Acetylcholinesterase inhibitors in the giant goldenrod root

Eight bioactive clerodane diterpenes from the root extract of Solidago gigantea Ait. (giant goldenrod) were quantified by high-performance thin-layer chromatography (HPTLC) and two newly developed hyphenated methods. One uses vanillin sulphuric acid derivatization and densitometry, and the other an inhibition assay of acetylcholinesterase (AChE) and video densitometry. Both methods gave figures of merit for quantification including 5.8-33.9 ng and 175.5-448.7 ng LOQs and 2.7-6.9 RSD% and 8.8-13.9 RSD% inter-day precisions, respectively. Based on the diterpenes' content of 14 root samples collected over a year from the same plant population, the fully flowering plant is suggested to collect the root as a source of these compounds. Excepting one diterpene (with the lowest retardation factor), the quantitative results for the richest sample obtained by the two methods were in harmony. The difference could be due to a matrix effect.