Biochemistry
Pawpaw fruits are rich in fatty acids, the major one being octanoate. They also contain cis-δ9- and cis-δ11-hexadecenoate, cis-δ9-, cis-δ11- and cis-δ13-octadecenoate.
The seeds have been shown to contain the chemicals asimitrin (an adjacent ring-hydroxylated bis-tetrahydrofuran acetogenin) and 4-hydroxytrilobin (an adjacent bis-THF ring with two flanking hydroxyl groups and an α,β-unsaturated γ-lactone with a 4-hydroxyl group). These chemicals seem to have selective cytotoxicity against prostate adenocarcinoma (PC-3) and colon adenocarcinoma (HT-29) cell lines, thus may become a useful chemotherapeutic chemical for these types of cancer.
The leaves also contain toxic annonaceous acetogenins, making them impalatable to most insects. The one notable exception is the zebra swallowtail butterfly (Eurytides marcellus), whose larvae feed on the leaves of various species of Asimina, conferring protection from predation throughout the butterfly's life, as trace amounts of acetogenins remain present, making them unpalatable to birds and other predators.
The bark of pawpaw trees contains other acetogenins, including asimin, asiminacin and asiminecin, which have been shown to be potent inhibitors of mitochondrial NADH:ubiquinone oxidoreductase, making A. triloba a promising source of pesticide and anti-tumour compounds.
Read more about this topic: Asimina Triloba