Antioxidant and acetylcholinesterase inhibitory activity of selected southern African medicinal plants

Alzheimer's disease (AD) is the most common type of dementia in the aging population. Enhancement of acetylcholine levels in the brain is one means of treating the disease. However, the drugs presently used in the management of the disease have various drawbacks. New treatments are required and in this study, extracts of Salvia tiliifolia Vahl. (whole plant), Chamaecrista mimosoides L. Greene (roots), Buddleja salviljblia (L.) Lam. (whole plant) and Schotia brachypetala Sond. (root and bark) were evaluated to determine their polyphenolic content, antioxidant and acetylcholinesterase inhibitory (AChEI) activity. The DPPH and ABTS assays were used to determine antioxidant activity and Ellman colorimetric method to quantify AChEI activity. Although all four plants showed activity in both assays, the organic extracts of C. mimosoides root was found to contain the highest AChEI activity (IC(50)=0.03 +/- 0.08 mg/ml) and B. salviifolia whole plant had the highest antioxidant activity (ABTS; IC(50)=0.14 +/- 0.08 mg/ml and DPPH; IC(50)=0.23 +/- 0.01 mg/ml). The results suggest that the tested plant species may provide a substantial source of secondary metabolites, which act as natural antioxidants and acetylcholincsterase inhibitors, and may be beneficial in the treatment of AD. (C) 2011 SAAB. Published by Elsevier B.V. All rights reserved.