Bioprospecting of Philippine Plants from Northern Samar with Butyrylcholinesterase-selective Inhibitory Activity

Abstract

The World Health Organization identified neurodegenerative disorders, such as Alzheimer’s disease (AD), as among the public health challenges that need attention. At present, commercially available AD drugs on the market target cholinesterases. Symptomatic treatment extensively focuses on the inhibition of acetylcholinesterase (AChE) because it plays a major role in the breakdown of the main neurotransmitter acetylcholine. However, recent studies suggest that inhibiting butyrylcholinesterase (BuChE) may be worth exploring because of its emerging relevance to AD. To search for potential selective BuChE inhibitors, 118 plants from Northern Samar, Philippines were investigated. The ethanol extracts of the plants were tested for in vitro AChE and BuChE inhibitory activity using Ellman's colorimetric method with modifications. At 100 ppm, 23 out of 118 plant extracts showed AChE or BuChE inhibition greater than 50%. Only 10 of the 23 plant extracts inhibited BuChE selectively, with IC50 values ranging from 13.48 ± 3.90 to 177.9 ± 15.8 ppm. The plant extracts with selective BuChE inhibitory activity include those from the stem of Curcuma zedoaria Rosc. (Zingiberaceae), bark of Sandoricum koetjape (Burm F.) Merr. (Meliaceae), leaves of Artocarpus heterophyllus Lam. (Moraceae), stem and bark of Erythrina variegata var orientalis Linn. (Leguminosae), leaves of Andrographis paniculata (Burm. f.) Nees (Acanthaceae), bark of Hibiscus tiliaceus Linn. (Malvaceae), leaves of Phyllanthus niruri Linn. (Phyllanthaceae), leaves of Annona squamosa Linn. (Annonaceae), and leaves of Hydrocolyte umbellata Linn. (Araliaceae). Further research into these plant extracts could yield herbal formulations and drugs that could be of particular interest in neurodegenerative diseases such as AD.