Anti-inflammatory, anti-bacterial and anti-acetylcholinesterase activities of two isoquinoline alkaloids-scoulerine and cheilanthifoline

Corydalis plants containing isoquinoline alkaloids are reported to possess promising pharmacological properties for the treatment of important diseases including cancer, inflammation, Alzheimer's disease and microbial infections. As part of a wider program investigating Bhutanese medicinal plants, we have previously identified eight isoquinoline alkaloids from C. dubia. Out of these, we report here on two of the major alkaloids, scoulerine (1) and cheilanthifoline (2) and their inhibitory activities against acetylcholinesterase (anti-AChE), tumor necrosis factor alpha (anti TNF-α) and a bacterial strain, Helicobacter pylori. Both alkaloids showed weak anti TNF-α and antibacterial activities. However, the anti-AChE activity of scoulerine (1) was promising as it significantly inhibited AChE with a minimum inhibitory requirement (MIR) value of 0.0015 nmol, which was two-fold better than the reference drug, galanthamine (MIR value of 0.003 nmol). As there are limited anti-Alzheimer's chemotherapeutics, scoulerine (1) is worthy of further exploration, including lead optimization, structure-activity-relationship studies, analog development, pharmacodynamics and in vivo animal studies.