Preparation and analysis of some acetosugar esters of abscisic acid and derivatives

Abstract

Racemic abscisic acid (ABA), the cis and trans l', 4'-diols (ABA diols) derived from ABA by reduction of the 4' ketone, and the corresponding 4'-0-acetates were converted into various acetosugar esters by reaction of their cesium salts with the I-chloroacetosugars derived from glucose, galactose, lactose, and maltose. Analytical separations of the acetosugar esters using high-performance liquid chromatography (LC) on reverse-phase columns were developed. Continuous flow secondary ion mass spectra (CFSIMS) of the various acetosugar esters were obtained and an LCICFSIMS protocol employing multiple reaction monitoring was used to detect ABA acetoglucose ester in an acetylated extract obtained from plant cells that had been treated with ABA.Key words: abscisic acid, acetosugar esters, synthesis, chromatography, mass spectrometry. Fig. 1) is a plant growth regulator that has also been implicated in a variety of stress-related responses (1). Several metabolites of endogenous and exogenously added ABA have been isolated and identified, including the reduction products, cis and trnrzs ABA l', 4'-diols (2-5); the oxidized derivative, phaseic acid (6-8); and the glucose esters (P-D-glucose, C-1-linked) of ABA and the aformentioned compounds (Fig. 1) (9-12). There has also been a report of the detection of a maltose ester of ABA (13).We were interested in following ABA metabolism, and in developing analytical methods to facilitate our studies; in particular, we sought to extend the utility of liquid chromatography-continuous flow secondary ion mass spectrometry (LC/ CFSIMS), which we had earlier used to detect ABA glucose ester in a plant extract (14), to other ABA-derived conjugates, which we felt were potential metabolites. To achieve these objectives, samples of potential metabolites or suitable derivatives thereof were required as standards.Previously, ABA glucose ester (P anomer) had been prepared by reaction of ABA (cesium or triethyl ammonium salt) with a-bromoacetoglucose followed by deacetylation of the intermediate acetoglucose ester with an enzyme preparation derived from sunflower seeds (Helianthus arirzus) (15, 16). ABA diols had been prepared by sodium borohydride reduction of ABA methyl ester, which yielded a mixture rich in both the 1', 4'-cis and -trans diols (17).To further extend earlier synthetic efforts as well as the use of LCICFSIMS in analysis of metabolite mixtures, we report here the preparation of various acetosugar derivatives of ABA (and deuterated ABA) and the diols, and acetylated diols of ABA, and the development of LC and LCICFSIMS protocols using these derivatives. The acetosugar derivatives were easily prepared and possessed good stability. Some deuterated analogs were prepared as an aid in assigning fragments in the mass spectrum and for potential use as internal standards. As an example of the utility of the developed protocol, a sample plant extract was analyzed.

Abscisic acid metabolism and lipid accumulation of a cell suspension culture of Lesquerella fendleri

“…indicate that exogenously applied ABA is taken up, metabolized by the L. fendleri cell culture and released/excreted back into the media. At the same time, this system presents a novel source of ABA-GE, which otherwise must be produced synthetically, with a low overall yield of 29 % (Balsevich et al 1996). This is particularly important for preparative purposes, since biotransformation of either (+) or (-)-ABA in Zea mays L. cv.…”

Engineering strategies for enhanced 1′, 4′-trans-ABA diol production by Botrytis cinerea

“…3 ). The structure of this substance is similar to ABA, and it has been reported to be a precursor substance for the synthesis of ABA [ 40 ].

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Non-lethal freezing effects on seed degreening in Brassica napus

“…The following chemicals were prepared as described previously: (+)-ABA and (-)-PA (Balsevich et al 1994), S-(+)-[8¢,8¢,8¢,9¢,9¢,9¢]-hexadeutero-ABA (d 6 -ABA) (Lamb et al 1996), (+)-7¢-hydroxy ABA (7¢-HOABA) (Nelson et al 1991), S-(+)-[8¢,8¢,8¢]-trideutero-ABA (d 3 -ABA) (Rose et al 1997), [7¢,7¢,7¢]-trideutero-PA (d 3 -PA) (Balsevich et al 1994), neoPA , DPA (Zeevaart and Milborrow 1976) and ABA-GE (Balsevich et al 1996). Seed extraction and purification used a rapid extraction method described previously .…”