Abstract: The emergence and rapid spread of the potentially fatal coronavirus disease 2019, caused due to infection by severe acute respiratory syndrome coronavirus-2, has led to worldwide interest in developing functional bioactive ingredients that act as immunomodulatory agents. In this study, we aimed to characterize Carica papaya extract and explore its potential as an immuno-modulator by performing in vitro cell screening. Papaya leaf water extract (PLW) was found to significantly increase the levels of nitric oxide (NO) and prostaglandin E2 (PGE2) by upregulating inducible nitric oxide synthase and cyclo-oxygenase-2 activity, respectively. Additionally, PLW increased the production of tumor necrosis factor-α and interleukin 1β in RAW 264.7 cells. Furthermore, PLW activated the expression of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) but not that of p38 mitogen-activated protein kinase. These results indicate that PLW increased the production of NO, PGE2, and pro-inflammatory cytokines by activating the JNK and ERK pathways in macrophages, thus demonstrating immunomodulatory properties. Finally, high-performance liquid chromatography fingerprint analysis indicated the presence of rutin, narirutin, and ρ-coumaric acid in PLW (6.30, 119.76, and 47.25 ppm, respectively). Treating cells with these compounds at non-toxic concentrations had no effect on NO production. Taken together, these results suggest that PLW may have potential as an immunity-enhancing supplement. © The Korean Society for Applied Biological Chemistry 2021.
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