A novel analytical ELISA-based methodology for pharmacologically active saikosaponins

Spot tests: past and present

Microchemistry, i.e., the chemistry performed at the scale of a microgram or less, has its roots in the late eighteenth and early nineteenth centuries. In the first half of the twentieth century a wide range of spot tests have been developed. For didactic reasons, they are still part of the curriculum of chemistry students. However, they are even highly important for applied analyses in conservation of cultural heritage, food science, forensic science, clinical and pharmacological sciences, geochemistry, and environmental sciences. Modern pregnancy tests, virus tests, etc. are the most recent examples of sophisticated spot tests. The present ChemTexts contribution aims to provide an overview of the past and present of this analytical methodology.

Immunological Separation of Bioactive Natural Compounds from Crude Drug Extract and Its Application for Cell-Based Studies

In this study, we present a review on a useful approach, namely, immunoaffinity column coupled with monoclonal antibodies (MAbs), to separate natural compounds and its application for cell-based studies. The immunoaffinity column aids in separating the specific target compound from the crude extract. The column capacity was stable even after more than 10 purification cycles of use under the same conditions. After applying the crude extract to the column, the column was washed with washing buffer and eluted with elution buffer. The elution fraction contained the target compound bound to MAb, whereas the washing fraction was the crude extract, which contained all compounds except a group of target compounds; therefore, the washing fraction was referred to as a knockout (KO) crude extract. Cell-based studies using the KO extract revealed the actual effects of the natural compounds in the crude extract. One-step separation of natural compounds using the immunoaffinity column coupled with MAbs may help in determining the potential functions of natural compounds in crude extracts.

Recent Progress in Saikosaponin Biosynthesis in Bupleurum

BACKGROUND

Chaihu is a popular traditional Chinese medicine that has been used for centuries. It is traditionally used to treat cold fever and liver-related diseases. Saikosaponins (SSs) are one of the main active components of chaihu, in addition to essential oils, flavonoids, and polysaccharides. Considerable effort is needed to reveal the biosynthesis and regulation of SSs on the basis of current progress.

OBJECTIVE

The aim of this study is to provide a reference for further studies and arouse attention by summarizing the recent achievements of SS biosynthesis.

METHODS

All the data compiled and presented here were obtained from various online resources, such as PubMed Scopus and Baidu Scholar in Chinese, up to October 2019.

RESULTS

A few genes of the enzymes of SSs participating in the biosynthesis of SSs were isolated. Among these genes, only the P450 gene was verified to catalyze the SS skeleton β-amyrin synthase. Several UDP-glycosyltransferase genes were predicted to be involved in the biosynthesis of SSs. SSs could be largely biosynthesized in the phloem and then transported from the protoplasm, which is the biosynthetic site, to the vacuoles to avoid self-poisoning. As for the other secondary metabolites, the biosynthesis of SSs was strongly affected by environmental factors and the different species belonging to the genus of Bupleurum. Transcriptional regulation was studied at the molecular level.

CONCLUSION

Profound discoveries in SSs may elucidate the mechanism of diverse the monomer formation of SSs and provide a reference for maintaining the stability of SS content in Radix Bupleuri.

Qualitative detection of ginsenosides in brain tissues after oral administration of high-purity ginseng total saponins by using polyclonal antibody against ginsenosides

Given the limited studies and conflicting findings, the transport character of ginsenosides crossing the blood-brain barrier (BBB) remains unclear. The present study was designed to qualitatively determine the distribution of ginsenosides in brain tissues after oral administration of ginseng total saponins, using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) combined with immunohistochemistry. In brain tissue homogenates, ginsenoside Rg1 was detectable and no other ginsenosides or their metabolites were found. No ginsenosides were detected in cerebrospinal fluid. Immunohistochemistry staining of brain tissue sections by using anti-ginsenoside polyclonal antibodies revealed the localization of ginsenosides in brain tissues. Furthermore, immunofluorescence double staining revealed that ginsenosides widely existed in vascular endotheliocytes and astrocytes, and in few neurons. These results indicated that Rg1 was the main component that entered the brain after oral administration of ginseng total saponins and that ginsenosides could cross the BBB, although the transport capability of ginsenosides through the BBB may be poor.

Enzyme-linked immunosorbent assay for the quantitative/qualitative analysis of plant secondary metabolites

Immunoassays are antibody-based analytical methods for quantitative/qualitative analysis. Since the principle of immunoassays is based on specific antigen-antibody reaction, the assays have been utilized worldwide for diagnosis, pharmacokinetic studies by drug monitoring, and the quality control of commercially available products. Berson and Yalow were the first to develop an immunoassay, known as radioimmunoassay (RIA), for detecting endogenous plasma insulin [1], a development for which Yalow was awarded the Nobel Prize in Physiology or Medicine in 1977. Even today, after half a century, immunoassays are widely utilized with some modifications from the originally proposed system, e.g., radioisotopes have been replaced with enzymes because of safety concerns regarding the use of radioactivity, which is referred to as enzyme immunoassay/enzyme-linked immunosorbent assay (ELISA). In addition, progress has been made in ELISA with the recent advances in recombinant DNA technology, leading to increase in the range of antibodies, probes, and even systems. This review article describes ELISA and its applications for the detection of plant secondary metabolites.

Monoclonal Antibodies and Immunoassay for Medical Plant-Derived Natural Products: A Review

Owing to the widespread application value, monoclonal antibodies (MAbs) have become a tool of increasing importance in modern bioscience research since their emergence. Recently, some researchers have focused on the production of MAbs against medical plant-derived natural products (MPNP), the secondary metabolites of medical plants. At the same time, various immunoassay methods were established on the basis of these MPNP MAbs, and then rapidly developed into a novel technique for medical plant and phytomedicine research in the area of quality control, pharmacological analysis, drug discovery, and so on. Dependent on the research works carried out in recent years, this paper aims to provide a comprehensive review of MAbs against MPNP and the application of various immunoassay methods established on the basis of these MAbs, and conclude with a short section on future prospects and research trends in this area.

A sensitive and specific indirect competitive enzyme‑linked immunosorbent assay for the detection of icariin

In the present study, a novel monoclonal antibody (MAb) specific for icariin (ICA) was prepared and characterized. A hybridoma‑secreting MAb against icariin was produced by fusing splenocytes immunized with an ICA‑bovine serum albumin conjugate with a hypoxanthine‑aminopterin‑thymidine‑sensitive mouse myeloma SP2/0 cell line. The antibody showed high specificity for ICA with almost no cross‑reactivity against the majority of structurally‑related chemicals. Subsequently, an indirect competitive enzyme‑linked immunosorbent assay (ELISA) for ICA was established and characterized. In this assay, an effective measuring range of 10‑1,000 ng/ml of ICA (R2=0.9828) was detected. Intra‑ and inter‑assay repeatability and precision were achieved with a relative standard deviation (RSD) of <10%. A mean recovery of 95‑115% was obtained, with an RSD of <10%. In addition, the levels of ICA in traditional Chinese herbal prescriptions were determined, and correlation between the ELISA and high‑performance liquid chromatography analyses of total ICA was obtained. These results demonstrated that a reliable ELISA method had been successfully developed to determine ICA in traditional Chinese herbs and may contribute to further clinical investigations.

New Perspectives on Specific Immune-Depletion Technique Using Monoclonal Antibodies against Small Active Molecules in Herbs

One of the main focuses in Chinese Medicine research is the identification of efficacious components in Chinese herbal medicine (CHM). Studies in such area are difficult due to the complexity and the synergistic characteristics of CHM. Current methods to track and separate active components are not adequate to meet the needs of revealing effects and identify substances and pharmacological mechanisms, which directly restrict the modernization and globalization of CHM. In this paper, a new methodology to deplete a single active component via immunoassay was introduced. The specific active component in a CHM mixture can then be identified and studied through comparative analyses of the pharmacological effects before and after immune depletion. With this new methodology, degree of contribution of a particular component to the whole complex herbal mixture can be elucidated, and its synergistic property with other components can be determined. The new method can reflect not only the overall combined pharmacological effects of CHM but also the effect of individual component. It is an effective way to explain the degree of contribution of one specific component to the overall activity of a CHM prescription.

Traditional Use, Pharmacology, Toxicology, and Quality Control of Species in Genus Bupleurum L

Many species of genus Bupleurum L. have been pharmaceutically used mainly in Asia and Europe for thousand years. Their roots are the most popular ingredients in Chinese materia medica prescriptions for the treatment of inflammatory diseases and auto-immune diseases. A plenty of chemical constituents have been isolated and identified from the species in Bupleurum L., such as saikosaponins, polysaccharides, volatile oils, flavonoids, polyacetylenes, lignins, and coumarins, most of which possess a variety of biological activities, especially for the hepatoprotective effect, antitumor activity, immunoregulation, and febrifuge efficacy. Therefore, the species in genus Bupleurum L. could be potential herbs of immunomodulator, antineoplastic, anti-oxidant, etc. Meanwhile, as potential toxicities have been discovered in some constituents, it is urgent to establish a comprehensive quality evaluation system to ensure the safety and efficiency of herbs. This paper reviews on the phytochemical and pharmacological studies, especially for the toxicology and quality control of the species in Bupleurum L., which is a reference for the species in this genus for safe usage and further development.

Association between effective dose of prednisolone, alone or in conjunction with other immunosuppressants, and titre of anti-bullous pemphigoid 180 antibody: a retrospective study of 42 cases

BACKGROUND

Corticosteroids, especially prednisolone or prednisone, are the most commonly used drugs for the treatment of bullous pemphigoid (BP). However, the appropriate initial effective prednisolone dose has not been established. Recently, a highly sensitive and specific ELISA for detection of autoantibodies to the non-collagenous extracellular domain (NC16A) of the 180 kDa transmembrane hemidesmosome component [bullous pemphigoid (BP)180] was developed, and the titre of anti-BP180 antibody was found to be closely related to disease activity.

AIM

To investigate the relationship between anti-BP180 antibody titre and effective prednisolone dose alone or in conjunction with other immunosuppressants.

METHODS

Anti-BP180 antibody titres were measured by ELISA for the NC16A domain of BP180 in the sera of patients with BP (n = 42) at the start of treatment. The effective prednisolone dose was calculated from the patients' records.

RESULTS

Higher anti-BP180 antibody titres correlated with a higher effective prednisolone dose. In particular, patients with antibody titres > 200 required a significantly higher effective prednisolone dose than did those with antibody titres ≤ 200.

CONCLUSIONS

A higher effective prednisolone dose may be necessary for patients who have both a high titre of anti-BP180 antibody and severe clinical disease.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update for the period 2005-2006

This review is the fourth update of the original review, published in 1999, on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2006. The review covers fundamental studies, fragmentation of carbohydrate ions, method developments, and applications of the technique to the analysis of different types of carbohydrate. Specific compound classes that are covered include carbohydrate polymers from plants, N- and O-linked glycans from glycoproteins, glycated proteins, glycolipids from bacteria, glycosides, and various other natural products. There is a short section on the use of MALDI-TOF mass spectrometry for the study of enzymes involved in glycan processing, a section on industrial processes, particularly the development of biopharmaceuticals and a section on the use of MALDI-MS to monitor products of chemical synthesis of carbohydrates. Large carbohydrate-protein complexes and glycodendrimers are highlighted in this final section.

Estrogen-like activities of saikosaponin-d in vitro: a pilot study

Saikosaponin-d (SSd), a saponin derivative with a similar structure to estradiol, was extracted from Bupleurum falcatum L. (Umbelliferae). It was found that SSd stimulated the proliferation of MCF-7 cells by using MCF-7 cell proliferation assay. Cell-cycle analysis revealed that the proliferation-stimulating effect was associated with a marked increase in the number of MCF-7 cells in S phase. These actions of SSd were dose-dependent at doses ranging from 10nM to 10 microM and could be significantly inhibited by the specific estrogen receptor (ER) antagonist ICI-182780. Co-incubation of MCF-7 cells with 1 microM of ER antagonist ICI-182780 abolished the inductive effects of SSd on estrogen response element (ERE)-luciferase activity, suggesting that the estrogenic effects of SSd were mediated through the estrogen receptors. To evaluate the relative involvement of estrogen receptor alpha (ERalpha) and estrogen receptor beta (ERbeta) in mediating the actions of SSd, ER-negative human cervical carcinoma (HeLa) cells were cotransfected with the ERE-luciferase reporter construct and either ERalpha or ERbeta construct. The results showed that SSd could activate ERE-luciferase activity via the ERalpha-mediated pathway in a dose-dependent manner (10 nM to 10 microM); whereas, the activation of ERbeta-mediated ERE-luciferase activity by SSd only occurred at a high concentration (10 microM). Furthermore, the ERalpha protein and mRNA levels were increased by treatment with SSd within 24h. These data support our hypothesis that SSd acts as a weak phytoestrogen. Presumably, the estrogenic effect of SSd is mediated by the estrogen receptor.

Saikosaponin a inhibits the proliferation and activation of T cells through cell cycle arrest and induction of apoptosis

In the present study, we aimed at examining the immunosuppressive activity of saikosaponin a, a triterpene saponin derived from Bupleurum falcatum L. (Umbelliferae), and the underlying mechanisms. Saikosaponin a significantly inhibited the proliferation and activation of T cells activated by concanavalin A (Con A) in a concentration-dependent manner. Additionally, it potently suppressed Con A-stimulated IL-2, IFN-gamma and TNF-alpha production in mouse T cells. Saikosaponin a also caused G0/G1 arrest of activated T cells through down-regulating the protein levels of CDK6 and Cyclin D3 and up-regulating the protein level of p27(kip). Furthermore, the compound dose-dependently induced apoptosis of Con A-activated T cells rather than those non-activated, as determined by Annexin V/PI staining. Besides, it induced a remarkable collapse of mitochondrial membrane potential and caused significant release of cytochrome c from mitochondria to cytosol. In summary, these results suggest that the G0/G1 arrest as well as the induction of apoptosis via mitochondrial pathway are involved in the immunosuppressive activity of saikosaponin a against activated T cells. This may herald a novel approach for further studies of saikosaponin a as a candidate for the treatment of inflammatory and autoimmune diseases.

Fast determination of saikosaponins in Bupleurum by rapid resolution liquid chromatography with evaporative light scattering detection

A rapid resolution liquid chromatography coupled with evaporative light scattering detection method was established for simultaneous determination of six saikosaponins, namely saikosaponin a, saikosaponin c, saikosaponin d, 6''-O-acetylsaikosaponin a, 3''-O-acetylsaikosaponin d and 6''-O-acetylsaikosaponin d in Bupleurum. The analysis was performed by using an Agilent Zorbax SB-C18 column (1.8 microm, 3.0 mm x 50 mm i.d.) at gradient elution of water and acetonitrile, and the saikosaponins were well separated within 12 min, which provided about a fourfold reduction in analysis time by comparing a conventional high performance liquid chromatography method. Owing to their low ultraviolet absorption, the saikosaponins were detected by evaporative light scattering. The standard curves to quantify the saikosaponins were constructed by the log-log plot, which showed good linearity with the correlation coefficients exceeding 0.9954. The detection limits and quantification limits ranged in 8.38-25.00 microg/mL and 25.13-45.00 microg/mL, respectively. Satisfactory intra-day and inter-day precisions were achieved with the relative standard deviation (R.S.D.) less than 6.58%, and the average recoveries obtained were in the range of 96.9-100.4%. In addition, MeOH-1.0% (v/v) pyridine was found to be the best the extraction solvent when compared to MeOH and MeOH-1.0% (v/v) ammonia water. A total of 23 samples of roots of Bupleurum from different species or locations were examined with this analytical method, and their chemical profiles provided information for the chemotaxonomic investigation. The results demonstrated that the analytical method is highly effective for the quality evaluation of Bupleurum species.

Determination of pseudojujubogenin glycosides from Brahmi based on immunoassay using a monoclonal antibody against bacopaside I

Bacopa monnieri (L.) Wettst. (Brahmi) is an Ayurvedic medicinal plant used for centuries as a memory enhancer. Dammarane-type triterpenoid saponins classified as pseudojujubogenin and jujubogenin glycosides are reported as the active components in this plant. In this study, the monoclonal antibody (MAb) against bacopaside I, a major pseudojujubogenin glycoside found in Brahmi, was produced and characterised. Bacopaside I was conjugated with bovine albumin serum to prepare an immunogen. Hybridomas secreting a monoclonal antibody against bacopaside I was produced by fusing splenocytes from an immunised mouse and SP2/0-Ag14 myeloma cells. The results showed that the antibodies were raised specifically against pseudojujubonin glycosides. An enzyme-linked immunosorbant assay (ELISA) using anti-bacopaside I MAb was performed in the range of 1.95-62.5 ng/mL of bacopaside I, with a limit of detection of 0.5 ng/mL. The method was validated and the practical use of the ELISA for analysing saponin glycosides from Brahmi was demonstrated.

Visual detection of saikosaponins by on-membrane immunoassay and estimation of traditional Chinese medicines containing Bupleuri radix

The purpose of this study was to describe the simple, rapid, and environmental-cost effective determination method for saikosaponins in complicated samples like Bupleuri radix and traditional Chinese medicines (TCM). Saikosaponin standards, extracts of Bupleuri radix and TCM, were applied to a polyethersulphone (PES) membrane and developed by acetonitrile-water (1:4, by volume). Saikosaponin a (SSa), SSc, and SSd were visually detected by an immunostaining method (called Eastern blotting technique) using a monoclonal antibody (MAb) against SSa. At least 62.5 ng of SSa, SSc, and SSd were clearly detectable individually. These coloring spot areas of saikosaponins on PES membrane were calculated by using the NIH Imaging software and three saikosaponins can be analyzed quantitatively between 62.5 ng and 1.0 microg. Saikosaponins in Bupleuri radix and TCM were determined and these results of SSa and total saikosaponin concentrations were in good agreement with those from the ELISA analysis.