Auto-hydrolysis of red clover as "green" approach to (iso)flavonoid enriched products

Investigation of red clover (Trifolium pratense) isoflavonoid residual complexity by off-line CCS-qHNMR

The importance of Trifolium pratense L. as a dietary supplement and its use in traditional medicine prompted the preparation of a thorough metabolite profile. This included the identification and quantitation of principal constituents as well as low abundant metabolites that constitute the residual complexity (RC) of T. pratense bioactives. The purity and RC of isoflavonoid fractions from standardized red clover extract (RCE) was determined using an off-line combination of countercurrent separation (CCS) and two orthogonal analytical methodologies: quantitative ¹H NMR spectroscopy with external calibration (EC-qHNMR) and LC-MS. A single-step hydrostatic CCS methodology (Centrifugal Partition Chromatography [CPC]) was developed that fractionated the isoflavonoids with a hexanes-ethyl acetate-methanol-water (HEMWat) 5.5/4.5/5/5, v/v solvent system (SS) into 75 fractions containing 3 flavonolignans, 2 isoflavonoid glycosides, as well as 17 isoflavonoids and related compounds. All metabolites were identified and quantified by qHNMR spectroscopy. The data led to the creation of a complete isoflavonoid profile to complement the biological evaluation. For example, fraction 69 afforded 90.5% w/w biochanin A (17), with 0.33% w/w of prunetin (16), and 0.76% w/w of maackiain (15) as residual components. Fraction 27 with 89.4% w/w formononetin (13) as the major component had, in addition, a residual complexity consisting of 3.37%, 0.73%, 0.68% w/w of pseudobaptigenin (11), kaempferol (10) and pratensein (8), respectively. Despite the relatively high resolving power of CPC, and not unexpectedly, the chromatographic fractions retained varying degrees of the original metabolomic diversity. Collectively, the extent of metabolomic diversity should be recognized and used to guide the development of isolation strategies, especially when generating samples for bioactivity evaluation. The simultaneous structural and quantitative characterization enabled by qNMR, supported by LC-MS measurements, enables the evaluation of a relatively large number of individual fractions and, thereby, advances both the chemical and biological evaluation of active principles in complex natural products.

Discovery of minor quality evaluation marker compounds for Chinese patent medicine products using a two-leveled metabolomics strategy

Chinese patent medicines (CPMs) are popularly used in clinical practice. Though the composition is complex, the quality of CPM is usually evaluated by the contents of a few main compounds. In this study, a two-leveled metabolomics strategy was proposed to discover minor marker compounds for different CPM products. Zhenqi Fuzheng (ZQFZ) granule was studied an example, where 15 batches from 3 producers were analyzed. The samples were separated using UHPLC on an Acquity UPLC® HSS T3 column, and then detected using Q-Orbitrap-MS. In the first level, 1475 common peaks were extracted and 95 compounds were identified using diagnostic ions and a homemade database. In the second level, the data were subjected to a two-way hierarchical clustering analysis and screened by variable importance value. In total 14 marker compounds were discovered which were responsible for the grouping of different ZQFZ products. Echinacoside (22), oleoside (13), loganic acid (5), salidroside (7), ligustrosidic acid (42), 6α-hydroxygeniposide (28), and oleoside 11-methyl ester (15) could be used to reflect the quality difference for ZQFZ granule products. The proposed strategy could also contribute to the discovery of quality control markers for other CPMs.