Synthesis and characterization of bio-based quaternary ammonium salts with gibberellate or l-tryptophanate anion

Abstract

Numerous biologically active acids can be transformed into an ionic form in a facile way and combined with appropriate quaternary ammonium cation to improve their application properties or biological activity. This study describes the synthesis of new quaternary ammonium salts with anions of gibberellic acid, a common plant growth regulator from the gibberellin group, or l-tryptophan, an important precursor of auxin biosynthesis. The surface-active tetrapentylammonium ion and natural substances such as acetylcholine, choline, and quinine were the sources of cations. Novel salts of gibberellic acid and l-tryptophan were obtained with high yields exceeding 97% as a result of the metathesis reaction or the neutralization of quaternary ammonium hydroxides. Phase transition temperatures, thermal and chemical stability, and solubility in solvents with different polarities were determined for all obtained salts. On the basis of studies regarding the influence of synthesized salts on the post-harvest longevity and quality of leaves of Convallaria majalis, it was established that the biological activity of the natural plant regulators in most cases was maintained. Therefore, it can be concluded that the conversion of the active substance into the form of a quaternary ammonium salt results in obtaining novel forms of plant growth regulators with favourable physicochemical properties while maintaining the efficacy of the biological active ingredients. Graphic abstract

Conversion of l‐Tryptophan Derivatives into Biologically Active Amino Acid Ionic Liquids

“…The increase in the concentration of active substances decreased biological activity, as reported in our previous studies. [38,41] AAIL 15 at a concentration of 0.5 ppm showed an efficiency that was over 10 % higher than that of the control (in standard cultivated hydroponic plants). Subsequent biological tests were performed for salts 2-5 and 14-18 by using an active substance concentration of 0.5 ppm.…”

“…The best method so far used by us to prevent the decomposition of the obtained salts were stored them in UV blocking vacuum desiccator over P 4 O 10 at 20°C. [38] Thermal analysis…”

“…Note that the lower the molecular weight of the salt is, the higher the thermal stability of the compound, as described in the literature. [34] The highest thermal stability (211°C) was shown by QAS with a tetramethylammonium cation (1), while the [a] -literature decomposition temperature of 5 % sample 181.7°C, [34] [b] -literature glass transition temperature À 12°C, [36] [c] -data from reference, [38] T m -melting point; T c -temperature of crystallization; T g -glass transition temperature; T 5% -decomposition temperature of 5 % sample. lowest thermal stability (146°C) was exhibited by AAIL 18 with the longest alkyl substituent (behentrimonium).…”

“…According to the literature, only small amounts of l-tryptophan are soluble in water (11 g per 1 L water), hot alcohol, dilute acid and hydroxide solutions. [43,38]…”

Bifunctional Double-Salt Ionic Liquids Containing both 4-Chloro-2-Methylphenoxyacetate and l-Tryptophanate Anions with Herbicidal and Antimicrobial Activity

“… 17 A convenient method of obtaining ammonium salts with an l -tryptophanate anion, which shows plant growth regulation activity and improved physicochemical properties, was described in previous reports. 18 , 19 Herbicidal ionic liquids (HILs) are a new approach to known bioactive compounds. The latest reviews outline the broad scope of this research topic, which provides numerous opportunities that still lie ahead of researchers in this field.…”