Qualitative and quantitative analysis of steroidal saponins in crude extracts from Paris polyphylla var. yunnanensis and P. polyphylla var. chinensis by high performance liquid chromatography coupled with mass spectrometry

High performance liquid chromatography coupled with electrospray ionization multi-stage tandem mass spectrometry (HPLC–ESI-MSn) and triple quadrupole mass spectrometric detection (HPLC–ESI-MS/MS), respectively, had been employed for the simultaneous identification and quantification of steroidal saponins in the rhizomes of Paris polyphylla var. yunnanensis and P. polyphylla var. chinensis, which are the qualified plants of "Chonglou" in Chinese. The HPLC experiments were performed by means of a reversed-phase C-18 column and a binary mobile phase system consisting of 0.1% aqueous formic acid and acetonitrile under gradient elution conditions. The characteristic fragmentation patterns of diosgenin- and pennogenin-type steroidal saponins were investigated using ESI-MSn in negative ion mode. The MSn data of the [M−H]− ions provided structural information on the sugar sequence of the oligosaccharide chains and the aglycones of steroidal saponins. As a result, ten and seven saponins were determined in P. polyphylla var. yunnanensis and P. polyphylla var. chinensis, respectively, including four unknown compounds. One unknown compound was tentatively identified as diosgenin-3-O-α-l-rhamnopyranosyl(1 → 4) [α-l-rhamnopyranosyl(1 → 2)]-β-d-glucopyranoside and the aglycones of the other three new compounds were reported from Chonglou for the first time. The developed HPLC–ESI-MS/MS method was validated and found to be satisfactorily linear, selective and robust. The limits of detection (LODs) and quantitation (LOQs) ranged, respectively, from 0.5 to 10 ng/mL and 2 to 34 ng/mL depending on six various compounds. The intra- and inter-day precisions of the method were evaluated and were less than 5.0%. Recoveries ranged from 92% to 104% for all compounds. The established quality evaluation method was successfully used for simultaneous quantification of six predominant steroidal saponins in the rhizomes of these two Paris species.