CHARACTERISATION AND APPLICATION OF NATIVE AND CROSS-LINKED CASHEW (Anacardium occidentaleL.) GUM IN TABLETTING
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ABSTRACT
The exudatefrom cashew tree, referred to as cashew gum (CG) had been investigated for use as binder in conventional tablet formulations. In this study,-clinroksesd derivatives of
the gum were synthesized and invgeastei d for their physicochemical anpdhysicotechnicla
properties and applicability in modifying drug release in tablet formulations. The crude dried latexes of CG were purified by extraction using acetoTnwe.o cross-linked derivatives of
the gum were synthesized by heati(nag), a 1:1 weight ratio of CG ancditric acid (CTR) at 140 oC for 30 min and (b), a 1:1:1 weight ratio of CG, CTR and glycerol (GLY) ato1C70
for 30 min. In each case, monobasic sodium phosphate was used as catalyst at 2 %w/w concentration. The cro-slisnking was demonstrated qualitativyebl y Differential Scanning Calorimetry (DSC), Fourier Transform Infrared F(TIR) and 13C Nuclear Magnetic Resonance 13(C NMR) and quantitatively by polymer yield. Determinations of moisture content, moisture loss on dryi,nsgwelling ratio, water holding anwdater sorption capacities
were used to characterize the derived polymers-.aScute toxicity studies were carrieodut
to ascertain the safety or otherwise of the c-rlionsksed derivative, CrosCCG. Wistar rats were fed with the polymer ovear 28-day periodand blood samples from the animals were
assessed for changes in hematological and biochemical parameters. The purified CG and its derivatives were used to formulate tablets of Venlafaxine hydrochloride (Ven. HCl), a water soluble antidepressant, using twhet granulation method. Increasing concentrations of CG
and its admixtures with MCC PH 102 were used as binder/matrix former in formulating the tablets. The synthesized derivative, CrosCCG, was assessed for drug release modification when used either alonoer in admixtures with HPMC ER (K100). The drug release
enhancingpropertyof the derivative was also investigated and compared with some known superdisintegrants, Croscamellose and Crospovidone at 3 %w/w disintegrant concentration.
Results obtained revealed that cr-olinsksing of CG with CTR yielded an esterified derivative that was insoluble in all common solvents. The esterification reaction occurred be–tween
OH of the sugar from the gum an–Cd OOH of CTR. Whilebeing insoluble, on ocntact with
water, however, the polymer sorped weart and swelled. Cro-slsinking of CG with a
combination of CTR and GLY yielded a polymer with improved yield and swelling potentials. Toxicity studies showed the polymer to have no apparent harmful efftehcet on
animals and did not cause changes in the blood parameters tested. When used in tableting, CG was found to form good tablets of Ven. HCl with a crushing strength of 5.9 KN and friability of 0.03 %. Increasing concentration of CG or its admixture witChCMPH 102
offered no added advantage. CrosCCG could not modify the release of drug from the formulated tablets when used alone. Admixtures of CrosCCG at concentroaft1io5nsand 25
%w/w respectivelywith HPMC K100 at 7.5 %w/wshowed a furthedr elay in release of the
drug. Concentrations lower than 10 %w/w of CrosCCG, however, showed a release enhancingability. At 3 %w/w concentration, CrosCCG surpassed both Croscamellose and Crospovidone inenhancingdrug release as observed from a 30 imn ivnitro dissolution data.
It can thus be concluded that, this work has led to the discovf earysafe novel cro-slsinking process that uses safe and environmentally friendly -clirnoksinsg agents in derivatisation processes. Cro-slisnking CG using this method has led toe tphroduction of a powerful drug release enhancinaggent.