Physicochemical Characterization of Plectranthus Edulis (Ethiopian Potato) Starch and its Evaluation as a Disintegrant In Paracetamol Tablet Formulations
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Date
2015-01
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Addis Ababa University
Abstract
Plectranthus edulis, Vatke (P. edulis) [fam., Lamiaceae], is an ancient Ethiopian tuber crop and
one of the traditional root crops indigenous to Ethiopia. It is a large (~1m high) and an erect
herbaceous plant with hirsute, decumbent and glandular stems, and leaves of lanceolate to
elliptic and root of swollen nodes which produces edible underground potato-like tubers.
Starch from the tubers of P. edulis was isolated using 0.075% (w/v) sodium metabisulphite and it
gave a yield of about 80.4% on dry weight basis. The starch was examined for the chemical
composition, amylose content, physicochemical properties and evaluated for its applicability as a
pharmaceutical disintegrant in tablet formulations.
The proximate composition of the starch on dry weight basis was found to be 0.14% ash, 0.21%
lipid, 0.43% protein, and 99.22% starch. The amylose content was 30.6%. Its true density,
moisture content and pH values were 1.47 g/ml, 11.2% and 6.6, respectively. Scanning electron
microscopy (SEM) of the starch granules showed characteristic morphology that was oblong
(elliptical) with some oval in shapes. The starch showed a monomodal normal granule size
distribution with a mean particle size of 36.2 μm and specific surface area of 0.302 m2/g. The
DSC thermograms of P. edulis starch exhibited higher T0 (69.2 oC), Tp (74.3 oC) and Te (83.3 oC)
values than potato starch. X-Ray Diffraction pattern of the starch was typical B-type with a
distinctive maximum peak at 17.5o 2θ. The FTIR spectral features of the starches show
characteristic peaks at 3325, 2930, 1462, 1377, 1155, 860 cm-1 attributed to various stretching
and bending vibrations of O–H, C–H, C–O, or C–O–C bonds for starches. It has typical swelling
power, solubility and moisture sorption pattern at different conditions of temp and relative
humidities. It possesses higher values relative to potato starch, but its solubility values are lower
than potato starch at all temp studied.
The comparative disintegrant abilities of these starches in paracetamol tablet formulations
prepared by wet granulation method were studied. The granules prepared with the starches (P.
edulis starch and potato starch) at different disintegrant concentrations were characterized for
particle size distribution and flow properties. The excellent flow property of the granules was
manifested by the weight uniformity of tablets. The crushing strength, friability, disintegration
time, and dissolution rate of the tablets were studied using standard methods. The results
II
indicated that the properties of paracetamol tablets formulated with both starches as disintegrants
were affected by their concentration and the compression force (CF). Increasing the
concentration of the starches reduced the crushing strength and disintegration time of the tablets
and increased the percent friability of the tablets. Conversely, increasing the CF increased
crushing strength and disintegration time of the tablets and reduced the percent friability of
tablets. The results have shown that P. edulis starch has favorably competed with potato starch as
a disintegrant in the paracetamol tablet formulations.
The optimization study of P. edulis starch as a disintegrant in paracetamol tablets was carried out
by selecting the CF (X1) and P. edulis starch concentration (X2) as factors, and crushing strength,
percent friability and disintegration time as response variables; and employing central composite
statistical design (CCD). Design-Expert 8.0.7.1 software was utilized in the experimental design,
statistical analysis and optimization process. Using the software several statistical parameters
were compared, quadratic model for all the three responses were selected, and the adequacy of
the models were checked by analysis of variance (ANOVA). The ANOVA results revealed that
quadratic model is significant for the terms (factors) and responses studied. A quadratic
mathematical model was developed; and the optimum formulation of paracetamol tablet
containing P. edulis starch as a disintegrant was obtained by simultaneous optimization of the
responses. From the optimum region, a CF (X1) of 14.40 KN and a disintegrant concentration
(X2) of 5.96% was selected to check the validity and predictability of the design. The predicted
values of crushing strength, friability and disintegration time of the formulation at the
aforementioned levels of factors closely matched with the results of actual experimentation.
Thus, the optimization technique provided the optimum formulation of paracetamol tablet
containing P. edulis starch as a disintegrant.
The results of the physicochemical characterization of P. edulis starch, as well as the
comparative and optimization study of the starch as a disintegrant in the tablet formulations
indicate that P. edulis can be used as an alternative source of starch for applications in the
pharmaceutical industry.
Keywords: Plectranthus edulis, Starch, Differential scanning calorimetry, Scanning electron
microscopy, X-ray diffraction, Tablet disintegrant, Optimization, Central Composite Design
Description
Keywords
Plectranthus edulis;Starch; Differential scanning calorimetry; Scanning electron microscopy; X-ray diffraction Tablet disintegrant;Optimization; Central Composite Design