Sarcorucinine-D Inhibits Cholinesterases and Calcium Channels: Molecular Dynamics Simulation and In Vitro Mechanistic Investigations.

Acetylcholinesterase (AChE) inhibitors and calcium channel blockers are considered effective therapies for Alzheimer's disease. AChE plays an essential role in the nervous system by catalyzing the hydrolysis of the neurotransmitter acetylcholine. In this study, the inhibition of the enzyme AChE by Sarcorucinine-D, a pregnane type steroidal alkaloid, was investigated with experimental enzyme kinetics and molecular dynamics (MD) simulation techniques. Kinetics studies showed that Sarcorucinine-D inhibits two cholinesterases-AChE and butyrylcholinesterase (BChE)-noncompetitively, with Ki values of 103.3 and 4.66 µM, respectively. In silico ligand-protein docking and MD simulation studies conducted on AChE predicted that Sarcorucinine-D interacted via hydrophobic interactions and hydrogen bonds with the residues of the active-site gorge of AChE. Sarcorucinine-D was able to relax contractility concentration-dependently in the intestinal smooth muscles of jejunum obtained from rabbits. Not only was the spontaneous spasmogenicity inhibited, but it also suppressed K+-mediated spasmogenicity, indicating an effect via the inhibition of voltage-dependent Ca2+ channels. Sarcorucinine-D could be considered a potential lead molecule based on its properties as a noncompetitive AChE inhibitor and a Ca2+ channel blocker.

Immunomodulatory activities of isolated compounds from the root-bark of Cussonia arborea.

CONTEXT: Cussonia arborea Hochst. ex A. Rich (Araliaceae) is a folk medicine used to treat various diseases. However, there is no report of the root phytochemistry. OBJECTIVE: This study isolates and identifies the immunomodulatory compounds from root-bark of C. arborea. MATERIALS AND METHODS: The methanol extract (18 g) was subjected to repeated column chromatography resulting in isolation of five compounds (1-5). Structure determination was achieved by analysis of their 1 D and 2 D NMR, and mass spectroscopy. The compounds (100-1.0 µg/mL) were examined immunomodulatory for effect on production of reactive oxygen species (ROS) from whole blood phagocytes and on proliferation of T-cells. The compounds cytotoxicity (100-1.0 µg/mL) was evaluated on NIH-3T3 normal fibroblast cells. RESULTS: Three pentacyclic triterpenoids [3, 23-dihydroxy-12-oleanen-28-oic acid (1), 3ß-hydroxylolean-12-en-28-oic (2) and 23-hydoxy-oxo-urs-12-en-28-oic acid (5)], two phytosterols: [stigmasterol (3)] and [3-O-ß-d-glucopyranosyl stigmasterol (4)] were all isolated from the methanol soluble extract. All the tested compounds (1-4) were found to be nontoxic on NIH-3T3 cells. Compound 1 and 2 moderately inhibited the production of ROS (IC50 = 24.4 ± 4.3 and 37.5 ± 0.1 µg/mL, respectively) whereas compound 2 exhibited the highest inhibitory effect (IC50 = 12.6 ± 0.4 µg/mL) on proliferation of phytoheamagglutinin (PHA) activated T-cells. CONCLUSIONS: The isolated compounds (1-5) are reported for the first time from this species. In addition, compound 2 with suppressive potential on production of intracellular ROS and proliferation of T-cells could be of immense value in control of autoimmune diseases as well as in immune compromised patients.