Determination of Ionization Constant Value in Water-Acetonitrile Binary Mixtures of Favipiravir and Comparison of Two Different C18 Columns

Abstract

Favipiravir (T-705) is an anti-viral agent that selectively and potently inhibits the RNA-dependent RNA polymerase of RNA viruses. The reverse phase liquid chromatography (RPLC) method is mostly preferred in the qualitative and quantitative analysis of this compound. This method is highly preferred for the determination of ionization/protonation (pKa) constants of compounds containing acidic and basic functional groups. The pKa value is important parameter to predict the physicochemical and biological properties of compounds. This parameter is an important data including the absorption, distribution, metabolism, excretion, and toxicity (ADMET) characterization of drugs. In this study, the RPLC method was developed using two different chromatographic columns for the determination of the pKa value of favipiravir in a water-acetonitrile binary mixture, and the chromatographic behavior of favipiravir was determined by changing the amount of acetonitrile in the mobile phase. The study was carried out at 37 ℃ column temperature and constant flow rates. The pKa value of the compound was determined by using sigmoidal and nonlinear models with the obtained retention data. The pKa value of hydrophilic favipiravir in water was calculated using the mobile phase pKa values and the macroscopic constants (mole fraction, dielectric constant, etc.) of acetonitrile. This important calculated physicochemical parameter is the first data obtained from the experimental study in the literature.

Keywords

• Favipiravir
• RPLC
• Retention time
• Ionization constant
• Hydrophilic compound

Favipiravirin Su-Asetonitril İkili Karışımlarında İyonlaşma Sabiti Değerinin Belirlenmesi ve İki Farklı C18 Kolonun Karşılaştırılması

Abstract

Favipiravir (T-705), RNA virüslerinin RNA'ya bağımlı RNA polimerazını seçici ve güçlü bir şekilde inhibe eden bir anti-viral ajandır. Bu bileşiğin kalitatif ve kantitatif analizinde en çok ters faz sıvı kromatografi (RPLC) metodu tercih edilmektedir. Bu metot, asidik ve bazik fonksiyonel grup içeren bileşiklerin iyonlaşma/protonasyon (pKa) sabitlerinin tayini için çok tercih edilmektedir. pKa değeri, bileşiklerin fizikokimyasal ve biyolojik özelliklerini tahmin etmeye yarayan önemli bir parametredir. Bu parametre ilaçların absorpsiyon, dağılım, metabolizma, atılım, toksitite (ADMET) karakterizasyonunu da içeren önemli bir veridir. Sunulan bu çalışmada, favipiravirin su-asetonitril ikili karışımında pKa değerinin tayini için iki farklı özellikteki kromatografik kolonlar kullanılarak RPLC metot geliştirilmiş ve asetonitrilin mobil fazdaki miktarının değişimiyle favipiravirin kromatografik davranışı da belirlenmiştir. Çalışma 37℃ kolon sıcaklığında ve sabit akış hızlarında gerçekleştirilmiştir. Elde edilen alıkonma verileriyle sigmoidal ve doğrusal olmayan modeller kullanılarak bileşiğin pKa değeri belirlenmiştir. Hidrofilik özellikte olan favipiravirin su ortamındaki pKa değeri, mobil faz pKa değerleri ve asetonitrilin makroskopik sabitleri (mol kesri, dielektrik sabiti, vs.) kullanılarak hesaplanmıştır. Hesaplanan bu önemli fizikokimyasal parametre literatürdeki deneysel çalışma ile elde edilen ilk veridir.

Keywords

• Favipiravir
• RPLC
• Alıkonma zamanı
• İyonlaşma sabiti
• Hidrofilik bileşik

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