2010, ‘Graviola anona Muricata’, canceractive.com
Fassa, P.,
2010, ‘Newly Discovered Herbs Revealed for Healing Cancer and Other Diseases’,
truthonmedicine.wordpress.com
McLaughlin,
J., ‘Paw Paw -Alternative Cancer Treatment’ Parts 2-7, smashcancer.com
Paw Paw Research.com,
2006, ‘Graviola is Inferior to Paw-Paw as a Cancer Treatment: Here’s why’,
pawpawresearch.com
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