PEANUT SKIN POLYPHENOLS: COMPOSITION, BIOACCESSIBILITY, AND ANTICANCER ACTIVITY IN CULTURED JURKAT LEUKEMIA CELLS

Abstract

Acute lymphoblastic leukemia is the most common cancer in children. Peanut skin polyphenols are known to exhibit in vitro anti-cancer properties, albeit to a lesser extent in leukemia cells. Furthermore, it remains unclear which polyphenols interact with cancer cell lines or affect cellular processes involved in cancer development and progression. Therefore, this study investigates the anti-leukemic activity and bioaccessibility of peanut skin polyphenols, aiming to identify specific polyphenols that interact with leukemia cells. The phenolic profile and content of peanut skins from peanut cultivar Georgia 06G was determined by first extracting with acidified aqueous acetone (acetone/water/acetic acid, 70:29.5:0.5, v/v/v) and quantified using the Folin assay, 4-(dimethylamino)cinnamaldehyde (DMAC) assay, and high-resolution UHPLC-MS/MS. The peanut skin extract (PSE) was rich in polyphenols, with total phenols of 780 ± 40 mg gallic acid equivalents per gram of PSE and total proanthocyanidins of 169 ± 15 mg (+)-catechin equivalents per gram of PSE. The extract contained primarily proanthocyanidins (procyanidins A2 and B2), (epi)catechin monomers, and various phenolic acids, stilbenes, and flavanols (quercetin). Further untargeted high-resolution mass spectrometry (HRMS) analysis tentatively identified additional proanthocyanidins, phenolic acids, and flavonoids in PSE. The extract was applied to Jurkat cells line as a model of childhood leukemia. PSE decreased Jurkat cell viability through RealTime-Glo™ MT Cell Viability and XTT assays, indicating antiproliferative activity. Subsequently, polyphenols were extracted from PSE-treated Jurkat cells to identify potentially active compounds that interact with Jurkat cells and contributed to its antiproliferative effect. This analysis revealed multiple compounds from PSE interact with Jurkat cells including protocatechuic acid, quercetin, (epi)catechin monomers and their galloyl derivatives, proanthocyanidins with A-type bonds, and methylated/prenylated

isoflavone/flavonoid aglycones. Lastly, to further evaluate the bioaccessibility of PSE, we examined the intestinal absorption and metabolism of PSE phenolics in Caco-2 cells, a model of the human intestinal barrier. PSE polyphenols had limited bioaccessibility with catechin, quercetin, procyanidin A2, and tentatively procyanidin A1. Certain polyphenols underwent extensive biotransformation into Phase II metabolites. Notably, procyanidin A2 was the most abundant phenolic compound detected in Jurkat cells after PSE treatment and was absorbed across Caco-2 cells. Additionally, we also detected methylated procyanidin A-type dimer in apical chamber of Caco-2 cell monolayer. Thus, these results suggest that peanut skins are a source of bioaccessible polyphenols that interact with leukemia cells, particularly procyanidin A- type dimers.