Table 2.

A summary of cancer prevention effects of beetroot in in vitro or in vivo models

No	Test items and dose	Experimental model	Dose and treatment duration	Cancer preventive effects	References
In vitro antioxidant and anti-inflammatory activities
1	Beetroot ethanol extract (lyophilized)	Cell-free system using DPPH NO inhibitory efficacy in mouse macrophage RAW 264.7 cell line	25-100 µg/mL	Good antioxidant, electron-donating ability and radical scavenging activity Increases inhibition rate of NO production in LPS-treated cells	[55]
2	Water extracts of beetroot	Cell-free system using standard chemical tests Cellular antioxidant activity assay in HT29 (human colon adenocarcinoma) cells Activity of phase II detoxification enzymes: glutathione S-transferases (GST) and quinone oxidoreductase (NQO1)	10% (v/v) extracts (24 h) 10% (v/v) (6-24 h)	Strongest antioxidant potential as compared with other plants No significant cytotoxic nor any protective effect against oxidative DNA damage in ROS challenged cells No significant ability to induce activity of phase II detoxification enzymes	[16]
3	Betanin (red beet extract diluted with dextrin; CAS-Nr.: 7659-95-2)	Comet assay in HT-29 cells Nrf2 dual luciferase reporter gene assay in Huh7 cells Antioxidant enzyme heme oxygenase-1 (HO-1) expression in Huh7 cells Glutathione (GSH) concentration in Huh7 cells	15 µM betanin (14 h) 1-15 µM betanin (24 h) 25 µM betanin (24 h) 1-15 µM betanin (24 h)	Prevents DNA damage Induces Nrf2 at 15 µM betanin Increases in HO-1 protein concentration Increases cellular GSH	[56]
4	Betanin (ABCR GmbH & Co. KG, Karlsruhe, Germany)	In vitro PMA-induced DNA damage in isolated human neutrophils (PMNs) DNA damage (Comet assay) in isolated human neutrophils Fluorometric analysis of caspase-3 activity	200 µM betanin (30 min) 20-200 µM (24 h) 20-300 µM (24 h)	Diminishes intracellular ROS level elevated by PMA stimulation (~3 fold) Decreases the percentage of DNA in the comet tails of the stimulated neutrophils Enhances caspase-3 activity in stimulated neutrophils	[57]
5	Betanin (ABCR GmbH & Co. KG)	In vitro H2O2-induced DNA damage in isolated human neutrophils and Caco-2 intestinal cells Caspase-3 activity	200 µM (24 h) 200 µM (24 h; neutrophils) 20-200 µM (24 h; Caco-2 cells)	Betanin reduces DNA damage (~14%) caused by H2O2 Enhances caspase-3 activity in neutrophils and Caco-2 cells Triggers apoptotic cell death	[58]
In vivo antioxidant and anti-inflammatory activities
6	Beetroot juice (79.3 mg/100 mL betaxanthins and 159.6 mg/100 mL betacyanins)	NDEA and CCl4-induced oxidative stress rat model	8 mL/kg/day for 28 days	Reduces DNA damage in blood leukocytes Restores the activity of some of the antioxidant enzymes in the liver Prevents xenobiotic-induced oxidative stress	[59]
7	Beetroot juice (79.3 mg/100 mL betaxanthins and 159.6 mg/100 mL betacyanins	Phase I and phase II enzymes, DNA damage and NDEA-induced liver injury model in rats	8 mL/kg/day for 28 days	Reduces biomarker levels of liver injury such as ALT, SDH, GGT and bilirubin Reduces DNA damage triggered by NDEA treatment	[60]
8	Beetroot ethanol extract (lyophilized)	Alcohol induced liver damage model in rats	200 or 400 mg/kg for 4 weeks	Decreases serum AST, ALT and γ-GTP concentrations Decreases fat accumulation and inflammatory cell infiltration Improves morphological characteristics of damaged liver lesion Exert protective effects in hepatotoxicity	[55]
9	Beetroot ethanol extract (evaporated dry)	Gentamicin-induced nephrotoxicity in rats Oxidative/nitrosative stress, inflammatory and apoptotic markers	250 and 500 mg/kg weight for 20 days before gentamicin treatment and there after concurrently with gentamicin for 8 days	Inhibits gentamicin-induced up-regulation of inflammatory markers and nitric oxide level Reduces the expression of apoptotic markers in the kidney cells. Reduces inflammatory infiltration in the kidney tubules	[2]
In vitro antiproliferative and other chemopreventive activities
10	Betanin and betaine isolated from beetroot extracts	MTT assay in HepG2 cells	0-200 µg/mL 800 µg/mL	Inhibits cell proliferation in a dose dependent manner Inhibits HepG2 cells by 25%	[67]
11	Betacyanins purified from beetroot	Sulforhodamine B (SRB), apoptosis marker assay in urinary bladder cancer cells (T24) and normal human skin keratinocytes (NCTC 2544)	50 µg/mL at 24, 48 and 72 h	Betacyanins and vitexin-2-O-xyloside synergistically inhibit proliferation of tumor cells and not normal cells Induces apoptosis markers in tumor cells	[68]
12	Beetroot extract (diluted with dextrin)	Trypan blue cell viability assay in human pancreatic (PaCa), breast (MCF-7) and prostate cancer (PC-3) cell lines	0.29-290 µg/mL at 72 h	Synergistic antiproliferative effects when used in combination with doxorubicin IC50 values reduced to almost 40%	[69]
13	Betanin/isobetanin enriched powder from beetroot	Cell proliferation, apoptosis and autophagy assay in mouse melanoma cell line (B16F10), human breast cancer lines (MCF-7, MDA-MB-231), human colorectal cells (HT-29) and normal human fibroblasts (MRC-5)	48 h IC50 about 25 µM for B16F10 and MCF-7 cells and 35 µM for MDA-MB-231 cells	Decreases cancer cell proliferation and viability. Increases the expression of apoptosis-related proteins and autophagosome vesicles	[70]
14	Betavulgarin isolated from beetroot	Breast cancer cells (MDA-MB-231 and MCF-7)	MDA-MB-231 (≥ 100 µM) and MCF-7 cells at ≥ 50 µM for 24 h	Suppresses proliferation, migration, colony formation, and mammosphere formation Reduces the size of the CD44+/CD24− subpopulation Reduces the expression of the self-renewal-related genes, c-Myc, Nanog and Oct4 Inhibits the Stat3/Sox2 signaling pathway and induces breast cancer stem cells death	[71]
In vivo antiproliferative and other chemopreventive activities
15	E162-water (78 µg/mL E162 dye powder in water)	N-nitrosomethylbenzylamine (NMBA)-induced tumors in the rat esophagus (F344 rats)	35 weeks	Reduces NMBA-induced esophageal papillomas by 45% Reduces rates of cell proliferation in cancerous lesions Reduces level of angiogenesis and inflammation Increases rate of apoptosis	[72]
16	Beetroot extract (betanin) (TCI America, Portland, OR, USA)	Mouse skin and lung carcinogenesis model	0.0025% (w/v) betanin in drinking water for 20 weeks	Inhibits TPA-induced promotion of mice skin tumors Reduces 60% of lung tumors	[73]
17	Betanin extract (betanin) (TCI America)	VC and B(a)P-induced lung tumors in mice	25 and 100 µg/mL betanin in drinking water for 20 weeks	Decreases tumor multiplicity and tumor load Induces caspase-3 expression Inhibits angiogenesis	[74]
18	Beetroot extract (extracted with 70% ethanol)	γ-ray irradiation in C57BL/6 mice	400 mg/mouse orally three times	Stimulates cell proliferation Minimizes DNA damage of splenocytes Repopulates S-phase cells Boosts differentiation of HSCs into burst-forming units Enhances level of hematocrit and hemoglobin and RBC	[76]
Chemoprevention clinical studies
19	Beetroot-carrot juice	Case report of a patient diagnosed with B-cell chronic lymphocytic leukemia (B-CLL)	330 mL of fresh raw beetroot- carrot juice orally (beetroot 200 g + carrots 250 g) 2 h before breakfast 6 times/week for 1.5 month 330 mL of fresh beetroot-carrot juice 6 times per week, in combination with the chlorambucil protocol 8 mg/day for 37 days	Decreases leukocyte and lymphocyte count from Reduces level of uric acid in blood Increases appetite, Improves fatigue Decreases leukocyte, lymphocyte and reticulocyte counts Improves renal function Improved blood urea, serum creatinine and uric acid levels Decreases LDH level	[77]
20	Beetroot (concentrated organic beetroot crystals)	Untreated squamous cell cancer of the head and neck (Randomized phase II Trial)	10 g Beetroot powder mixed with 4-8 oz 12 weeks	Duration of study from December 2014-May 2018 Unpublished	ClinicalTrials.gov Identifier: NCT02058849
21	Dietary supplement: beetroot juice	Malignant breast tissue neoplasm	5-day dietary nitrate intervention programme, taking 3 doses of 7 cl (centiliter) (0.4 g nitrate per dose) concentrated beetroot juice	Duration of study from May 2019-June 2020 Unpublished	ClinicalTrials.gov Identifier: NCT03944226

NO, nitric oxide; LPS, lipopolysaccharide; ROS, reactive oxygen species; NDEA, N-nitrosodiethylamine; ALT, alanine aminotransferase; SDH, sorbitol dehydrogenase; GGT, gamma glutamyl transferase; AST, aspartate aminotransferase; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; VC, vinyl carbamate; B(a)P, benzo(a)pyrene; RBC, red blood cell.