Absorbance Ratio and First Order Derivative Spectroscopic Methods for Simultaneous Determination of Sacubitril and Valsartan in Bulk and Tablet Dosage Form

 

Murugan S1,2*, Vetrichelvan T1

1Department of Pharmaceutical Analysis, Adhiparasakthi College of Pharmacy, Melmaruvathur-603319, Tamilnadu, India.

2Research Scholar, The Tamilnadu Dr. M.G.R. Medical University, Chennai-600032, Tamilnadu, India.

*Corresponding Author E-mail: msm_apcp07@yahoo.com

 

ABSTRACT:

Two UV-spectrophotometric methods have been developed and validated for simultaneous estimation of Sacubitril (SAC) and Valsartan (VAL) in bulk and tablet dosage form. The Method A employs absorbance ratio method, which involves formation of Q-absorbance equation at 242.0 nm (isoabsorptive point) and also at 253.5 nm (λmax of SAC). Method B employs first order derivative, the wavelengths selected for quantitation were 233.0 nm for VAL (Zero cross for SAC) and 247.0 nm for SAC (Zero cross for VAL). For both the methods drugs were linear between the range of 4.9–24.5 µg/ml for SAC and 5.1–25.5 µg/ml for VAL using methanol and distilled water as solvents. The correlation coefficient was found to be 0.9995 for SAC and 0.9996 for VAL for method A and 0.9998 for SAC and 0.9999 for VAL for method B, respectively. The precision (intraday, interday) of methods was found within limits (RSD < 2%). It could be concluded from the results obtained in the present investigation that the two methods for simultaneous estimation of SAC and VAL in bulk and tablet dosage form are simple, rapid, accurate, precise and economical and can be used, successfully, in the quality control of tablet formulations and other routine laboratory analysis.

 

KEYWORDS: Sacubitril, Valsartan, Absorbance ratio method, First order derivative method.

 

 

 

INTRODUCTION:

Sacubitril (SAC) (Fig.1) is chemically 4-[[(2S, 4R)-5-ethoxy-4-methyl-5-oxo-1-(4-phenyl-phenyl) pentan-2-yl] amino]-4-oxobutanoic acid. Sacubitril is an antihypertensive drug used in combination with valsartan for the treatment of heart failure[1]. Valsartan (VAL) (Fig.2) is chemically N-(1-oxopentyl)-N-[[2’-(1H-tetrazol-5-yl) [1,1’-biphenyl]-4yl] methyl]-L-valine. It is a potent, highly selective, orally active, specific angiotensin II receptor antagonist used as a hypotensive drug[2]. On literature survey, several methods were reported for the estimation of SAC and VAL individually and in combination with other drugs[3-10]. So we have developed a novel, simple, rapid, accurate, precise, economical and highly sensitive UV spectrophotometric methods for assay of SAC and VAL in bulk and tablet dosage form and validated according to ICH guidelines.

 

Fig. 1 Chemical structure of Sacubitril

 

 

Fig. 2 Chemical structure of Valsartan

 

 

MATERIALS AND METHODS:

Instrumentation:

The instrument used in the present study was Shimadzu double beam UV/Visible spectrophotometer (Model UV- 1700) with spectral band width of 1nm. All weighing was done on electronic balance (Model Shimadzu AUX -220).

 

Reagents and Chemicals:

Analytically pure sample of sacubitril and valsartan was procured from Beijing mesochem technology co.ltd. (China). The pharmaceutical dosage form used in this study was a Cidmus 100mg tablets manufactured by Novartis pharmaceuticals, (Switzerland) labeled to contain 49mg of sacubitril and 51mg of valsartan was purchased from welcome healthcare, Mumbai.

 

Preparation of stock standard solutions:

Stock standard solution of SAC (490𝜇g/ml) and VAL (510𝜇g/ml) were prepared by dissolving 49mg of SAC and 51mg of VAL in 100ml of Methanol in 100ml volumetric flask, separately with vigorous shaking.

 

METHODS:

Method A: Absorbance ratio method:

In this method, solutions of SAC and VAL (10μg/ ml, each), were prepared separately by appropriate dilution of standard stock solution with distilled water and scanned in the spectrum mode from 200 to 400nm. From the overlain spectra of these drugs, wavelength selected for Q-absorbance equation at 242.0nm (isoabsorptive point) and also at 253.5nm (λmax of SAC). The overlain UV absorbance spectrum of SAC and VAL is shown in Fig.3.

 

Fig.3. Zero order overlain spectra of 10μg/ml of SAC and VAL respectively

 

A set of equations for absorbance ratio method were framed using these A (1%, 1 cm) values which are given below:

 

 

 

Where, A1 and A2 are absorbance of mixture at 253.5nm and 242.0nm; 𝑎𝑥1 and 𝑎𝑥2, A (1%, 1cm) of SAC at 253.5 nm and 242.0nm, respectively; and 𝑎y1 and 𝑎y2, A (1%, 1cm) of VAL at 253.5 nm and 242.0 nm, respectively. CSAC and CVAL are concentrations of SAC and VAL in mixture.

 

Concentration CSAC and CVAL can be obtained as follows:

 

 

Method B: First order derivative method:

In this method, solutions of SAC and VAL (10μg/ml, each), were prepared separately by appropriate dilution of standard stock solution with distilled water and scanned in the spectrum mode from 200nm to 400nm. The absorption spectra thus obtained were derivatized for first order. From the overlain spectra of these drugs, the wavelengths selected for quantitation were 233.0nm for VAL (Zero cross for SAC) and 247.0nm for SAC (Zero cross for VAL). The overlain first order derivative spectra of SAC and VAL is shown in Fig.No.4.

 

Fig.4. First order derivative overlain spectra of 10μg/ml of SAC and VAL respectively

 

Analysis of Marketed Tablet Formulation:

For the estimation of drugs in the commercial formulation, twenty tablets were weighed accurately. The average weight was calculated and then crushed to obtain fine powder. A quantity of tablet powder equivalent to about 51mg of VAL was transferred to 100 ml volumetric flask; 50ml methanol was added and sonicated for 15min, volume was then made up to the mark with methanol. The resulting solution was mixed and filtered through whatmann filter paper no 41 and filtrated. 2ml was withdrawn and diluted to 100ml using distilled water to get 9.8μg/ ml of SAC and 10.2μg/ ml of VAL, For absorbance ratio method the concentration of SAC and VAL were determined by measuring absorbance of sample solution for Q-absorbance equation at 242.0nm (isoabsorptive point) and also at 253.5nm (λmax of SAC). The concentration of SAC and VAL were determined by measuring absorbance of sample solution in first order derivative at 247.0 and 233.0nm, respectively. Concentration of SAC and VAL in the diluted solution was obtained from calibration curves. Amount of sacubitril and valsartan in mg/tab was then calculated, by multiplying the concentration obtained with dilution factor.

 

Validation:

The proposed methods were validated as per ICH guidelines.

 

Linearity:

Different aliquots (1-5ml) of SAC from standard stock solution of SAC (490 𝜇g/ml) was transferred into series of 100ml volumetric flasks, separately and the volume was made up to the mark with distilled water to get concentrations 4.9, 9.8, 14.7, 19.8 and 24.5μg/ml, Similarly, different aliquots (1-5 ml) of VAL from standard stock solution of VAL (510 𝜇g/ml) was transferred into series of 100ml volumetric flasks, separately and the volume was made up to the mark with distilled water to get concentrations 5.1, 10.2, 15.3, 20.4 and 25.5μg/ml, respectively. The absorption spectrum was recorded at 242.0nm for SAC and VAL and also at 253.5nm for SAC and VAL in absorption ratio method. The absorption spectrum were derivatized for first order and recorded by measuring absorbance of sample solution in first order derivative at 247.0 and 233.0nm, respectively.

 

Accuracy:

To the preanalysed sample solutions, a known amount of standard stock solution was added at different levels i.e. 50, 100 and 150 %. The solutions were reanalyzed by proposed method.

Precision:

The reproducibility of the methods was determined by analyzing tablets at different time intervals on same day in triplicates (Intra-day assay precision) and on three different days (Inter-day assay precision).

 

RESULT AND DISCUSSION:

The methods discussed in the present work provide a convenient and reliable way for quantitative determination of SAC and VAL in combined dose tablet formulation. For absorbance ratio method the wavelength selected for Q-absorbance equation at 242.0nm (isoabsorptive point) and also at 253.5nm (λmax of SAC). The absorption spectra thus obtained were derivatized to get first order. From the overlain spectra of these drugs, wavelength selected for quantitation were 247.0 and 233.0nm in first order derivative, respectively. Percent label claim for SAC and VAL in tablet analysis was found in the range of 99.46 to 100.74% in absorption ratio method and 99.68 to 100.54% in first order derivative method. Percent recovery for SAC and VAL, was found in the range of 99.88 to 100.13% in absorption ratio method and 99.80 to 100.19% in first order derivative method with relative standard deviation well below 2 indicating accuracy of the methods. Intra-day and Inter-day precision studies were carried out by analyzing tablet formulation, three times on the same day and on three different days, respectively. Relative standard deviation for intra-day and inter-day precision studies was satisfactorily well below 2.0 indicating high degree of precision and reproducibility of the methods.

 

Table 1. Results of Analysis of Tablets

Tablet sample

Label claim (mg/tab)

% Label claim (n = 6)

%RSD

Method 1

Method 2

Method 1

Method 2

Sacubitril

 49

99.46

99.68

0.5576

0.6894

Valsartan

 51

100.74

100.54

0.6577

0.4323

 

Table 2. Results of Recovery Studies

Recovery level

Initial amount (𝜇g/mL)

 Concentration of std drug added

(𝜇g/mL)

%Recovery (𝑛 = 3)

 

 

 

Method 1

Method 2

 

SAC

VAL

SAC

VAL

SAC

VAL

SAC

VAL

50%

9.8

10.2

4.9

5.1

99.87

100.52

99.46

99.63

100%

9.8

10.2

9.8

10.2

99.38

99.54

99.86

100.22

150%

9.8

10.2

14.7

15.3

100.40

100.34

100.08

100.74

 

 

 

Mean

 

99.88

100.13

99.80

100.19

 

 

CONCLUSION:

The proposed UV spectrophotometric methods employed here proved to be simple, economical, rapid, precise and accurate. Thus these can be used for routine simultaneous estimation of sacubitril and valsartan in tablet dosage form instead of processing and analyzing each drug separately.

 

ACKNOWLEDGMENT:

The management of ACMEC trust is hereby thanked by one of the author Mr. S. Murugan for their support in doing this research.

 

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Received on 06.03.2019           Modified on 17.05.2019

Accepted on 21.06.2019         © RJPT All right reserved

Research J. Pharm. and Tech. 2019; 12(11):5251-5254.

DOI: 10.5958/0974-360X.2019.00908.9