Evaluation of Selected Zimbabwean Plant Extracts as Inhibitors of Hematopoietic Prostaglandin D₂ Synthase

Abstract

Increased expression of hematopoietic prostaglandin D₂ synthase (H-PGDS) is responsible for allergic reactions promoting the inflammatory processes. A total of fifteen plant extracts were screened for their inhibitory activity against H-PGDS using 1-chloro-2, 4-dinitrobenzene (CDNB) as a substrate at 0.3 mg.mL⁻¹. Seven of these plant extracts that were effective inhibitors of H-PGDS were then used to determine the half maximum inhibitory concentrations (IC₅₀s). Parinari curatellifolia leaf ethanol extract was the most potent plant extract with an IC₅₀ of 3.8μg.mL⁻¹ that was comparable to 2.1 μg.mL⁻¹ of the standard Cibacron blue. P. curatellifolia extract directly inhibited H-PGDS activity, which was a kind of reversible inhibition of mixed type with respect to both GSH and CDNB as substrates. The results obtained in this study validate the ethnomedicinal use of P. curatellifolia in the reduction of symptoms of inflammation.

KEYWORDS:

• 1-chloro-2
• 4-dinitrobenzene
• anti-inflammatory
• glutathione S-transferases
• Parinari curatellifolia

Additional information

Funding

This work has been supported by funds from the International Foundation of Science (IFS), Stockholm, Sweden; Grant Number F/3413-03 and the International Science Program (ISP) through the International Programme in the Chemical Sciences (IPICS: ZIM01). We thank Professor Bengt Mannervik (Uppsala) for the donation of the H-PGDS heterelogously expressed in E. coli. Support from the University of Zimbabwe Research Board is greatly acknowledged.