Characterization and evaluation of acid-modified starch of Dioscorea oppositifolia (Chinese yam) as a binder in chloroquine phosphate tablets

ABSTRACT

The use of starches as natural polymers for

pharmaceutical applications remains attractive because

they are cheap, readily available, biodegradable and

capable of modification (Lawal et al., 2007; Yiu et al.,

2008; Okunlola et al., 2010). Native starch is a white

powder with a bland taste and flavor, and is insoluble in

cold water. Due to the sub-optimal properties of native

starches, modifications are efficient methods of improving

their suitability as excipients for specific pharmaceutical

uses. Physical modification entails subjecting the

starch to heat-moisture treatment and annealing, while

chemical modification includes oxidation, acid thinning,

hydroxypropylation and acetylation. Starches have been

chemically modified by acid hydrolysis for over 150

years (Yiu et al., 2008). This process involves suspending

starch in an aqueous solution of hydrochloric acid or

sulphuric acid at certain temperatures. In the presence of

strong acid and heat, the glycosidic bonds between the

monosaccharides in the starch polymer are cleaved (Yiu et

al., 2008). Acid modification has been shown to change the

physicochemical properties of starch without destroying

its granular structure, yielding starch with increased

solubility and gel strength but decreased viscosity; the

extent of hydrolysis depends on starch consistency, the

acidity of the medium, the hydrolysis temperature and the

duraton of hydrolysis (Odeku et al., 2009).

Read Download