Epithalon Tetrapeptide Analytical Assay & Storage Standards

Epithalon tetrapeptide degrades via hydrolysis of its labile Asp-Gly bond. This specific cleavage generates a des-Gly byproduct, impacting peptide purity. The molecule's zwitterionic nature (pI 3.2) and molecular weight (390.35 g/mol) necessitate reverse-phase HPLC for separation. Optimal peak symmetry requires an ion-pairing agent at 30°C.

Degradation kinetics reveal first-order Asp-Gly cleavage. A rate constant of 3.2 × 10⁻⁶ s⁻¹ occurs at pH 7.4 and 22°C. The des-Gly byproduct shows an 8.1-minute retention time. Detection occurs at 214 nm on Hypersil GOLD C18 columns.

Chromatographic resolution from synthetic impurities requires precise mobile phase control. A 0.8 mL/min flow rate is used. A 22-28% acetonitrile gradient is applied over 12 minutes. Mass spectrometry confirms the protonated molecular ion [M+H]⁺ at m/z 391.17. A characteristic y3 fragment (m/z 277.08) confirms sequence.

Lyophilized formulations containing 4% D-mannitol demonstrate enhanced solid-state stability. Annual degradation at -20°C is 0.23%. Solution formulations, however, show 5.7% degradation at 4°C after 30 days. The peptide exhibits an absorption maximum at 214 nm (π→π* transition).

Reverse-phase HPLC assesses Epithalon tetrapeptide purity. A C18 column separates components. Acetonitrile/water with trifluoroacetic acid forms the mobile phase. Hydrophobic interactions drive differential partitioning with the stationary phase. Molecules elute based on polarity. UV detection at 214 nm quantifies the separated peptide. The main peak appears at 6.4 minutes.

Epithalon tetrapeptide, MW 390.35 g/mol, shows a peak symmetry (tailing factor) of 1.09. This value indicates efficient peak shape. The column and mobile phase conditions support the tetrapeptide's unique Ala-Glu-Asp-Gly sequence. A 175 Å pore size C18 column is used.

A Hypersil GOLD C18 column (150 × 4.6 mm, 3 µm) is employed. Mobile Phase A contains 0.1% TFA in water. Mobile Phase B uses 0.085% TFA in acetonitrile. A flow rate of 0.8 mL/min is maintained. Column temperature is held at 30°C. Detection occurs at 214 nm.

Electrospray ionization in positive-ion mode generates the Epithalon [M+H]+ ion. The mass spectrometer detects this protonated species at m/z 391.35. Precise molecular mass confirmation occurs within ±0.02 Da. Characteristic b and y ions, resulting from peptide bond cleavages, provide definitive sequence elucidation. This confirms the tetrapeptide's structural integrity.

The b3 ion, detected at m/z 318.15, and the y2 ion, at m/z 175.08, specifically confirm the Ala-Glu-Asp-Gly sequence integrity. These distinct fragment ions provide unambiguous structural corroboration.

Chromatographic separation employs a Hypersil GOLD C18 column (150 × 4.6 mm, 3 µm particle size). Mobile phases include 0.1% (v/v) TFA in water and 0.085% (v/v) TFA in acetonitrile. A 0.8 mL/min flow rate is maintained. Column temperature is 30°C.

Ionization occurs in a heated capillary at 350°C. Nitrogen acts as the nebulizing gas. A retention time of 6.4 minutes aligns with UV absorbance detection at 214 nm. This corroborates peptide identity prior to mass spectrometry.

Elemental analysis determines a compound's empirical formula by combusting the sample. Carbon, hydrogen, and nitrogen atoms oxidize into CO2, H2O, and NOx gases. These products separate chromatographically. Quantification via thermal conductivity detectors establishes precise percentage composition.

Epithalon tetrapeptide (C14H22N4O9) requires precise characterization. CHN analysis, calibrated with acetanilide, verifies its theoretical formula. Found composition: 43.08% carbon, 5.69% hydrogen, 14.37% nitrogen. These values align closely with theoretical. Deviations within ±0.5% confirm peptide integrity.

Residual moisture determination in lyophilized Epithalon utilizes Karl Fischer titration. Samples stored in Type I amber borosilicate vials. A methanol-based solvating agent is used with Hydranal-Composite 5 titrant. Nitrogen gas prevents atmospheric moisture interference.

Accurate calibration uses a certified sodium tartrate dihydrate standard. Moisture content was found below 1.2%. Detection precision is ±0.05%. Consistent low moisture minimizes hydrolytic degradation during -20°C storage.

Epithalon tetrapeptide degrades via pH-dependent hydrolysis. The Asp-Gly amide bond undergoes cleavage. A cyclic succinimide intermediate forms. This pathway yields des-Gly-Epithalon, confirmed by mass spectrometry. Degradation kinetics are first-order above pH 6.5. Half-life reduces from 72 hours (pH 7.4) to 28 hours (pH 8.0) at 37°C.

Des-Gly-Epithalon (MW 333.29 g/mol) constitutes the major degradation product. Mass spectrometry confirms its identity. Neutral loss of 57.05 Da indicates C-terminal glycine cleavage.

Cyclic succinimide intermediate formation dominates the degradation pathway. A transient HPLC peak at 5.2 minutes (214 nm) evidences this. It displays a characteristic 197 nm UV shoulder.

Lyophilized Epithalon, reconstituted in 10 mM sodium acetate buffer (pH 4.5) with 0.01% benzyl alcohol, shows superior stability. Refrigerated solutions (4°C) maintain >98.5% purity for 14 days. Purity assessment used RP-HPLC (Hypersil GOLD C18, 0.8 mL/min, 30°C).

Temperature dramatically influences degradation rates. Rates triple at 25°C (t½=9.2 days) versus 4°C (t½=28.5 days). This behavior aligns with Arrhenius kinetics, exhibiting an 18.7 kcal/mol activation energy. Oxidation is not a primary pathway; the methionine-free sequence precludes thioether oxidation.

Lyophilized Epithalon tetrapeptide achieves >99.5% purity over 24 months at -20°C. D-mannitol (4% w/v) acts as a cryoprotectant. Residual moisture below 1.2% inhibits Asp-Gly bond hydrolysis. The matrix T_g of -32°C necessitates uninterrupted sub-zero storage, preventing amorphous phase collapse. Degradation follows Arrhenius kinetics.

Thermal cycling between -20°C and room temperature accelerates degradation. Each freeze-thaw cycle introduces 0.12% aggregate formation, detected by SEC-HPLC (TSKgel G2000SWXL). Vial headspace oxygen below 0.5% suppresses oxidative deamidation of the glutamic acid residue. Storage at 4°C in phosphate-buffered saline (pH 7.4) results in 7.3% aspartyl epimerization within 72 hours, confirmed by chiral RP-HPLC.

Optimal long-term storage involves Type I amber borosilicate vials. Vials are backfilled with argon. Minimal headspace oxygen is maintained. Stability monitoring employs Karl Fischer for moisture. Differential scanning calorimetry determines T_g. SEC-HPLC detects aggregation. Chiral RP-HPLC tracks epimerization. Specific methods monitor oxidative deamidation.

Epithalon tetrapeptide degrades via hydrolytic cleavage of its labile Asp-Gly peptide bond. A cyclic succinimide intermediate forms at neutral-to-basic pH. This mechanism yields 5% des-Gly degradation within 48 hours at pH 7.4. Buffering to pH 4.5 with 10 mM sodium acetate preserves >99.0% purity for 14 days.

Mobile phase composition affects stability. Analytical HPLC employs 0.1% (v/v) trifluoroacetic acid in water. Another option is 0.085% (v/v) TFA in 100% acetonitrile. These mobile phases help control degradation.

A Hypersil GOLD C18 column (150 × 4.6 mm; 3 µm, 175 Å) separates components. Flow rate is 0.8 mL/min. Column temperature is 30°C. UV absorbance detection at 214 nm is standard. Epithalon tetrapeptide elutes at 6.4 minutes. A peak symmetry of 1.09 indicates good shape.

Lyophilized solid-state storage is common. A 4% (w/v) D-mannitol excipient is included. This formulation enhances long-term stability. Proper storage minimizes degradation pathways.