Phenylethanoid Glycosides: A Mini Review on their Anti-liver Injury Effects and Underlying Mechanisms

Phenylethanoid glycosides (PhGs) are water-soluble natural compounds widely distributed in the plant kingdom, attracting significant attention from medicinal chemists due to their promising potential in pharmaceutical applications. PhGs exhibit a broad range of activities, including neuroprotective, hepatoprotective, anti-inflammatory, antioxidant, and immunomodulatory effects. This review aims to update the hepatoprotective effects of total PhG extracts and individual PhG compounds, as well as the underlying mechanisms. Additionally, we describe the structural characteristics, representative PhG compounds, and their structure–activity relationships. In brief, total PhG extracts can exert synergistic protection by reducing serum alanine aminotransferase/aspartate aminotransferase levels, suppressing oxidative stress, and attenuating inflammatory responses. Representative PhGs, including acteoside (verbascoside), echinacoside, forsythoside A (also known as forsythiaside A), and cistanoside A, protect against liver injury through modulation of the Nrf2/HO-1, NF-κB, MAPK, and TGF-β/Smad pathways, thereby regulating oxidative stress, inflammation, apoptosis, fibrosis, and lipid metabolism. Structurally, PhGs consist of a phenylethyl alcohol core, cinnamoyl residues, and glycosyl moieties. Structure–activity relationship analyses indicate that caffeoyl substitution, multiple phenolic hydroxyl groups, and optimal glycosylation patterns are key determinants of hepatoprotective efficacy.