Abstract:
Our recent studies have demonstrated multiple health-promoting benefits from black
walnut kernels. These biological functions of black walnuts are likely associated with their bioactive
constituents. Characterization of phenolic compounds found in black walnut could point out
underexplored bioactive activities of black walnut extracts and promote the development of novel
applications of black walnut and its by-products. In the present study, we assessed bioactivity profiles
of phenolic compounds identified in the kernels of black walnuts using a high-throughput screening
(HTS) approach. Black walnut phenolic compounds were evaluated in terms of their total antioxidant
capacity, antioxidant response element (ARE) induction, and anticancer activities. The anticancer
activities were identified by evaluating the effects of the phenolic compounds on the growth of
the tumorigenic alveolar epithelial cells (A549) and non-tumorigenic lung fibroblast cells (MRC-5).
Out of 16 phenolic compounds tested, several compounds (penta-O-galloyl-β-d-glucose, epicatechin
gallate, quercetin, (–)-epicatechin, rutin, quercetin 3-β-d-glucoside, gallic acid, (+)-catechin, ferulic
acid, syringic acid) exerted antioxidant activities that were significantly higher compared to Trolox,
which was used as a control. Two phenolic compounds, penta-O-galloyl-β-d-glucose and quercetin
3-β-d-glucoside, exhibited antiproliferative activities against both the tumorigenic alveolar epithelial
cells (A549) and non-tumorigenic lung fibroblast cells (MRC-5). The antioxidant activity of black
walnut is likely driven not only by penta-O-galloyl-β-d-glucose but also by a combination of multiple
phenolic compounds. Our findings suggested that black walnut extracts possibly possess anticancer
activities and supported that penta-O-galloyl-β-d-glucose could be a potential bioactive agent for the
cosmetic and pharmaceutical industries.
Description:
Supplementary Materials: Figure S1: Data distribution of controls (Trolox,
DL-sulforaphane, tert- butylhydroquinone) in total antioxidant capacity and antioxidant response element (ARE)
activation assays. Figure S2: Data distribution of controls (Trolox, DL-sulforaphane) in cytotoxicity assays.