INTRODUCTION:

1. Introduction of Lisinopril

Figure 1: Structure of Lisinopril

Drug Name: Lisinopril

Empirical Formula: C21H31N305

Molecular Weight: 405.488g/mol

Melting Point: 160⁰C

pKa: 1.62, 3.66, 6.07 and 10.33

Kingdom: Organic compounds

Lisinopril, sometimes referred to as (S)-1-[N2-(1-carboxy-3phenylpropyl)-L-lysyl]-L-proline, has the following molecular structure: Lisinopril is a synthetic peptide derivative made up of three primary parts: a carboxylic acid (carboxyl) group, a proline residue, and a lysine (L-lysyl) residue.

· The amide bond that joins the lysine and proline residues forms the peptide’s backbone.

· The carboxylic acid group is situated at the end of the lysine side chain.

· The phenyl group is joined to the lysine residue, contributing to the phenylpropyl section of the molecule. Lisinopril’s chemical formula is C₂₁H₃₁N₃O₅. Lisinopril’s pharmacological characteristics stem from this structure, which enables it to block the angiotensin-converting enzyme (ACE) and work as a medication to treat heart failure and hypertension.^1,2,3

Mechanism: Under normal circumstances, angiotensin II would increase vascular resistance and oxygen consumption because it constricts coronary blood arteries and is positively inotropic. Proliferation of vascular smooth muscle cells and myocyte hypertrophy may result from this activity in the long run.3 because lisinopril inhibits the angiotensin converting enzyme (ACEI), angiotensin I cannot be converted to angiotensin 11.3.4 this reduces the proliferation of vascular smooth muscle cells and myocyte hypertrophy that occur in patients who are not treated. Bradykinin levels elevated in ACEI-using patients also have vasodilator effects. Lisinopril also prevents angiotensin from being converted to angiotensin 1.5 by renin.^4,5

Uses: Hypertension (high blood pressure), Prevention of heart attack and stroke, Heart failure.⁶

2. Introduction of UV spectrometer:

The technique of UV-visible spectrometry is employed to examine how molecules absorb, transmit, and reflect ultraviolet (UV) and visible light. It aids in the identification of materials, measurement of their concentrations, and investigation of chemical reactions by observing how they interact with light in the visible and ultraviolet portions of the electromagnetic spectrum.

UV-visible spectrometry measures a sample’s light absorption in the visible and ultraviolet (UV) portions of the electromagnetic spectrum. This absorption happens when the energy of the incident photons is equal to the energy needed to activate the ground state electrons in the sample. Beer-Lambert’s Law states that the amount of light absorbed is proportionate to the absorbing species’ concentration. It is possible to determine details about the sample’s structure, concentration, and chemical makeup by measuring the absorbance at particular wavelengths.^7,8,9

MATERIALS AND METHODS:

Materials: All the chemicals used during experimental work are of the analytical grade. Lisinopril standard was gifted by the Biochem Pharmaceutical Industries Ltd. Listril 2.5mg was obtained commercially.

Instrumentations: Digital weighing balance of Model: JEWEL 110 and UV visible spectrometer of Model no. AU 2702 Systronics (India) Limited was used with 1 cm matched quartz cells. The equipment was controlled by a PC installed properly with the UV probe software.

Selection wavelength: The peaks were seen in the spectra at 223nm when the solutions were scanned in the 200–400nm range using 0.1N NaOH as a reference. The medication complies with Lambert’s law between 10 and 50µg/ml. The quantification was done using a linearity plot.

Preparation of standard solution: A 10ml volumetric flask was filled with the roughly 10 mg pure medication after it had been weighed. To obtain a stock solution with a concentration of 1000µg/ml, the medication was fully dissolved in a few millilitres of 0.1N NaOH and then added to the final volume using NaOH. The final concentration of standard solutions was obtained by pipetting out aliquots of the standard stock solution and diluting it with water appropriately.

Analysis of Tablet Formulation: Ten tablets of the Listril-2.5mg brand were weighed and triturated into a fine powder in order to estimate the amount of lisinopril in the pharmaceutical formulation using the above procedure. A calibration curve was used to calculate the concentration for both methods. Tablet powder equivalent to 10mg was weighed, transferred to a 100ml volumetric flask, and dissolved in a few ml of 0.1N NaOH with the help of ultra sonication for 15 minutes. These were then filtered to get the stock solution of 100μg/m. Different dilutions were prepared from tablet solution and analysed six times.^10,11,12

Analytical Method Development and Validation:

UV-Spectroscopic method was used for estimation of Lisinopril. The developed method was validated by determining the specificity, linearity, precision, recovery, and solution stability according to USP and ICH guidelines.

1.Range/Linearity: Solutions of different concentrations were prepared in the range of 10ppm to 50ppm by diluting the stock solution. Absorbance was noted for solutions of different concentration at λmax and calibration curve was constructed by plotting concentration on X-axis against absorbance’s on Y-axis.

2.Precision: It was performed on six samples from the same batch samples were analyzed content using UV spectrophotometer.

2.1. Intraday Precision: The Intraday precision was estimated by calculating % Relative Standard Deviation (%RSD) for the Analysis within a day (24 Hrs), at various time intervals.

2.2. Interday Precision: Interday precision was estimated by calculating Relative Standard Deviation (RSD) for the analysis of six replicates on three consecutive days.

3. Accuracy: An accuracy study was carried out by extracting 10ml of 80%, 100%, and 120% of solution of standard separately. Each concentration was prepared in duplicate and each one was analyzed in triplicate.

4. Ruggedness: Ruggedness was studied to measure the reproducibility of method under variation in condition other than laboratory.

5. Robustness: Robustness was studied by changing the wavelength of UV spectrophotometer at 223nm ± 2nm and analyzing test sample in triplicate using UV-Spectroscopy.

6. LOD and LOQ: The Limit of detection of an analytical procedure can be described as the lowest concentration of the analyte in a sample that can be detected by it, but not necessarily quantified as an exact value.

LOD = 3.3* SD/Slope

The Limit of quantification of an analytical procedure can be described as the lowest concentration of the analyte in a sample that can be quantified with suitable accuracy and precision as an exact value.^13,14

LOQ = 10*SD/Slope

RESULT AND DISCUSSIONS:

Selection of Wavelength: UV-spectrum of standard showed maximum absorbance (λ max) value at 223nm. UV-spectrum obtained for test solution showed maximum absorbance value at 223nm which was closer to that of standard maximum absorbance.

Figure 2. UV Spectrum of Lisinopril

Figure 3. Calibration curve of Lisinopril

1. Range and Linearity: Highest concentration should not exceed Absorbance range more than 1.8, hence range was selected between 10-50 ppm.

Table 1. Result of Linearity

Concentration (ppm)	Absorbance
10	0.095
20	0.182
30	0.285
40	0.382
50	0.478
Mean	0.284
SD	0.152
RSD	0.5371
%RSD	53.71
CC	0.999
Intercept	-0.0054
Slope	0.0096
Equation of Line: y=0.0097×-0.0054

The Correlation coefficient is greater than 0.999 which indicates linearity of the method.

2. Precision: It was performed on six samples from the same batch samples were analyzed UV spectrophotometer.

Intraday precision: The value of % Relative Standard Deviation for intraday precision are given in table no. 2

Table 2. Result of Intraday precision

Sr. No	Time (Hr)	Concentration (ppm)	Absorbance
1	0	20	0.182
2	2	20	0.187
3	4	20	0.183
4	8	20	0.189
5	12	20	0.188
6	24	20	0.185
Mean		0.185
SD		0.002
RSD		0.015
%RSD		1.510

The overall % RSD of sample was less than 2 % indicating the precision of the method.

Interday precision: The value of % Relative Standard Deviation for interday precision are given in table no. 3.

Table 3. Result of Interday precision

Sr. No	Time (Hr)	Concentration	Absorbance
			Day 1	Day 2	Day 3
1	0	20 ppm	0.185	0.183	0.184
2	2	20 ppm	0.187	0.186	0.183
3	4	20 ppm	0.183	0.180	0.184
4	8	20 ppm	0.189	0.186	0.189
5	12	20 ppm	0.188	0.181	0.187
6	24	20 ppm	0.185	0.180	0.182
Mean			0.1861	0.1826	0.1848
SD			0.0022	0.0028	0.0026
RSD			0.0119	0.0153	0.0142
%RSD			1.197	1.535	1.428

In Interday precision for 3 consecutive days the %RSD values were found well within 2% limit, indicating that the current method is repeatable.

3. Accuracy: An Accuracy study carried by taking absorbance of sample at 80%, 100% and 120%. each one is analyzed in triplicate.

Table 4. Result of Accuracy

Level	Absorbance	Mean	SD	RSD	% RSD	Cumulative % RSD
80 %	0.182	0.1816	0.0015	0.0084	0.840	1.0003
	0.180
	0.183
100%	0.183	0.183	0.002	0.0109	1.092
	0.185
	0.181
120 %	0.185	0.187	0.002	0.0107	1.069
	0.187
	0.189

The data provided in above table indicates method reproducibility, the cumulative % RSD for these samples was less than 2%, indicating the accuracy of method.

4. Ruggedness:

Table 5. Result of Ruggedness

Sr. No.	Parameter
1	Analyte	X	Y
2	System	A	B
3	Day	Monday	Tuesday
4	Time	Morning	Afternoon
5	Conc. (ppm)	20	20
6	Absorbance	0.186	0.185
		0.188	0.183
		0.182	0.185
Mean		0.1853	0.1843
SD		0.0030	0.0011
RSD		0.0164	0.0062
%RSD		1.648	0.626

The %RSD for the sample was less than 2% shows the Ruggedness of the method.

5. Robustness: The % of RSD of Robustness testing under different altered conditions is given in table.

Table 6. Result of Robustness

Sample No.	Conc. (ppm)	% Drug Content
Sample No.	Conc. (ppm)	At 221 nm	At 225 nm
1	30	0.285	0.288
2	30	0.278	0.290
3	30	0.283	0.294
Mean		0.282	0.290
SD		0.0029	0.0030
RSD		0.0104	0.0105
% RSD		1.04	1.05

The %RSD of Robustness is less than 2%. This table indicates that current method is robust.

6. LOD and LOQ:

Table 7. Result of LOD & LOQ

Parameter	Conc. (ppm)	Absorbance	SD	%RSD	Calculation
LOD	20	0.182	0.0035	1.894	0.0287
	20	0.189
	20	0.185
LOQ	20	0.181	0.0036	1.948	0.1269
	20	0.186
	20	0.188

The %RSD was less than 2% which indicates the method is valid.

CONCLUSION:

The techniques suggested are straightforward, economical, and delicate. Accuracy, linearity, and precision are confirmed Because of the results’ reproducibility, Lisinopril’s bulk and pharmaceutical formulations can be estimated with success. The devised approach was proven to be straightforward, sensitive, accurate, selective, quick, and cost-effective for determining the dosage of lisinopril in tablets. Lisinopril responded to Beer’s law in the concentration range of 10–50 µg/ml and showed maximum absorption at 223 nm. A linear regression with a correlation coefficient (r2) of 0.999 was observed in the suggested approach for determining lisinopril (y= 0.0097x – 0.0054). Extensive reproducibility of an analytical procedure under standard operating conditions was demonstrated by both intraday and interday investigations. In the formulation of the tablet, there is no interference.

REFERENCES:

1. http://en.wikipedia.org/wiki/Lisinopril

2. http://www.drugbank.ca/drugs/DB00722

3. Indian Pharmacopoeia. Ministry of Health and Family Welfare New Delhi. 2007; 2:1306.

4. British Pharmacopoeia. Stationery Office Books (TSO) London, United Kingdom. 2005; 2: 1199.

5. United States Pharmacopoiea-USP-24, NF-19, Asian Edition, United States Pharmacopoeial Convention, INC Twin brook Parkway, Rockville, MD, U.S.A. 2000; 979.

6. European Pharmacopoeia. European Directorate for Quality medicine and health care; Monograph number ISBN: 9789287160577.1120; 2007: 2277.

7. British National Formulary. British Medical Associations. Royal Pharmaceutical Society of Great Britain. 2005; 98.

8. Martindale: The complete drug reference, 36^th edition, pharmaceutical press, Lambeth High Street, London. 2009: 1307-1311, 1325-1326.

9. Stanisz B. Estimation of the applicability of differential spectroscopic method for the determination of lisinopril in tablets and for the evaluation of its stability. Acta Pol. Pharm. 2004; 61(5): 327-334.

10. Rahman N, Anwar N, Kashif M. Application of pi-acceptors to the spectrophotometric determination of lisonopril in commercial dosage forms. Farmaco. 2005; 60(6-7): 605611.

11. Paraskevas G, Atta-Politou J, Koupparis M. Spectrophotometric determination of lisinopril in tablets using 1-fluoro-2, 4-dinitrobenzene reagent. J. Pharm. Biomed. Anal. 2002; 29(5): 865-872.

12. Aktas ES, Ersoy L, Sagirli O. A new spectrofluorimetric method for the determination of lisinopril in tablets. Farmaco. 2003; 58(2): 165-168.

13. El-Gindy A, Ashour A, Abdel-Fattah L, Shabana MM. Spectrophotometric, spectroflourimetric and LC determination of lisinopril, J. Pharm. Biomed. Anal. 2001; 25(5-6): 913-922.

14. PART 2: Validation of Analytical Procedure: Methodology Q2B, ICH Harmonized Tripartite Guidelines. 1996: 6-12.

Received on 10.06.2024 Modified on 22.07.2024

Asian J. Pharm. Ana. 2024; 14(3):142-146.

DOI: 10.52711/2231-5675.2024.00025