Zhi-Hong Jiang

Network-based drug discovery by integrating systems biology and computational technologies

Network-based intervention has been a trend of curing systemic diseases, but it relies on regimen optimization and valid multi-target actions of the drugs. The complex multi-component nature of medicinal herbs may serve as valuable resources for network-based multi-target drug discovery due to its potential treatment effects by synergy. Recently, robustness of multiple systems biology platforms shows powerful to uncover molecular mechanisms and connections between the drugs and their targeting dynamic network. However, optimization methods of drug combination are insufficient, owning to lacking of tighter integration across multiple ‘-omics’ databases. The newly developed algorithm- or network-based computational models can tightly integrate ‘-omics’ databases and optimize combinational regimens of drug development, which encourage using medicinal herbs to develop into new wave of network-based multi-target drugs. However, challenges on further integration across the databases of medicinal herbs with multiple system biology platforms for multi-target drug optimization remain to the uncertain reliability of individual data sets, width and depth and degree of standardization of herbal medicine. Standardization of the methodology and terminology of multiple system biology and herbal database would facilitate the integration. Enhance public accessible databases and the number of research using system biology platform on herbal medicine would be helpful. Further integration across various ‘-omics’ platforms and computational tools would accelerate development of network-based drug discovery and network medicine.

Enhancement of Oral Bioavailability of 20(S)-Ginsenoside Rh2 through Improved Understanding of Its Absorption and Efflux Mechanisms

The development of 20(S)-ginsenoside Rh2 (Rh2s) as a chemoprevention agent is limited by its low oral bioavailability. The goals of this study were to determine the mechanisms responsible for its poor oral absorption and to improve its bioavailability by overcoming the barrier to its absorption. Comprehensive studies were conducted using the following models: 1) monolayers of Caco-2, parental, and multidrug resistance gene (MDR1)-overexpressing Madin-Darby canine kidney II (MDCKII) cells; 2) pharmacokinetics in wild-type (WT) FVB, MDR1a/b knockout [MDR1a/b(−/−)] FVB, and A/J mice; and 3) intestinal perfusion in WT, MDR1a/b(−/−) FVB, and A/J mice. Two P-glycoprotein (P-gp) inhibitors, verapamil and cyclosporine A, substantially decreased the efflux ratio of Rh2s from 28.5 to 1.0 and 1.2, respectively, in Caco-2 cells. The intracellular concentrations of Rh2s were also significantly increased (2.3- and 3.9-fold) in the presence of inhibitors. Similar results were obtained when transcellular transport of Rh2s were determined using MDR1-overexpressing MDCKII cells in the absence or presence of cyclosporine A. Compared with WT mice, the plasma Cmax and AUC0–∞ of Rh2s were substantially increased by 17- and 23-fold in MDR1a/b(−/−) FVB mice, respectively. In the A/J mice, the oral bioavailability of Rh2s (0.94% at 5 mg/kg and 0.52% at 20 mg/kg) was substantially increased by P-gp inhibitor to 33.18 and 27.14%, respectively. As expected, deletion or inhibition of P-gp significantly increased absorption and steady-state plasma concentration of Rh2s in a mouse intestinal perfusion model. In conclusion, Rh2s is a good substrate of P-gp, and inhibition of P-gp can significantly enhance its oral bioavailability.

The in Vitro Structure-Related Anti-Cancer Activity of Ginsenosides and Their Derivatives

Panax ginseng has long been used in Asia as a herbal medicine for the prevention and treatment of various diseases, including cancer. The current study evaluated the cytotoxic potency against a variety of cancer cells by using ginseng ethanol extracts (RSE), protopanaxadiol (PPD)-type, protopanaxatriol (PPT)-type ginsenosides fractions, and their hydrolysates, which were prepared by stepwise hydrolysis of the sugar moieties of the ginsenosides. The results showed that the cytotoxic potency of the hydrolysates of RSE and total PPD-type or PPT-type ginsenoside fractions was much stronger than the original RSE and ginsenosides; especially the hydrolysate of PPD-type ginsenoside fractions. Subsequently, two derivatives of protopanaxadiol (1), compounds 2 and 3, were synthesized via hydrogenation and dehydration reactions of compound 1. Using those two derivatives and the original ginsenosides, a comparative study on various cancer cell lines was conducted; the results demonstrated that the cytotoxic potency was generally in the descending order of compound 3 > 20(S)-dihydroprotopanaxadiol (2) > PPD (1) > 20(S)-Rh2 > 20(R)-Rh2 ≈ 20(R)-Rg3 ≈ 20(S)-Rg3. The results clearly indicate the structure-related activities in which the compound with less polar chemical structures possesses higher cytotoxic activity towards cancer cells.

Ethnobotanical study of medicinal plants used by Hakka in Guangdong, China

ETHNOPHARMACOLOGICAL RELEVANCE An ethnobotanical survey was conducted to collect information on the use of medicinal plants by the Hakka living in Guangdong. AIM OF THE STUDY This investigation was to document valuable knowledge represented by Hakka herbal medicine. MATERIALS AND METHODS Information was obtained from semi-structured interviews, personal conversations with practitioners, direct observations, and by reviewing studies of Hakka and Cantonese reported in the literature. RESULTS Our data covered 94 species belonging to 77 genera in 40 families. We found that most species used for medical purposes were for hepatitis (14 species) and skin diseases (12 species). These disorders are prevalent and are primarily treated with medicinal plants. For treatment, the plants were mainly used as teas (Luica, Bugingca and Lopêdca), medicinal baths and soups. The Hakka and non-Hakka people living in Guangdong use different medicinal plants and, in some cases, use the same medicinal plants differently. CONCLUSIONS The fast disappearance of traditional culture and natural resources due to urbanization and industrialization suggests that unrecorded information may be lost forever. Thus, there is an urgent need both to record this valuable Hakka medicinal knowledge and to encourage its transfer to the next generation.

Ligand Binding to Tandem G Quadruplexes from Human Telomeric DNA

Ligand-induced stabilization of intramolecular telomeric G quadruplexes produced in the single-stranded overhang of the human telomere has become an attractive strategy for the development of anticancer drugs. Several distinct solution conformations of human telomeric G quadruplexes have been elucidated in the presence of sodium and potassium cations. The K-form, hybrid-type G-quadruplex structure has been considered to be a physiologically relevant conformation of the human telomeric sequence, and thus, can be specifically targeted by G-quadruplex-interactive, small-molecule ACHTUNGTRENNUNGdrugs. Recently, a beads-on-a-string model was proposed for the telomeric overhang, in which every four consecutive Grich repeats adopt an individual G-quadruplex structure, and two G-quadruplex units are connected by one TTA linker. c, 4] Ligand binding to the G quadruplex has mostly been investigated on telomere sequences producing a single G quadruplex, but few studies of ligand binding to beads-on-a-string G quadruplexes have been reported. To gain insight into the beads-on-a-string model and the nature of ligand binding, we undertook the polymerase stop assay on human telomere sequences of three to eight repeats (Table S1 in the Supporting Information) with TMPyP4, a G-quadruplex-interactive ligand, and sanguinarine (Scheme 1), a natural isoquinoline alkaloid. The results described in this paper confirm the beads-on-astring structure of telomeric overhang and suggest a mode of ligand binding between tandem G-quadruplex beads. These observations should be taken into account for structure-based design of anticancer drugs targeting human telomeric DNA. Sanguinarine is a natural isoquinoline alkaloid isolated from the North American herb bloodroot (Sanguinaria canadensis). It was approved by the FDA in 2003 to be added to oral cleansing products as an antibacterial agent. Sanguinarine also possesses potent anticancer activity. We have previously reported its DNA-binding activity and distinct sequence selectivity to double-stranded DNA, which was proposed to be one of the molecular mechanisms of its anticancer activity. The structural similarity of sanguinarine with berberine, another isoquinoline alkaloid possessing G-quadruplex-binding activity, prompted us to speculate that sanguinarine is probably a G-quadruplex binder. In this communication, we report its binding to the ACHTUNGTRENNUNGtelomeric overhang using DNA polymerase stop assays. DNA templates Tem-3 and Tem-4 (Table S1), which contains three and four human telomeric repeats d ACHTUNGTRENNUNG(TTAGGG), respectively, were employed, and TMPyP4 was used as the reference compound in the assay. Neither TMPyP4 nor sanguinarine blocked DNA synthesis on Tem-3, because an intramolecular Gquadruplex structure could not form with three human telomeric repeats on Tem-3 (Figure 1). In contrast, both sanguinarine and TMPyP4 produced paused bands in DNA synthesis on Tem-4. The position of the paused bands was the same for the two ligands. For each ligand, a series of concentration-dependent paused bands appeared at the beginning of the G-quadruplex-forming site, that is, the first site of G-rich repeats in Tem-4 (from 3’ to 5’). In the presence of 3 mm TMPyP4, the polymerase reaction was totally suppressed to give no elongation of the primer. The tight binding of sanguinarine and TMPyP4 to the K-form hybrid-type G-quadruplex structure was clearly indicated from the large increase in the melting temperature (DTm) of dAGGG ACHTUNGTRENNUNG(TTAGGG)3 (11.4 8C for sanguinarine and 9.5 8C for TMPyP4 in a 2:1 ligand/DNA molar ratio). ACHTUNGTRENNUNGFurthermore, a broad negative induced band at 351 nm in the CD spectra confirmed the interaction between sanguinarine and the K-form G quadruplex formed by dAGGG ACHTUNGTRENNUNG(TTAGGG)3 (Figure 2). Regarding the mode of ligand binding to the G quadruplex, NMR, 10a,11] fibre diffraction, and single-crystal X-ray crystallographic analyses have confirmed that a variety of planar aromatic binders including TMPyP4 interact with the G quadruplex by end stacking rather than intercalation between G tetrads. TMPyP4 was also found to stack onto the external loop of a bimolecular G quadruplex in a crystal structure. Recently, electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) has been used to analyze complexes of G quadruplexes with ligands, since G quadruplexes can maintain their structure in the gas phase in the presence of a suitable cation such as NH4 + . ESI-MS showed the ammonium ion to be loScheme 1. Chemical structures of sanguinarine and TMPyP4.

Identification of five hepatotoxic pyrrolizidine alkaloids in a commonly used traditional Chinese medicinal herb, Herba Senecionis scandentis (Qianliguang)

Senecio scandens Buch.-Ham is a plant source for a commonly used traditional Chinese medicinal (TCM) herb Qianliguang. A TCM herbal proprietary product containing Qianliguang as the major herb for the treatment of sinusitis has been used in China for several decades, and has also been exported to other regions and countries worldwide. In the present study, the aqueous extract of S. scandens collected in the Shanxi Province of China was determined, for the first time, to contain hepatotoxic and tumorigenic pyrrolizidine alkaloids (PAs) by using high-performance liquid chromatography/mass spectrometric (HPLC/MS) analysis in various scanning modes. A total of nine toxic and two non-toxic PAs were detected in the aqueous extract of S. scandens, of which six PAs, namely neoplatyphylline, senecionine, senecionine N-oxide, seneciphylline, seneciphylline N-oxide and senkirkine, were unequivocally characterized, while other PAs were tentatively assigned as jacobine, jacozine N-oxide (or erucifoline N-oxide), 7-tigloylplatynecine, usaramine and an isomer of yamataimine. The estimated total content of toxic PAs in S. scandens was 10.82 microg/g herb, which was significantly higher than that (> or =1 microg/g herb) recommended by Belgium and Germany not to be used clinically. Among the PAs definitively identified, senecionine, seneciphylline, and senkirkine are known tumorigens capable of inducing liver tumors in experimental animals, while seneciphylline N-oxide and senecionine N-oxide are probably tumorigenic due to their potential conversion into seneciphylline and senecionine via metabolic reduction in the body. Thus, the current finding of the presence of toxic/tumorigenic PAs in S. scandens challenges the safety of using this TCM herb and its proprietary products.

Inhibition of P-Glycoprotein Leads to Improved Oral Bioavailability of Compound K, an Anticancer Metabolite of Red Ginseng Extract Produced by Gut Microflora

Ginsenosides are hydrolyzed extensively by gut microflora after oral administration, and their metabolites are pharmacologically active against lung cancer cells. In this study, we measured the metabolism of various ginsenosides by gut microflora and determined the mechanisms responsible for the observed pharmacokinetic behaviors of its active metabolite, Compound K (C-K). The results showed that biotransformation into C-K is the major metabolic pathway of ginsenosides after the oral administration of the red ginseng extract containing both protopanaxadiol and protopanaxatriol ginsenosides. Pharmacokinetic studies in normal mice showed that C-K exhibited low oral bioavailability. To define the mechanisms responsible for this low bioavailability, two P-glycoprotein (P-gp) inhibitors, verapamil and cyclosporine A, were used, and their presence substantially decreased C-Ks efflux ratio in Caco-2 cells (from 26.6 to <3) and significantly increased intracellular concentrations (by as much as 40-fold). Similar results were obtained when transcellular transport of C-K was determined using multidrug resistance 1 (MDR1)-overexpressing Madin-Darby canine kidney II cells. In MDR1a/b(−/−) FVB mice, its plasma Cmax and AUC0–24h were increased substantially by 4.0- and 11.7-fold, respectively. These increases appear to be due to slower elimination and faster absorption of C-K in MDR1a/b(−/−) mice. In conclusion, C-K is the major active metabolite of ginsenosides after microflora hydrolysis of primary ginsenosides in the red ginseng extract, and inhibition/deficiency of P-gp can lead to large enhancement of its absorption and bioavailability.

Quantitative comparison and metabolite profiling of saponins in different parts of the root of Panax notoginseng.

Although both rhizome and root of Panax notoginseng are officially utilized as notoginseng in “Chinese Pharmacopoeia”, individual parts of the root were differently used in practice. To provide chemical evidence for the differentiated usage, quantitative comparison and metabolite profiling of different portions derived from the whole root, as well as commercial samples, were carried out, showing an overall higher content of saponins in rhizome, followed by main root, branch root, and fibrous root. Ginsenoside Rb2 was proposed as a potential marker with a content of 0.5 mg/g as a threshold value for differentiating rhizome from other parts. Multivariate analysis of the metabolite profile further suggested 32 saponins as potential markers for the discrimination of different parts of notoginseng. Collectively, the study provided comprehensive chemical evidence for the distinct usage of different parts of notoginseng and, hence, is of great importance for the rational application and exploitation of individual parts of notoginseng.

Distribution of ellagic acid derivatives and a diarylheptanoid in wood of Platycarya strobilacea

Abstract 4- O -Xylosides of ellagic acid, 3′- O -methylellagic acid and 3,3′-di- O -methylellagic acid have been isolated from the sapwood of Platycarya strobilacea ; these compounds were absent in the heartwood. A new diphenylether-type diarylheptanoid, named platycarynol, was also isolated from the heartwood, together with ellagic acid, 3′- O -methylellagic acid and two known terpenoids.

A new catechin oxidation product and polymeric polyphenols of post-fermented tea.

A new epicatechin oxidation product with a 3,6-dihydro-6-oxo-2H-pyran-2-carboxylic acid moiety was isolated from a commercially available post-fermented tea that is produced by microbial fermentation of green tea. The structure of this product was determined by spectroscopic methods. A production mechanism that includes the oxygenative cleavage of the catechol B-ring of (-)-epicatechin is proposed. In addition, polymeric polyphenols were separated from the post-fermented tea and partially characterised by (13)C NMR spectroscopy and gel-permeation chromatography. The polymers appear to be primarily composed of epigalloacetechin-3-O-gallate and the molecular weight (Mn) of the acetylated form was estimated to be ∼3500.