Vijay Agarwal et al. / Journal of Pharmacy Research 2011,4(7),

Research Article ISSN: 0974-6943 Vijay Agarwal et al. / Journal of Pharmacy Research 2011,4(7), Available online through www.jpronline.info Preformulational and delayed release formulation study on Senna leaf powder and Calcium sennoside Vijay Agarwal 1*, Arundhati Bhattacharya 2 Meenakshi Bajpai 3, College of Pharmaceutical Sciences, Rajkumar Goel Institute of Technology,5 Km. Stone, Delhi - Meerut Road,Ghaziabad (Uttar Pradesh) 201003,India Received on: 12-04-2011; Revised on: 18-05-2011; Accepted on:21-06-2011 ABSTRACT In majority of herbal formulations, preformulations and post formulation studies are lacking. Hence an attempt is made to evaluate preformulation and post formulation characteristics of senna leaf powder and calcium sennoside. The purpose of the present investigation was to achieve delayed release delivery of sennosides using Cellulose acetate phthalate (CAP) as an enteric coating agent. The enteric film was prepared using non-aqueous solvents like acetone and ethyl alcohol. In vitro release studies for prepared tablets were carried out in 0.1N hydrochloric acid & phosphate buffer ph 6.8. The drug release from the coated systems was monitored using high performance liquid chromatography (HPLC). The surface of the tablet was coated with Cellulose acetate phthalate to ensure that the tablet was more ph dependent and trigger the drug release only at higher ph. It was found that Cellulose acetate phthalate alone was sufficient to protect the core tablets in stomach environment. Key words:cellulose acetate phthalate, Enteric coating, Sennosides, Delayed release INTRODUCTION Senna is a well known drug, used in the Ayurvedic and Allopathic systems of medicine for treatment of constipation. The laxative action of senna and its formulations is due to the presence of sennosides A and B. [1] Senna known as Tinnevelly senna, family Leguminoseae, [2-4] mainly act upon the large intestine. The glycosides are absorbed from the intestinal tract and the anthraquinone are excreted into the colon, where they stimulate and increase the peristaltic movements of the colon by local action. This results in decreased absorption of water and thereby a bulky and softer fecal mass is produced. This suggests their action in intestine and no effect in stomach. [5-7] By targeting the sennoside to intestine with the help of enteric coating, we can ensure that entire quantity of drug is made available to intestine thereby averting any possible loss during passage through the stomach. [8] EXPERIMENTAL AND METHODS Materials Reference standard of calcium sennoside and calcium sennoside were purchased from Natural Remedies Private Limited, Bangalore, India and Garlico Herbal Concentrate, Mandsaur, Madhya Pradesh, India respectively. Senna leaf powder was obtained by grinding the dried leaves. Ethyl cellulose, polyvinyl pyrrolidone, microcrystalline cellulose, acetone, Starch and Fast green dye were obtained from Centre Drug House, New Delhi, India. Cellulose acetate phthalate was obtained from Acros organics, New Jersey, USA. Other materials in the study such as Talc, Magnesium stearate, Propylene glycol, Sorbiton mono-oleate were of pharmacopoeial grade (supplied by Qualigens, Mumbai, India). Methnol and water (obtained from Rankem, New Delhi, India) were also used of HPLC grade throughout the study. Methods Instrumentation [9-10] A HPLC pump of CECIL, U.K (model no CE-4200) was used to deliver the mobile phase (Methanol : water- 9:1) to the analytical column, SPHER ODS, 4.6 mm X 250mm,5µm. The eluant was monitored at 260 nm with the help of UV-visible detector. The flow rate was 0.5ml/min. Preformulation study of senna leaf powder and calcium sennoside Preformulation study was performed on senna leaf powder and calcium sennoside. The identification test, loss on drying, solubility, average bulk density, average compressibility index, average hausner s ratio, thin layer *Corresponding author. Vijay Agarwal College of Pharmaceutical Sciences, Rajkumar Goel Institute of Technology, 5 Km.Stone,Delhi-Meerut Road,Ghaziabad (Uttar Pradesh) 201003,India Tel.: + 91-9891383464 E-mail:vagarwal5@rediffmail.com chromatography and particle size analysis were carried out prior designing and development of the formulations. Procedure that evaluates the each characteristic was same for both drugs. Calibration curve of reference standard Different concentrations of reference standard solutions (0.1µg/ml to 0.25 µg/ ml) were prepared from the stock solution which was prepared by dissolving 5 mg of sample in 5 ml of water. A calibration curve was prepared by plotting concentration and peak area on X & Y axis respectively. Retention time (Rt) for sennosides was 6.12 minutes. Identification test Identification test was performed as per given in official books. Loss on drying Moisture content was determined by transferring 1gm of powdered drug to the electronic moisture analyzer (citizen scale I pvt. Ltd, Mumbai, India) and heated at 100 o C for 2 hrs. Moisture content was within the pharmacopoeias limit as shown in table-1 Initial weight Final weight Moisture % = --------X 100 Final weight Solubility Sufficient quantity of drug was dissolved in suitable solvent by shaking with mechanical shaker and added the some extra quantity of drug for preparing the supersaturated solution. Solubility of drug in different solvents (water, alcohol, chloroform, ether) was determined by using HPLC (table-1). Bulk density & Compressibility index Initial volume and untapped density were measured by transferring 20 gm of drug into a measuring cylinder of 100 ml and after 100 tapping the final volume was determined. Bulk volume and compressibility index were determined using the formula. Mass Bulk Density = - Bulk Volume Tapped Density Untapped Density Compressibility Index = X 100 Tapped Density Hausner s ratio Hausner s ratio was determined by calculating the tapped density and untapped density. The procedure was same as used for bulk density and compressibility index. Tapped density Hausner ratio = Untapped density

Vijay Agarwal et al. / Journal of Pharmacy Research 2011,4(7), Thin layer chromatography 0.5gm/5ml test solution and 10mg/ml reference solution were prepared by using equal volume of alcohol and water as solvent. Retention factor of sennoside A, B & D was determined by adopting the pharmacopoeial procedure. Particle size analysis Particle size analysis was performed by preparing the suspension of drugs in diluted glycerin. Frequency distribution of particles was determined by using photomicroscope (Model-RXL-5T, Radical instruments, Japan) with considering some other parameters such as average total area, total outer perimeter, average length and average breadth. Estimation of sennoside Solution of drug (conc - 10µg/ml) was prepared by using water as solvent. 20µl of filtered solution was injected to HPLC for determining the concentration of sennoside. The total amount of sennosides present in 100mg was determined (% sennoside) with using the calibration curve of reference standard. Preparation of core tablets Preparation of senna leaf powder core tablets Weighed amounts of senna leaf powder & ethyl cellulose (table-2) were moistened with PVP in isopropyl alcohol which was then passed through 16 mesh sieve. Granules were prepared using PVP (5, 10, 15%); PVP (10%) with EC (5, 10, 15%) and PVP (15%) with EC (5, 10, 15%). Granules were dried at 50 o C. The dried granules were again passed through 20 mesh sieve. Talc and magnesium stearate on dry weight basis were added to the granules and mixed well. Tablets were compressed with flat round punch of 12 mm diameter. Before tablet preparation, the blend was subjected to pre-compression parameters like bulk density, tapped density, angle of repose, percentage compressibility and hausner s ratio. Preparation of calcium sennoside core tablets Dispensed the materials as per the formula (table-3) and moistened slowly with sufficient quantity of starch paste (5, 10, and 15%) till suitable dough was formed. The dough was then passed through 16 mesh sieve and granules so obtained were dried in an oven at temperature of 60 o C for 1.5 hours. The dried granules were again passed through 20 mesh sieve. Talc and magnesium stear- Table 1 Preformulational characteristics of senna leaf powder and calcium sennoside Characteristics Senna leaf powder Calcium sennoside % Moisture content 11.8 % 5.0 % Solubility Water 1 in 526 of water 1 in 149 of water (Slightly soluble) (Slightly soluble) Alcohol 1 in 555 of alcohol 1 in 163 of alcohol (Slightly soluble) (Slightly soluble) Chloroform 1 in 1250 of chloroform 1 in 5882 of chloroform (Very slightly soluble) (Very slightly soluble) Ether 1 in 3333 of ether( 1 in 8333 of ether( Very slightly soluble) Very slightly soluble) Average Bulk density (gm/cm 3 ) 0.44 0.91 Average Compressibility index 23.42 20.02 Average Hausner s ratio 1.30 1.25 Retention factor Sennoside A 0.74 0.93 Sennoside B 0.63 0.77 Sennoside D 0.95 1.0 Particle size analysis Average total area 14.41 µm 8.11µm Average of outer 10.90 µm 9.35µm perimeter Average length 4.13 µm 3.21µm Average breadth 2.34 µm 1.48µm Sennoside % 2.9 % 7.0 % Table 2 Formulation of senna leaf powder tablet Excipients % used/tablet Batch Code A1 A2 A3 A4 A5 A6 A7 A8 A9 PVP (K-30) 5 10 15 10 10 10 15 15 15 Ethyl cellulose - - - 5 10 15 5 10 15 Talc 2 2 2 2 2 2 2 2 2 Magnesium stearate 1 1 1 1 1 1 1 1 1 Table 3 Formulation of calcium sennoside tablet Ingredients (mg) Batch Code E1 E2 E3 Calcium sennoside 172 172 172 Microcrystalline cellulose 119 119 119 Starch paste (%) 5 %(qs) 10 %(qs) 15 %(qs) Talc 6 6 6 Magnesium stearate 3 3 3 ate on dry weight basis were added to the granules and mixed well. These granules were then compressed in a single punch machine (Hicon instruments, Delhi, India) using 10 mm diameter, flat and round punch. Before tablet preparation, the mixture blend was also subjected to pre-compression parameters that were used for senna leaf powder tablets. Enteric coating of senna leaf powder and calcium sennoside tablets Preparation of enteric coating solution Enteric coating solutions were prepared by using Cellulose acetate phthalate in different percentage as shown in table-8. Cellulose acetate phthalate was dissolved in Ethyl alcohol, Sorbiton mono-oleate, and part of the Acetone. To ensure proper dispersion, the dye, Titanium dioxide, Talc and Vanillin were properly dispersed in Acetone by stirring. After the particle size reduction or dispersion occurred, the colorant solution was added to the solution. Propylene glycol was added to the final solution and composition brought to proper volume with Acetone. Preparation was properly agitated to assure proper distribution of Propylene glycol and the colorant in suspension. Coating process The enteric coating of calcium sennoside and senna leaf powder tablets was done by conventional rotating pan using different concentration of cellulose acetate phthalate as enteric coating material. The desired volume of the coating solution was sprayed on pre-warmed tablet bed in a pan coater. The tablets were coated and dried with the help of inlet air having temperature 40 o to 50 o C. The inlet temperature for coating process was optimized by taking different temperature ranging from 30-70 o C. The coating procedure was repeated till the desired level of coating was achieved. The percentage mass increase of the tablet upon coating was taken to be indicative of the coat thickness. The final drying stage was done by stopping the spraying of coating solution and keeping the coated tablets at the same bed temperature for 20 min. Evaluation of enteric coated tablets The coated tablets were evaluated for official specifications. In vitro disintegration study According to USP, a tablet was placed in each of the six tubes of the apparatus and one disc was added to each tube. Disintegration apparatus was operated using the simulated gastric fluid (0.1N HCl), maintained at 37 o C as the immer- Table 4 Characteristics of senna leaf powder tablet Batch Compressibility Angle Bulk Density Hausner Hardness Code Index of Repose (gm/cm 3 ) Ratio (Kg/cm 3 ) A-1 17.85 45.0 0.310 1.217 1.7 A-2 16.0 44.45 0.309 1.190 2.2 A-3 10.20 38.93 0.283 1.113 2.5 A-4 11.42 30.46 0.297 1.128 3.0 A-5 8.13 27.90 0.285 1.085 3.7 A-6 5.03 26.56 0.292 1.052 5.2 A-7 5.25 35.64 0.277 1.055 2.7 A-8 3.86 33.56 0.279 1.04 3.6 A-9 5.06 29.01 0.267 1.053 4.2 Table 5 Characteristics of calcium sennoside powder tablet Batch Compressibility Angle of Bulk Density Hausner Hardness Code Index Repose (gm/cm 3 ) Ratio (Kg/cm 3 ) E-1 14.78 33.37 0.694 1.173 3.4 E-2 7.15 29.11 0.617 1.076 4.8 E-3 4.95 29.44 0.265 1.052 6.5 sion fluid. After 1hr of operation, baskets were lifted from the fluid and tablets were observed for disintegration. Apparatus was operated again, using the simulated intestinal fluid (buffer solution of ph-6.8) as the immersion fluid, till the tablets disintegrated. In vitro dissolution study In vitro release of sennoside from senna leaf powder and calcium sennoside tablets were done in USP-II dissolution apparatus (DS 8000, Labindia pvt. Ltd, Navi Mumbai, India) by using 900 ml of 0.1N HCl as initial medium, rotation at 100 rpm for 2 hour at temperature 37 o C. After 2hrs, 5 ml of sample was withdrawn from basket for determining the sennoside content and also drained the acid from vessel and added the 900 ml of ph-6.8 phosphate buffer. Continued to operate the apparatus for 2hrs. The samples were analyzed by HPLC. Statistical Analysis There was no linear relationship between concentration of calcium sennoside and peak area in calibration curve of reference standard, so simple linear regression analysis had been applied after best fitting of straight line. This

Vijay Agarwal et al. / Journal of Pharmacy Research 2011,4(7), Table 6 Mean and Standard deviation of parameters used for senna leaf powder formulations (n=6) Table 10 Effect of different percent of CAP on disintegration time in different disintegration media (for senna leaf powder tablets) Batch Bulk Density Compressibility Index Hausner Ratio Angle of Repose Hardness Code Mean SD Mean SD Mean SD Mean SD Mean SD Parameters Different % of CAP containing senna leaf powder tablets 4% 8% 12% 16% 20% A1 0.3106 0.00709 17.85 2.10164 1.2175 0.03133 45.0083 1.26358 1.7666 0.15055 A2 0.3094 0.00792 16.0066 0.79217 1.1901 0.0116 44.4516 1.58721 2.2666 0.20655 A3 0.2838 0.00633 10.205 0.21389 1.1131 0.00271 38.9316 0.73393 2.5666 0.15055 A4 0.2971 0.01324 11.42 2.17688 1.1288 0.02888 30.4633 1.94627 3 0.17888 A5 0.2851 0.00538 8.13 0.38120 1.0851 0.00160 27.9083 1.19427 3.7 0.20976 A6 0.292 0.01143 5.035 0.19937 1.0526 0.00196 26.5666 1.06991 5.2666 0.20655 A7 0.2775 0.00983 5.2566 0.19001 1.0551 0.00222 35.645 0.85284 2.7666 0.15055 A8 0.2798 0.00828 3.86 0.10099 1.04 0.00109 33.565 0.48003 3.6333 0.15055 A9 0.2676 0.00723 5.0633 0.14459 1.053 0.00154 29.0116 0.50590 4.2666 0.20655 Table 7 Mean and Standard deviation of parameters used for calcium sennoside formulations (n=6) Batch Bulk Density Compressibility Index Hausner Ratio Angle of Repose Hardness Code Mean SD Mean SD Mean SD Mean SD Mean SD E1 0.6948 0.08938 14.785 1.67900 1.17366 0.02312 33.3766 0.38877 3.4333 0.15055 E2 0.6173 0.04252 7.15 0.44721 1.07666 0.00492 29.1116 0.76462 4.8 0.17888 E3 0.2655 0.01023 4.9533 0.09244 1.052 0.00109 29.44 0.44913 6.5666 0.15055 Table 8 Formulae for enteric coating solution Ingredients (%) Batch code EC-1 EC-2 EC-3 EC-4 EC-5 Cellulose acetate phthalate 4 8 12 16 20 Propylene glycol 3 3 3 3 3 Sorbiton mono- oleate (span-80) 1 1 1 1 1 Ethyl alcohol 45 45 45 45 45 Dye (Fast green) 0.05 0.05 0.05 0.05 0.05 Vanillin 0.1 0.1 0.1 0.1 0.1 Talc 0.5 0.5 0.5 0.5 0.5 Titanium dioxide 0.5 0.5 0.5 0.5 0.5 Acetone q.s to100% q.s to100% q.s to100% q.s to100% q.s to100% Table 9 Effect of temperature on tablet coating TemperatureRanges ( O C) Effect on Tablet Coating 30-40 Wet tablet bed 40-50 No problem 50-60 No problem 60-70 Tablets adhere to one another straight line defined the functional relationship between two variable, X (concentration of sennoside) and Y (peak area). The linear regression equation was Y= 1925.7X + 74.21, where Y was dependent variable (ordinate), X was the independent variable (abscissa), and 74.21 and 1925.7 were the Y intercept and slope of line respectively. The correlation coefficient was 0.9647 and r 2 was 0.9307. When best fit line was start from origin (Y intercept set 0), the equation become Y=2255.6X. All tablet formulations were tested for drug content using the slope and the intercept obtained from the standard curve. Mean and standard deviation (SD) of different parameters of all the formulations were calculated, where n=6 (Table 6 & 7). These calculated parametric mean and standard deviation value of different batches were also compared using the graphical presentation (Figure 2-11). RESULTS AND DISCUSSION The dianthrone glycosides, Sennoside A and B are of medicinal interest because of their strong laxative properties. All official pharmacopoeias suggest the measurement of Sennosides B as total Sennosides present in Senna. Hence Senna leaf powder and Senna extract were estimated for total Sennoside content. The total Sennoside content of senna leaf powder and senna extract were found to be 2.9% and 7% respectively. Since, Sennosides were estimated as a major constituent for Senna, all the formulations were analysed by HPLC method for Sennosides content. Senna leaf powder and calcium sennoside were undergo preformulation study with considering some important characteristics such as percentage moisture content, solubility, average bulk density, average compressibility index, average hausner s ratio, estimation of sennoside, thin layer chromatography and particle size analysis. All preformulation characteristics were evaluated using official standard procedures. The data s of these characteristics were found under the limit of pharmacopoeias standard (table-1). Sennoside tablets were successfully manufactured using wet granulation method. Wet granulation was used to formulate the tablets without using propyl paraben, sodium carbonate, stearic acid, citric acid, polyethylene glycol and sugar derivatives such as lactose, glucose and sorbitol due to their incompatibility with sennoside. Disintegration time in 55 min 65 min 79 min 94 min 111min 18 sec 12 sec 37 sec 22 sec 17sec ph 6.8 phosphate buffer Disintegration time in Fail Fail Unchanged Unchanged Unchanged 0.1 N HCl after 2 hours after 2 hours after 2 hours Table 11 Effect of different percent of CAP on disintegration time in different disintegration media (for calcium sennoside tablets) Parameters Different % of CAP containing calcium sennoside tablets 4% 8% 12% 16% 20% Disintegration time in 16 min 18 min 22 min 27 min 33 min ph 6.8 phosphate buffer 30 sec 12 sec 8sec 15 sec 27 sec Disintegration time Fail Fail Unchanged Unchanged Unchanged in0.1 N HCl after 2 hours after 2 hours after 2 hours Table 12 Characteristics of senna leaf powder and calcium sennoside tablets, before & after coating Characteristics Senna Leaf Powder Tablets Calcium Sennoside Tablets Before Coating After Coating Before Coating After Coating Disintegration Time 46 min, 25 sec 79 min, 37 sec 15 min, 15 sec 22 min, 8sec % Drug Release 77.4% 64.1% 100.1% 98.4% After 2 hours Drug Content 101.8% 99.7% 102.5% 100.4% All formulations (A1 to A9) of senna leaf powder were evaluated for precompression and post compression parameters, of which batch A6 was found to show better results (Table-4) in all characteristics in comparision to that of other batches, therefore batch A6 was selected for further studies. Similarly three formulations (E1 to E3) of senna extract were evaluated, of which batch E2 was selected for further studies due to better characteristics as mentioned in table-5. The values of precompression parameters evaluated were found to be within the prescribed limits and indicated good free flowing property. Numbers of factors are important for oral intestinal drug delivery system. One of the factors for selection of an approach is solubility of the drug. Tablets of water soluble drug may release a significant amount of drug from the surface in the physiological environment of stomach before reaching at the site of action. In such a situation either the tablets can be enteric coated or application of compression coat will retard the drug release in gastrointestinal tract. Calcium sennoside and senna leaf powder are water soluble drugs. Hence, an attempt was made to inhibit the drug release in the physiological environment of stomach and to ensure total drug release in intestine by enteric coating using cellulose acetate phthalate (CAP). The inlet temperature for coating process was optimized by taking different temperature ranging from 30-70 o C but efficient enteric coating temperature was optimized between 40-50 o C as shown in table-9. Five batches of each drug were satisfactorily coated using different concentration (4, 8, 12, 16, & 20 % w/v) of cellulose acetate phthalate. Non aqueous solvents (Ethyl alcohol & Acetone) were used in coating system. The non aqueous system is particularly suited to coating the drugs that are sensitive to water and / or heat. Propylene glycol was used as plasticizer in coating system, produced good film characteristics. Study revealed that 12% cellulose acetate phthalate when used as enteric coating material gives better results. Tablets that were coated with 4% and 8% CAP solution, did not pass the disintegration test (table-10 & 11) and also released some amount of drug in 0.1N HCl solution during dissolution test. Senna leaf powder and calcium sennoside tablets that were coated with 12%, 16% and 20% of CAP containing solution, passed the disintegration test. 16% and 20% CAP solutions directly affected the disintegration time and drug release of tablets. So batch EC-3 (table-8) was selected as enteric coating solution for coating the core tablets of senna leaf powder and calcium sennoside. Coating uniformity was of primary importance, especially when the coating functions as a major influence on drug release, such as a tablet that has received too little coating would release drug too rapidly, while release from a tablet that has received too much coating material will almost certainly release drug slowly than expected. After enteric coating, disintegration time for both type of tablet was increased. It increased from 46 min, 25 sec to 79 min, 37 sec for senna leaf powder tablet and from 15 min, 15sec to 22 min, 8 sec for calcium sennoside tablet (table-12). Both type of tablets were released approximately 100% of drug, before and after enteric coating.

Vijay Agarwal et al. / Journal of Pharmacy Research 2011,4(7), Figure 1 Chromatogram of calcium sennoside (reference standard) Figure 5 Graphical presentation of mean ± standard deviation of hausner ratio of senna leaf powder batches, using mean error bar Figure 2 Graphical presentation of mean ± standard deviation of compressibility index of senna leaf powder batches, using mean error bar Figure 6 Graphical presentation of mean ±Standard deviation of hardness of senna leaf powder batches, using mean error bar Figure 3 Graphical presentation of mean ± standard deviation of angle of repose of senna leaf powder batches, using mean error bar Figure 7 Graphical presentation of mean ±standard deviation of compressibility index of calcium sennoside batches, using mean error bar Figure 4 Graphical presentation of mean ±Standard deviation of bulk density of senna leaf powder batches, using mean error bar Figure 8 Graphical presentation of mean ±standard deviation of angle of repose of calcium sennoside batches, using mean error bar

Vijay Agarwal et al. / Journal of Pharmacy Research 2011,4(7), Figure 9 Graphical presentation of mean ±Standard deviation of bulk density of calcium sennoside batches, using mean error bar Figure 11 Graphical presentation of mean ±Standard deviation of hardness of calcium Sennoside batches, using mean error bar enteric polymer remains intact in stomach but release the content once it reaches the intestine. When Cellulose acetate phthalate was used as an enteric coating material for core tablets of senna leaf powder and calcium sennoside, the initial loss of 5-8% Sennosides in stomach could be completely averted. The results of this study indicates that enteric coated tablets using 12% Cellulose acetate phthalate are suitable for drug like Sennosides which are mainly active in the lower GIT. ACKNOWLEDGEMENT The authors are grateful to Rajkumar Goel Institute of Technology, Ghaziabad for providing the necessary facilities. Figure 10 Graphical presentation of mean ± standard deviation of hausner ratio of calcium sennoside batches, using mean error bar Delayed release tablets of senna powder and calcium sennoside were subjected to in vitro dissolution testing using USP type II apparatus. Enteric coated formulations of senna leaf powder and calcium sennoside released 64.1% and 98.4% of drug respectively after 2 hour. CONCLUSION The development of enteric coated tablets has been one way of preventing active drug from coming into contact with gastric mucosa. For these dosage forms to be effective they must not disintegrate in the stomach but they must release the drug after leaving the stomach. While this can be studied in vitro, there is no real substitute for confirming reliable performance in vivo. % of cellulose acetate phthalate was optimized for gastric resistance because REFERENCES 1. Shah SA, Ravishankara MN, Nirmal A, Shishoo CJ, Rathod IS, Suhagia BN, Estimation of individual sennosides in plant materials and marketed formulations by an HPTLC method, Journal of Pharmacy and Pharmacology, 52(4), 2000, 445-449. 2. United States Pharmacopoeia 27, U.S pharmacopoeia convention, Inc, Rockville, MD, Webcom limited, Toronto, 2004, 1686-1688. 3. The international pharmacopoeia, Quality specifications Geneva world health organization, III rd ed, Vol 3, 1988, 284-289. 4. British Pharmacopoeia, Vol. 3, Her Majesty s Stationary Office, London, 2004, 1738-1739. 5. Momin M, Pundarikakshudu K, Design, development and in vitro evaluation of sennosides tablets containing pectin HPMC for colonic drug delivery, Indian Journal of Pharmaceutical Sciences, 67(4), 2007, 394-401. 6. Fairbairn JW, The active constituents of the vegetable purgatives containing anthracene derivatives, Journal of Pharmacy and Pharmacology, 1, 1994, 683-686. 7. Franz G, The senna drug and its chemistry, Pharmacology, 47, 1993, 2-6. 8. Momin M, Pundarikakshudu K, In vitro studies on guar gum based formulation for the colon targeted delivery of sennosides, Journal of Pharmacy and Pharmaceutical Sciences, 7(3), 2004, 325-331. 9. Azam MM, Ling YT, An improved HPLC method for estimation of Sennoside in Senna, Indian Journal of Pharmaceutical Sciences, 4, 2002, 178-181. 10. Dutta A, De B, Seasonal variation in the content of sennosides and rhein in leaves and pods of Cassia fistula, Indian Journal of Pharmaceutical Sciences, 60(6), 1998, 388-390. Source of support: Nil, Conflict of interest: None Declared