Orthogonality in the selection of biphasic solvent systems for off-line two-dimensional countercurrent chromatography from Polygonum cuspidatum Sieb. et Zucc

Emodin-8-O-Glucoside-Isolation and the Screening of the Anticancer Potential against the Nervous System Tumors

Emodin-8-O-glucoside (E-8-O-G) is a glycosylated derivative of emodin that exhibits numerous biological activities, including immunomodulatory, anti-inflammatory, antioxidant, hepatoprotective, or anticancer activities. However, there are no reports on the activity of E-8-O-G against cancers of the nervous system. Therefore, the aim of the study was to investigate the antiproliferative and cytotoxic effect of E-8-O-G in the SK-N-AS neuroblastoma, T98G human glioblastoma, and C6 mouse glioblastoma cancer cells. As a source of E-8-O-G the methanolic extract from the aerial parts of Reynoutria japonica Houtt. (Polygonaceae) was used. Thanks to the application of centrifugal partition chromatography (CPC) operated in the descending mode using a mixture of petroleum ether:ethyl acetate:methanol:water (4:5:4:5 v/v/v/v) and a subsequent purification with preparative HPLC, E-8-O-G was obtained in high purity in a sufficient quantity for the bioactivity tests. Assessment of the cancer cell viability and proliferation were performed with the MTT (3-(bromide 4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium), CTG (CellTiter-Glo®) and BrdU (5-bromo-2'-deoxyuridine) assays, respectively. E-8-O-G inhibits the viability and proliferation of SK-N-AS neuroblastoma, T98G human glioblastoma multiforme, and C6 mouse glioblastoma cells dose-dependently. E-8-O-G seems to be a promising natural antitumor compound in the therapy of nervous system tumors.

Retention correlation and orthogonality between reversed phase countercurrent chromatography and liquid chromatography based on solvent strength

Correlation of elution performance between reversed phase countercurrent chromatography and liquid chromatography was investigated using five selected natural components. Theoretical guidance for orthogonality of two-dimensional countercurrent chromatography and liquid chromatography was proposed. The difference in retention behavior between countercurrent chromatography and liquid chromatography was studied when the mobile phase was composed of methanol and water by measuring the partition behavior of five selected compounds in two typical biphasic solvent systems composed of n-hexane-ethyl acetate-methanol-water and chloroform-methanol-water. An orthogonal diagram between countercurrent chromatography and liquid chromatography was obtained by normalized treatment of the measured partition coefficients and capacity factors. The experimental results showed that each biphasic solvent system used for countercurrent chromatography had a high orthogonality with liquid chromatography when a specific volume ratio was used.

Cytochrome P450-mediated herb-drug interaction (HDI) of Polygonum multiflorum Thunb. based on pharmacokinetic studies and in vitro inhibition assays

BACKGROUND

Polygonum multiflorum Thunb. (PM) is well known both in China and other countries of the world for its tonic properties, however, it has lost its former glory due to liver toxicity incidents in recent years.

PURPOSE

The purpose of this study is to determine whether the occurrence of herb-drug interaction (HDI) caused by PM is associated with cytochrome P450 (CYP450) based on pharmacokinetic studies and in vitro inhibition assays. The objective was to provide a reference for the rational and safe use of drugs in clinical practice.

METHODS

In this study, raw PM (R), together with its two processed products which included PM by Chinese Pharmacopoeia (M) and PM by "nine cycles of steaming and sunning (NCSS)" ("9"), were prepared as the main research objects. A method based on fluorescence technology was used to evaluate the inhibition levels of raw and processed PMs, as well as corresponding characteristic compounds on seven recombinant human cytochrome P450s (rhCYP450s). The pharmacokinetics of sulindac (a representative of commonly used nonsteroidal anti-inflammatory drugs) and psoralen (a major compound of Psoralea in combination with PM) in rat plasma were studied when combined with raw and different processed products of PM.

RESULTS

The inhibitory level order of the three extracts on major different subtypes of CYP450 (CYP1A2, CYP2B6, CYP2C8, CYP2C19, CYP2D6, and CYP3A4) was: R > M > "9". However, the inhibition level of R and "9" is higher than that of M on CYP2C9. Further studies showed that trans-THSG and emodin could selectively inhibit CYP3A4 and CYP1A2, respectively. Epicatechin gallate mainly inhibited CYP3A4 and CYP1A2, followed by CYP2C8 and CYP2C9. Genistein mainly inhibited CYP3A4, followed by CYP2C9 and CYP2C8. CYP3A4 and CYP2C9 were also inhibited by daidzein. The inhibitory effects of all the PM extracts were associated with their characteristic compounds. The results of HDI showed that R increased sulindac exposure to rat blood, and R and M increased psoralen exposure to rat blood, which were consistent with corresponding metabolic enzymes. Overall, the in vitro and in vivo results indicated that PM, especially R, would be at high risk to cause toxicity and drug interactions via CYP450 inhibition.

CONCLUSION

This study not only elucidates the scientific connotation of "efficiency enhancement and toxicity reduction" of PM by NCSS from the perspective of metabolic inhibition but also contributes to HDI prediction and appropriate clinical medication of PM.

A Strategy for Pinpointing Natural Bioactive Components Using Two-Dimensional Bioassay Profilings Combined with Comprehensive Two-Dimensional Countercurrent Chromatography × High-Performance Liquid Chromatography

Inspired by the interpretation of two-dimensional (2D) nuclear magnetic resonance spectra, an efficient strategy was proposed for pinpointing bioactive components from complex natural products. An off-line comprehensive countercurrent chromatography (CCC) × high-performance liquid chromatography (HPLC) was employed to achieve a 2D chemical chromatogram, and 2D bioassay profilings were obtained from bioassays of the eluent of the first dimension (¹D) CCC and the eluent of the second dimension (²D) HPLC. Then 2D chemical chromatograms and 2D bioassay profilings were matched for pinpointing bioactive natural components from complex matrices. Thus, bioactive components in a complex matrix could be efficiently analyzed, separated, and bioactivity-determined. This experimental scheme was successfully demonstrated with a traditional medicinal herb Polygonum cuspidatum Sieb. et Zucc. The feasibility of this 2D strategy was verified with tyrosinase inhibition assay, α-glucosidase inhibition assay, DPPH radical scavenging assay, and ABTS^•+ decolorization assay. Eight natural inhibitors were successfully pinpointed and identified from P. cuspidatum. Both pieceid-2″-O-gallate (10) and vanicoside B (20) were screened and identified as natural tyrosinase inhibitors for the first time. Meanwhile, vanicoside B (20) was also found as the strongest α-glucosidase inhibitor among all the isolated components. Most of the compounds exhibited much higher radical scavenging activities. Compared with traditional methodology based on one-dimensional chromatographic separation, the present 2D strategy would be more precise, efficient, and convenient to screen and separate bioactive compounds from complex matrices.