Innovative eco-friendly stability-indicating HPLC-PDA method for simultaneous determination of the emerging antiviral drugs against COVID-19 infection molnupiravir and favipiravir; degradation kinetic studies along with LC-MS based structure elucidation

Abstract

The adoption of the principles of green chemistry in analytical procedures lowers the negative influence on both people and the environment, which presently has become the key goal. Additionally, the need for advanced analytical techniques for the simultaneous determination of antiviral combinations is highly recommended, one of those novel combinations that recently proved effective emerging antiviral drugs in the treatment of SARS-COV-2 is molnupiravir (MOL) and favipiravir (FAV). Therefore, the establishment of simple and precise stability-indicating HPLC-PDA method for their simultaneous determination is crucial for the probable co-formulation. The stability of MOL was studied along with FAV after forced degradation of both under different stress conditions Separation of MOL, FAV, and their corresponding degradation products was achieved by simple isocratic HPLC-PDA method using a mobile phase comprised of 25.0 mM phosphate buffer (pH 3.0 ± 0.05) − methanol (70:30, v/v) at flow rate 1.0 mL/min. A Zorbax C18 (250 × 4.6 mm, 5 μm; Agilent Technologies, USA) column was used for the separation of the components and the column oven was maintained at 30 °C, the selected wavelength for detection of both analytes and their degradation products was 230.0 nm. The method was linear over the range of 1.0 – 200.0 µg/mL for both MOL and FAV. MOL was found to be susceptible to all forced degradation conditions, namely, acid, alkali, oxidative, thermal, and photodegradation while FAV was susceptible only to acid, alkali, and oxidative degradation. The probable degradation mechanisms were assumed through the evaluation of the MS1 fragmentation pattern of the degradation products, also studying the kinetic behavior of the degradation reactions. Furthermore, the greenness profile for the proposed method was evaluated utilizing the new Complementary Green Analytical Procedure Index method (ComplexGAPI), and analytical greenness (AGREE) metrics with a score of the later one equals to 0.61 that indicated the greenness evaluation of the method. In addition, the new blue applicability grade index (BAGI) which is complementary to the green metrics showed a score of 85.0 that presents a good applicability potential of the method. The proposed method is the first sustainable, stability-indicating method developed for the simultaneous determination of this potential combination that would help in manufacturing both drugs in a fixed-dose drug combination.