Paw paw and cancer: annonaceous acetogenins from discovery to commercial products
Extracts of paw paw (Asimina triloba, Annonaceae) are among the most potent of the 3500 species of higher plants screened for bioactive compounds in our laboratories at Purdue University. The paw paw is a small tree native to eastern North America; its edible fruits (sometimes referred to as “Indiana Bananas”) have nurtured mankind for centuries. Activity-directed fractionation of the paw paw extracts, using the brine shrimp lethality bioassay, led to the isolation and molecular characterization of over 50 unique annonaceous acetogenins. Fractionation of extracts from related species resulted in the identification of over 150 additional acetogenins. The annonaceous acetogenins are derivatives of long-chain (C32 or C34) fatty acids. They are potent inhibitors of mitochondrial (complex I) as well as cytoplasmic (anaerobic) production of adenosine triphosphate (ATP) and the related nucleotides. The powerful cytotoxicity, in vivo antitumor, pesticidal, antimalarial, anthelmintic, piscicidal, antiviral, and antimicrobial effects indicated a myriad of potentially useful applications. Commercial development of these compounds uses natural mixtures of active components, incorporated into pesticidal, topical, and dietary supplement products. Successful applications and commercial products include a shampoo, highly effective in treating infestations of head lice, fleas, and ticks; a series of pesticidal sprays, which protects host plants against a diversity of pests; and an ointment for treatment of oral herpes (HSV-1) and other skin afflictions. The extract (in capsule form) enhances a mixture of natural anthelmintics. In addition, an encapsulated extract has been effectively used by certain cancer patients as a botanical supplement product.