New limonoids from Coptidis Rhizoma-Euodiae Fructus couple.

A pair of inseparable new limonoids, named euodirutaecins A and B, were isolated from the Coptidis Rhizoma-Euodiae Fructus couple, together with two new single compounds evodirutaenin A and shihulimonin A1, and the known limonoids rutaevin, limonin, 12α-hydroxyrutaevin, and alkaloids rutaecarpine and evodiamine. Structures of these compounds were identified by spectral analyses and quantum chemical computational method, and the six limonoids were also evaluated for cytotoxicities against NCI-N87 and Caco-2 cell lines.