Variations in the Anticancer Activity of Free and Bound Phenolics of Finger Millet (Eleusine coracana (L) Gaertn; Variety KMR-301) Seeds

Abstract

• Procyanidin B1, 3-O-methyl quercetin and Epigallocatechin are the major phenolics of FM-FP. • FM-BP is rich in Protocatecheuic acid, Ferulic acid and Vanillic acid. • FM-FP exhibited better cytotoxicity against breast cancer cell lines compared to FM-BP. • FM-FP induced fragmentation of DNA and apoptotic cell death in breast cancer cells. Finger millet (FM, Eleusine coracana (L) Gaertn; also known as “ragi” in Kannada language) is one of the widely used millets especially in south India and parts of Africa. FM is consumed in various forms that include porridge, mudde (ball), dosa (a pan cake), idly (a savory rice cake) and biscuits/cookies. FM is also used in the form of malted drink known as “malted ragi or ragi malt”. FM is a rich source of dietary fiber, tannins, phenolic compounds and calcium. Prior studies have shown health beneficial properties such as anti-diabetic and anti-inflammatory effects of FM, and ascribed those properties to the presence of dietary fiber and phenolic compounds. But, very minimal information is available pertaining to the effect of FM phenolic compounds on cell lines representing carcinomas of colon and rectum; and breast. Hence, we have studied the effect of FM phenolic compounds on colorectal carcinoma and breast cancer cell lines. Sequentially extracting the seeds by 70% ethanol and 10% alkali generated free (FM-FP) and bound (FM-BP) phenolic compounds respectively. UPLC-QTOF-MS was used to determine the phytochemical composition. Antioxidant potential was determined by ferric reducing antioxidant power assay (FRAP) and radical scavenging activity (DPPH assay). Effect of FM-FP and FM-BP on cellular proliferation was determined by sulforhodamine-B assay. Staining the untreated and treated cells with acridine orange and ethidium bromide followed by analyzing the stained cells using fluorescence microscope yielded key information about impact of extracts on cell death. Effect on cell cycle was determined by staining the cells with DAPI followed by analyzing the stained cells using NC-3000. Analysis of the UPLC-QTOF -MS data showed the presence of phenolics and phenolic acid derivatives, flavonoids and aminoacids in the FM-FP and FM-BP fractions. Both fractions exhibited ferric ion reduction ability and DPPH radical scavenging potential. But, the effect of FM-FP and FM-BP on cell proliferation varied significantly from cell line to cell line. FM-FP exhibited better cytotoxic potential compared to FM-BP when tested against breast cancer cell lines. Cytotoxic FM-FP induced G0/G1 or G2/M arrest in a cell line dependent fashion and increased the fragmentation of DNA leading to accumulation of cells in Sub-G1 phase. In summary, results of our study demonstrated the strength of finger millet free- and bound phenolic compounds for exhibiting antioxidant property, and the potential to modulate the proliferative potential of breast and colorectal cancer cells.