Research Article MECHANICAL AND TABLET COATING PROPERTIES OF CASHEW TREE (ANACARDIUM OCCIDENTALE L) GUM-BASED FILMS KWABENA OFORI-KWAKYE*, HILDA AMEKYEH, MARIAM EL-DUAH AND SAMUEL LUGRIE KIPO Department of Pharmaceutics, Faculty of Pharmacy and Pharmaceutical Sciences, College of Health Sciences, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana; Email: koforikwakye@yahoo.com Received: 6 August 2012, Revised and Accepted: 7 September 2012 ABSTRACT The mechanical and coating properties of cashew gum-based films, using paracetamol as a model drug, was investigated. Cashew gum was acidic and the acidity did not markedly change with concentration and storage time. However, gum viscosity increased significantly with concentration and storage time. Swelling index of the gum was ~ 3.3 and was largely unaffected by pH of media used. Free films of cashew gum, cashew gum/hydroxypropyl methylcellulose (HPMC), and cashew gum/ carboxymethyl cellulose (CMC) were prepared by solvent casting using glycerol as a plasticizer and the folding endurance, tensile strength, percentage elongation and Young’s modulus of the films determined. Cashew gum films were smooth, uniform and transparent while cashew gum/HPMC and cashew gum/CMC films lacked uniformity and surface smoothness, respectively. Addition of a plasticizer to the gum imparted flexibility to the films. Increase in cashew gum and plasticizer concentration increased the folding endurance and percentage elongation of the films. Tensile strength increased with increase in gum concentration but decreased with increase in plasticizer concentration. Young’s modulus decreased when cashew gum and plasticizer concentrations were increased. Film coating of 7.5 % w/v cashew gum formulation to paracetamol tablet cores enhanced the mechanical strength of the tablets. However, film coating of the tablet cores did not markedly affect disintegration and drug release properties of the tablets compared to the uncoated tablets. Also, no significant difference in drug release was observed in 0.1 M HCl (pH 1.5) and phosphate buffer pH 6.8 used. Cashew gum when applied at 7.5 % w/v could be useful as non-functional film coatings for conventional solid dosage forms. Keywords: Anacardium occidentale, Cashew gum, film coating, mechanical properties of films, non-functional coating INTRODUCTION Cashew tree gum is obtained as exudates from the stem bark of Anacardium occidentale L. (family: Anacardiaceae), a tree that grows in many tropical and subtropical countries 1, 2 . The gum has been studied extensively for potential pharmaceutical and biomedical applications 2 – 9 because it is naturally-occurring, generally non- toxic, widely available, hydrophilic, inexpensive, biocompatible and biodegradable. Quite recently, Lippia sidoides essential oil was successfully encapsulated in nanoparticles of cashew gum/chitosan polymeric matrix with the presence of the oil in the nanoparticles having been confirmed by FTIR and bioassays. The nanoparticles were demonstrably effective in killing the larvae of dengue vector in a sustained release manner 10 . Cashew gum prepared as layer by layer films were studied by atomic force microscopy and voltammetry and were found to detect dopamine in low concentrations. These layer by layer cashew gum films therefore have potential application in nanobiomedical devices as electrochemical sensors 11 . Cashew gum/carboxymethyl cellulose/glycerol composed films produced by casting have also been shown to have potential as materials for technological applications 12 . Natural gums and other polysaccharides such as cashew gum, amylose, chitosan, pectin, khaya gum and albizia gum are hydrophilic film formers and have been fabricated as film coatings for the pharmaceutical 13 – 16 , food and packaging industries 1, 17, 18, 19 . Film coating of tablets can mask the bitter or unpleasant taste and odour, ease swallowing, as well as protect the tablet cores against moisture and light. Film coated tablets exhibits high mechanical strength which protects the integrity of the tablet cores during packaging and handling. Film-coated tablets may exhibit immediate- release (non-functional), modified-release (functional, e.g. enteric coating and extended release coating) and targeted drug delivery properties. The use of natural gums and other polysaccharide-based film coatings are also known to increase the shelf life of food products by eliminating or minimizing dehydration, rancidity and darkening of the food surface 1 . Polysaccharide-based films may act as barriers against water vapour and gases and enhance mechanical handling properties of foods 19 . The film-forming property of cashew gum is attributable to the good rheological properties and the chemical composition of the biopolymer . The gum is a complex polysaccharide with highly branched galactan framework of (1→3)-linked β–D- galactopyranosyl units interspersed with β-(1→ 6) linkages and is chemically composed of 61 % galactose, 14 % arabinose, 7 % rhamnose, 8 % glucose, 5 % glucuronic acid and < 2 % other sugar residues 7, 20 . The crude gum contains Ca 2+ , Mg 2+ , Fe 2+ and Zn 2+ and trace amounts of K + and Na + as neutralized cations, the level of which reduces after purification 8 . The presence of glucuronic acid (pKa ~ 3.5) enables cashew gum to behave as a polyanion at pH > 4 21 , which enhances its ability of interacting with cations. The objective of this study was to evaluate the mechanical properties of cashew gum-based free films prepared by solvent casting, as well as the coating properties of the films on paracetamol tablet cores. MATERIALS AND METHODS Materials Crude cashew tree gum (moisture content, 13.00 ± 2.83 %; insoluble matter, 0.40 ± 0.07 %,) was obtained from a cashew tree plantation at Nkoranza in the Ashanti Region of Ghana, as natural exudates from the stem bark of Anacardium occidentale Linn, family Anacardiaceae. The plant was authenticated and the gum collected and supplied by a retired officer of FORIG, Ghana. The crude gum was purified (percentage yield ~ 77 %) using a previously described procedure 8 . The purified cashew gum (moisture content, 11.20 ± 0.14 %; insoluble matter, 0.20 ± 0.03 %) was used for the study. Paracetamol powder BP, lactose and magnesium stearate were supplied by Kinapharma Ltd., Accra, Ghana. Maize starch, polyvinyl pyrrolidone (PVP), carboxymethyl cellulose were obtained from Tradewinds Chemists, Kumasi, Ghana, while talc and hydroxypropyl methylcellulose (HPMC E15, viscosity of 2% solution @ 15 cPs) were supplied by Amponsah-Effah Pharmaceuticals Ltd., Kumasi, Ghana. All other chemicals used in this study were of analytical reagent grade. Swelling capacity of purified cashew gum The swelling capacity of purified cashew tree gum in three dispersion media, namely: distilled water, 0.1 M HCl (pH 1.5) and phosphate buffer pH 6.8 was determined using a previously reported method 22 . Asian Journal of Pharmaceutical and Clinical Research Vol 5, Suppl 4, 2012 ISSN - 0974-2441 Academic Sciences