Cycloartane Triterpenes from the Aerial Parts of Actaea racemosa

Investigating the phytochemical equivalence of the aerial parts of Actaea racemosa (syn. Cimicifuga racemosa) relative to the widely used roots/rhizomes, this study provides a perspective for the potential use of renewable ("green") plant parts as a source of black cohosh botanical preparations. In addition to the characterization of Nω-methylserotonin as one representative marker of the Actaea alkaloids, nine cycloartane triterpenes were isolated and characterized, including the two new triterpene glycosides (1S,15R)-1,15,25-trihydroxy-3-O-β-d-xylopyranosyl-acta-(16S,23R,24R)-16,23;16,24-binoxoside (1) and 3-O-α-l-arabinopyranosyl-(1S,24R)-1,24,25-trihydroxy-15-oxo-acta-(16R,23R)-16,23-monoxoside (2). Their structures were elucidated by spectroscopic data interpretation. The relative configuration of 1 was deduced by (1)H iterative full-spin analysis (HiFSA), making it the first example of the complete analysis of the complex (1)H NMR spectrum of a triterpene glycoside. In addition to the new compounds 1 and 2, the aerial plant parts were shown to contain the previously known binoxosides 3, 4, 6, and 7, the monoxoside 8, and the binoxols 5 and 9. Overall, the metabolome of the aerial plant parts consists of a variety of Actaea triterpenes, similar to those found in roots/rhizomes, a tendency toward C-1 and C-7 hydroxylation of the cycloartanol skeleton, a greater abundance of aglycones, and the presence of comparable amounts of Nω-methylserotonin.