Riboflavin as a Regulator of Cellular Metabolism: From the Classic Vitamin B2 to a Key Redox Factor

Riboflavin, i.e., vitamin B2, was first isolated by Kuhn and Győrgy in 1933, who reported that it acts as a growth factor. Riboflavin has long been known to play a key role in energy metabolism and cellular respiration, and its deficiency negatively affects skin and mucous membrane health. More recent studies have found it to regulate mitochondrial metabolism and to serve as the core of flavin coenzymes (FAD, FMN), which enable the respiratory chain and β-oxidation. Riboflavin also plays a key role as an antioxidant. While it is not a classic free antioxidant, it supports the enzymatic antioxidant system by supporting glutathione reductase, thioredoxin reductase, and ROS neutralization. On the other hand, when exposed to light, riboflavin exhibits photosensitizing properties that generate reactive oxygen species. As a result, it can initiate oxidative processes involving lipids, proteins, and nucleic acids, thereby exhibiting a prooxidative effect. The aim of this review is to provide an overview of the current understanding of the role of riboflavin in cellular and human health.