Immunochromatographic assay for miroestrol and deoxymiroestrol, its cross-reactivity, and application in Pueraria mirifica (white Kwao Krua) analysis

INTRODUCTION

Miroestrol (Mi) and deoxymiroestrol (Dmi) are trace, yet potent, phytooestrogens found in white Kwao Krua [Pueraria candollei var. mirifica (Airy Shaw & Suvat.) Niyomdham, PM]. However, the analysis of these substances is difficult because of complex matrix effects and their various analogues. In addition, alteration in the cross-reactivity of a gold nanoparticle (AuNP)-based immunochromatographic assay (ICA) resulting from the electrostatic adsorption between antibodies and AuNPs has not yet been evaluated.

OBJECTIVES

This study aims to develop, characterise, and validate ICA with a monoclonal antibody exhibiting similar reactivity against Mi and Dmi (MD-mAb).

MATERIALS AND METHODS

The ICA performance was validated for cross-reactivity and performance in comparison with those of indirect competitive enzyme-linked immunosorbent assays (icELISAs) with MD-mAb and mAb exhibiting specificity against Mi (Mi-mAb).

RESULTS

The ICA showed a limit of detection (LOD) at 1 and 16 μg/mL for Mi and Dmi, respectively. The cross-reactivity of the ICA with Dmi was lower (6.25%) than that observed with the icELISA (120%). Cross-reactivity of ICA against other compounds of the PM was also correlated with those of icELISA; no false-positive/negative results were observed. The repeatability and reproducibility of the ICA were confirmed. The results obtained using ICA in samples of PM are correlated with the concentrations determined through icELISAs.

CONCLUSION

An ICA with MD-mAb was constructed and validated. However, direct conjugation via the electrostatic adsorption of mAb-AuNPs was expected to alter the cross-reactivity of ICA, especially that of the analyte analogue Dmi.

mirifica crude extract loaded transdermal gels

In this study, permeation behaviors and chemical stability of miroestrol and deoxymiroestrol from Pueraria candollei var. mirifica (PM), Thai traditional medicine, crude extract containing transdermal gels were firstly evaluated. Three different PM extract containing gels were formulated, including hydroalcoholic and microemulsion gels using carbomer, and silicone gel using silicone elastomer. In vitro permeation through porcine ear skin demonstrated that the flux and 24 h cumulative permeation of miroestrol and deoxymiroestrol were in the order of hydroalcoholic > silicone > microemulsion gels. Hydroalcoholic gel provided the highest partition coefficient from gel onto skin, and thus the skin permeability coefficient. After 24 h permeation, no miroestrol and deoxymiroestrol remained deposited in the skin. Accelerated study using heating-cooling revealed insignificant difference between the remaining percentages of miroestrol and deoxymiroestrol in aqueous and non-aqueous based gels. Long-term stability study showed that miroestrol contents remained constant for 90 d and 30 d under 5 ± 3 °C and 30 ± 2 °C, 75 ± 5%RH, respectively; whereas the percentage of deoxymiroestrol decreased significantly after 30 d storage, irrespective of storage conditions. Acute dermal irritation test on New Zealand White rabbits showed that PM hydroalcoholic gels were non-irritant, with no signs of erythema or oedema.[Figure: see text].

Fragment antigen-binding (Fab) antibody-based lateral flow immunoassay for rapid and sensitive detection of potent phytoestrogen, deoxymiroestrol

Pueraria candollei is an ingredient of Thai herbal medicine, dietary supplements, and cosmetics. The in vitro and in vivo studies of this plant supported anti-osteoporotic activity and used for hormone replacement therapy. Deoxymiroestrol shows the most potent phytoconstituent in tuberous root of P. candollei with estrogenic activity. The quality controls are important for good agricultural practice (GAP) and good manufacturing practice (GMP) of plant-derived raw materials. The rapid detection of lateral flow immunoassay (LFIA) using colloidal gold is simply method, easy visualize detection and produce less waste than conventional chromatographic detection. In this study, LFIA for qualitative detection of deoxymiroestrol using antigen-binding fragment antibody (Fab) was developed. The result showed that the developed LFIA displays specific detection of deoxymiroestrol. Cross reactivity of this method was analyzed with miroestrol, isomiroestrol and methylisomiroestrol which showed 39.97%, 7.71% and 5.72%, respectively. After optimal condition, limit of detection (LOD) for deoxymiroestrol is 250 ng/ml. Plant samples were applied to strip test compare with indirect competitive ELISA using polyclonal antibody to confirm the application of LFIA. The results of LFIA method were comparable with those from ELISA. This developed lateral flow immunoassay can apply to detect deoxymiroestrol for the rapid testing. The developed method can use for quality control in plant samples as deoxymiroestrol is biomarker compound in P. candollei.

Kwakhurin-magnetic particles conjugates enable fast enzyme immunoassay for the detection of kwakhurin in Pueraria candollei

INTRODUCTION

Kwakhurin (Kwa) is one of the unique isoflavonoids produced in Pueraria candollei var. mirifica (P. candollei), which has long been used as folk medicine for rejuvenation in Thailand. Recently, the use of P. candollei-derived products has widely spread among Japanese women for cosmetic purposes. Correspondingly, there has been an increase in the number of reports regarding possible health hazards caused by estrogenic activity inherent to the plant; thus, the need for a detailed evaluation of the phytoestrogen content of P. candollei-derived products has gained a sense of urgency in recent years.

OBJECTIVE

This study aims to develop a rapid enzyme immunoassay that can be applied to the quantitative analysis of Kwa in P. candollei and its derived products.

MATERIAL AND METHOD

A rapid and sensitive immunoassay was developed with a combination of Kwa-specific monoclonal antibody (MAb 11F) and Kwa-magnetic particles (MPs) conjugates, which increased the surface area of the solid phase, resulting in a decrease in the immunoreaction time.

RESULT

This novel MPs-based enzyme immunoassay (MPs-EIA) was used to determine Kwa concentration in the range from 2.44 to 78.1 ng/mL with a limit of detection of 1.90 ng/mL. Validation analyses revealed that the proposed MPs-EIA protocol was sufficiently precise and accurate for effective quantitative analysis of Kwa in P. candollei and its derived products.

Quantification of methylisomiroestrol, a phytoestrogen of Pueraria candollei, by enzyme-linked immunosorbent assay in comparison with high-performance liquid chromatography

Pueraria candollei is a phytoestrogen-rich herb used to treat estrogen deficiency disorders; however, quality control of P. candollei-related health products is required for consistency of clinical outcomes. Estrogenically active (+)-7-O-methylisomiroestrol could be a potential chemical marker that facilitates the prediction of the overall estrogenic activity of P. candollei. The analytical performance of ELISA using newly produced monoclonal antibodies against methylisomiroestrol was compared with HPLC analysis. The developed indirect competitive ELISA (icELISA) was highly sensitive to methylisomiroestrol for detection, with an LOQ of 2.9 ng/mL, whereas the LOQ was 1.15 μg/mL by HPLC. The results from method validation indicated acceptable precision (1.71-6.37 % and 0.13-2.40 %) and accuracy (99.23-102.54 % and 96.84-101.88 %) of the methylisomiroestrol analysis using icELISA and HPLC. These methods were effectively applied for the determination of the methylisomiroestrol content in P. candollei samples. Apart from the plant tubers, the stem was observed as a source of methylisomiroestrol. The developed ELISA was more effective than HPLC in detecting a small quantity of methylisomiroestrol in the plant samples [0.23 × 10^-3% (w/w) to 0.628 × 10^-3% (w/w) dry weight]. Therefore, the ELISA could be a useful tool for the standardization of P. candollei, which is the crucial step to improve the quality of plant-derived products.

Expression of actively soluble antigen-binding fragment (Fab) antibody and GFP fused Fab in the cytoplasm of the engineered Escherichia coli

The expression of recombinant antibody fragments in the cytoplasmic space of Escherichia coli and the refolding process for restoring the structure and activity of such antibodies are not efficient. Herein, fragment antigen-binding (Fab) antibodies against miroestrol and deoxymiroestrol (MD-Fab) and their fusions with a green fluorescent protein (GFP) were expressed. The reactive MD-Fabs were successfully expressed as soluble and active forms in the cytoplasm of the SHuffle® T7 E. coli strain. Regarding the construct of MD-Fab alone, V_H-C_H1 could associate V_L-C_L into Fab in the oxidizing cytoplasm of the E. coli strain, and no additional in vitro refolding was needed. In the case of the fusions with GFP, when the C-terminus of V_H-C_H1 was linked with the N-terminus of GFP, the MD-Fab binding reactivity was retained, but the fluorescent activity of GFP interfered. When the C-terminus of GFP was linked to the N-terminus of V_L-C_L, the binding activity of MD-Fab was not observed. The constructed MD-Fabs had higher specificity toward deoxymiroestrol than the parental monoclonal antibody clone 12G11. In conclusion, MD-Fabs could be expressed using SHuffle® T7 E. coli cells. This process could be considered an economical, productive, and effective method to produce antibody fragments for immunoassay techniques.

Preparation of a highly specific single chain variable fragment antibody targeting miroestrol and its application in quality control of Pueraria candollei by enzyme-linked immunosorbent assay

INTRODUCTION

Miroestrol is the potent phytoestrogen isolated from White Kwao Krua (Pueraria candollei var. mirifica (Airy Shaw & Suvat.) Niyomdham, a Thai traditional medicinal plant. Nowadays, various health supplementary products featuring White Kwao Krua are available worldwide. A sensitive and rapid analytical method for quantification of miroestrol is necessary for quality control of these products.

OBJECTIVES

To prepare a single-chain variable fragment (scFv) antibody specific to miroestrol and develop a scFv-based enzyme-linked immunosorbent assay (ELISA) for quantitative analysis of miroestrol in plant materials and health supplementary products.

METHODS

A gene encoding anti-miroestrol scFv antibody was constructed and expressed in Escherichia coli SHuffle T7 strain. Anti-miroestrol scFv antibody was characterised and applied to ELISA. The developed scFv-based ELISA method was validated for its sensitivity, specificity, accuracy and precision.

RESULTS

Anti-miroestrol scFv antibody was highly specific to miroestrol. The scFv-based ELISA was applied to determine miroestrol in the range 0.06-7.81 μg/mL, with the limit of quantification of 0.06 μg/mL miroestrol. The accuracy of the assay was validated by its 95.08-103.99% recovery from the spiked miroestrol recovery experiment and in good correlation with the results from the monoclonal antibody-based ELISA. The relative standard deviation of the intra- and inter-assay were less than 6.0%.

CONCLUSION

The developed scFv-based ELISA was sensitive, specific, accurate, and precise for determination of miroestrol and useful for quality control of P. candollei plant raw materials and supplementary products.

Development of a simple and rapid method for the detection of isomiroestrol in Pueraria candollei by an immunochromatographic strip test

Pueraria candollei (P. candollei) is a traditional Thai herb widely used for estrogen replacement therapy because it contains many unique chromenes that possess potent estrogenic activity, one of which is known as isomiroestrol. Since isomiroestrol is a promising compound that is solely present in P. candollei, it can be used as an identifying marker for standardization of P. candollei. Here, we developed a lateral-flow immunochromatographic strip (ICS) test using a colloidal gold nanoparticle-conjugated anti-isomiroestrol monoclonal antibody (12C1-mAb) for the detection of isomiroestrol in plant samples and products of P. candollei. The advantages of the developed ICS over an enzyme-linked immunosorbent assay are its simplicity and rapidity, as the ICS test can be completed 15 min after dipping the strip into the analyte solution. The detectable concentration of isomiroestrol was 7.0 µg/mL. Considering the demand for the standardization of P. candollei due to concerns regarding its quality, our ICS test using isomiroestrol as an identifying marker would be effective and useful to assess the presence of isomiroestrol.

Anti-miroestrol polyclonal antibodies: a comparison of immunogen preparations used to obtain desired antibody properties

Immunogen quality is one important factor that contributes to desirable antibody characteristics. Highly specific antibodies against miroestrol can be used to develop a quality control immunoassay for Pueraria candollei products. In this study, we investigated how various immunogen preparations affect antibody properties. The results show that immunogen prepared using the Mannich reaction provides antibodies with higher specificity and sensitivity against miroestrol than immunogen prepared with the periodate reaction. The results suggest the Mannich reaction maintains the original structure of miroestrol and generates useful antibodies for developing immunoassays.