Journal of Pharmacy And Bioallied Sciences

SYMPOSIUM - HERBAL DRUGS AND BOTANICALS - RESEARCH ARTICLES
Year
: 2015  |  Volume : 7  |  Issue : 4  |  Page : 321--324

Stability studies of silymarin nanoemulsion containing Tween 80 as a surfactant


Rabea Parveen1, Sanjula Baboota1, Javed Ali1, Alka Ahuja1, Sayeed Ahmad2,  
1 Department of Pharmaceutics, Bioactive Natural Product Laboratory, Faculty of Pharmacy, Jamia Hamdard, New Delhi, India
2 Department of Pharmacognosy and Phytochemistry, Bioactive Natural Product Laboratory, Faculty of Pharmacy, Jamia Hamdard, New Delhi, India

Correspondence Address:
Sayeed Ahmad
Department of Pharmacognosy and Phytochemistry, Bioactive Natural Product Laboratory, Faculty of Pharmacy, Jamia Hamdard, New Delhi
India

Abstract

Background: Silymarin, a flavonolignan from "milk thistle" (Silybum marianum) plant is used almost exclusively for hepatoprotection. Because of its low bioavailability, it was incorporated into a nanoemulsion formulation. The aim of the present study was to check the stability of silymarin nanoemulsion at different temperatures for 3 months. Materials and Methods: The oil-in-water based nanoemulsion formulation was prepared by titration method. Silymarin nanoemulsion was characterized by droplet size, viscosity, and refractive index. Droplet size, viscosity, and refractive index were determined every month. The shelf-life of silymarin nanoemulsion was determined by accelerated stability testing. Results: It was found that there was no significant change in the droplet size, viscosity, and refractive index at refrigerator and room temperature during the period of 3 months. The half-life of the optimized nanoemulsion formulation was found to be 4.74 years at room temperature. Conclusion: These results indicated that stability of silymarin can be enhanced in nanoemulsion formulation using Tween 80 as a surfactant.



How to cite this article:
Parveen R, Baboota S, Ali J, Ahuja A, Ahmad S. Stability studies of silymarin nanoemulsion containing Tween 80 as a surfactant.J Pharm Bioall Sci 2015;7:321-324


How to cite this URL:
Parveen R, Baboota S, Ali J, Ahuja A, Ahmad S. Stability studies of silymarin nanoemulsion containing Tween 80 as a surfactant. J Pharm Bioall Sci [serial online] 2015 [cited 2020 Dec 4 ];7:321-324
Available from: https://www.jpbsonline.org/text.asp?2015/7/4/321/168037


Full Text



There are a number of herbal preparations, which are effectively used as herbal alternatives to prescribed drugs. While using herbal drugs, researchers have faced with a problem of low bioavailability, which is due to several reasons such as instability, low membrane permeability, and poor solubility. To overcome these problems, several pharmaceutical approaches have been used for enhancing bioavailability of herbal drugs such as liposomes, microspheres, microemulsion or nanoemulsion, self-microemulsifying drug delivery system, and many more.[1]

Nanoemulsions are the only kinetically stable formulations. The long term physical stability of nanoemulsions (without apparent flocculation or coalescence) makes unique from other drug delivery systems, and therefore are sometimes referred to as approaching thermodynamic stability.[2] Nanoemulsions have a higher solubilization capacity than simple micellar solutions. Moreover, due to this property nanoemulsions offer several advantages over unstable dispersions (emulsions and suspensions) such as rapid onset of action (no extra time for dispersion), reduced intersubject variability in terms of gastrointestinal fluid volume, and longer shelf life. Nanoemulsions are transparent dispersions of oil and water stabilized by an interfacial film of surfactant and co-surfactant molecules having a droplet size of 10–200 nm. Nanoemulsions have been known to increase the therapeutic efficacy of many herbal drugs as well as to enhance the physical and chemical stability of the drugs.[3] Nanoemulsions are well characterized and are a promising drug delivery system with practical applications in pharmaceutical, cosmetic, and chemical industries. They have been used for different routes of administrations such as intravenous, oral, and topical with reduced drug side effects and improved pharmaceutical and pharmacological effects of the drugs given.[4]

There are several herbal drugs having bioavailability or stability problems, which are incorporated into a nanoemulsion drug delivery system such as silymarin, colchicine, genistein, curcumin, etc., and showed improved biopharmaceutic properties of the drugs.[1],[5],[6],[7]

Silymarin is a complex mixture of four flavonolignan isomers: Silybin (70–80%), silychristin (20%), silydianin (10%), and isosilybin (0.5%), obtained from Silybum marianum. Silymarin is primarily indicated in conditions such as hepatitis, hepatitis A infection, jaundice, and can also be given in adjunctive therapy as an alternative drug of choice in cirrhosis. Due to a problem of poor aqueous solubility and low bioavailability, it was incorporated into oil-in-water based nanoemulsion to increase its bioavailability.[8]

But, the stability of drug product is one of the problems associated with the drug delivery systems such as emulsions, microemulsions, and nanoemulsions. Stability of a drug or formulation may be defined as the capability of a particular formulation in a specific container/closure system to remain within its physical, chemical, microbiological, toxicological, protective, and informational specifications.[9] Nanoemulsions have been known to enhance the physical as well as the chemical stability of drugs. Therefore, the main objective of the present study was to perform the stability studies of silymarin nanoemulsion formulation.

 Materials and Methods



Materials and reagents

Silymarin was provided from Ranbaxy (Gurgaon, India) and Sefsol 218 (propylene glycol-monocaprylic ester) from Nikko Chemicals (Tokyo, Japan) as gift samples. Tween 80 (polyoxyethylene sorbitan monooleate) was purchased from Merck (Schuchardt, Hohenbrunn, Germany). Water was taken from Milli-Q water purification system (Millipore, Billerica, MA). All other components used for the formulation of nanoemulsion were pharmaceutically acceptable for oral administration.

Formulation and characterization of silymarin nanoemulsion

The silymarin nanoemulsion was prepared by spontaneous emulsification method (aqueous phase titration method). Detailed description of their preparation, physical stability, characterization, and optimization is given in our previously published article.[3] An optimal stable nanoemulsion formulation of silymarin (20 mg/kg body weight p.o.) was developed containing Sefsol-218 as an oily phase (5% w/w), 35% w/w of Smix (mixture of Tween 80 as a surfactant and ethanol as a co-surfactant in the ratio of 2:1), and double distilled water as an aqueous phase (60% w/w). This formulation was optimized on the basis of visual observation, optimum globule size, and minimum polydispersity index.

Stability studies of silymarin nanoemulsion formulation

The formulation of silymarin dosage form may lead to a decrease in the assay of silymarin due to mechanical stress, compression, manufacturing processes, excipients, storage conditions, heat, moisture, and alkaline pH. Therefore, it was necessary to check the stability of the silymarin nanoemulsion formulation.

Stability studies on optimized nanoemulsion were performed by keeping the sample at refrigerator temperature (5°C) and room temperature (25°C). These studies were performed for the period of 3 months. The droplet size, viscosity, and refractive index were determined during storage.

Nine batches of the selected formulation were prepared out of which three batches of nanoemulsion formulations were subjected to accelerated stability conditions. The formulation was taken in glass vials and kept at three different temperatures (40 + 2°C) (stability chamber), 25 + 2°C (room temperature), and 5 + 2°C (refrigerator) at ambient humidity. Samples were withdrawn periodically at predetermined time intervals (0, 15, 30, 45, 60, and 90 days) and evaluated for any physical change in the formulation and drug content.[10] Zero time samples were used as controls. Analysis was carried out at each time interval by taking 1.0 mL of each formulation and diluting it to 5.0 mL with methanol and quantified by reported high performance thin layer chromatography (HPTLC) method.[11] The sample was applying on HPTLC plate and the content of silybin was quantified using solvent chloroform: Acetone: Formic acid (9:2:1, v/v/v) (Rf of silybin 0.46 ± 0.05) in the absorbance mode at 296 nm.

The amount of drug degraded and the amount remaining at each time interval was calculated. Order of degradation was determined by the graphical method. Degradation rate constant (K) was determined at each temperature. Arrhenius plot was constructed between log K and 1/T to determine the shelf life of optimized nanoemulsion formulation. The degradation rate constant at 25°C (K25) was determined by extrapolating the value of 25°C from Arrhenius plot. The shelf life (T0.9) for each formulation was determined by using the formula:

[Inline:1]

 Results and Discussion



Formulation and characterization of silymarin nanoemulsion

The silymarin nanoemulsion formulation was prepared successfully by spontaneous emulsification method using Sefsol-218 and Smix (mixture of Tween 80 and ethanol) and double distilled water. The nanoemulsion was observed visually and found clear transparent and easily flowable liquid. The droplet size of the formulation was 41.22 ± 0.00314 nm with a polydispersity index of 0.165.

Stability studies of silymarin nanoemulsion formulation

Stability of the drug or a formulation is the extent to which a product retains, within the specified limits, throughout its period of storage and use, the same properties and characteristics possessed at the time of its packaging. Stability testing evaluates the effect of environmental factors on the quality of the drug substance or a formulated product, which is utilized for prediction of its shelf life, determine proper storage conditions, and suggest labeling instructions. Moreover, the data generated during the stability testing are an important requirement for regulatory approval of any drug or formulation. Therefore, optimized nanoemulsion formulation was characterized by droplet size, viscosity, and refractive index for the period of 3 months.

During stability studies droplet size, viscosity, and refractive index were determined at two different temperatures of 5°C and 25°C. These parameters were determined at predetermined time intervals (0, 15, 30, 45, 60, and 90 days). No drastic change was observed in the values of droplet size, viscosity, and refractive index at refrigerated and room temperature indicated that optimized formulation is stable and suitable for oral delivery of silymarin.

Accelerated stability was checked when the formulation were kept at three different temperatures (40 + 2°C, 25 + 2°C, and 05 + 2°C). The drug concentration remaining was quantified at predetermined time intervals (0, 15, 30, 45, 60, and 90 days) where zero time sample was taken as control (100%). The formulations kept at three different temperatures were analyzed individually [Table 1], [Table 2], [Table 3]. The percentage of undecomposed silymarin remaining in the nanoemulsion formulations was 208.17 μg/mL, 208.11 μg/mL, and 206.67 μg/mL at 5°C, 25°C, and 40°C, respectively, after 90 days of storage.{Table 1}{Table 2}{Table 3}

To check the order of degradation of silymarin, natural (ln) of percent drug remaining when plotted against time gave the straight line, which signifying that the degradation of silymarin in nanoemulsion formulation followedfirst order kinetics [Figure 1]a, [Figure 1]b, [Figure 1]c. From degradation constant (K) values obtained from [Figure 1]a, [Figure 1]b, [Figure 1]c, half-life and the shelf life of the formulation prepared were calculated [Table 4]. It was seen that the shelf life of the formulation was 3.8 years when stored at refrigerator temperature. Arrhenius plot was constructed by plotting ln K versus reciprocal of absolute temperature (1/T) [Figure 2]. The slope obtained from plot gave the energy of activation of silymarin in the nanoemulsion formulation. The activation energy was 3.426 Kcal/mole.{Figure 1}{Table 4}{Figure 2}

 Conclusion



The slight decrease in the assay of silymarin was observed in the formulations stored at different temperatures. lt was concluded that the degradation of silymarin in nanoemulsion formulation followfirst order kinetics. The shelf life of nanoemulsion formulation was 3.8 years, which could be achieved only with formulation stored in the refrigerator.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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