Current Knowledge on Beetroot Bioactive Compounds: Role of Nitrate and Betalains in Health and Disease

Abstract

An increase in the prevalence of noncommunicable chronic diseases has been occurring in recent decades. Among the deaths resulting from these conditions, cardiovascular diseases (CVD) stand out as the main contributors. In this regard, dietary patterns featuring a high content of vegetables and fruits, such as the Mediterranean and the DASH diets, are considered beneficial, and thus have been extensively studied. This has resulted in growing interest in vegetable-derived ingredients and food-supplements that may have potential therapeutic properties. Among these supplements, beetroot juice, which is obtained from the root vegetable Beta vulgaris, has gained much attention. Although a significant part of the interest in beetroot juice is due to its nitrate (NO₃^-) content, which has demonstrated bioactivity in the cardiovascular system, other ingredients with potential beneficial properties such as polyphenols, pigments and organic acids are also present. In this context, the aim of this review article is to analyze the current knowledge regarding the benefits related to the consumption of beetroot and derived food-supplements. Therefore, this article focuses on nitrate and betalains, which are considered to be the major bioactive compounds present in beetroot, and thus in the derived dietary supplements.

Keywords: beetroot; betalains; dietary supplement; nitrate.

Figure 1

Nitrate–nitrite–nitric oxide pathway. Adapted from Niayakiru et al., 2020 [11].

Figure 2

Conversion of nitrate and nitrite into nitrosamines. NO₃⁻: nitrate, NO₂⁻: nitrite, NO: nitric oxide, HNO₂: nitrous acid, H₂N₂O: nitrosamines, HN₂O₂: nitrosamides, Vit C: vitamin C. Adapted from Berends et al., 2019 [40].

Figure 3

Classification of the two main groups of betalains present in beetroot. All the chemical structures included in this figure were obtained from Khan et al., 2015 [46].

Figure 4

Antioxidant effects induced by betanins through Nrf2. Betanins enhance the Nrf2-Keap1 complex dissociation (A) and enhance Nrf2 nuclear translocation (B). Additionally, betanins can also activate MAPK (C), which, in turn, phosphorylates and stabilizes Nrf2 (D), contributing to its nuclear translocation. As a result, nuclear Nrf2-ARE binding is increased, resulting in enhanced transcription of genes encoding antioxidant and phase II enzymes. ARE: antioxidant response element, Keap1: Kelch-like repressor protein ECH-associated protein 1, MAPK: mitogen-activated protein kinase and Nrf2: nuclear factor erythroid 2-related factor 2.

Figure 5

Anti-inflammatory effects of betanins through the modulation of Nrf2-Keap1 and NF-κB-IKB complex dissociation. IKB: KB inhibitor, IKK: ikB kinase, Keap1: Kelch-like repressor protein ECH-associated protein 1, NF-κB: nuclear factor κB and Nrf2: nuclear factor erythroid 2-related factor 2.