Immunochromatographic assay for the detection of kwakhurin and its application for the identification of Pueraria candollei var. mirifica (Airy Shaw & Suvat.) Niyomdham

Development and characterisation of highly specific monoclonal antibody-based immunoassays for the detection and quantification of genistein-7-O-[α-rhamnopyranosyl-(1→6)]-β-glucopyranoside in Derris scandens (Roxb.) Benth

INTRODUCTION

The stem of the plant species Derris scandens (Roxb.) Benth. (DS) contains genistein-7-O-[α-rhamnopyranosyl-(1→6)]-β-glucopyranoside (GTG), which is a unique marker. Previous analyses of GTG using antibody-based immunoassays were compromised because of their high cross-reactivity with structurally related compounds of DS, thereby limiting their applicability in DS quality control.

OBJECTIVE

Conjugation of GTG with carrier proteins was achieved using the Mannich reaction to produce a highly specific monoclonal antibody (mAb) targeting GTG (anti-GTG mAb).

METHODS

The anti-GTG mAb was generated using hybridoma technology and characterised using an indirect competitive enzyme-linked immunosorbent assay (icELISA). Both lateral-flow immunoassay (LFIA) and icELISA were developed to detect and quantify GTG in DS raw materials and associated products.

RESULTS

icELISA using the anti-GTG mAb showed 100% specificity for GTG, with only 1.77% cross-reactivity with genistin and less than 0.01% cross-reactivity with other compounds. icELISA demonstrated a linear range for GTG determination between 62.5 and 2000 ng/mL. The limits of detection (LOD) and quantification were 49.68 and 62.50 ng/mL for GTG, respectively. The precision of the analysis ranged from 1.28% to 4.20% for repeatability and from 1.03% to 7.05% for reproducibility. The accuracy of the analysis ranged from 101.97% to 104.01% for GTG recovery. GTG levels determined via icELISA were consistent with those confirmed via high-performance liquid chromatography (HPLC) (R2 = 0.9903). Moreover, the LOD of LFIA for GTG was 500 ng/mL.

CONCLUSION

Immunoassays utilising specific anti-GTG mAbs were successfully developed, including LFIA for rapid GTG detection and icELISA for GTG quantification.

Bioimprinting as a Receptor for Detection of Kwakhurin

Bioimprinting was performed against ovalbumin (OVA) to confer its binding cavities for kwakhurin (Kwa), an isoflavonoid, produced solely by Pueraria candollei var. mirifica (P. candollei). The characterization of bioimprinted-OVA (biOVA), evaluated by an enzyme-linked immunosorbent assay (ELISA), revealed that it functioned as a specific receptor for Kwa. Using biOVA, two systems, i.e., an indirect competitive ELISA (icELISA) and the even simpler and more rapid competitive enzyme-linked bioimprinted-protein assay (cELBIA), were developed as novel techniques for the quantitative analysis of Kwa in P. candollei and its related products. The two analysis methods were found to have limits of detection (LOD) of 4.0 and 2.5 µg/mL, respectively. The high reliability of the developed icELISA and cELBIA using biOVA was also demonstrated by various validation analyses. Subsequently, bioimprinting was performed using eight other proteins to investigate them as candidate scaffolds for the generation of binding cavities for Kwa. Interestingly, two bioimprinted-IgG monoclonal antibodies (biMAbs) recognized Kwa, but their original binding affinity to hapten was lost. That is, the MAbs obtained a new binding ability to Kwa in exchange for their original binding affinity, raising the possibility that biMAb could be alternatively used as a probe for the quantitative analysis of Kwa as well as biOVA. This is the first report of small molecules recognition by MAbs used as proteins for bioimprinting.

Lateral flow immunoassay for small-molecules detection in phytoproducts: a review

Phytoproducts are involved in various fields of industry. Small-molecule (Mw < 900 Da) organic compounds can be used to indicate the quality of plant samples in the perspective of efficacy by measuring the necessary secondary metabolites and in the perspective of safety by measuring the adulterant level of toxic compounds. The development of reliable detection methods for these compounds in such a complicated matrix is challenging. The lateral flow immunoassay (LFA) is one of the immunoassays well-known for its simplicity, portability, and rapidity. In this review, the general principle, components, format, and application of the LFA for phytoproducts are discussed.

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.