Impact of degree of substitution of acetylated Ofada rice starch polymer on the release properties of nimesulide microspheres

  • Adenike Okunlola University of Ibadan, Ibadan, Nigeria
  • Temitope Owojori University of Ibadan, Ibadan, Nigeria


Nimesulide microspheres were prepared by the quasi-emulsion solvent diffusion method, using acetylated starches of the indigenous Ofada rice (Oryza glaberrima Steud) with degrees of substitution (DS) 1.42 and 2.62. Full 23 factorial experimental design was performed using DS (X1), drug: polymer ratio (X2) and polymer concentration (X3) as independent factors; size, entrapment, swelling and time taken for 80% drug release (t80) were the dependent variables.Contour plots were generated and data from in vitro release studies were fitted to various kinetic models. Nimesulide microspheres were near -spherical, with size 50.91±16.22 to 74.24±24.73 µm for microspheres containing starch DS 1.42 and 21.05±4.25 to 46.10±3.85 µm for starch DS 2.62. Drug entrapment was 56.75±0.45 to 98.28±2.30 %. DS had the most influence on size, swelling and dissolution time (p = 0.01) and this was confirmed from the contour plots. The interaction between factors DS and drug: polymer ratio (X1X2) had the highest influence on microsphere properties (p = 0.04). Drug release fitted into first order, Higuchi and Korsmeyer models.  Acetylated starch of Ofada rice DS 2.62 was found more suitable for the formulation of microspheres with reduced size, and swelling, higher entrapment and prolonged drug release. 

Author Biographies

Adenike Okunlola, University of Ibadan, Ibadan, Nigeria
Dr. Adenike Okunlola PhD is a Senior lecturer in the Department of Pharmaceutics & Industrial Pharmacy, University of Ibadan. She is a recipient, Fulbright African Research Scholar and recipient - Indian National Science Academy-Tata (INSA-JRD TATA). Fellowship for post-doctoral research. Dr. Adenike Okunlola’s research focus is on the development of novel polymers of natural origin as an innovative approach to drug delivery. The objective is to identify and validate natural polymers such as starches, gums and pectins with significant potential as alternative excipients to currently used synthetic polymers in drug delivery that, with proper research efforts, can be comparatively cost effective import substitutes
Temitope Owojori, University of Ibadan, Ibadan, Nigeria

Temitope Awojori holds a Bachelor of Pharmacy degree from Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria. He obtained his MSc degree in Pharmaceutics (2015) and is actively involved in Pharmaceutical Manufacturing.


How to Cite
OKUNLOLA, Adenike; OWOJORI, Temitope. Impact of degree of substitution of acetylated Ofada rice starch polymer on the release properties of nimesulide microspheres. Journal of Excipients and Food Chemicals, [S.l.], v. 7, n. 1, p. 4-16, mar. 2016. ISSN 21502668. Available at: <>. Date accessed: 06 dec. 2023.
Original Research Articles


Acetylation; Degree of substitution; factorial design; Nimesulide; Ofada rice starch