PROHEXADIONE

Prohexadione (BX-112 free acid) is a plant growth regulator. Prohexadione inhibits gibberellin biosynthesis of plants[1][2].

ChEBI: Prohexadione is a 4-oxo monocarboxylic acid that is cyclohexanecarboxylic acid which is substituted by oxo groups at positions 3 and 5, and by a propanoyl group at position 4. A plant growth regulator, it is used (commonly as the corresponding calcium salt, known as prohexadione-calcium) as an anti-lodging agent in small-grain cereals. It has a role as an agrochemical, a plant growth regulator and a gibberellin biosynthesis inhibitor. It is a 4-oxo monocarboxylic acid and a beta-triketone. It is a conjugate acid of a prohexadione(2-).

Prohexadione is commonly produced and used as its calcium salt. Its commercial production is via an improved two-step synthesis that enhances yield and environmental efficiency. The process begins with a direct C-alkylation of ethyl 3-hydroxy-5-oxocyclohex-3-ene-1-carboxylate using propionyl chloride in the presence of bases like triethylamine and catalysts such as DMAP, avoiding the traditional O-alkylation route. This yields ethyl 3,5-dioxo-4-propionyl-cyclohexanecarboxylate, which is then hydrolysed and reacted with calcium hydroxide to form prohexadione-calcium. The method eliminates the need for column chromatography, reduces effluent generation, and achieves high purity (>96%) and yield (>65%), making it commercially viable and environmentally friendly.

Growth retardent. Gibberellin biosynthesis inhibitor.

This plant growth regulator (FWfree-acid = 178.19 g/mol), also named 3- hydroxy-5-oxo-4-propionylcyclohex-3-ene-1-carboxylic acid, inhibits the biosynthesis of growth active gibberellins (GAs), thereby reducing longitudinal shoot growth. Prohexadione resembles 2-oxoglutaric acid, the co-substrate the dioxygenases that catalyze hydroxylation steps in late stages of GA biosynthesis. Its primary target of is 3b hydroxylation, thereby reducing levels of GA1 (the highly active form) and bringing about theaccumulation of its immediate precursor (inactive). Targets: flavanone 3-dioxygenase flavonol synthase; and gibberellin biosynthesis.

[1] Paulson GS, et al. Effect of a plant growth regulator prohexadione-calcium on insect pests of apple and pear. J Econ Entomol. 2005 Apr;98(2):423-31. DOI:10.1093/jee/98.2.423
[2] Vavilala DT, et al. Prohexadione, a plant growth regulator, inhibits histone lysine demethylases and modulates epigenetics. Toxicol Rep. 2014 Nov 4;1:1152-1161.
[3] Feng N, et al. Prohexadione-calcium alleviates saline-alkali stress in soybean seedlings by improving the photosynthesis and up-regulating antioxidant defense. Ecotoxicol Environ Saf. 2021 Sep 1;220:112369. DOI:10.1016/j.ecoenv.2021.112369
[4] McGrath MJ, et al. Evidence that prohexadione-calcium induces structural resistance to fire blight infection. Phytopathology. 2009 May;99(5):591-6. DOI:10.1094/PHYTO-99-5-0591

Plant Growth Regulator