The Dermal Layer of Sweet Sorghum (Sorghum bicolor) Stalk, a Byproduct of Biofuel Production and Source of Unique 3-Deoxyanthocyanidins, Has More Antiproliferative and Proapoptotic Activity than the Pith in p53 Variants of HCT116 and Colon Cancer Stem Cells

Abstract

There is a growing interest in the utilization of sweet sorghum as a renewable resource for biofuels. During the biofuel production process, large quantities of biomass are generated, creating a rich source of bioactive compounds. However, knowledge of sweet sorghum stalk is lacking. We measured the phenolic content (Folin-Ciocalteu assay), antioxidant activity (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) assay), and phytochemical composition (LC-MS) in both the pith and dermal layer of the stalk. We further tested the antiproliferative (5-bromo-2'- deoxyuridine assay) and proapoptotic (terminal deoxynucleotidyl transferase dUTP nick end labeling assay) activities of these extracts using HCT116 cells and colon cancer stem cells (CCSCs) with and without the tumor suppressor gene p53. For the first time, we show that the dermal layer extract of sweet sorghum contains more of the 3-deoxyanthocyanidins apigeninidin and luteolinidin than the pith, and this is associated with more anticancer activity. Furthermore, luteolinidin suppressed CCSC proliferation more than apigeninidin. In addition to being renewable biofuel, sweet sorghum may also serve as a source of health-promoting compounds.