Hydroxypropyl Methylcellulose Reduces Particle Adhesion and Improves Recovery of Herbal Extracts During Spray Drying of Chinese Herbal Medicines

Abstract

The effectiveness of hydroxypropyl methylcellulose (HPMC) as an anti-adherent during spray drying of traditional Chinese herbal extracts was explored. A small amount of HPMC (minimum concentration 8%) was sufficient to overcome problematic particle adhesion, whereas a large amount of maltodextrin (50%) was required for the same effect. HPMC exerted a strong anti-adhesive effect that was independent of the type of HPMC, raw materials used, and the process used to synthesize HPMC. The anti-adhesion mechanism was studied through an analysis of the surface tension of the prepared solutions before spray drying, the glass transition temperature (T _g ), and X-ray photoelectron spectroscopy (XPS) of spray-dried powders. The T _g of powders containing more than 8% HPMC was approximately 40°C and did not increase linearly with the HPMC concentration. The surface tension of Crataegi fructus extract was 54.1 ± 0.2 mN/m and further decreased to 46.6 ± 0.2 mN/m upon addition of HPMC to 24%. When the concentration of HPMC increased to 8%, potassium could not be detected on the surface of dried powders by XPS. These results suggest that modification of the surface properties of sprayed droplets/particles by HPMC increased the HPMC surface coverage of the particles and reduced adhesion during spray drying.

Keywords:

• Adhesion
• Crataegi fructus
• Hydroxypropyl methylcellulose
• Mechanism
• Spray drying

ACKNOWLEDGMENTS

The authors acknowledge Dr. Hansen Luan of the National Pharmaceutical Engineering Research Center and Dr. Dong Jiang of the East China University of Science and Technology for their help in experiments.

Notes

^a The characteristics are nil for CFE because of zero yield.

^b Mean values ± standard deviation of triplicate experiments.

^c There is a large error for the angle of repose for CFE + 2% E5 due to powder particle aggregation.

^a C (%), O (%), K (%) indicate the molar percentages of the C, O, and K elements on the powder surfaces.

^b The real concentrations of potassium in powders were determined by a polarized Zeeman atomic absorption spectrometer.

^c Mean values ± standard deviation of triplicate experiments.

^a Mean values ± standard deviation of triplicate repeats.

^b HZ E5 was HPMC E5 (equivalent to HPMC E5 from Dow) supplied by Huzhou Hopetop Pharmaceutical Co. Ltd.

^c XY 603 was HPMC ShinEust 603 (equivalent to HPMC E3 from DOW) obtained from Dalian Yejian Trading Co. Ltd.

^d XY SM-4 was HPMC ShinEust SM-4 (equivalent to HPMC A4 from DOW) obtained from Dalian Yejian Trading Co. Ltd.

^e E5 was HPMC E5 supplied by Dow Co. Ltd.

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