Comparative FTIR, Compaction and In vitro Dissolution Studies of Plectranthus esculentus Modified Starches in Metronidazole Tablet Formulations by Direct Compression

Wet and dry granulation methods for tablet manufacturing tend to be problematic for thermolabile and moisture sensitive drugs, and few excipients are available for use in direct compression (DC) due to stringent requirements. This study aimed to evaluate the drug/excipients compatibility, compaction and in vitro dissolution properties of Plectranthus esculentus modified starches in tablets using metronidazole as a model drug by DC. Native starch extracted from P. esculentus was modified by three methods and we produced three modified starches namely; acid hydrolyzed P. esculentus starch (APS), pregelatinized P. esculentus starch (PPS), and ethanol dehydrated pregelatinized P. esculentus starch (PPE). For drug/excipient compatibility studies, Fourier Transform Infrared Spectroscopy (FTIR) was used. Powder compaction was evaluated using Heckel model, while in vitro dissolution studies were conducted using USP basket method. The starches were evaluated in comparison with microcrystalline cellulose (MCC PH 101). The FTIR peaks revealed no interaction of these excipients with the drug. Compaction studies indicate that the modifications yielded starches of comparable compact behaviors with MCC PH 101 especially APS and PPE, they both plastically deformed with PPE producing the hardest tablets. APS and PPS disintegrate faster 2.83 and 1.42 min respectively which were significantly different from the disintegration time of MCC PH 101 and PPE which are higher 35.34 and 45.53 min respectively. For the in vitro dissolution, APS and PPS, their T50 and T90 were achieved in less than 10 min, T50 and T90 for PPE were achieved at 38 and 58 min respectively, while for MCC PH 101 both T50 and T90 were not observed after 60 min. APS produced metronidazole tablets of better quality in terms crushing strength, friability and drug-release profile. Acid hydrolysis of P. esculentus starch produced good directly compressible excipient that can be use in DC for immediate release tablet formulations.