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Paw Paw Offers Hope for Cancer

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Dr. McLaughlin

Dr. McLaughlin

The pawpaw tree is indigenous to several areas of North America. 

Some have theorized that it receives its name due to its similar appearance to the papaya fruit; however, the two fruits are totally unrelated.  Pawpaw is of the scientific family Annonaceae, which includes several unusual tropical fruits. 

There are about eight different species of pawpaw; however it is the species Asimina triloba that was used by Dr. Jerry McLaughlin in his research, and it is only this species that contains the special annonaceous acetogenins that have been shown to so powerful in fighting insects, cancer cells, parasites, lice, and other attackers.  The pawpaw is a cousin to the fruit known as graviola, but research has proven that although graviola has some similar natural chemical compounds, it is not as desirable or as powerful as Asimina triloba for medical use.  Unfortunately, however, some opportunistic companies will market graviola as an equal.   It is not.

 The trees themselves are not large as far as trees go.  Some are about the size of large shrubs, although many grow as high as 25 feet, and sometimes a little more.  The fruit itself is about the size of a large human fist–usually 3-6 inches long– and is considered by many to be very tasty.  It is often compared to a combination of some sort of banana, coconut, mango, and possibly others. One reason that it is not available too often in retail settings is that it spoils quickly after it is harvested.  However, those who are fortunate enough to find a ripe fruit on a tree and eat it fresh are usually rewarded with a very pleasant tasting experience.

The fruit is also highly nutritious–very rich in proteins, good fats, and complex carbohydrates.  It is normally ripe in the fall, usually in September.  The explorers Meriwether Lewis and William Clark were known to have survived on pawpaw for about a month during their famous exploratory trip.

As a child, Jerry McLaughlin ate the fruit and felt that there must be something biologically active.  As a Professor of Pharmacognosy at Purdue University, he spent over 20 years studying this fruit.  He discovered the presence of a natural chemical in the tree called an acetogenin.  An acetogenin is a long-chained, fatty acid substance with some very unique properties.  Over 400 of these compounds have been found in nature, many of them by researchers working with Dr. McLaughlin at Purdue University.  In other parts of the world, researchers have been looking for acetogenins in other fruits of the same family.  However, the double-ringed features of the powerful acetogenins in the Asimina triloba have not been found to date in those other fruits.

Interestingly enough, the acetogenins that are so powerful are not as plentiful in the fruit as in the twigs of the tree.  Also, Dr. McLaughlin found that the acetogenin levels peaked in the twigs during the month of May.  Just as important, he found the levels of acetogenins vary even by location of the Asimina triloba trees.  Some groves produce higher levels than others.  Thus, if someone is considering using pawpaw as a treatment, it is not only important to ensure that the product is from the Asimina triloba species of pawpaw, but also that the product is standardized–in other words, the manufacturer uses an extraction process for the acetogenins and ensures that a guaranteed set amount (standardized amount) of acetogenins is actually in the product.  At this point, only one manufacturer in the world has the capability of accomplishing this, partially because Dr. McLaughlin has licensed his patent and methodology to them.

Steven Horne of Tree of Light Publishing put out a handout about the only standardized pawpaw product available.  Good quick source of information.  Published in 2003, some of the information about the antioxidants is a little outdated since recent tests by the Josephine Ford Cancer Center in Detroit indicate that using antioxidants with pawpaw does not interfere with the pawpaw action.

Look What’s Hidden in the Paw Paw Tree Fruit

During World War II, when bananas were scarce, Jerry L. McLaughlin’s dad gave him some “Indiana bananas” — the custard-like fruit of Asimina triloba, better known as the pawpaw tree. Though only about 4 years old at the time, McLaughlin recalls, “I threw up and never forgot them.”

A pharmacognosist at Purdue University in West Lafayette, Ind., McLaughlin now searches for plants possessing natural medicinal properties. Based on his unforgettable encounter with the Indiana banana, he focused a few years ago on the pawpaw. After all, he notes, “parmacology is simply toxicology at a lower dose.” The result: He reports finding a family of biologically active compounds — acetogenins — “that’s very good against cancer, and also terrific at killing insects.”

A crude extract of pawpaw twigs killed brine shrimp at a concentration of just 0.04 parts per million (ppm)–well below the 70 ppm concentration of strychnine needed to elicit the same effect. One novel acetogenin his team isolated from the pawpaw extract — asimicin — also proved lethal to blowfly larvae, two-spotted spider mites, Mexican bean beetles, mosquito larvae, melon aphids, striped cucumber beetles and a nematode. McLaughlin expects that natural asimicin-based pesticides, for which he holds a patent, may be marketed within four or five years.

McLaughlin also subjected brine shrimp to extracts from the pawpaw’s relatives. He hit a lode with Annona bullata, a Cuban native closely related to the “custard apple.” From this plant he extracted two acetogenins with anticancer prospects. In tests conducted by a major pharmaceutical company, one of those acetogenins — bullatacin — proved 1 million times more potent than the common anticancer drug cisplatin in inhibiting the growth of human ovarian tumors transplanted into mice. The National Cancer Institute is currently testing his acetogenins in in vitro trials, he says.

The acetogenins’ mode of action differs from that of most anticancer drugs: Rather than killing a cell by scrambling its DNA, they starve the rapidly divinding cells of the ATP that fuels them. As a result, McLaughlin says, “I don’t think we’ll have to worry about these [acetogenins] ever causing cancer–as some anticancer agents do.”

“Nor do we have to rely on Cuba to get bullatacin, the most potent acetogenin,” McLaughlin notes. In the March JOURNAL OF NATURAL PRODUCTS, he and his co-workers will announce isolating bullatacin and six other biologically active acetogenins–including a new compound, trilobacin–from the common pawpaw. The report also shows that trilobacin exhibited high levels of growth suppression in cultured cells of some leukemias, small-cell lung cancer, colon cancer, melanoma, ovarian cancer and renal cancer.

If the pawpaw contains so many potentially toxic agents, how can anyone stomach its fruit? In moderation, McLaughlin observes, the ripe fruit can prove quite edible. But his team’s assays indicate that unripe fruits “are almost as toxic as the twigs — really potent.” And that makes sense, he suspects, “because nature wanted to discourage animals from eating it and spreading its seeds before the fruit was ripe.”

Source:  Paw Paw


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