Isoalloxazinebased

Isoalloxazine-based compounds are chemical species built on the isoalloxazine nucleus, a rigid, tricyclic heteroaromatic ring system that forms the core of the flavin family. The isoalloxazine ring system underpins biologically important cofactors and many synthetic dyes, conferring distinct redox and photophysical properties.

In nature, the principal isoalloxazine-containing molecules are riboflavin (vitamin B2) and its phosphorylated derivatives flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). These cofactors participate in a wide range of oxidation–reduction reactions, serving as carriers of one- or two-electron equivalents in flavoproteins. The isoalloxazine core can be modified at several positions, particularly N1, N3, and C8, to tune redox potential, absorption, and fluorescence, while preserving the tricyclic framework.

Chemically, isoalloxazine-based compounds are often colorless to yellow and exhibit notable photophysical behavior, including fluorescence in many derivatives. They can participate in reversible redox couples, existing as oxidized flavin, a semiquinone, or a hydroquinone species. These properties enable applications as fluorescent probes for flavin-dependent enzymes, as well as components in photoredox catalysis and dye-sensitized systems. The ribityl side chain found in natural cofactors influences solubility and enzyme recognition, but many synthetic isoalloxazines are designed without it for material or catalytic applications.

Applications span biochemistry, medicinal chemistry, and materials science. They are used as cofactors or probes to study flavoproteins, as dyes and photosensitizers, and as redox mediators in light-driven processes. Synthesis generally involves construction of the fused tricyclic ring and subsequent selective functionalization at nitrogen or carbon positions.