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 have 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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