On the basis of these results, treatment given in microwave did not change the chemical structure, modify, or degrade MGG.
That is, the chemical nature and safety of the material was retained throughout and after microwave treatment. High energy
(such as that used in microwave) did not affect the chemical characteristics of gellan gum. There was only a change in its
Figure 4: FT-IR spectra of (a) pure gellan gum and (b) modified gellan gum.
Results of various physicochemical properties of PGG and MGG are shown in Table III. Flow properties of the powder are determined
from the value of the angle of repose. Powder flowability depends on three general areas: the physical properties of the particle
(e.g., shape, size, compressibility), the bulk powder properties (e.g., size distribution, compaction), and the processing
environment (e.g., storage, humidity) (39). Angle of repose, Hausner ratio, flow rate through an orifice, and shear-cell methods
are described in the US Pharmacopeia (40). The average particle size of PGG and MGG was 240 and 160 µm. Bulk and tapped densities are listed in Table III. The
angle of repose of PGG and MGG was 43° and 37°, respectively. Results reveal that PGG and MGG exhibited passable and fair
flow, respectively. Results of flow property and compressibility conclude that MGG is not suitable for direct compression.
Therefore, granulation is recommended to improve flow. Compressibility data of MGG are superior to those of PGG.
Table III: Results of physicochemical properties of pure and modified gellan gum.
To investigate the disintegrant properties and the versatilities of the MGG, lactose, and DCP, tablets were prepared and evaluated
for DT, hardness, and friability (see Table IV). There was an acceptable hardness and friability for lactose and DCP tablets.
The incorporation of MGG in lactose tablets resulted in a marginal increase in hardness and a decrease in friability. DCP
tablets remain unchanged , most likely because of the presence of facilitated flow and densification of the granule in the die. DCP shows higher fragmentation propensity as compared with lactose,
which could be one of the reasons for higher hardness values of DCP tablets compared with lactose tablets.
Table IV: Results of lactose and DCP tablets containing modified gellan gum.
Lactose tablets showed relatively faster disintegration (Batch A1) than DCP tablets (Batch B1), which may be attributed to
an increased water uptake by lactose tablets. The slightly higher DT of DCP tablets compared with lactose tablets may be attributed
to higher crushing strength and poor aqueous solubility (41). Results reveal that tablets containing an insoluble excipient
(DCP) and MGG (Batch B2) showed substantial decrease in DT as compared with Batch B1, which contained no disintegrant. For
lactose tablets with and without MGG, there was a decrease in DT. Lactose is a water-soluble excipient, and hence it works
as an auxiliary disintegrant. A comparison of batches A2 and B2 shows that there was more decrease in DT in batch B2. Therefore,
MGG led to excellent results in the presence of a hydrophobic excipient (DCP).
The following results were concluded when PGG was treated in microwave:
• There was remarkable reduction in viscosity but swelling remain intact
• Flow property and compressibility of MGG was changed as compared with PGG
• DSC thermograms proved that there was a change in energy requirements of MGG but not removal or addition of any peaks
• X-ray diffraction revealed that there was a change of nature from amorphous to crystalline, which indicates only a physical
• There were no chemical degradation, changes, or modification in functional groups of MGG, indicating no chemical changes
in the structure, which was proved with FT-IR analysis.
MGG was explored as a disintegrant in lactose and DCP tablets. MGG functions as a disintegrant in tablet formulation and shows
excellent DT with DCP (hydrophobic excipient) as compared with lactose (hydrophilic excipient).
The areas in which further work can be conducted include using a fluid-bed dryer or spray dryer for preparing a modified excipient.
MGG can be used in combinations and ratios of presently accepted super disintegrating agent such as crospovidone, sodium starch
glycolate, and croscarmellose.
Results of this study show that modified gellan gum can be used as a disintegrant in tablet formulation. Only physical modification
was carried out in the microwave oven. Modified gellan gum shows excellent swelling capacity, flow property, and compressibility.
Dhiren P. Shah* is an assistant professor in the department of pharmaceutics at CK Pithawala Institute of Pharmaceutical Science and Research,
Via Magdalla Port, Nr. Malvan Mandir, Dumas Road, Surat, Gujrat, India 395 007, tel. +91 261 6587286, fax: +91 261 272399.
Girish K. Jani is a principal at SSR College of Pharmacy (UT of Dadra and Haveli, India).
*To whom all correspondence should be addressed.
Submitted: Sept. 10, 2008. Accepted: Oct. 1, 2008.
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