INTRODUCTION:

In recent years, the formulation of poorly soluble compounds presented interesting challenge for formulation scientist in pharmaceutical industries and 50% of new chemicals entities exhibit poor aqueous solubility and the ones of drug is lovastatin¹ ^2,3. Lovastatin (LV) is a statin group, a specific and potent competitive inhibitor of 3-hydroxy-3 methyl glutaryl coenzyme A (HMG-CoA), hence a potent cholesterol-lowering drug⁴. Statin therapy represents the basis for the management of hypercholesterolemia and the prevention of cardiovascular disease ²because of efficacy and safety. Statins are generally safe and well-tolerated⁵.

Lovastatin is a drug that includes Biopharmaceutical Classification System class 2 with characteristic poorly soluble in the water and high permeability^6,7. LV is a lipophilic statin, undergoes hepatic and enteric metabolism via enzyme CYT cytochrome P450 (P450 3A4)⁸.

Lovastatin is an inhibitor of HMG CoA reductase as a key in the synthesis of cholesterol ⁵. Absorption lovastatin after administration orally is 30% and exhibits low oral bioavailability estimated < 5% because of rapid metabolism in the gut and liver. Lovastatin and its active b-hydroxy acid metabolite have short half-life plasma between 1,1-1,7 hour, and steady-state concentrations are achieved within 2-3 days to the patient with a normal kidney. A formulation with a high degree of oral absorption and extended delivery potential would be highly desirable for lovastatin^9,10.

LV appears as a white, non-hygroscopic crystalline powder, a highly lipophilic drug [log P = 4,3] but poorly water-soluble (0,4x10^-3mg/mL)⁴ ¹¹^,¹². Since the therapeutic efficacy of drug molecules depend on their solubility, it is important to enhance drug solubility in an aqueous environment to achieve the maximum therapeutic effect. Moreover, the aqueous solubility is the critical factor for evaluating the bioavailability of orally administered drugs with lower water solubility¹³.

The figure of lovastatin can see below.

Fig. 1 Structure of Lovastatin

The Insolubility of lovastatin in the water needs to overcome increasing solubility lovastatin in the gastrointestinal tract and avoid the first-pass metabolism. Lipid-based formulations represent a unique solution to the delivery of poorly soluble compounds. A lipid dosage form typically consists of one or more drugs dissolved in a blend of lipophilic excipients such as triglycerides, partial glycerides, surfactant, or co-surfactant. Among the lipid-based system, the SMEDDS, SNEDDS is a promising technology to improve the rate and extent of absorption of poorly water-soluble drugs, which significantly facilities enhancing oral bioavailability¹² ¹⁴. SNEDDS (Nano-Emulsifying Drug Delivery System) that composition is lipid, surfactant, and co-surfactant. The oil phase selection is based on the oil's ability to dissolve lovastatin on the gastric fluid. Anhydrous formulation's high solvent capacity generally decreases upon formulation dispersion and digestion in the gastrointestinal tract, thereby resulting in drug supersaturation. If a sufficiently long and stable period of drug saturation can be achieved, intestinal drug absorption can be increased ¹⁵ Various oils are used for SNEDDS formulation. Usually, long-chain triglycerides slightly digestible than medium-chain triglycerides, but long-chain triglycerides increasing lymphatic absorption so that they avoid first-pass metabolism ¹⁶. This study aims to determine lovastatin's solubility in the different vehicle include oils, fatty acids, surfactant, and co-surfactant and to select higher soluble in lovastatin.

MATERIALS AND METHODS:

Materials: Lovastatin was purchased from Sanbe Farma Bandung Pharmaceutical Ind., Acetonitrile, and Methanol grade of HPLC Merck®, Aquabidest, almond oil, oleic acid, tween 20 Corn oil, olive oil, and sunflower oil, tween 80, PEG 400 and propylene glycol was purchased from CV Global Pratama.

Calibration of lovastatin:

Lovastatin stock solution was prepared by dissolving lovastatin 10 mg in acetonitrile 100 mL using the volumetric flask. Then diluted at ranging 2-16 µg/mL.

Preparation of sample:

The solubility of lovastatin was determined in all components (almond oil, sunflower oil, corn oil, soybean oil, olive oil, oleic acid, tween 20, tween 80, cremophor R.H. 40, propylene glycol, and polyethylene glycol. Each component was taken of 5 ml in vial 10 mL then added to all a few of lovastatin until saturated. The mixtures were mixing using a magnetic stirrer for 10 minutes, then using a sonicator for 10 minutes. Put in the water bath for 15 minutes at temperature 40°C. The mixtures were standing for 24 hours, and the combinations were centrifugated at 6000 rpm for 10 min. Filtered the varieties using membrane filter 0.45µm, then supernatant transferred to vials. An aliquot of sample @ 2 µL added acetonitrile until 5 mL, then moved to vial 1.5 mL and injected into the HPLC system.

High Performance Liquid Chromatography

Quantitative estimation of lovastatin analyzed using HPLC (Waters) with column C18 (ZOBRAX Eclipse XDB Agilent technologies, Santa Clara, USA) (4,6x 150 mm, 5µm) and U.V. at room temperature. A mobile phase using acetonitrile and water (70:30 v/v) and the flow rate was 1 ml/min and detection at 238 nm, and the injection volume of 5µL and run time was fixed at 6 minutes. Selection mobile phase modification from aqueous buffer (0,05 M ammonium phosphate and 0,01 M Phosphoric acid buffer and acetonitrile) (50:50) ¹¹

Method Validation

The method validated for precision, accuracy, and linearity, LOD, and LOQ. Linearity was evaluated using the average of nine concentration levels at range 2-16 µg/mL. For precision and accuracy studies, 3 three concentration levels (8,10, and 12 µg/mL). The method's precision expressed by the percent relative standard deviation (% RSD) of the regressed concentration was used. The accuracy of the process was determined by regression concentration represented as a percentage of the nominal concentration¹⁷ ^18,19.

Linearity:

The linearity of the calibration curve of lovastatin at concentration levels range 2- 16 µg/mL was found with a regression coefficient (0,999) and intercepted in figure 2.

Fig.2. Callibration curve of lovastatin wit regression coefficient= 0,999 and intercept= 8156 and slope = 27876

Table 1. Validation Method of lovastatin

Validation method	Value
Linearity	R2= 0,999
Accuracy (% recovery)	95-108%
Precision (RSD)	0.3 and 1.38 %
LOD (Limit of Detection)	0.48µg/mL
LOQ (limit of Quantification)	1.60µg/mL

Table 2. Solubility lovastatin (LV) in different oils, surfactant, and cosurfactant

Component	Concentration (µg/mL)
Almond oil	2.04
Sunflower oil	1.40
Soybean oil	2.01
Olive oil	2.25
Oleic acid Myoglyol Isoprophyl myristate	3.67 2.47 1.70
PEG 400	20.5
Propilenglycol	5.54
Cremophor RH 40	9.85
Tween 20	16.99
Tween 80	19.04

DISCUSSION:

The Validation of lovastatin using HPLC (Waters) with column C18 (ZOBRAX Eclipse XDB Agilent technologies, Santa Clara, USA) (4,6x 150 mm, 5µm) at room temperature. A mobile phase using acetonitrile and water (70:30 v/v) and the flow rate was 1 ml/min and detection of UV at 237 nm, and the injection volume of 5µL and run time was fixed at 6 minutes. The retention time of lovastatin in 3.863 repectively^20,21.

Linearity of the calibration curve of lovastatin at concentration levels range 2- 16 µg/mL was found with a regression coefficient (0,999) and exhibit good linearity (r²>0,99) and the equation regression is y = 27876x- 8156²².

Accuracy is one of the most critical parameters of an analytic methodology. It can be expressed as the percentage of recovery of the known amount of drug in the sample. The result of recovery showed that the mean accuracy level of lovastatin was 95-108%. The results are a good agreement with acceptable value for validation of an analytic procedure (recovery =80-120%)

Precision is the measure of the degree of repeatability of an analytic method under regular operation and expressed as the relative standard deviation. The result of accuracy with 3 level concentration (8, 10, and 12 µg/mL), showed that RSD 1, 38 respectively, indicating that the method presents an excellent precision because below 2% ^16,23.

The detection limit (LOD) and Limit of Quantification (LOQ) test for the procedure are performed on samples containing very low concentration analytes. LOD is defined as the lowest amount of analyte that can be detected above baseline noise. LOQ is defined as the lowest amount analyte, which can reproducibly be quantitated above the baseline noise. In this study, LOD for 5 µL injection of lovastatin was 0.48 µg/mL, and LOQ was 1,60 µg/mL. With a relative standard deviation lower than 10% ²⁴.

Solubility studies are one of the critical parameters to achieve the desired concentration of drug in systematic circulation in order to elicit pharmacological respons ²⁵. Drug efficacy can be severely limited by low aqueous solubility. This study aims to select oils, surfactants, and co-surfactant that the extent of the solubility of the lipophilic drug (lovastatin)—this selection of components used for formulation SNEDDS. The result of solubility lovastatin (LV) in parts can see in Table 1.

The solubility of lovastatin is higher in unsaturated fatty acids than in triglycerides and the result showed that lovastatin high soluble in oleic acid than almond oil, olive oil, sunflower oil, myglyol, and isoprophyl myristat. As we know that almond oil contains more than 90% unsaturated fatty acid (62-76% oleic acid, 25-30% linoleic acid, palmitate acid 4-9%). The solubility of lovastatin in olive oil (oleic acid 55-83%, linoleic acid 3.5-21%), soybean oil (oleic acid 17-26%, linoleic acid 50-57%), and sunflower oil (linoleic acid 66%, oleic acid 21%) is lower than oleic acid²⁶

This solubility of lovastatin in surfactant tween 80 higher than tween 20 and cremophor R.H. 40 because HLB of tween 80 is 15, HLB of tween 20 is 16.7, and HLB of cremophor R.H. 40 is 14-16. HLB value showed of lipophilicity of surfactant and HLB value lower, means more lipophilic, and HLB value higher means more hydrophilic. Tween 80 is more lipophilic than others surfactant, so has the ability to the solubility of lovastatin than others ²⁶

The solubility of lovastatin in co-surfactant showed than PEG 400 higher than propylene glycol. It showed that PEG 400 has a polarity index of 12.4, and propylene glycol has a polarity index of 32.1. The increasingly of index polarity, more hydrophilic and otherwise.

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Received on 21.12.2020 Modified on 15.01.2021

Research J. Pharm. and Tech 2021; 14(12):6285-6288.

DOI: 10.52711/0974-360X.2021.01087