Evaluation Of Haricot Bean Retrograded Resistant Starch As A Film Forming Excipient In Oral Colontargeted Delivery Of Mesalamine

The colon has been evaluated intensively for about three decades as a site of drug delivery, notrnonly for local colonic pathologies but also for systemic delivery of small therapeuticrnmolecules, protein and peptide drugs. As a site for drug delivery, colon offers a near neutralrnpH, reduced digestive enzymatic activity, a long transit time and an increased responsivenessrnto absorption enhancers. Targeting drugs to the colon has two major implications in colonicrndisorders, explicitly reduced systemic toxicity and increased local therapeutic efficacy. rnThe main objective of this study is to prepare haricot bean retrograded resistant starch andrnevaluate its potential as film forming excipient in tablet formulation for oral colon-targetedrndelivery of mesalamine. rnTo prepare retrograded resistant starch, haricot bean starch was dispersed in distilled water inrnthe ratio of 1:4 and autoclaved (121 °C) for about 1 h until complete disruption of starchrngranules and then the gelatinized starch de-branched using pullulanase enzyme. The productrnobtained was autoclaved (121 °C) for about 1 h, cooled to room temperature and then stored inrna refrigerator for 24 h at 3 °C. This step was repeated 10 times. The slurry obtained in the rnprevious stage was treated with heat stable alpha amylase, amyloglucosidase and then withrnpepsin to obtain enzyme resistant starch type 3 (RS3). The product obtained was washed four rntimes with plenty of hot water (90 °C) and the residue was left to dry in an oven overnight.rnGravimetric method was used to determine the RS3yield.In-vitro methods, dissolution andrnfermentation studies were used to determine the release profiles of mesalamine in the GI tract. rn rnThe yields of haricot bean RS3 were in the range of 74.7- 78.0% per dry mass of haricot beanrnstarch. The inherent nature of haricot bean and extrinsic factors (processing conditions) mayrnhave contributed for such high yield. Haricot bean native starch had showed CA-type starchrnpolymorphism. The in-vitro mesalamine cumulative percentage releases of all coatingrnformulations, which differ either in RS3: EC (Ethyl cellulose) ratio or in their film thickness, in rnsimulated gastrointestinal fluids were less than 4% during the 7 h study period. The cumulative rnpercentage releases of mesalamine of the different coating formulations in the fermentationrnstudy were in the range of 57-82% in 12 h of the study period. rnThe results indicate that haricot bean resistant starch has a good potential to be used as a filmrnforming excipient in oral colon-targeted delivery of drugs.

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