Studies on Antitumour Cyclic Hexapeptides RA Obtained from Rubiae Radix, Rubiaceae (IV): Quantitative Determination of RA-VII and RA-V in Commercial Rubiae Radix and Collected Plants

Abstract

Distribution and quantitative variations of antitumour cyclic hexapeptides RA-V and RA-VII in Rubia and related species were investigated by means of HPLC. In the roots of Rubia cordifolia and R. tinctorum known as the commercial crude drug Rubiae Radix, the presence of cyclic hexapeptides was recognized in most of the former, but not in all of the latter. The average contents of RA-V and RA-VII in R. cordifolia were 94 mg/kg and 36 mg/kg, respectively. In collected plants RA-V and RA-VII were detected in both aerial parts and roots of R. akane, but its related species, R. tinctorum, Galium species, Hedyotis species, Paederia scandens, Pentas bussei, and Bouvardia hybrida did not contain the antitumour cyclic hexapeptides. Also, seasonal changes of RA-V and RA-VII contents were investigated with respect to the aerial parts and roots of R. akane. From the results, it was revealed that their contents gave maximum values in both parts at mid-summer.