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Curcumin, a polyphenolic compound derived from Curcuma longa, possesses diverse pharmacologic effects such as anti-inflammatory, antioxidant, antiproliferative and antiangiogenic activities. However, curcumin has poor bioavailability and low dissolution rate due to poor absorption, rapid metabolism, and rapid systemic elimination. The aim of the study was to improve the solubility and dissolution rate of curcumin by solid dispersions. Polyethylene glycol (PEG 6000) and swellable polymers such as hydroxylpropyl methylcelluloses (HPMCs) and polyethylene oxide (PEO), were applied to improve dissolution and oral absorption of curcumin. The solid dispersions (SDs) in different ratios were prepared by hot melting method. The dissolution rate of SDs was tested in simulated gastric fluid (buffer pH 1.2) and simulated intestinal fluid (buffer pH 6.8). Samples were collected at 10, 20, 30, 60, 90, 120 minutes and replaced with an equivalent amount of fresh medium to maintain a constant dissolution volume. High-performance liquid chromatography (HPLC) method was used to determine concentration of curcumin after dissolution test. The dissolution rate of curcumin was enhanced by the incorporation into hydrophilic carrier (e.g. PEG 6000, HPMC 4000, HPMC 6, and PEO). The best percentage of drug release was observed with curcumin: PEG 6000: HPMC 4000 in ratio 1:8:4. Through the selection of polymers with optimal ratio, the SDs could increase the dissolution rate of curcumin.

The aim of this study was to modify the rice starch to prolong the release of drug in gastric fluid. Various types of Vietnamese rice were introduced in the study as the matrix of sustained release dosage form. Rice was thermally modified in water for a determined time at different temperatures. The rice starch was first ground and sieved. Then the powder was physically modified by heat and finally dried in an oven. The modified rice starch appeared as an odorless fine white powder. The tablet containing modified rice starch and Paracetamol were prepared by the wet granulation method. The dissolution rate of tablets was evaluated in simulated gastric fluid without pepsin (buffer pH 1.2). HPLC method was used to determine the amount of drug release. The matrix tablet containing thermally modified starch showed sustained release as compared to the control. The thermally modified starch could be a novel pharmaceutical excipient for sustained release dosage form design.

The study aimed to investigate a new method of thermal modification which was microwave method for controlling drug release of rice starch. The Vibigaba sprouted rice starch (Vietnam) was selected as the model rice. The rice was thermally modified in water for a determined time at different power. The rice starch was first ground and sieved. Then, the powder was physically modified by heat via the microwave and finally dried in an oven. Tablets containing the modified sprouted rice starch of Paracetamol were prepared by the wet granulation method. The dissolution rate of tablets was evaluated in simulated gastric fluid without pepsin (buffer pH 1.2). The matrix tablet containing thermally modified sprouted rice starch showed a sustained release, indicating that the sprouted rice under microwave method could be a promising material for a sustained release dosage form.

Around current 40% of potential active agents are poorly water-soluble drugs. Solid dispersion (SD) technique is one of the most common techniques used to increase the dissolution rate of a poorly water-soluble drug. The aim of this research was to investigate a capability of SD in improving dissolution rate of curcumin, a poorly water-soluble drug in acidic and neutral media. SDs were prepared by melting and solvent methods. Hydroxypropyl methylcellulose 6, polyethylene glycol 6000, poloxamer 407 were used as carriers in the SDs. The dissolution rate of SDs was tested in simulated gastric fluid (buffer pH 1.2) and simulated intestinal fluid (buffer pH 6.8). The structural behaviors of drug were characterized by power X-ray diffraction (PXRD) and Fourier transform spectroscopy (FTIR). The presence of poloxamer 407 in SDs of curcumin improved dissolution rate of the drug. The crystalline structure of the drug was changed to amorphous form. The study indicated that the melting method with poloxamer 407 was the promising approach to enhance dissolution rate of curcumin and hence, suggesting further solutions to achieve the best product containing curcumin which could improve bioavailability of the drug.