Phenolic Rich Pawpaw Extract Fraction Is Cytotoxic to Carcinomic Human Alveolar Basal Epithelial Cell Line A549

Pawpaw (Asimina triloba), a deciduous species of the eastern U.S., bears the largest edible fruit of all indigenous woody species. Pawpaw fruit, rich in phenolic and antioxidant components as well as essential amino acid, vitamins, and minerals, has also been identified as a major source of a group of anticancer compounds, acetogenins. The objective of the study was to investigate the cytotoxicity of lyophilized pawpaw extract and phenolic rich fraction with a lung cancer cell line.  Extracts used in this study include the whole extract (W), Fraction 2 (F2), and Fraction 5 (F5). Brine shrimp assay and cell proliferation assay were performed to assess toxicity of these extracts. Pawpaw pulp was extracted with 100% acetone twice, and then lyophilized. Acetonic (AcOH) extract was first made with fruit pulp of popular pawpaw cultivars ‘NC-1’ and ‘Overleese’, which was lyophilized and then reconstituted with double distilled water (DDH₂O), followed by fractionation with different solvents in the order of DDH₂O, 50% methanol (MeOH), 100% MeOH, 100% AcOH and 50% AcOH. Fractioned extracts were lyophilized again and phenolic content (PC) and antioxidant capacity (AC) were estimated with Folin-Ciocalteu assay and ferric reducing/antioxidant power (FRAP) assay. Both AC and PC of F5 were found significantly greater than that of either whole extract or F2. Cytotoxicity of pawpaw extracts were assessed by cell proliferation assay with carcinomic human alveolar basal epithelial cells (A549). While cytotoxicity of whole pawpaw extracts against A549 cells was modest, F5, the phenolic rich fraction showed considerable toxicity to this cell line. The present findings suggest that the possible usefulness of this phenolic rich fraction in cancer treatment regimen.