Preparation Of Glimepiride Hibiscus Rosa Sinensis Biology Essay


The main purpose of the present work was to develop matrix tablets of Glimepiride with Hibiscus rosa-sinensis leaves mucilage and Povidone and to study its functionality as a matrix forming agent for sustained release tablet formulations. Mucilage from Hibiscus rosa-sinensis leaves was isolated, purified and characterized. Physicochemical properties of dried powdered mucilage of Hibiscus rosa-sinensis leaves mucilage were studied. Various formulations of Glimepiride Hibiscus rosa-sinensis leaves mucilage and Povidone were prepared. The formulated tablets were tested for mechanical properties, friability, swelling behavior, in vitro drug release pattern and the dissolution data was treated with mathematical modeling and the optimized formulation was tested for accelerated stability studies. The formulated tablets were found to have good mechanical properties, good swelling properties. The in vitro dissolution data was perfectly fitting to zero order and the release of drug from the formulation followed Higuchi's release. The accelerated stability studies revealed that the tablets retain their characteristics even after stressed storage conditions. From this study it was concluded that the dried Hibiscus rosa-sinensis leaves mucilage and Povidone combination can be used as a matrix forming material for making sustained release matrix tablets.

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Key words: Glimepiride, Hibiscus rosa-sinensis, Povidone, matrix tablets, sustained release.


Hibiscus rosa-sinensis, (Malvaceae family) commonly known as China rose is a popular landscape shrub, creates a bold effect with its medium-textured, glossy dark green leaves and with 4-6 inch wide and up to 8 inch long, showy flowers, produced throughout the year and grows up to 7-12 feet1. Glimepiride is an oral hypoglycemic agent, which is a commonly prescribed drug for the treatment of patients with type II diabetes mellitus. It belongs to sulfonyl ureas drug class. Glimepiride is a weak acid with PKa of 5.3. Glimepiride is practically insoluble in water and acidic environment but highly permeable (class 2) according to the Biopharmaceutical classification System (BCS) 2. The oral absorption is uniform, rapid and complete with nearly 100% bioavailability. The pharmacokinetics and dosage schedule supports once daily sustained release formulations for Glimepiride for better control of blood glucose levels to prevent hypoglycemia, enhance clinical efficacy and patient compliance3, 4. The purpose of present work was to design and evaluate sustained release tablets of Glimepiride using Hibiscus rosa-sinensis leaves mucilage and Povidone combination as release retardant for making sustained release matrix tablets.



Glimepiride was obtained as a gift sample from Dr. Reddy's Laboratories, Hyderabad, India. Hibiscus rosa-sinensis leaves were collected from plants growing in local areas of Anantapur, India. The plant was authenticated at the Department of Botany, Sri Krishnadevaraya University, Anantapur, India. Povidone, Micro crystalline cellulose (Avicel) and Magnesium stearate were procured from SD Fine chemicals (Mumbai, India). All other chemicals used were of analytical reagent grade and double distilled water was used throughout the experiments.

Extraction of mucilage:

The fresh Hibiscus rosa-sinensis leaves were washed with water. The leaves were crushed and soaked in water for 5-6 h, boiled for 30 m and left to stand for 1 h to allow complete release of the mucilage into the water. The mucilage was extracted using a multi-layer muslin cloth bag to remove the marc from the solution. Acetone (three times the volume of filtrate) was added to precipitate the mucilage. The mucilage was separated, dried in an oven at 400C, collected, ground, passed through a # 80 sieve and stored in desiccator at 300C & 45% relative humidity till use 5.

Purification of the Mucilage:

The crude mucilage (1%) was homogenized (Potter homogenizer) with cold dilute tri chloro acetic acid solution (5%). The solution was centrifuged (3500 rpm for 20 m), neutralized with sodium hydroxide by drop wise addition and then dialyzed for 30 h against distilled water. The mucilage was precipitated with ethanol (in the quantities of three times the volumes) and washed successively with ethanol, acetone and diethyl ether5, 6.

Drug-excipient compatibility studies 7:

Differential scanning calorimetry: The Differential Scanning Calorimetric analysis was carried out using Differential Thermal Analyzer (Shimadzu DSC-60, Shimadzu Limited, Japan). A 1:1 ratio of drug and excipient was weighed into aluminum crucible and the DSC thermo grams were recorded at a heating rate of 100C/min in the rage 20 0C to 350 0C, at a nitrogen flow of 20 ml/min.

Infrared spectra analysis:

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Fourier Transform Infrared (FTIR) spectra were recorded on samples prepared in potassium bromide (KBr) disks using a Shimadzu Corporation, (Tokyo, Japan) Model-1601 PC. Samples were prepared in KBr disks by means of a hydrostatic press at 6-8 tons pressure. The scanning range was 500 to 4000 cm-1.

Preparation of matrix tablets:

Sustained release matrix tablets of Glimepiride with Hibiscus rosa-sinensis leaves mucilage and Povidone were prepared by using different drug: mucilage ratios. Hibiscus rosa-sinensis leaves mucilage and Povidone were used as matrix forming materials while microcrystalline cellulose as a diluent and Magnesium stearate as a lubricant. All ingredients used were passed through a # 100 sieve, weighed and blended. The granules were prepared by wet granulation technique and evaluated for its flow properties. The granules were compressed by using 10 mm flat faced punches8, 9. The compositions of formulations were showed in Table No. 1.

Evaluation for granules: 10-12

The granules so obtained were evaluated for flow properties viz., Angle of repose, Loose Bulk Density, Tapped Bulk Density, Carr's Index and Hausner ratio.

Evaluation of tablets: 10-13

The formulated tablets were evaluated for uniformity in Thickness, uniformity in weight, hardness, Friability, Content uniformity.

Swelling behavior of matrix tablets:

One tablet from each formulation was kept in a Petri dish containing phosphate pH 7.4. At the end of 2 h, the tablet was withdrawn, kept on tissue paper and weighed, repeated for every 2 h till the end of 12 h. The swelling index was calculated by following equation14.

S.I = {(Mt-M0) / M0} X 100

Where, S.I = Swelling Index, Mt = Weight of tablet at time 't' and

Mo = Weight of tablet at time 0.

In vitro drug release studies:

Release of Glimepiride from the matrix tablets was studied 900 ml phosphate buffer ( pH 7.4) using United States Pharmacopoeia (USP) 6-station Dissolution Rate Test Apparatus (Model Electro lab, TDT- 06T, Mumbai, India) with a rotating paddle stirrer at 50 rpm and 37 ± 0.50C. A sample of Glimepiride matrix tablets equivalent to 2 mg of Glimepiride was used in each test. Samples from dissolution fluid were withdrawn at regular intervals filtered (0.45 μm) and absorbance was measured at 229 nm for Glimepiride content15 using a UV/ visible double-beam spectrophotometer (Elico L210, India). The drug release experiments were conducted in triplicate (n = 3).

Drug release kinetics:

To analyze the mechanism of drug release from the prepared formulations, the data obtained from in vitro release studies were subjected to Zero order16, First order16, Higuchi's17, Korsmeyer Peppa's18 and Hixson Crowell models16.

Scanning Electron Microscopy:

The optimized formulation (F-5) was selected for Scanning Electron Microscopy (SEM) analysis. The tablet surface morphology was studied at zero time and 4th h of dissolution.

Accelerated Stability Studies of optimized matrix tablets:

The promising formulation (F-5) was tested for a period of 3 months at different temperatures of 400C with 75% RH, for their drug content19.


The DSC scan of Glimepiride showed a short endothermic peak at 209.130C (Figure 1). The thermo gram of formulated matrix tablets with Hibiscus rosa-sinensis leaves mucilage and Povidone showed an endothermic peak of drug at 193.200C (Figure 2) indicating a slight change in terms of shifting towards the lower temperature. It has been reported that the quantity of material used effects the peak shape and enthalpy. Thus these minor changes in the melting endotherm in the drug could be due to the mixing of the drug and excipients which lower the purity of each component in the mixture and may not necessarily indicate potential incompatibility.

The major IR peaks observed in Glimepiride were 3344.3 (3300-3500) (N-H), 2900.7 (2850 - 3000) (C-H), 2900.7 (3300 - 2500 (O-H), 1427.2 and 1342.4 (1350 -1550) (N=O), 1072.3 (1220 -1020) (C-N) and 1033.8 (1000 -1300) (C-O) (Figure 3). Infrared absorption spectrum of Hibiscus rosa-sinensis leaves mucilage and Povidone (1:1:1) spectrum shows prominent peaks at wave numbers 2920.0 (2850 - 3000) (C-H), 3379.1 (3300 - 3500) (NH), 1029.1 (1000 - 1300) (C-O) cm-1 (Figure 4). The major IR peaks observed in matrices were 3344.3 (3300-3500) (N-H), 2900.7 (2850 - 3000) (C-H), 2900.7 (3300 - 2500 (O-H), 1427.2 and 1342.4 (1350 -1550) (N=O), 1072.3 (1220 -1020) and (C-N) 1033.8 (1000 -1300) (C-O). This indicates that there were no chemical incompatibility between Glimepiride and the polymers (Hibiscus rosa-sinensis leaves mucilage and Povidone) used.

The Angle of repose of granules was found to be 27.830±1.266 indicated the granules had excellent flow properties. The Loose Bulk density and Tapped Bulk density were found to be 0.58±0.014 and 0.79±0.154 g/ml respectively which was used to calculated the Carr's index and Hausner ratio values. The Carr's index and Hausner ratio values were found to be 26.58±2.160 % and 1.25±0.120 respectively. These trials were conducted in triplicates (n=3).

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The thickness was ranged from 2.85±0.035 to 3.48±0.074 mm; the hardness was ranged from 6.50±1.45 to 8.10±1.40 kg/cm2. The loss on friability was ranged from 0.44±0.03 to 0.85±0.05 % (less than 1%). The drug content in the formulated tablets was ranged from 99.5±2.56 to 100.5±3.67 %. These trials were conducted for five times (n=5).

The rate of release was faster in F-1 and slower in F-5. The release of Glimepiride was sustained as the proportion of Hibiscus rosa-sinensis leaves mucilage and Povidone increased and the overall time of release of the Glimepiride from the matrix tablet was also increased. The release of Glimepiride form the formulation showed zero order release and the formulations gave slope (n) and regression coefficient (r) values were 0.006705, 0.995252 respectively and shown in Table No. 4. The In-vitro drug release profile of Glimepiride from formulated matrix tablets was further studied using first order, whose slope and regression coefficient values were -0.00176, -0.9823 respectively and represented in Table No. 4. The slope and regression coefficient values for Higuchi model (3.308515 and 0.993936), for Korsmeyer Peppa's (0.304558 and 0.968565) and for Hixson-Crowell's Models (-0.00092 and -0.99214). These values were represented in Table No.5 and shown in Figures 7, 8, 9, 10 and 11. Drug releases from matrix tablets were by drug dissolution, drug diffusion or a combination of both.

The surface morphology of formulated tablet at zero time and different interval indicate the release of drug from dosage form by diffusion mechanism. The SEM photographs of tablet were shown in Figure 12.

The accelerated stability studies further proved the formulation is stable even at accelerated environmental conditions. The physicochemical properties before and after stability studies were shown in Table No.6.


The present study revealed that Hibiscus rosa-sinensis leaves mucilage and Povidone combination appears to be suitable for use as a release retardant in the manufacture of sustained release matrix tablets because of its good swelling, good flow and suitability for matrix formulations. From the dissolution study, it was concluded that dried Hibiscus rosa-sinensis leaves mucilage in combination with Povidone can be used as an excipient for making sustained release matrix tablets.


The authors are thankful to Dr. Reddy's Laboratories (Hyderabad, India) for providing the pure drug sample.