CHARACTERISATION AND APPLICATION OF NATIVE AND CROSS-LINKED CASHEW (Anacardium occidentaleL.) GUM IN TABLETTING

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.