5-Deoxyflavin (5-Deoxyriboflavin, CAS 26908-38-3, C₁₇H₁₈N₄O₂, MW ~310 g/mol) is a synthetic riboflavin (Vitamin B2) analog where the C5′ hydroxyl (-OH) group of the D-ribityl side chain is replaced by a hydrogen atom (-H). This single atomic substitution — the removal of one oxygen atom — has profound biochemical consequences. In native riboflavin, the C5′-OH serves as the obligatory phosphorylation site for flavokinase (ATP:riboflavin 5′-phosphotransferase, EC 2.7.1.26), the enzyme that converts riboflavin to flavin mononucleotide (FMN) — the first committed step in flavin coenzyme biosynthesis. FMN is subsequently converted to flavin adenine dinucleotide (FAD) by FAD synthetase (EC 2.7.7.2). Both FMN and FAD serve as the redox-active prosthetic groups in over 150 human flavoproteins, including Complex I and II of the mitochondrial electron transport chain, NADPH oxidases, nitric oxide synthases, and the entire family of flavin-dependent monooxygenases, oxidases, and dehydrogenases. By eliminating the C5′-OH, 5-deoxyflavin completely blocks phosphorylation by flavokinase — preventing conversion to FMN and consequently to FAD. The compound therefore cannot participate in the endogenous flavin coenzyme pool, making it a non-metabolizable, non-activatable flavin analog. Critically, 5-deoxyflavin retains the full, unmodified isoalloxazine ring — preserving identical UV-Vis absorption (λmax 370 and 445 nm), fluorescence (λem ~525 nm), ground-state and excited-state redox potentials, and 1e−/2e− redox capability of riboflavin — while the sole C5′-OH → H modification renders it metabolically inert. This unique combination of complete photochemical/redox fidelity and complete biochemical silence is what makes 5-deoxyflavin the reference-standard non-metabolizable probe for flavin research.

5-Deoxyflavin serves as a non-metabolizable flavin probe across five principal experimental paradigms: (1) Competitive inhibition of flavokinase — 5-deoxyflavin binds to the riboflavin-binding pocket of flavokinase but cannot be phosphorylated due to the absent C5′-OH, enabling precise kinetic characterization of the enzyme’s substrate recognition determinants and phosphorylation mechanism (Kᵢ, Vmax, and substrate-specificity profiling). (2) Flavoprotein reconstitution — apo-flavoproteins (flavoenzymes with the FMN/FAD cofactor removed by dialysis against KBr or acidic ammonium sulfate) can be reconstituted with 5-deoxyflavin to generate catalytically inactive holoenzyme complexes — enabling structural studies (X-ray crystallography, cryo-EM, NMR) of the cofactor-binding site in a locked, non-turnover conformation without catalytic interference from residual enzymatic activity. (3) Cellular flavin transport studies — because 5-deoxyflavin cannot be trapped intracellularly as FMN/FAD (the usual metabolic sink that drives riboflavin uptake via the RFVT1-3/SLC52A1-3 transporters), it serves as an ideal probe to dissect transporter kinetics and substrate specificity without the confounding factor of intracellular metabolic trapping. (4) Isoalloxazine ring redox mechanistic studies — 5-deoxyflavin retains the full isoalloxazine ring system capable of both one-electron (semiquinone) and two-electron (hydroquinone) redox transitions, enabling researchers to study the intrinsic redox chemistry of the isoalloxazine chromophore by spectroelectrochemistry, stopped-flow kinetics, and laser flash photolysis — without phosphate-dependent conformational effects, protein interactions, or coenzyme interconversion artifacts. (5) Photoinduced electron transfer (PET) research — as a riboflavin analog with identical isoalloxazine photophysics, 5-deoxyflavin exhibits the same excited-state redox properties including the extraordinarily negative *Flₛₑ/Fl•− reduction potential (~-2.4 V vs NHE), but without complications from ribityl-chain phosphorylation that can introduce competing photochemical pathways — making it the preferred chromophore for fundamental flavin photochemistry, time-resolved transient absorption spectroscopy, and biomimetic photocatalytic studies.

Flavin photochemistry is centered on the isoalloxazine ring — the tricyclic chromophore (7,8-dimethylbenzo[g]pteridine-2,4(3H,10H)-dione) that endows riboflavin, FMN, and FAD with their characteristic yellow color, green fluorescence (λem ~525 nm), and extraordinary redox versatility. The isoalloxazine ring can exist in three oxidation states: oxidized (Flₛₑ, quinone form, yellow, λmax ~370 and 445 nm), one-electron reduced semiquinone (Fl•− or FlH•, radical anion or neutral radical, red to blue depending on protonation state, pKa ~8.3), and two-electron reduced hydroquinone (FlH₂ or Flred, fully reduced, colorless). This 1e−/2e− redox capability is the mechanistic foundation of all flavin biochemistry and photochemistry — flavins are unique among biological redox cofactors in their ability to mediate both obligate one-electron (radical) and obligate two-electron (hydride) chemistry from a single active site. In the ground state, the Flₛₑ/Fl•− one-electron reduction potential is approximately -0.30 V vs NHE (pH 7) for free riboflavin — modest and physiologically accessible within the mitochondrial matrix redox environment (NADH/NAD+ ~ -0.32 V). However, upon photoexcitation to the singlet excited state (*Flₛₑ), the reduction potential is thermodynamically shifted to approximately -2.4 V vs NHE — making photoexcited flavins among the strongest biological photoreductants known, capable of reducing substrates with reduction potentials as low as -2.0 V. This enormous ~2.1 V driving force arises from the photon energy (~2.7 eV for λmax 445 nm) being funneled into the redox potential of the excited state, enabling electron transfer from substrates that would be thermodynamically impossible in the ground state. The two-electron Flₛₑ/FlH₂ reduction potential (ground state) is approximately -0.21 V vs NHE — also physiologically accessible — allowing flavins to mediate hydride (H−) transfer, formal hydrogen atom transfer, and coupled proton-electron transfer (PCET) reactions. This rich redox landscape — combining 1e− radical chemistry, 2e− hydride chemistry, and photoactivated super-reductant behavior all within a single small-molecule chromophore — explains why flavins are Nature’s most versatile redox cofactors, found in every domain of life and spanning functions from DNA photolyase repair to circadian rhythm regulation (cryptochromes), from mitochondrial respiration to bioluminescence. 5-Deoxyflavin preserves this entire isoalloxazine photochemical and redox repertoire while eliminating metabolic interconversion — enabling researchers to study flavin photophysics and redox chemistry in a biochemically silent background, free from the confounding effects of FMN/FAD formation and flavoprotein incorporation.

5-Deoxyflavin occupies a unique and irreplaceable position in the flavin analog landscape, distinguished from riboflavin and other synthetic flavins by the specific C5′-OH → H substitution and its functional consequences. Native riboflavin (Vitamin B2, C₁₇H₂₀N₄O₆, MW 376.36 g/mol) bears the full D-ribityl side chain with four hydroxyl groups — the C5′-OH being the essential phosphorylation site — and is the natural precursor to FMN and FAD. Riboflavin is ideal for physiological studies but its rapid intracellular phosphorylation and incorporation into dozens of flavoproteins makes it impossible to distinguish effects mediated by riboflavin itself versus its FMN/FAD metabolites. Lumiflavin (7,8,10-trimethylisoalloxazine, C₁₃H₁₂N₄O₂, MW 256.26 g/mol) is the photodegradation product of riboflavin — the entire ribityl chain is replaced by a methyl group at N10. It retains the isoalloxazine chromophore but has poor aqueous solubility, no biochemical recognition by flavoproteins, and altered redox potentials due to N10-methyl substitution — limiting its use to spectroscopic standards and computational modeling. Lumichrome (7,8-dimethylalloxazine, MW 242.23 g/mol) is the fully dealkylated photoproduct — an alloxazine with blue-shifted fluorescence and significantly altered redox behavior, used as a fluorescent probe but not a functional flavin surrogate. 5-Deazaflavin (5-deaza-isoalloxazine) replaces the N5 nitrogen with carbon — a fundamental ring modification that converts the isoalloxazine from a 1e−/2e− redox system to a strict obligate 2e− hydride-transfer system incapable of forming a semiquinone radical intermediate — widely used to probe the distinction between one-electron and two-electron flavin mechanisms but fundamentally altering the redox landscape being studied. 8-Dimethylamino-flavins are electron-rich analogs with elevated ground-state reduction potentials, used to tune redox potential in artificial flavoenzymes. 5-Deoxyflavin stands apart from all of these: it retains the full, unmodified isoalloxazine ring — preserving identical UV-Vis absorption (λmax 370 and 445 nm), fluorescence (λem ~525 nm, ΦF ~0.26), ground-state redox potentials (E°′ Flₛₑ/Fl•− ~ -0.30 V; E°′ Flₛₑ/FlH₂ ~ -0.21 V), 1e−/2e− capability, and excited-state photophysics of riboflavin — while the sole C5′-OH → H modification renders it completely metabolically inert with respect to flavokinase phosphorylation and FMN/FAD biosynthesis. It is the only flavin analog that delivers complete isoalloxazine photochemical/redox fidelity combined with complete biochemical silence — making it the reference-standard non-metabolizable probe for fundamental flavin research across the fields of mechanistic enzymology, photobiology, bioinorganic chemistry, and biomimetic catalysis. Researchers who need to study the isoalloxazine ring without metabolic interference have no alternative that matches 5-deoxyflavin’s combination of chemical authenticity and biochemical inertness.

Every shipment includes: COA (HPLC purity ≥98.0% or ≥95.0%, full impurity profile, appearance — yellow to orange-yellow crystalline powder, identification by HPLC retention time vs 5-deoxyflavin reference standard, UV-Vis spectral conformity λmax 370 ± 2 nm and 445 ± 2 nm, loss on drying ≤0.5%, residue on ignition ≤0.1%, heavy metals ≤10 ppm with Pb ≤2 ppm / As ≤1 ppm / Hg ≤1 ppm / Cd ≤1 ppm, residual solvents per USP <467> / ICH Q3C), MSDS, Structure Confirmation Report (¹H-NMR spectrum with full peak assignments confirming C5′-deoxy modification — diagnostic: absence of C5′-OH proton and appearance of C5′-H₃ methyl signal; ¹³C-NMR spectrum; HRMS [M+H]+ confirming molecular formula C₁₇H₁₈N₄O₂ and MW ~310 g/mol), HPLC Chromatogram (signed and dated, with retention time and peak area percent), UV-Vis Absorption Spectrum (250–550 nm in aqueous buffer, pH 7.0, confirming characteristic isoalloxazine near-UV and visible bands), BSE/TSE-Free Statement, Non-GMO Statement, Allergen Statement, HALAL Certificate, KOSHER Certificate, ISO 22000 + HACCP, ISO 9001:2015, FDA Facility Registration, Stability Data (2–8°C real-time 24-month and 25°C/60%RH accelerated 6-month), and Complete Lot Traceability from synthesis batch to finished product. Free sample available for qualified academic and industrial researchers. MOQ: 100 mg (Research Grade), 1 g (Technical Grade). All documents provided in English. Custom synthesis, bulk quantities, and additional analytical characterization (e.g., single-crystal XRD, cyclic voltammetry, time-resolved fluorescence, transient absorption spectroscopy) available upon request for qualified research programs.