Entrapment of andrographolide in cross-linked alginate pellets: II. Physicochemical characterization to study the pelletization of andrographolide.

This paper deals with the characterization of pellets containing andrographolide in two parts. The first part deals with characterization of the pellets to ascertain the identity and integrity of andrographolide. Part two involves characterization of the pellets containing Andrographis paniculata extract (33.3%) prepared in the paper I for their micromeritic properties like Particle size, Particle size distribution, Sphericity measurements like Shape ratio and Aspect ratio, Tapped density, Compressibility index, Hausner's ratio and Angle of repose. In addition, our aim was also to derive information about the mechanism of gelation with entrapment of andrographolide to supplement results obtained about the release mechanisms deduced in paper I. Since this work requires use of techniques like FTIR, FTRaman, MTDSC and XRPD, it was necessary to prepare alginate micropellets using pure andrographolide (99.89%) rather than the multicomponent extract using the same procedure discussed in paper I. The integrity of the drug was maintained in the cross-linked micropellets as was seen in the MTDSC and FTIR spectra supported by the FTRaman spectra. The depolymerisation transitions, the reversing and non-reversing heat flow signals were determined using the MTDSC and interpreted to study the mechanism of pelletization. The MTDSC profiles also confirmed the integrity of the drug by exhibiting a sharp endotherm at 232(o)c that is the melting point of andrographolide. The XRPD spectrum of the micropellets ascertained that the crystallinity of andrographolide was maintained. The relationship of the nature of the drug present in the micropellets related to release mechanisms is discussed. In conclusion, it can be said that andrographolide can be successfully incorporated into cross-linked micropellets of alginate without affecting its integrity or nature to deliver it as a bitterless monoherbal preparation.