Pawpaw is toxic to some cancer cells, but such effects have not been shown in humans.
The major components of Pawpaw are compounds known as acetogenins. They prevent the cell from making ATP, an important energy source. In lab studies, the extract was shown to kill cancer cells that were resistant to commonly used chemotherapy drugs such as Adriamycin, and appear to be more toxic to cancer cells than to normal cells. However, this has not been shown in humans. The plant extract is used in anti-lice shampoo and in pesticides.
Pawpaw extract has been shown to be effective as an anti-lice shampoo.
Studies have not evaluated Pawpaw’s ability to kill parasites. There is laboratory-based evidence that attribute this ability to other closely related plants.
Pawpaw has been shown to be effective against cancer cells in test tubes, but experiments in mice produced conflicting results. There are no published clinical studies in humans to determine the safety of Pawpaw for cancer treatment.
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There are several Web sites that promote pawpaw as an effective treatment for cancer. However, there is very little scientific evidence to support such claims.
Asimina triloba, commonly known as Pawpaw, is native to North America and has edible bean-shaped fruits.
In vitro studies show that Pawpaw extract has cytotoxic effects against cancer cell lines including those resistant to Adriamycin (1); and antiangiogenic activity (9). Compounds known as acetogenins are thought to be the active constituents (2). Clinical studies have not been conducted.
Extracts of Pawpaw twigs and leaves have been used in anti-lice shampoos (3) and as pesticides (4).
Annonacin, a major constituent of Pawpaw, and the crude fruit extract cause neurotoxicity, in vitro (10). Asimina triloba should not be confused with graviola, also known as Brazilian Paw paw, or with papaya, another fruit with a similar texture and appearance.
Acetogenins, the active constituents of Pawpaw fruit, inhibit Complex I of the electron transport chain and NADH oxidase, a protein in the plasma membrane (1). With the decrease in regenerable NAD, the ATP levels drop, leading to subsequent cell death by apoptosis.
In vivo experiments have demonstrated Pawpaw’s cytotoxicity in mice (5). Pawpaw extract is also cytotoxic to Multi-Drug Resistant cells in vitro (1). This is thought to occur via acetogenin’s inhibition of the 170 kDa plasma membrane glycoprotein (the P-170 glycoprotein), an efflux pump used by cells resistant to drugs like Adriamycin (1).
Annonacin, a major ingredient of Pawpaw fruit, and the crude fruit extract were shown to be toxic to cortical neurons (10).
McLaughlin J L, Benson GB, Forsythe JW. A novel mechanism for the control of clinical cancer: Inhibition of the production of adenosine triphosphate (ATO) with a standardized extract of paw paw (Asiminoz triloba, Annonaceae). http://www.pawpawresearch.com/pawpaw-trials1.pdf. Accessed February 26, 2015.