Acetylcholinesterase inhibition properties of Hypericum foliosum Aiton

Hypericum (Guttiferae) is a large genus (ca 450 species) of herbs or shrubs that has been used in folk medicine since the antiquity [1]. Their health benefits, demonstrated through the number of pharmacological and clinical trials [2], have been attracting attention to the scientific community for the study of the Hypericum genus. In spite of the intense research on both chemical constituency and biological activity, studies on acetylcholinesterase (AChE) inhibition are limited to a few species [3]. Therefore, in this study, methanolic extracts from eight anatomical parts of the endemic Azorean Hypericum foliosum Aiton (aerial parts; flowers; old leafs; young leafs; stems; stem bark; root and seed capsules) were evaluated for their potential anti-AChE activity by using a modified Ellman et al. [4] technique. The results reveal that six of the eight anatomical parts displayed significant AChE inhibition with an IC50 value below 1000µg/mL. From all samples assayed, the stems were the most effective with an IC50 value of 130µg/mL, followed by the root (170g/mL) and the stem bark (200µg/mL) samples. The leaf samples did not present any difference (840µg/mL). Aerial parts displayed an IC50 of 460µg/mL. The flower and seed capsule samples were less effective with an IC50 value above 2500µg/mL. These results reveal a promising plant, particularly the stems, root and stem bark, containing powerful anti-AChE inhibitors that could provide novel poly-pharmacological leads for a more detailed future investigation.

References: 1. Robson, N. K. B. (2003). Hypericum botany. In E. Ernst, Hypericum: the Genus Hypericum. Taylor and Francis. New York.

2. Barnes, J. et al. (2001)J. Pharm. Pharmacol. 53: 583–600.

3. Hernandez, M. et al. (2010) Food Chem. 120: 1076–1082.

4. Ellman, G. et al (1961) Biochem. Pharmacol. 7: 88–95.