Inhibition of the Activities of Pro-inflammatory Enzymes and Total Phenolic Contents of Leaf Extracts of Strychnos spinosa

Aims: Strychnos spinosa Lam. is a deciduous tree used in folkloric medicine to treat inflammatory-related conditions. The aim of this study was to establish the effect of leaf extracts of S. spinosa on the activity of pro-inflammatory cyclooxygenase (COX) enzymes and to determine the total phenolic contents of S. spinosa leaves.

Study Design: An in vitro study.

Place and Duration of Study: Department of Paraclinical Sciences, Faculty of Veterinary Sciences, University of Pretoria, Pretoria between June 2013 and November 2013.

Methodology: Extracts were obtained by maceration with acetone, methanol and dichloromethane/methanol (1/1). Fractions were prepared by liquid–liquid fractionation of the acetone extract. COX activity was evaluated using a COX inhibitor screening assay kit, Cayman, MI, USA. The total phenolic content of the extracts were determined using the Folin–Ciocalteau method.

Results: The extracts significantly (P = .05) inhibited COX enzyme activity. The n-butanol, water and hexane fractions selectively inhibited COX-1, with IC50 values of 14.66 ± 0.01, 15.25 ± 0.20 and 14.93 ± 0.01 pg/mL, respectively. The dichloromethane/methanol extract (Dcm/MetE) and methanol extract (MetE) selectively inhibited COX-2, with IC50 values of 15.51 ± 0.05 and 14.47 ± 0.12 pg/mL, respectively. The alkaloid fraction inhibited both COX-1 and COX-2, with IC50 values of 15.42 ± 0.01 and 14.81±0.11 pg/mL, respectively. The water fraction had the highest phenolic content (78 ± 3.71 mg/g galic acetone extract , and the acetone extract had the lowest (8.0 ± 0.01 mg GAE/g).

Conclusion: The selective inhibition of COX-1 and COX-2 by the extracts point to the potential of S. spinosa as a potent anti-inflammatory agent. The results support the use of leaf extracts of S. spinosa in traditional medicine for the treatment of inflammation-related conditions.