Abscisic acid analogs with a geometrically rigid conjugated acid side-chain.

The plant hormone abscisic acid (ABA) plays a central role in adaptive responses to abiotic stresses that adversely affect crop growth and productivity. However, ABA photoinstability limits its use in agriculture. To overcome this drawback, in this study, we developed photostable ABA analogues, the (+)-BP2A compound series (compounds 5–9), in which the dienoic acid side chain of ABA was replaced with phenylacetic acid. All BP2A analogues showed higher stability against UV-B irradiation at 302 nm than ABA, and compounds 6 and 7 barely decomposed even under sunlight. In physiological assays, (+)-BP2A and (+)-compound 7, in which the α,β-unsaturated carbonyl group of BP2A was reduced, exhibited ABA-like activities, including inhibition of seed germination and induced drought tolerance in Arabidopsis. Biochemical studies revealed that (+)-compound 7, unlike (+)-BP2A, did not activate pyrabactin resistance-like (PYL) receptors in vitro and was converted to (+)-BP2A in plants, suggesting that it functions as a prodrug PYL agonist. Furthermore, (+)-compound 7 inhibited seed germination of tomato, lettuce, and rice. Thus, this compound represents a potential plant growth regulator that induces ABA-type responses in agricultural fields.

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Photostable Abscisic Acid Agonists with a Geometrically Rigid Cyclized Side Chain

Takeuchi

Mimura

Ohnishi

et al. 2022

“…Many efforts have been made to keep the bioactivity of ABA and reduce its photosensitivity, − such as replacing the double bond or hydrogen in Δ 2 (the location of the double bond) of the ABA side chain to a benzene ring and cyclopropyl or fluorine to relieve cis – trans isomerization. However, the bioactivities of these new compounds were much less than that of ABA.…”

Section: Introductionmentioning

confidence: 99%

Lignosulfonate Improves Photostability and Bioactivity of Abscisic Acid under Ultraviolet Radiation

Gao

Tao

et al. 2017

Abscisic acid (ABA), as a commonly used plant growth regulator, is easy to be degraded and lose its bioactivity under sunshine. To select an eco-friendly and efficient photoprotectant for the improvement of photostability and bioactivity of ABA when exposed to ultraviolet (UV) light, we tested the effects of three biodegradable natural-derived high polymers, sodium lignosulfonates 3A [molecular weight (MW) > 50000, with degree of sulfonation (DS) of 0.48] and NA (20000 < MW < 50000, with DS of 0.7) and calcium lignosulfonate CASA (MW < 20000, with DS of 0.7), on the photodegradation of ABA. Lignosulfonates 3A, NA, and CASA showed significant photostabilizing capability on ABA. Lignosulfonate 3A showed preferable photostabilizing effects on ABA compared to CASA, while NA showed an intermediate effect. That indicated that lignosulfonate with a high MW and low DS had a stronger UV absorption and the hollow aggregate micelles formatted by lignosulfonate protect ABA from UV damage. Approximately 50% more ABA was kept when 280 mg/L ABA aqueous solution was irradiated by UV light for 2 h in the presence of 2000 mg/L lignosulfonate 3A. The bioactivity on wheat (JIMAI 22) seed germination was greatly kept by 3A in comparison to that of ABA alone. The 300 times diluent of 280 mg/L ABA plus 2000 mg/L 3A after 2 h of irradiation showed 20.8, 19.3, and 9.3% more inhibition on shoot growth, root growth, and root numbers of wheat seed, separately, in comparison to ABA diluent alone. We conclude that lignosulfonate 3A was an eco-friendly and efficient agent to keep ABA activity under UV radiation. This research could be used in UV-sensitive and water-soluble agrichemicals and to optimize the application times and dosages of ABA products.

“…Remarkably, also enynes showed an excellent receptor fit ensuring the same distance between essential functional groups. Furthermore, phenyl groups have been introduced to replace or stabilize the ( E , Z )-diene side chain at positions C-3/4/5 ( 20 ), , or positions C-2/3 ( 21 ) , adding rigid motifs to the target molecules (Figure ). Likewise, the ( Z )-double bond at positions C-2/3 has been incorporated into a cyclohexene ring ( 22 ), while the ( E , Z )-diene moiety could also be replaced by an isosteric amide bridge ( 23 ) via peptide coupling of a suitable amino acid with an intermediate cyclohexenoneacetic acid .…”

Section: Abscisic Acidmentioning

confidence: 99%

Inspired by Nature: Isostere Concepts in Plant Hormone Chemistry

Frackenpohl

Abel

Alnafta

et al. 2023

Chemical concepts such as isosteres and scaffold hopping have proven to be powerful tools in agrochemical innovation processes. They offer opportunities to modify known molecular lead structures with the aim to improve a range of parameters, including biological efficacy and spectrum, physicochemical properties, stability, and toxicity. While recent biochemical insights into plant-specific receptors and signaling pathways trigger the discovery of the first lead structures, the disclosure of such a new chemical structure sparks a broad range of synthesis activities giving rise to diverse chemical innovation and often a considerable boost in biological activity. Herein, recent examples of isostere concepts in plant-hormone chemistry will be discussed, outlining how synthetic creativity can broaden the scope of natural product chemistry and giving rise to new opportunities in research fields such as abiotic stress tolerance and growth promotion.