Design and Synthesis of Hapten for Paclobutrazol

Paclobutrazol (PBZ) is a kind of plant growth regulator that belongs to the triazole chemical group. It is a racemic mixture of the (2R, 3R) and (2S, 3S) enantiomers that display some fungicidal activity. A hapten is a small molecule that can bind to a specific antibody but isn’t immunogenic by itself. They could be modified to be immunogenic by conjugation to a large carrier molecule. With an unrelenting drive in the life-science industry, Creative Biolabs has developed rapid, sensitive, and efficient platforms to accelerate antigen preparation and to optimize antibody production. In particular, we’d like to offer multiple cost-effective solutions for global scientists to synthesis high-quality paclobutrazol haptens and also provide various suitable carriers according to clients’ project requirements.

Introduction to Paclobutrazol

(R,R)-paclobutrazol is a (2RS, 3RS)-1-(4-chlorophenyl)-4, 4-dimethyl-2-(1H-1, 2, 4-trizol-1-yl)-pentan-3-ol in which both stereocenters have R configuration. It is an enantiomer of a (S,S)-paclobutrazol and belongs to the triazole family. Paclobutrazol comprises a triazole ring and a benzene ring-chloro coupled to a carbon chain open. It is a plant growth regulator, a cell elongation, and an internode extension inhibitor broadly applied in many farm crops to produce fruit throughout the year by retarding gibberellin (GA) synthesis, a hormone responsible for vegetative plant growth. In reality, studies are manifesting that paclobutrazol remains active in the soil for a long-term time, which has impacts on the growth and development of subsequent crops by impairing plant vigor. This compound also shows a certain level of fungicidal activity because of its capacity as a triazole to inhibit sterol biosynthesis.

The chemical structure of paclobutrazol. Fig.1 The chemical structure of paclobutrazol.

Hapten Design &Synthesis Services at Creative Biolabs

The concept of hapten stems from the Greek, meaning “to fasten.” It can be tightly linked to a carrier molecule, most often a protein, by a covalent bond. The hapten-carrier complex can induce the production of antibodies and becomes immunogenic to elicit an immune response, which the unbound hapten cannot do. Then, the hapten reacts specifically with the antibodies produced against it to generate an immune or allergic response. At Creative Biolabs, we have extensive expertise in artificial antigen preparation and provide multiple strategies for hapten design and synthesis.

A general synthetic route of paclobutrazol antigen. Fig.2 A general synthetic route of paclobutrazol antigen. (Xu, 2019)

Cross-reactivity of Anti-paclobutrazol Antibody

The IC50 value and cross-reactivity of paclobutrazol and other triazole compounds have been reported. Despite most triazole fungicides contain the same moieties (a 1,2,4-triazolyl group and a mono- or dichlorinated phenyl group), the cross-reactivity of anti-paclobutrazol antibodies with uniconazole is about 0.7% and with triadimefon is less than 0.2%. No inhibition is found up to 4000 ng/mL of the other analogs, including difenoconazole, cyproconazole, epoxiconazole, flutriafol, propiconazole, triadimenol, triadimefon, hexaconazole, tebuconazole, and tricyclazole. The evidence suggests that 1,2,4-triazolyl group isn’t the major part of antibody recognition.


  • One-stop, customer-tailed services for paclobutrazol hapten design and synthesis
  • Extensive expertise in artificial antigen preparation and anti-hapten antibody production
  • Cost-effective, time-saving technical platforms offer clients high-quality hapten-carrier complexes with low price

Many small molecular compounds in nature have stimulated inspiration to the pharmaceutical industry for the development of novel and effective antibody drugs based on their structural characteristics. As a well-known expert and a reliable partner in the biotechnology field, Creative Biolabs has launched a series of rapid and sensitive strategies to design available hapten-carrier conjugates and introduces the best solutions for paclobutrazol hapten synthesis. If you’re interested in our services, please don’t hesitate to contact us or directly send us an inquiry.


  1. Xu, C.L.; et al. Food Immunoassay. FOOD SCI NUTR. 2019.
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