Evaluation of disintegrating properties of Borassus flabellifer Mucilage

Ravi Kumar¹*, Rajarajeshwari N.²

¹Research Scholar, Shri Jagdish Prasad Jhabarmal Tibrewala University, Rajasthan

²Visveswarapura Institute of Pharmaceutical Sciences, Bangalore

ABSTRACT:

Plant products serve as an alternative to synthetic products because of local accessibility, eco friendly nature and lower price compared to imported synthetic products. Natural gums and mucilage have been widely explored as pharmaceutical excipients. Tablet disintegration has received considerable attention as an essential step in obtaining fast drug release. The present study was undertaken to isolate mucilage from Borassus flabellifer endosperm and explored its use as disintegrant by formulating tablets of metformin. Extracted Mucilage was subjected to toxicity studies for its safety and preformulation studies for its suitability as a disintegrating agent. The extracted mucilage is devoid of toxicity. No chemical interaction between drug and excipients was confirmed by FTIR, TLC and DSC studies. Mouth dissolving tablets of metformin were prepared and compared with different concentrations viz; 0.5,1, 1.5, 2.0 and 2.5%(w/w) of Borassus flabellifer mucilage powder and Ac-Di-Sol®. The prepared tablets were characterized by FTIR, TLC and DSC studies. Ten formulations were prepared and evaluated for physical parameters such as thickness, hardness, friability, weight variation, drug content, disintegration time and drug dissolution. The formulated tablets had good appearance and better drug release properties. The study revealed that Borassus flabellifer mucilage powder was effective as disintegrant in low concentrations (1%). The mucilage was found to be a superior disintegrating agent than Ac-Di-Sol®. Studies indicate that the extracted mucilage may be a good source of pharmaceutical adjuvant, specifically a disintegrating agent.

KEYWORDS: Borassus flabellifer mucilage, natural excipient, Metformin HCl, disintegrant, croscarmellose sodium.

INTRODUCTION:

Mucilage is glutinous substance which mainly consists of polysaccharides, proteins and uranides. Dried up mucilage or the concentrated mucilage is called as gum. The main difference between them is that mucilage does not dissolve in water whereas gum dissolves in water. Mucilage is formed in the normal growth of plant by mucilage secreting glands. Mucilage and gum are well known since ancient times for their medicinal use. In modern era they are widely used in Pharmaceutical industries as thickeners, water retention agents, suspending agents and disintegrants. Naturally the demand of these substances is increasing and new sources are tapped. India due to geographical and environmental positioning has traditionally been a good source for such products.

Plant products serve as an alternative to synthetic products because of local accessibility, eco-friendly nature and lower prices as compared to imported synthetic products. Natural gums and mucilage have been widely explored as pharmaceutical excipients^1-4 and have been known since ancient times for

their medical uses. In India, natural gums and mucilage are well known for their medicinal uses. They are widely used in the pharmaceutical industry as thickeners, water-retention agents, emulsion stabilizers, gelling agents, suspending agents, binders, film formers, and sustained-release agents^5-6. They also are used in the manufacturing of cosmetics, textiles, paints, and paper⁷. As their demand continues to increase, new sources are constantly being explored. However, large quantities are still imported from Europe to meet the increasing demand⁸.

The documented literature available on the evaluation of natural gums and mucilage as disintegrants in the formulation of dispersible and fast disintegrating tablets is limited with more being in the development of fast disintegrating tablets using semi synthetic cellulose derivatives like Ac-Di-Sol®, Explotab® as superdisintegrants. Natural gums and mucilage are preferred to semi synthetic and synthetic excipients because of their lack of toxicity, low cost, availability, soothing action, and non-irritant nature⁹.

The concept of “mouth dissolving drug delivery system” emerged from the desire to provide patients with more convenient means of taking their medication. Difficulty of swallowing pills primarily affects the geriatric and paediatric populations. Dysphagia or difficulty in swallowing is seen to afflict nearly 35% of the general population¹⁰. Fast dissolving tablets (FDT) are the solid unit compressed dosage forms which disintegrate or dissolve rapidly in the mouth without the need for chewing and water. FDTs are also called as fast melt, fast disintegrating or orally disintegrating tablets. The advantages of mouth dissolving dosage forms are increasingly being recognized in both industry and academia¹¹. The FDTs have potential advantages over conventional oral dosage forms with their improved patient compliance, convenience of administration, enhanced bioavailability and rapid onset of action.

Metformin HCl, chemically N,N-dimethyl-imidodicarbonimidic diamine hydrochloride, is widely used for the management of non-insulin dependent diabetes mellitus (NIDDM). Unlike other biguanide drugs, metformin HCl does not induce lactic acidosis. Metformin HCl can be directly compressed with specific excipients into tablets having desired hardness, disintegrating ability, and acceptable dissolution characteristics^12-13.

The Borassus flabellifer is a tall and erect palm, with large, fan-shaped leaves which are quite unlike the pinnate leaves of other palms. Borassus is from a Greek word describing the leathery covering of the fruit and flabellifer means “fan-bearer”. Synonyms of the plant include jaggery palm, Palmyra palm, toddy palm, wine palm. This species is globally distributed from Africa to Australia. Within India, it is found throughout tropical regions, especially along the peninsular coast and in West Bengal and Bihar. It is often cultivated. The Palmyra palm has long been one of the most important trees of Cambodia and India. The different parts of the plant is used for the various ailments like secondary syphilis, antiperiodic, heart burns, liver and spleen enlargement etc. Other than these pharmacological uses the juice of the plant is used in preparation of health drinks, jellies etc. The leaves are use to make baskets, hats and many other useful items. Borassus flabellifer contains albuminoids, fats and the fresh pulp is reportedly rich in vitamins A and C. The fresh sap is reportedly a good source of vitamin B-complex. Male inflorescence constitutes spirostane-type steroid saponins like borassosides and dioscin. It also contains 20 known steroidal glycosides and carbohydrates like sucrose. It also contains bitter compound called flabelliferrins, these are steroidal saponins^14-17. The endosperm contains a high proportion of mucilage. The two major polysaccharides present in this endosperm are galactomannan and mannan.

The objective of present study was to isolate and investigate the suitability of the Borassus flabellifer mucilage (BFM) as a disintegrant to develop FDTs of the selected model drug metformin HCl. The disintegration and swelling properties of FDT were compared with widely used super disintegrant like Ac-di-sol. Metformin HCl, an antidiabetic drug, was selected as the model drug as it was widely used in the treatment of Type–II diabetes.

MATERIALS AND METHODS:

Materials

Metformin HCl, talc, magnesium stearate, aspartame, aerosil were obtained from Zydus Research centre, Ahmedabad, India as gift samples. Borassus flabellifer endosperm was procured from the local market. All the other solvents, reagents and chemicals used were of either Pharamcopoeial or analytical grade. Different instruments viz; Vernier calipers, Monsanto hardness tester, Roche friabilator and disintegration apparatus were supplied by Electro Lab, Mumbai, India. USP XXIII dissolution apparatus-2 was from Electro Lab, Mumbai, India and 1601 PC Shimadzu UV Spectrophotometer from Shimadzu, Japan.

Methods

Isolation and purification of mucilage from Borassus flabellifer endosperm¹⁸

The endosperm of Borassus flabellifer fruit contains mucilage. To increase the yield of the mucilage the endosperm of Borassus flabellifer fruit were extracted by different solvents. The endosperm of Borassus flabellifer were collected, cut into small pieces and dried using tray dryer at 37°C for 24 h at room temperature, made fine powder by crushing in a mixer. The fine powder was soaked in different solvents such as water, hot-water, phosphate buffer solution (PBS) of pH 4.0, 6.8, 9.2, separately for 2-3h and heated up to 80-90°C for 30-45 min for complete release of the water soluble mucilage into the solvents.

Table 1: Composition of different batches of Metformin HCl FDTs

Ingredients( mg/ tablet)	Formulation Code
	F1	F2	F3	F4	F5	F6	F7	F8	F9	F10
Metformin HCl	500	500	500	500	500	500	500	500	500	500
BFM*	3	6	9	12	15	--	--	--	--	--
Cross carmellose sodium	--	--	--	--	--	3	6	9	12	15
Aspartame	6	6	6	6	6	6	6	6	6	6
Magnesium stearate	6	6	6	6	6	6	6	6	6	6
Talc	3	3	3	3	3	3	3	3	3	3
Aerosil	3	3	3	3	3	3	3	3	3	3
Flavor (orange)	6	6	6	6	6	6	6	6	6	6
Avicel	73	70	67	64	61	73	70	67	64	61
Total weight of tablet	600	600	600	600	600	600	600	600	600	600

BFM*: Borassus flabellifer mucilage

The mucilage was then extracted by using a multi layer muslin/cheese cloth bag to remove the marc and concentrated viscous solution under reduced pressure at 60-70°C. Acidified ethanol (5% HCl in 75% ethanol) was added to the concentrated viscous solution with constant stirring. The gel like precipitate was formed and separated by filtration. The precipitate was washed 2-3 times with 75% and 95% ethanol. After complete washing of the precipitate with ethanol 95%, brownish white powder was obtained. The powder was dried in an oven at 37°C, collected, grounded, passed through a # 80 sieve and stored in a desiccator till use. The brownish white powder was considered as mucilage for pharmaceutical use physicochemical characterisation, phytochemical screening and toxicity studies of the isolated mucilage were carried out as per the reported procedure^19-22.

Drug Excipient Compatibility Studies

Fourier Transform Infrared (FTIR) Spectroscopy

The Fourier-transform infrared spectra of Metformin hydrochloride and physical mixture of drug with other excipients in the ratio 1:1 were obtained by using a FTIR spectrophotometer (FTIR 8300, Shimadzu, Japan). Samples were prepared by KBr pressed pellet technique. The scanning range was 500-4000 cm^-1.

Differential Scanning Calorimetry (DSC)

DSC analysis was performed using Shimadzu DSC-60, Shimadzu Limited Japan. A 1:1 ratio of drug and excipient was weighed into aluminum crucible. And sample was analyzed by heating at a scanning rate of 20⁰C over a temperature range 20⁰-300⁰C under nitrogen environment.

Thin Layer Chromatographic analysis (TLC)

Drug and Excipients were subjected to TLC analysis. The solvent system for TLC of Metformin HCl was glacial acetic acid: Butanol: water (10:40:50). After development of the TLC plates, the plates were sprayed with a mixture of equal volumes of a (100g/L) solution of sodium nitroprusside, (100g/L) solution of potassium ferricyanide and a (100g/L) solution of sodium hydroxide prepared 20min before use and Rf values of pure drug and drug with different excipients were calculated and compared.

pH stability testing of the drug

Weighed quantities of the drug (100 mg) was dissolved in different media with different pH conditions like distilled water, 0.1 M hydrochloric acid (pH 1.2), Acetate buffer (pH 4.5), Phosphate buffer (pH 6.8) etc. The study was conducted for a period of one day and the samples were withdrawn at intervals of 1 hour, 4 hour and 24 hours. The samples were analyzed by HPLC and spectrometrically.

Preparation of fast dissolving tablets of Metformin HCl by direct compression method²³

Fast dissolving tablets of Metformin HCl were prepared by the conventional direct compression technique using BFM powder and Ac-Di-Sol® at concentrations of 0.5, 1, 1.5, 2 and 2.5 % w/w. All the required ingredients as per the formulation table were weighed and passed through Size 40# sieve. The Mixture was then blended in a double cone blender for 15 mins. The powder blend was evaluated for flow properties. The composition of each formulation is given in table 1.

Evaluation of powder Blend^24-28

Pre compression parameters

Bulk Density (D_b)

It is the ratio of total mass of powder to the bulk volume of powder. It was measured by pouring the weighed powder (passed through standard sieve # 20) into a measuring cylinder and the initial volume was noted. This initial volume is called the Bulk volume. From this, the bulk density is calculated according to the formula mentioned below. It is expressed in gm/ml and is given by

Where, M is the mass of powder, V_o is the Bulk volume of the powder.

Tapped density (D_t)

It is the ratio of total mass of powder to the tapped volume of powder. The tapped volume was measured by tapping the powder to constant volume (in a bulk density apparatus). It is expressed in gm/ml and is given by

Where, M is the mass of powder, V_t is the tapped volume of the powder.

Angle of Repose (θ)

The frictional forces in a loose powder can be measured by the angle of repose, θ. It is indicative of the flow properties of the powder.

It is defined as the maximum angle possible between the surface of a pile of powder and the horizontal plane.

tan θ = h / r, θ = tan^-1 (h / r)

Where, θ is the angle of repose, h is the height in cms; r is the radius in cms.

The powder mixture was allowed to flow through the funnel fixed to a stand at definite height (h). The angle of repose was then calculated by measuring the height and radius of the heap of powder formed. Care was taken to see that the powder particles slip and roll over each other through the sides of the funnel. Values for angle of repose ≤ 30^o usually indicate a free flowing material and angles ≥ 40^o suggest a poorly flowing material.

Carr’s Index (I)

It indicates powder flow properties. It is expressed in percentage and is given by

Where, D_t is the tapped density of the powder, D_b is the bulk density of the powder

Hausner’s ratio

Hausner’s ratio is an index of ease of powder flow; it is calculated by following formula.

Hausner ratio = Tapped density/Bulk density

Compression of tablet

After evaluation of granule blend were then blended with talc, magnesium stearate, aerosil and compressed into tablets using12 mm flat face round tooling on a Cemach rotary tablet punching machine.

Evaluation of tablet^29-32

All the tablets were evaluated for following different parameters which includes;

General appearance

Five tablets from different batches were randomly selected and organoleptic properties such as color, odor, taste, shape, were evaluated.

Thickness and diameter

Thickness and diameter of tablets were determined using Vernier caliper. Five tablets from each batch were used, and an average value was calculated. It is expressed in mm.

Hardness

For each formulation, the hardness of five tablets was determined using the Monsanto hardness tester. It is expressed in Kg/cm².

Friability

The friability of the tablet was determined using Roche Friabilator. It is expressed in percentage (%). 10 tablets were initially weighed (W_initial) and transferred into the friabilator. The friabilator was operated at 25 rpm for 4 mins. The tablets were weighed again (W_final). The % friability was then calculated by

Weight Variation

Twenty tablets were randomly selected from each batch individually weighed, the average weight and standard deviation of 20 tablets was calculated.

In vitro dispersion test

This test is performed to ensure disintegration of tablets in the salivary fluid, if it is to be used as an oro-dispersible tablet. In vitro dispersion time was measured by dropping a tablet in a measuring cylinder containing 6 ml of simulated salivary fluid of pH 6.8. Five tablets from each formulation were randomly selected and in vitro dispersion time was performed and the time for the tablet to completely disintegrate into fine particles was noted. Standard deviation was also determined and in vitro dispersion time is expressed in seconds.

In vitro disintegration test

The in vitro disintegration time of a tablet was determined using disintegration test apparatus as per I.P. specifications. One tablet was placed in each of the 6 tubes of the basket. Placed a disc to each tube and run the apparatus using pH 6.8 (simulated saliva fluid) maintained at 37±2⁰C as the immersion liquid. The assembly should be raised and lowered between 30 cycles per minute in the pH 6.8 maintained at 37±2⁰C. The time in seconds taken for complete disintegration of the tablet with no palpable mass remaining in the apparatus was measured and recorded.

Drug content

Twenty tablets were taken randomly and individual tablet were crushed, an amount of the powder equivalent to 500 mg of metformin HCl was dissolved in the 50 ml of distilled water. Shaken for 10 min and added sufficient distilled water to produce 100 ml and filtered, diluted suitably and analyzed for drug content at 233 nm using UV-Visible spectrophotometer (UV 1601- Shimadzu, Japan).

Wetting time

A piece of tissue paper (12cmx10.75cm) folded twice was placed in a Petri dish (Internal Diameter=9cm) containing 6 ml of simulated saliva pH 6.8. A tablet having amaranth powder on the upper surface was placed on the tissue paper. Time required to develop red color on the upper surface of tablet was recorded as wetting time. Three tablets from each formulation were randomly selected and the average wetting time was noted. Wetting time corresponds to the time taken for the tablet to disintegrate when placed gently on the tissue paper in a petridish. This method will duplicate the in-vivo disintegration as the tablet is motionless on the tongue. Lesser the wetting time indicates more porous the tablets.

Water absorption ratio

A piece of tissue paper folded twice was placed in a small petri dish containing 6 ml of simulated intestinal fluid (pH 6.8). A tablet was put on the paper and the time required for complete wetting was measured. The wetted tablet was then weighed.

Water absorption ratio R, was determined using following equation,

R = W_a – W_b/ W_b × 100

Where W_a = weight of tablet after absorption

W_b = weight of tablet before absorption

In vitro dissolution study

The release rate of metformin HCl from fast dissolving tablets was determined using USP Dissolution Testing Apparatus II (Paddle type). The dissolution test was performed using 900 ml of simulated intestinal fluid (pH 6.8), at 37 ± 0.5⁰C at 50 rpm. A sample (5 ml) of the solution was withdrawn from the dissolution apparatus every 2 min. for 12 min, and the samples were replaced with fresh dissolution medium. The samples were filtered through Whatmann filter paper no. 41. Absorbance of these solutions was measured at 233 nm using UV spectrophotometer. To increase the reliability of the observations, the dissolution studies were performed in triplicate.

Water Uptake study

The super disintegrants are hygroscopic in nature. It is an inherent property of the superdisintegrant to absorb moisture. Hence, the extent of moisture absorption is to be determined. Ten tablets from each formulation were kept in a desiccator, over calcium chloride, at 37ºC for 24 hours. This was done to remove maximum amount of moisture as possible from the tablets. The tablets were weighed and exposed to 82.5 % RH (which was achieved by adding 13.1 ml of sulphuric acid in a desiccator and kept aside for three days) at room temperature for a week. One batch of control tablets (without superdisintegrant) was kept to assess the moisture uptake due to other excipients. The tablets were weighed and the increase in weight was reported.

In vivo disintegration time

Six healthy human volunteers were selected and their written consent was obtained. Each volunteer randomly took one tablet and kept on the tongue. The time taken for complete disintegration of the tablet on the tongue was noted. It is expressed in seconds. After the test, mouth was washed with distilled water. Three trials were performed at different time intervals.

Mouth feel

The same human volunteers participated in taste evaluation test, were asked to give their opinion about the feeling of smoothness or grittiness of the dispersion soon after the tablet got disintegrated.

Drug release kinetics

To examine the drug release kinetics and mechanism, the release kinetics of the developed formulations were analyzed according to zero order, first order kinetics, Higuchi and Korsmeyer-Peppas model. The correlation coefficients (r²) were calculated for linearity

Scanning Electron Microscopy (SEM)

The surface morphology of the optimized batch was examined by SEM. The samples were placed on double sided adhesive tapes and scanning electron photographs was taken by using Jeol- JSM-5600 LV, Japan at 35 X magnification.

Stability Studies

The stability of selected formulations was tested according to International Conference on Harmonization guidelines for zone III and IV. The tablets were stored at 25±2^oC/60± 5% RH and 40±2^oC/75 ±5% RH test conditions in stability chamber for three months. After an interval of one month samples were withdrawn and tested for disintegration time, hardness, friability, drug content and in vitro drug release.

RESULT AND DISCUSSION:

In the present study, metformin HCl fast dissolving tablets were prepared by using natural disintegrant such as isolated BFM and its efficiency was compared with synthetic super disintegrants like croscarmellose sodium.

The mucilage was extracted using solvents such as distilled/demineralised water, hot water, PBS pH 4.0, pH 6.8 and pH 9.2 and the yield of the dry water soluble mucilage was varied depends upon the solvents used. Percent yield of the dry water soluble mucilage was 45%, 60%, 22%, 30% and 35% in distilled/demineralised water, hot water, PBS pH 4.0, PBS pH 6.8, and PBS pH 9.2 respectively. The solvents like distilled/demineralised water, hot water and phosphate buffer pH 9.2 could be used for extraction for better yield.

Drug Excipient Compatibility Study

Fourier Transform Infrared (FTIR) Spectroscopy

Compatibility study of drug and various excipients were conducted by employing FTIR spectral studies. The FTIR spectra of metformin HCl and the physical mixture of metformin HCl and other excipients are presented in figure 1 and 2 respectively. Pure metformin HCl spectra showed principal peaks at C=N- (stretching) 1625.9, 1564.2, 1669 cm^-1, C-N-(stretching) 1060.8, 1039.6, 1030.77 cm^-1, N-H-(stretching) 3371.3, 3294.2, 3174.6 cm^‑1 corresponding to its functional groups, confirming the purity of the drug as per established standards. All the above characteristic peaks appear in the spectra of physical mixture of metformin HCl and other excipients, indicating no modification or interaction between the drug and excipients.

Figure 1: FTIR Spectra of Metformin HCl

Figure 2: FTIR Spectra of physical mixture of drug and excipients

Differential Scanning Calorimetry (DSC)

The DSC analysis (Figure 3) of pure metformin HCl showed a characteristic, sharp endotherm peak at 226°C corresponding to its melting point and indicates the crystalline nature of the drug. The DSC analysis of physical mixture of drug and excipients (figure 4) revealed negligible change in the melting point of metformin HCl in the presence excipients, indicating no modification or interaction between the drug and excipients.

Figure 3: DSC Thermogram of Metformin HCl

Figure 4: DSC Thermogram of physical mixture of drug and excipients

Thin Layer Chromatographic analysis

Thin layer chromatography was carried out to check for the possible drug excipient interaction. The R_f value of pure metformin HCl was found to be 0.85. In the presence of excipients, the R_f value of the drug was unchanged and found to be between 0.83 to 0.85. The Rf values of the drug and the drug-excipient were almost similar indicating that there was no interaction. Hence, it can be concluded that the drug metformin HCl was found to be compatible with the excipients used in the designed formulation.

pH stability testing of the drug

The pH stability studies of Metformin HCl were carried out in different pH media by afore mentioned procedure. It was found that the drug (Metformin HCl) was stable for a period of one day in all pH conditions. The results are shown in figure 5 to10.

Figure 5: Chromatogram of drug in Figure6: Chromatogram of drug in

distil water at the of 1 hour distil water at the end of 24hour

Figure 7:Chromatogram of drug Figure 8: Chromatogram of drug

in 0.1 M HCl at the end of 1 hour in 0.1 M HCl at the end of 24 hour

Figure 9: Chromatogram of drug in Figure 10: Chromatogram of drug

in Phosphate buffer at the end of 1 hour Phosphate buffer at the end of 24 hour

Precompression parameters of metformin HCl powder blend

Since, the flow properties of the powder mixture are important for the uniformity of mass of the tablets, hence the blend of all the batches were evaluated for precompression parameters like angle of repose was found to be between 26.3±0.02 to 32.6±0.01 indicating fair to good flow properties. Bulk density was found to be between 0.53±0.01 to 0.57±0.03g/cm³ and tapped density between 0.67±0.01 to 0.74±0.02 g/cm³. Hausner’s ratio was found to be between 1.22±0.03 to 1.32±0.01. Carr’s Index was found to be between 16.9±0.03 to 23.7±0.01. All the formulations showed good blend properties for direct compression and hence tablets were prepared by direct compression technology. Results of precompression parameters of metformin HCl powder blend is shown in table 2.

Table 02: Results of Precompression parameters of metformin HCl powder blend

Formulation code	Angle of repose(^o)*	Bulk density (gm/cm^3)*	Tapped density (gm/cm^3)*	Carr’s index (%)*	Hausner ratio (HR)*	Bulkiness (cc/g)*
F1	27.3±0.02	0.54±0.04	0.73±0.03	22.8±0.01	1.32±0.01	1.75±0.01
F2	27.9±0.03	0.55±0.02	0.72±0.01	18.7±0.02	1.24±0.01	1.75±0.01
F3	26.3±0.04	0.57±0.03	0.67±0.02	19.9±0.01	1.24±0.01	1.72±0.02
F4	26.3±0.02	0.55±0.03	0.67±0.02	16.9±0.03	1.22±0.03	1.79±0.03
F5	27.6±0.04	0.55±0.01	0.70±0.02	19.9±0.04	1.27±0.02	1.82±0.03
F6	26.9±0.05	0.54±0.03	0.73±0.03	21.5±0.02	1.35±0.04	1.72±0.20.01
F7	30±0.02	0.53±0.01	0.67±0.01	20.8±0.02	1.26±0.05	1.89±0.02
F8	28.0±0.03	0.57±0.01	0.74±0.02	23.1±0.01	1.29±0.02	1.75±0.04
F9	32.6±0.01	0.56±0.02	0.74±0.02	23.7±0.01	1.30±0.04	1.79±0.05
F10	28.1±0.01	0.57±0.02	0.71±0.03	19.0±0.01	1.24±0.02	1.75±0.02

*All values are expressed as mean ± SD, n=3

Table 03: Results of evaluation of metformin HCl FDTs

Formulation code	Thickness (mm)*	Diameter (mm)*	Hardness (kg/cm^2)*	Friability (%)***	Drug content (%)**	Weight variation (mg)**	pH of the solution	Mouth feel
F1	4.1±0.02	11.00±0.04	3.1±0.14	0.24±0.05	100.43±0.06	599±0.01	7.4	+
F2	4.2±0.01	11.00±0.03	2.9±0.16	0.32±0.01	101.91±0.01	604±0.02	7.5	+
F3	4.2±0.01	12.00±0.02	3.3±0.14	0.39±0.02	100.12±0.02	598±0.03	7.4	+
F4	4.0±0.01	12.00±0.01	2.9±0.10	0.55±0.04	99.12±0.01	599±0.01	7.2	+
F5	4.1±0.02	11.00±0.02	2.8±0.12	0.65±0.02	98.34±0.02	600±0.03	7.5	+
F6	4.2±0.01	12.00±0.03	3.2±0.14	0.33±0.03	100.12±0.04	598±0.04	7.2	+
F7	3.9±0.03	12.00±0.01	3.0±0.16	0.21±0.05	101.34±0.05	601±0.05	7.1	+
F8	3.8±0.05	11.00±0.02	2.8±0.12	0.54±0.06	98.12±0.04	602±0.06	7.1	+
F9	4.0±0.01	11.00±0.01	3.2±0.16	0.23±0.04	99.45±0.05	598±0.07	7.2	+
F10	3.9±0.03	12.00±0.01	2.8±0.12	0.33±0.03	101.34±0.01	602±0.04	7.5	+

*All values are expressed as mean ± SE, n=5; **All values are expressed as mean ± SE, n=20; ***All values are expressed as mean ± SE, n=10; '+' good palatable mouth feel; '-' poor palatable mouth feel.

Post compression parameters of metformin HCl FDTs

The data obtained from post-compression parameters in all the formulations, the thickness of the tablets was found to be 3.8±0.05 to 4.2±0.01mm. The diameter of the tablets was found to be 11.00±0.01 to 12.00±0.03 mm. Tablets were prepared using direct compression. Tablets were obtained of uniform weight due to uniform die fill, with acceptable weight variation as per Pharmacopoeial specification. Hardness of the all the formulations were measured in kg/cm². The hardness of all formulations was found to be 2.8±0.12 to 3.3±0.14 kg/cm². Drug content of all the formulations were found to be in the range of 98.12±0.04 to 101.34±0.05%., which is within acceptable limits. Friability values of all the formulations were within the limit i.e. less than 1.0% indicated that tablets had a good mechanical resistance. pH of the solution of all the tablets was found to be between 7.1 to 7.5, which suggest that the tablets can be conveniently administered orally and will not cause any discomfort. Results of Evaluation of metformin HCl fast dissolving tablets are shown in Table 03.Comparison between in vitro disintegration time, in vivo disintegration time and in vitro dispersion time of metformin FDTs shown in figure 11.

It was observed that the increased concentration of cross carmellose sodium, decreases disintegration time and optimized the drug release. Cross carmellose sodium in the concentration of 2% acts as potential disintegrant and disintegrates the tablet within 42 sec fulfilling the criteria of mouth dissolving tablet (3min). This rapid disintegration of the fast dissolving tablets were due to penetration of water into the pores of the tablets, it quickly wicks water into the tablet through capillary action, which leads to the swelling of super disintegrants to create enough hydrodynamic pressure for quick and complete disintegration of the tablet. This in vitro dispersion time gives direct information regarding super- disintegrating nature of disintegrants used.

Figure 11: Comparison between in vitro disintegration time, in vivo disintegration time and in vitro dispersion time of various formulations of metformin HCl FDTs

On the other hand it was observed that the increased concentration of BFM decreases disintegration time and wetting time upto 1% concentration in the tablet, but further increase in the concentration of mucilage showed increase in disintegration time and wetting time. Natural super disintegrants showed less disintegration time compared to synthetic super disintegrant. For predicting the wetting and disintegration time, a prepared mouth dissolving tablet was put in the petri plate and wetting and disintegration rate was noted at the intervals of 4, 8, 12, 16 and 18 seconds. Wetting time was used as a parameter to correlate with disintegration time in oral cavity. This is an important criterion for understanding the capacity of disintegrants to swell in presence of little amount of water. Since the dissolution process of a tablet depends upon the wetting followed by disintegration of the tablet, the measurement of wetting time may be used as another confirmative test for the evaluation of dispersible tablets. Figure 12 depicts the relation between the concentration of super disintegrants and wetting time. The wetting time of the formulated metformin hydrochloride tablets were found in the range of 18±1.43 to 50±1.02 sec. 1% w/w concentration of BFM shows less wetting time compared to other formulations.

Figure 12: Comparison of wetting time of various formulations of metformin HCl FDTs

Water absorption ratio was performed to know the moisture sorption and water uptake properties of super disintegrants. Increase in water absorption ratio with decrease in disintegration time and wetting time was seen with an increase in concentration of super disintegrants. The water absorption ratios of the formulated tablets using BFM and Ac-Di-sol as super disintegrants. The results were found in the range of 25±1.18 to 80 ±1.29%. The prepared formulations were subjected for mouth feel. The volunteers felt good taste in all the formulations. As the drug is not bitter and presence of aspartame in all the formulations showed good, palatable taste. Comparison of water absorption ratio of metformin FDTs using BFM and Ac-Di-sol as super disintegrants shown in figure 13.

Figure 13: Comparison of water absorption ratio of various formulations of metformin HCl tablets

The dissolution profiles of all formulations showed above 90% within 10 min. From drug release profile it was observed that increase in concentration of BFM increases the drug release upto 1% concentration in the tablet, but further increase in the concentration of BFM does not show any increase in the dissolution rate. In case of formulation F2, the 50% and 90% of drug release was found within 2 and 5min respectively. Compared to crosscarmellose sodium formulations, BFM formulations showed faster release of drug, this is due to more swelling property of BFM. From drug release it was observed that, as the proportion of crosscarmellose sodium increased, the overall time for release of the drug from the tablet was also increased. Drug releases from tablets were by drug dissolution, drug diffusion or a combination of both. Comparison of Dissolution profile of various formulations of metformin HCl tablets was shown in figure 14.

Figure 14: Comparison of dissolution profile of various formulations of metformin HCl FDTs

From the above findings it indicated that the isolated mucilage powder was found to have better disintegrating property compared to the synthetic superdisintegrant. The least wetting time, disintegration time and better dissolution profile of formulation F2 proved the superior disintegrant property of the isolated mucilage. Therefore formulation F2 having disintegrant BFM in the concentration of 1% was selected as the optimized formulation. The study reveals that formulations prepared by using 1% BFM exhibited good dissolution and uniform dispersion characteristics necessary for mouth dissolving tablets as compared to marketed, conventional tablets of metformin.

Dissolution profile of the optimized formulation (F2) was compared with the marketed formulation of Metformin HCl (GlyciphageÒ). Marketed formulation of metformin releases 100% drug in 35 minutes. Where as optimized formulation F2 released 100% drug in 5 minutes shows its superiority over marketed formulation. Comparison of Dissolution profile of marketed and optimized formulation of metformin HCl tablets is shown in figure 15.

Figure 15: Comparison of dissolution profile of marketed and optimized formulation of metformin HCl FDTs

Moisture uptake study

Moisture uptake of different formulations was reported. Results were compared with control tablets. Since all excipients were same in all formulations, any difference in moisture uptake may be due to difference in type or concentration of disintegrant added. From the observations it was known that moisture uptake of disintegrant follows the order Ac-Di-Sol> BFM. The formulations containing BFM has shown lower water absorption capacity than those containing Ac-Di-Sol. With the same superdisintegrant, there was a linear increase in water uptake with increase in concentration of superdisintegrants. The Moisture Uptake of tablets containing various concentrations of BFM and Ac-Di-Sol were shown in figure 16 and 17 respectively.

Figure 16: Moisture Uptake of tablets containing various concentrations of BFM

Figure 17: Moisture Uptake of tablets containing various concentrations of Ac-Di-solÒ

Scanning Electron Microscopy

Figure 18 displays the scanning electron photographs of tablets of optimized batch F2. Form the photograph it indicated that the tablet structure shows a lot of pores large than 10 µm. Saliva can easily penetrate into the tablet to disintegrate it almost instantaneously.

Figure 18: SEM photographs of optimized batch of metformin HCl FDT (F2)

Drug release kinetics study

To know the kinetics of drug release the in vitro release data’s were subjected to kinetic treatment. Next, the model fitting of the release profiles were performed using PCP DISSO-V2 software to observe the mechanism. The correlation coefficient values obtained for all five models are tabulated in table 4. The formulations F2 and F8 showed first order and other formulations showed Peppas model. From the values obtained, it is proved that formulations F2 and F8 dissolution (release) of the drugs follows first order may be due to rapid diffusion or the porous nature. The values of diffusion co-efficient (n) for formulations F1, F3, F4, F5, F6, F7, F9 and F10 are shown to be 0.3716, 0.3681, 0.3556, 0.3247, 0.2945, 0.2793, 0.3626 and 0.2924 respectively which indicates that the release of drug occurs by diffusion following Fickian transport mechanism, as all diffusion co-efficient values shows less than 0.5.

Stability study

The stability study for tablets was carried out according to ICH guidelines at real time (25 ±2^oC/60±5% RH) and accelerated (40±2 ^o/75±5% RH) 40±2/75±2% RH for three months by storing the sample in stability chamber. The different parameters that were studied are disintegration time, hardness, friability, drug content and dissolution rate.

The optimized formulation was found to be stable in terms of physical appearance, drug content, disintegration time and in vitro drug release even after the evaluation for 3 months. The formulation was stable under accelerated conditions of temperature and humidity. The results of stability studies of optimized batches were shown in table 05 and in figure 19.

Table 04: Model fitting of the Release Profile from metformin HCl FDTs

Formulation code	Mathematical Models (Kinetics)
	Zero Order	First Order	Higuchi Matrix	Peppas	Hixson Crowell	‘n’ values	Best fit Model
F1	0.8475	0.9842	0.9923	0.9949	0.9612	0.3716	Peppas
F2	0.7239	0.9625	0.9600	0.9532	0.9221	0.2396	First order
F3	0.8388	0.9835	0.9913	0.9977	0.9611	0.3681	Peppas
F4	0.8325	0.9870	0.9893	0.9924	0.9599	0.3556	Peppas
F5	0.8117	0.9741	0.9840	0.9844	0.9851	0.3247	peppas
F6	0.7774	0.9774	0.9769	0.9870	0.9397	0.2945	Peppas
F7	0.7482	0.9690	0.9706	0.9923	0.9326	0.2793	Peppas
F8	0.744	0.9703	0.9605	0.9557	0.9396	0.2542	First order
F9	0.8375	0.9812	0.9901	0.9965	0.9642	0.3626	Peppas
F10	0.7764	0.9724	0.9769	0.9843	0.9389	0.2924	Peppas

Figure 19: Stability data for optimized formulation metformin HCl FDTs (F2)

Parameters	25 ± 2^oC / 60 ± 5% RH	40± 2^oC / 75 ± 5%
Shape
Round	Round
color
White	White
Odor
Orange	Orange
Weight Variation ( mg)
604±0.02	604±0.02
Thickness(mm)
4.2±0.01	4.2±0.03
Hardness (kg/cm^2)
2.9±0.16	2.9±0.16
Friability (%w/w)
0.32±0.01	0.32±0.01
Disintegration time (sec)
21 ± 0.14	18 ± 0.14
Wetting time (sec)
18 ± 1.43	18 ± 1.43
Water absorption ratio (%)
63.2 ± 0.20	63.2 ± 0.20
% Drug content
101.91±0.01	101.91±0.01
%CDR
95.1	95.1

Table 05: Stability Studies for optimized formulation of metformin HCl FDTs (F2)

CONCLUSION:

In the present study the disintegrating properties of the Borassus flabellifer mucilage has been studied in comparison with croscarmellose sodium. The isolated natural disintegrant exhibits faster drug dissolution in comparison to the super disintegrant. Isolated mucilage exhibited potentially as a rapidly disintegrating agent for faster drug dissolution and improved bioavailability, thereby helping in effective therapy and improving patient compliance. It may be exploited as a gelling agent. It may well be used as a binder due to its sticky nature when hydrolyzed with water. The fruit mucilage can also be used as a suspending agent. Therefore, in the years to come, there will be continued interest in natural mucilages and their modifications aimed at the development of better materials for drug delivery systems.

ACKNOWLEDGEMENTS:

The authors are thankful to ICMR for the financial support for this research project (21/12/17/09/HSR, dated: 24/06/2010). The authors are also thankful to Zydus Research centre, Ahmadabad, India for generous gift sample of metformin HCl.

REFERENCE:

1. Monif T, Malhotra A K, Kapoor VP. Cassia fistula seed galactomannan: potential binding agent for pharmaceutical formulation. Indian Journal of Pharmaceutical sciences. 54(6); 1992: 234-40.

2. Kapoor VP, Banerji R, Prakash D. Leguminous seeds: Potential industrial sources for gum, fat and protein. Journal of Scientific and Industrial Research. 51; 1992: 1-13.

3. Robert KM, Daryl K, Granner & Victor W. Harper’s Illustrated Biochemistry. McGraw-Hill. 2006.

4. Verma,PRP, Balkishen R. Studies on Leucaena leucocephala seed gum: emulsifying properties. Journal of Scientific and Industrial Research. 62; 2003: 198-206.

5. Reid JSG, Edwards ME. Food Polysaccharides and their Applications. New York, 1995.

6. Kapoor VP, Banerji R, Prakash D. Leguminous seeds: Potential industrial sources for gum, fat and protein. Journal of Scientific and Industrial Research. 51; 1992: 1-22.

7. Verma PRP, Balkishen R. Studies on Leucaena leucocephala seed gum: rheological properties. Journal of Scientific and Industrial Research. 61; 2002: 437-433.

8. Whistler RL. Industrial Gums, Academic press, New York,1973.

9. Santanu C, Madhusmruti K, Satya Prakash S, Niranjan C P. Comparative study on effect of natural and synthetic superdisintigrants in the formulation of fast dissolving tablets, International Journal of Green Pharmacy, 2(1); 2008: 22-26.

10. Parakh SR, Gothoskar AV. A review of mouth dissolving tablet technologies. Pharmaceutical technology. 27(11); 2003:92-98.

11. Dobetti L. Fast-melting tablets: developments and technologies. Pharmaceutical technology. 2001:44-50.

12. Stepensky D, Friedman M, Srour W, Hoffmann A. Preclincal evaluation of pharmacokinetic-pharmacodynamic rationale for oral CR metformin formulation. Journal of Control Release. 71; 2001: 107-15.

13. Vidon N, Chaussade S, Noel M, Franchisseur C, Huchet B, Berneir JJ. Metfomin in the digestive tract. Diabetes Research and Clinical Practice. 4; 1988: 223-9.

14. Pullaiah T. Flora of Andhra Pradesh (India), Vol-III, Scientific Publishers, Jodhpur, 1997.

15. Nadkarni KM. Indian Materia Medica, Vol-1, Popular Prakashan, Bombay, 2002.

16. Morton JF. Notes on Distribution, Propagation and Products of Borassus Palms (Arecaceae) Economic Botany,1988,42(3),420-41.

17. Masayuki Yoshikawa, Fengming Xu. New Spirostane- Type Steroid Saponins with antidiabetogenic Activity from Borassus flabellifer. Chemical and Pharmaceutical bulletin. 55(2); 2007:308-16.

18. Kapoor LD. Hand Book of Ayurvedic Medicinal Plants, CRC Press, Newyork, 2005.

19. Kokate CK. Practical Pharmacognosy, Vallabh Publication, Delhi, 2006.

20. Indian Pharmacopoeia, the Indian Pharmacopoeia Commission, Ghaziabad. 2007.

21. Martin Alfred. Physical Pharmacy USA, 1991.

22. Knudsen LF, Curtiss JM. The use of the angular formulation in biological assays. Journal of American Statistical Society. 42; 1947:282-96.

23. Gohel M, Patel M, Amin A, Agarwal R, Dave R, Bariya N. Formulation design and optimization of mouth dissolve tablets of nimesulide using vacuum drying technique. AAPS Pharm SciTech. 5(3); 2004: 1-6.

24. Mohanchandran PS, Sindhumol PG, Kiran TS. Superdisintegrants: an overview. International journal of Pharmaceutical Sciences Review and Research. 6(1); 2011: 105-109.

25. Chang RK, Guo X, Burnside B, Couch R. Fast-dissolving tablets. Pharmaceutical Technology. 24(6); 2000: 52–58.

26. Sharma S, Gupta GD. Formulation and characterization of fast dissolving tablet of Promethazine theoclate. Asian Journal of Pharmaceutics. 2; 2008: 70-72.

27. Sreenivas SA, Dandagi PM, Gadad AP, Godbole AM. Orodispersible Tablets: New-fangled Drug Delivery System-A Review. Indian Journal of Pharmaceutical Education and Research. 39; 2005: 177-180.

28. Jaysukh J, Dhaval A, Kantilal R. Orally Disintegrating Tablets: A Review, Tropical Journal of Pharmaceutical Research. 8; 2009: 161-72.

29. Banker GS and Anderson GR. The Theory and practice of Industrial Pharmacy. Varghese Publishing House, Mumbai, 1987.

30. The British Pharmacopoeia, Department of health/ by spationary office on behalf of the medicine and health care product regulatory agency, Crown Copy Right, 5th edition. 2005:1303-1304, 2588-2589, A133.

31. The United State Pharmacopoeia 24/NF19, Asian edition, the official compendia of standard United States Pharmacopoeial Convection Inc. Rockville.1995: 1015, 1016 and 1791.

32. Qalaji-Rawas MM, Simons ER and Simons KJ. Fast disintegrating Sublingual Tablets: Effect of Epinephrine Load on Tablet Characteristics. AAPS Pharm Sci Tech. 2006; 7(2): E1-E7.

Received on 13.08.2012

Accepted on 21.08.2012

© A&V Publication all right reserved

Research Journal of Pharmaceutical Dosage Forms and Technology. 4(4): July-Aug. 2012, 227-239