Abstract
2′,3′-iso-Benzoabscisic acid (iso-PhABA), an excellent selective abscisic acid (ABA) analog, was developed in our previous work. In order to find its more structure-activity information, some structural modifications were completed in this paper, including the substitution of phenyl ring and replacing the ring with heterocycles. Thus, 16 novel analogs of iso-PhABA were synthesized and screened with three bioassays, Arabidopsis and lettuce seed germination and rice seedling elongation. Some of them, i.e., 2′,3′-iso-pyridoabscisic acid (iso-PyABA) and 2′,3′-iso-franoabscisic acid (iso-FrABA), displayed good bioactivities that closed to iso-PhABA and natural (+)-ABA. Some others, for instance, substituted-iso-PhABA, exhibited certain selectivity to different physiological process when compared to iso-PhABA or (+)-ABA. These analogs not only provided new candidates of ABA-like synthetic plant growth regulators (PGRs) for practical application, but also new potential selective agonist/antagonist for probing the specific function of ABA receptors.
Highlights
Some solid findings were established by the discussion of structure-activity relationship
The bioactivity of substituted-iso-aryl-abscisic acid (ABA) decreased with an increased size of group in the aryl ring
Substituted-iso-PhABA 4b–4d observed highest IC50 values for the rice seedlings elongation, which was the most efficient assay for the control agents. These results indicated that these analogs might have selectivity and preference to different ABA receptors
Summary
The crucial role of abscisic acid (S-(+)-ABA 1, Figure 1) as a phytohormone in a wide variety of physiological processes of plants, including inhibiting or promoting growth, maintaining bud and seed dormancy, affecting flowering and sex differentiation, as well as conducting environmental stresses response [1,2,3,4,5,6,7,8], motivates numerous scientific investigations into the agricultural application of ABA.the widely using of abscisic acid (ABA) has been hindered by its rapid metabolism in plants and light isomerization in vitro [9,10,11,12,13,14,15,16,17]. Methoxyl [18], alkynyl [19], or fluorine atoms [20,21] at the 80 or 90 -positionm and halogen atoms [22,23] at the 30 -position had been introduced to avoid 80 -hydroxylation and Michael addition, and the corresponding analogs displayed excellent ABA-like activities. They are too expensive to practical use in field due to their complicated synthetic routes. A successful case of 80 -hydroxylation resistant analog was 20 ,30 -benzoabscisic acid 2 [24,25]
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