Effect of phenyl substitutents in benzyl quaternary ammonium derivatives of (+)-limonene on plant growth-retardant activity

Abstract

The growth-retardant activity of 26 benzyl quaternary ammonium derivatives of (+)-limonene was evaluated using two bioassays, one based on the root growth of cucumber seed and the other on total fresh weight increase of alfalfa seeds exposed to dilute aqueous solutions of each compound. Inhibition of human blood serum cholinesterase was also determined manometrically. A highly significant correlation between serum cholinesterase inhibition and plant growth retardation found for 24 compounds on cucumber and 22 compounds on alfalfa suggests that these derivatives retard plant growth by inhibition of an enzyme system associated with a growth process. Electron withdrawing groups on the benzene ring, such as nitro and cyano, caused inactivation. A chloro group at 2 or 4 produced more activity than substitution at position 3. Monobromo and monomethyl derivatives substituted at 2 and 3 were equally active, while substitution at C-4 approximately doubled activity. The disubstituted chloro and methyl benzyl compounds were all highly active, regardless of the positions of these groupings.he ability of certain quaternary ammonium compounds to reduce stem elongation of bean plants without caus-T ing abnormal, formative changes was first reported by Mitchell et al. (1949). One of the most active compounds was a quaternary ammonium carbamate, designated Amo-1618(4-hydroxyl-5-isopropyl -2 -methylphenyltrimethylatnmonium chloride, 1-piperidine carboxylate), prepared from the terpene thymol by R. L. Shriner at the University of Illinois. Much work has been done on the synthesis and testing of derivatives ofAmo-l618 (Krewson et al., 1959). Knight et al. (1969) have studied the influence on plant growth-retardant activity of various substituents of aryl quaternary ammonium, phosfonium, and sulfonium compounds. 3-Chloro-and 4-chloro-benzyltributyl ammonium bromides were the most active compounds.The plant growth-retardant activity of six benzyl quaternary ammonium derivatives synthesized from the terpene (+)-limonene, found abundantly in citrus peel oil, has been reported (Newhall and Pieringer, 1966). The effect of chain length in n-alkyl quaternary ammonium derivatives of (+)-limonene on plant growth has also been studied (Pieringer and Newhall, 1968). Two additional benzyl quaternary ammonium compounds, prepared from (+)-limonene, have been reported (Newhall and Pieringer, 1969), and their effect on the growth of citrus described (Pieringer and Newhall, 1970).All of these limonene derivatives have somewhat different structural requirements for plant growth-retardant activity than other known growth regulants. A highly significant correlation between the plant growth-retardant activities of Florida Citrus Experiment Station, IFAS, Lake Alfred, Fla. 33850 these compounds and their ability to function as inhibitors of human blood serum (pseudo) cholinesterase has been demonstrated (Newhall, 1969).In the present study, 18 additional, new, substituted benzyl quaternary ammonium derivatives of (+)-limonene were synthesized both to det...

Studies on plant growth‐regulating substances. XXIX. The plant growth‐retarding properties of certain quaternary ammonium halides

“…The present results are, in general, similar to those obtained with the benzylnicotinium salts (I) (Mitchell et al 1949), the benzyl quaternary ammonium derivatives of ( + )-limonene (V) (Newhall, 1971), the benzyltri-n-butylammonium salts (IV) (Knight et al 1969) and the benzyltri-n-butylphosphonium salts (Cathey, 1964) in all of which compounds substituted in the 2-and/or 4-positions of the benzyl group are the most active. In their work on the benzyltri-n-butylammonium bromides, however, Knight et al (1969) suggested that a substituent in the 4-position might be essential for activity.…”

Properties of Kaurene Synthetase from Marah macrocarpus

“…The plant growth retardant Amo-1618 and several synthetic quaternary ammonium derivatives of limonene exhibited a good correlation between their activities as plant growth retardants and pseudocholinesterase inhibitors (19,20). Experiments by Riov and Jaffe (16,24,25) led them to suggest that acetylcholine might serve as an endogenous plant growth retardant.…”

Mode of action of 2-hydroxycyclohexyl quaternary ammonium plant regulators

“…Concentrations of test compounds giving 50% enzyme inhibition or 50% growth retardation are recorded as /50's in millimoles per liter (mM). These /50 values were determined from semilog plots of concentration against enzyme inhibition or growth retardation as previously described (Newhall, 1971).…”

“…They also have shown an excellent correlation between bean ChE inhibition and retardation of the growth of secondary bean roots for a number of plant growth regulators (Riov and Jaffe, 1973c). A correlation has been reported between growth retardant activity and serum ChE inhibition for a series of quaternary ammonium derivatives of (+)-limonene (Newhall, 1969(Newhall, , 1971.…”