Receptor binding activities of Schefflera triterpenoids and oligosaccharides

Roots and leaves of Schefflera bodinieri were studied for their activity in the central nervous system (CNS) by bioassay-guided isolation in conjunction with receptor binding assays. As demonstrated in preliminary screening, ethanol extracts of leaves and roots of S. bodinieri showed strong binding affinity to a number of CNS receptors. Chemical investigation of this plant species was then conducted and fourteen plant ingredients were obtained. In this study, nine of these isolated compounds were tested by fifteen receptor binding assays for their CNS activities. Results showed that three compounds, namely bodinone, bodinone glycoside and D-sorbitol, were able to selectively bind to muscarine receptors, a trisaccharide bound to Ca2+ channel and 5HT-2 receptors, stigmasterol 3-O-glucoside bound to 5HT-2 receptors, and bodirin A bound to dopamine-2 receptors with IC50 values at microM level. In the drug-interaction studies, bodinone, bodinone glycoside, bodirin A, bodinitin A and the trisaccharide were found to affect binding affinity of certain specific binding agents to the 5HT1C, 5HT2, opiate, beta-adrenergic and histamine 1 receptors. These observations suggest interactions between the plant ingredients and receptors as well as synergistic effect of various compounds at receptor level.