Antioxidant and anti‑inflammatory effects of esculin and esculetin (Review)

Abstract

Fraxinus chinensis Roxb is a deciduous tree, which is distributed worldwide and has important medicinal value. In Asia, the bark of Fraxinus chinensis Roxb is a commonly used traditional Chinese medicine called Qinpi. Esculetin is a coumarin compound derived from the bark of Fraxinus chinensis Roxb and its glycoside form is called esculin. The aim of the present study was to systematically review relevant literature on the antioxidant and anti-inflammatory effects of esculetin and esculin. Esculetin and esculin can promote the expression of various endogenous antioxidant proteins, such as superoxide dismutase, glutathione peroxidase and glutathione reductase. This is associated with the activation of the nuclear factor erythroid-derived factor 2-related factor 2 signaling pathway. The anti-inflammatory effects of esculetin and esculin are associated with the inhibition of the nuclear factor κ-B and mitogen-activated protein kinase inflammatory signaling pathways. In various inflammatory models, esculetin and esculin can reduce the expression levels of various proinflammatory factors such as tumor necrosis factor-α, interleukin (IL)-1β and IL-6, thereby inhibiting the development of inflammation. In summary, esculetin and esculin may be promising candidates for the treatment of numerous diseases associated with inflammation and oxidative stress, such as ulcerative colitis, acute lung and kidney injury, lung cancer, acute kidney injury.

Keywords: anti-inflammatory; antioxidant; esculetin; esculin.

Figure 1

Antioxidant and anti-inflammatory effects of Fraxinus chinensis Roxb. TLR4, toll-like receptor 4; GPx, glutathione peroxidase; SOD, superoxide dismutase; GSH, glutathione; IKK, IκB kinase.

Figure 2

Structural formula of esculetin and esculin.

Figure 3

Schematic diagram of the antioxidant and anti-inflammatory mechanisms of esculetin and esculin. TLR4, toll-like receptor 4; Keap1, Kelch-like ECH-associated protein 1; Nrf2, nuclear factor erythroid 2-related factor 2; HO-1, heme oxygenase-1; CAT, chloramphenicol acetyltransferase; GSH, glutathione; NQO1, NADPH quinone oxidoreductase; SOD, superoxide dismutase; GPx, glutathione peroxidase; GSTP1, glutathione S-transferase Pi; GST, glutathione-S-transferase; RNS, reactive nitrogen species; MDA, malondialdehyde; ROS, reactive oxygen species; ERK, extracellular regulated protein kinase; JNK, c-Jun N-terminal kinase; MCP-1, monocyte chemoattractant protein-1; iNOS, inducible isoform of nitric oxide synthase; ICAM, intracellular adhesion molecule; MPO, myeloperoxidase.