|Year : 2010 | Volume
| Issue : 2 | Page : 253-259
Studies on some physicochemical properties of Leucaena Leucocephala bark gum
Vijetha Pendyala1, Chandu Baburao2, KB Chandrasekhar3
1 Siddharth Institute of Pharmacy, Sattenapalli, Andhra Pradesh, India
2 Faculty of Pharmacy, 7th April University, Zawia, Libya
3 Department of Chemistry, JNTUA, Anantapur, Andhra Pradesh, India
|Date of Submission||16-Apr-2010|
|Date of Decision||03-Jun-2010|
|Date of Acceptance||09-Jun-2010|
|Date of Web Publication||2-Nov-2010|
Siddharth Institute of Pharmacy, Sattenapalli, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Gum exudates from Leucaena Leucocephala (Family: Fabaceae) plants grown all over India were investigated for its physicochemical properties such as pH, swelling capacity and viscosities at different temperatures using standard methods. Leucaena Leucocephala bark gum appeared to be colorless to reddish brown translucent tears. 5 % w/v mucilage has pH of 7.5 at 28°C. The gum is slightly soluble in water and practically insoluble in ethanol, acetone and chloroform. It swells to about 5 times its original weight in water. A 5 %w/ v mucilage concentration gave a viscosity value which was unaffected at temperature ranges (28-40°C). At concentrations of 2 and 5 %w/v, the gum exhibited pseudo plastic flow pattern while at 10 %w/v concentration the flow behaviour was thixotropic. The results indicate that the swelling ability of Leucaena Leucocephala (LL) bark gum may provide potentials for its use as a disintegrant in tablet formulation, as a hydro gel in modified release dosage forms and the rheological flow properties may also provide potentials for its use as suspending and emulsifying agents owing to its pseudo plastic and thixotropic flow patterns.
Keywords: Leucaena Leucocephala, gum, pH solubility, viscosity
|How to cite this article:|
Pendyala V, Baburao C, Chandrasekhar K B. Studies on some physicochemical properties of Leucaena Leucocephala bark gum. J Adv Pharm Technol Res 2010;1:253-9
|How to cite this URL:|
Pendyala V, Baburao C, Chandrasekhar K B. Studies on some physicochemical properties of Leucaena Leucocephala bark gum. J Adv Pharm Technol Res [serial online] 2010 [cited 2022 Oct 5];1:253-9. Available from: https://www.japtr.org/text.asp?2010/1/2/253/72272
| Introduction|| |
Pharmaceutical excipients are components of dosage forms that enable the formulations to acquire some characteristics which will establish the basic features of the formulated product. These excipients control physicochemical properties as well as the release profiles and availability of the drug in the system  . The physicochemical properties of a compound are measurable characteristics by which the compound may interact with other systems. The ability of excipients to provide their intended function and perform through out the shelf life of the product must be established such that the information will justify the choice, concentration and characteristics that may influence the final product  .
One of the commonly used groups of compounds as excipients is natural polymer. Natural polymers are polysaccharides composed of a large group of polymers with varying chemical composition, large derivitizable groups and a wide range of molecular weights. They are characterized by low toxicity, high stability and biodegradability. These properties make them appealing as pharmaceutical excipients  .
Since the ability of these polymers to provide its intended action chiefly lies on its physical and chemical properties, such properties as solubility, swelling capacity, pH, effect of temperature, and viscosity among others should be established for any potential excipient. Acacia, tragacanth, albizia, guar gum are examples of natural polymers that have been used as excipients in pharmaceutical formulations  .
They are used as binders and disintegrants in tablets and as suspending and flocculating agents. LL gum is a natural polymer, obtained as exu dates from bark of Leucaena Leucocephala. It is necessary to determine the properties of these gums before been used as excipients in any formulation in order to achieve the goal intended of the formulation. The aim of this work therefore is, to establish some of the physicochemical properties of Leucaena Leucocephala bark gum as excipients in pharmaceutical formulations.
| Materials and Methods|| |
Collection and Treatment of Gum
Leucaena Leucocephala bark gum was obtained from the bark of Leucaena Leucocephala trees grown around Andhra Pradesh, Gujarat states, India. The gum was collected around midNovember during the day time. The plant material had been identified and authenticated in the Department of Botany of AC College Guntur. For the processing of the gum, the method of Femi- Oyewo et al,  was adopted with some modifications. The gum was dried in an oven at 40°C for 2 h and size reduced using a blender. It was hydrated in double strength chloroform water for 5 days with intermittent stirring to ensure complete dissolution and then, strained through a 75΅m sieve to obtain particulate free slurry which was allowed to sediment. Thereafter, the gum was precipitated from the slurry using absolute ethanol, filtered and defatted with di- ethyl ether. The precipitate was dried in the oven at 40°C for 48 h. The dried flakes were pulverized using a blender and stored in an air tight container.
In order to characterize the gum, it was subjected to the following physicochemical tests:
Determination of Solubility in various solvents
The solubility of LL gum was determined in cold and hot distilled water, acetone, chloroform and ethanol. 10mg sample of gum was added to 10ml of each of the above mentioned solvents and left overnight. 5ml of the clear supernatants were taken in small preweighed evaporating dishes and heated to dryness over a digital thermostatic water bath. The weights of the dried residue with reference to the volume of the solutions were determined using a digital top loading balance and expressed as the percentage solubility of the gums in the solvents  .
The method of Bowen and Vadino  was adopted. A 5g quantity of the gum powder was placed in a 200ml measuring cylinder and tapped 200 times. The volume (Vi) of the gum in the cylinder was recorded. Water was added to the mass to reach the 100ml mark, in the cylinder and left to stand for 24 h. The new volume of the gum in the cylinder was then recorded as Vii.
The swelling capacity (Τ) was calculated as the ratio of the final volume (Vii) to the initial volume (V 1 ).
Determination of Apparent Viscosity of the gum
A digital Brookfield viscometer was used for this study. It measures the torque required to rotate an immersed spindle in a fluid. The instrument features a rotating spindle with multiple speed transmission and interchangeable spindles that measure a variety of viscosity ranges. Different concentrations (2.0, 5.0 and 10%w/v) of the gum mucilage samples were prepared in a 600ml beaker, appropriate enough to immerse the spindle groove in the fluid. Speed of rotation was varied (10, 20, 50, and 100 R. P. M) to determine its effect on the viscosity values since drag force is known to alter with changes on the spindle size and rotational speed. For each concentration and at each rotational speed triplicate measurements were made.
Determination of the pH of Gum
The pH of the gum mucilage (5%w/v concentration) was determined using a Global pH meter. The pH meter was set to neutral (7.4) at a room temperature of 28 °C and the electrode was immersed into the mucilage. The reading on the meter recorded. Triplicate measurements were made.
Effect of storage time on viscosity
Different concentrations (2.0, 5.0 and 10 %w/v) of LL gum mucilage were prepared and their viscosities at a range of storage temperatures (28-40°C) were determined over a period of 21 days, using a Brookfield viscometer as described above.
| Results and Discussion|| |
Gums are polysaccharides with numerous sugar molecules and, therefore partially dissolve in water. The observed sparing solubility of LL gum in water may be due to the linear nature of the polymer, which has been reported to be less soluble compared to the branched components  . Solubility values presented in [Table 1] showed that LL gum is insoluble in the three organic solvents (acetone, chloroform and ethanol) but slightly soluble in water (hot and cold). As depicted also in [Table 1], the gum had a swelling capacity of 5.0, indicating that the gum contains linear polymers. It was reported that swelling of a linear polymer without dissolution is an indication that it is cross-linked  . The cross-links tie the macromolecular chains together by primary covalent bonds thereby transforming each particle into a single giant molecule. The swelling ability of polymers enables it to absorb water and reduce the fluidity of ! Stool one of the major uses of gums. Crosslinked polymers are also suitable for use as disintegrants because they form hydro gels, they can be used for controlled release dosage forms. The viscosity of LL gum is found to be dependent on concentration at the same shear rate. It increases with increase in gum concentration. The variation in cohesiveness of the mucilage is apparent as viscosity of the gum was more at 10%w/v compared with values at 2 and 5%w/ v concentrations. Generally, molecules in a fluid have different shapes and sizes. The force required to move these molecules in the fluid is determined by their type of bond, shape and size. The presence of air makes the material compressible, and therefore the more the slurry is compressed, the greater the viscosity  . This probably explains why LL gum has a higher viscosity value which is more viscous at a concentration of 10 °low/v compared with 2 and 5 %w/v mucilage concentrations. Though, most fluid's viscosities decrease as temperature increases, change in temperature had no significant effect on the viscosity of the gum mucilage. Result of viscosity values at different storage times showed an initial increase, followed later by a decrease [Figure 1] and [Figure 2]. The rise and fall in viscosity could be attributed to the nature of the gum as it hydrates over time. Hydration was more pronounced with 2%w/v LL gum concentration compared with 5%w/v concentration. LL gum at concentrations of 2 and 5%w/v exhibited pseudo plastic flow pattern using a spindle no. 62 and a guard leg. However, the 10% w/v concentration could not be sheared with the same spindle size because it was out of range, but at 50 R.P.M the flow pattern was observed to be thixotropic. These flow patterns are of immense importance in liquid formulations such as suspensions owing to their ability to keep the preparation suspended. Ram reported that, for an ideal suspension, it is best to have high viscosity during storage (preventing sedimentation) and low viscosity when sheared to ease administration  . This is achieved by the use of pseudo plastic as well as thixotropic suspending agents which can maintain the suspensions in flocculated form.
|Table 1: Basic physico-chemical properties of Leucaena Leucocephala bark gum|
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| Conclusion|| |
The results obtained indicated that on physical examination LL gum occurs as colorless to reddish brown, translucent tears. The gum mucilage is acidic with a pH of 4.2 at 28°C. It is slightly soluble in water and practically insoluble in semi-polar solvents like ethanol, acetone and chloroform. It swells to about 5 times it original weight in water. The viscosity of the gum was found to increase as the gum concentration increased and, at concentrations of 2 and 5%w/v, LL gum was observed to exhibit pseudo plastic flow pattern while at 10%w/v concentration the flow behavior was thixotropic when sheared at 50 R.P.M.
In conclusion, the swelling ability of LL gum may provide potentials for its use as a disintegrants in tablet formulation, as a hydro gel in modified release dosage forms and as a suspending agent and emulsifying agent owing to its pseudo plastic and thixotropic properties.
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[Figure 1], [Figure 2]