Pharmaceutical Grade 9-β-D-Arabinofuranoside Ara-G with Reliable Quality for Research and Production

English name: Ara-Guanosine (Ara-G)

9-(BETA-D-ARABINOFURANOSYL) GUANINE

CAS No:38819-10-2

Molecular formula: C10H13N5O5

Molecular weight: 283.241

EINECS Accession number: 221-386-9

Ara-Guanosine (Ara-G) is a purine nucleoside analog with potent antiviral and, to a lesser extent, antineoplastic (anti-cancer) activity. As a raw material (Active Pharmaceutical Ingredient, API), it is a white to off-white, odorless crystalline powder. Chemically, it is designated as 9-β-D-arabinofuranosyladenine (Ara-A). Its molecular formula is C₁₀H₁₃N₅O₄, and it possesses a molecular weight of 267.24 g/mol. The CAS registry number for Vidarabine is 5536-17-4. The raw material is typically supplied with a purity of ≥98% (often ≥99% by HPLC for high-grade pharmaceutical use).

As a raw material, the physical characteristics of Vidarabine are critical for formulation (e.g., ophthalmic ointments, intravenous injections, or research solutions).

• Appearance: Fine, crystalline powder.

• Solubility: Vidarabine is slightly soluble in water (approx. 1.5–2.0 mg/mL at 25°C) and very slightly soluble in ethanol and chloroform. It is more soluble in dilute acids and alkalis. This low aqueous solubility is a key parameter formulators must address when developing liquid dosage forms.

• Melting Point: The substance decomposes upon melting, typically in the range of 257–260°C.

• Stability: In the solid state, Vidarabine is relatively stable when stored in a dry, light-resistant container. However, in aqueous solution, it is susceptible to deamination (enzymatic or chemical conversion) to hypoxanthine arabinoside (Ara-Hx), which has significantly reduced antiviral activity. Therefore, solutions must be freshly prepared or stabilized.

Vidarabine acts primarily as a DNA polymerase inhibitor. Once taken up by virally infected cells, Vidarabine is phosphorylated intracellularly to the active triphosphate (Vidarabine triphosphate, Ara-ATP). The mechanism involves two key steps:

• Selective Inhibition: Ara-ATP preferentially inhibits viral DNA polymerase (specifically Herpesviridae) compared to host cellular DNA polymerases. This selective toxicity is the basis of its antiviral action.

• Chain Termination: Ara-ATP is incorporated into the growing viral DNA chain. Because it lacks the required 3'-hydroxyl group (present in deoxyadenosine), it acts as a non-reversible chain terminator, halting viral replication.

For regulatory compliance (e.g., USP, EP, JP), raw material Vidarabine must meet several rigorous standards:

• Assay (by HPLC): 98.0% – 102.0% on an anhydrous basis.

• Related Substances: Limits for specific impurities, notably Ara-Hx (NMT 2.0%), as well as any unspecified individual impurity (NMT 0.1%) and total impurities (NMT 2.0%).

• Residual Solvents: Must comply with ICH Q3C guidelines (Class 1 and 2 solvents limited or absent).

• Heavy Metals: NMT 20 ppm (typically lower for injectable grades).

• Water Content (Karl Fischer): NMT 6.0% (the material is hygroscopic to a degree).

• Microbial Limits: Total aerobic microbial count (TAMC) ≤ 1000 CFU/g, absence of S. aureus, P. aeruginosa, and Candida albicans.