A New Fluorescence Detection Method for Tryptophan- and Tyrosine-Derived Allelopathic Compounds in Barley and Lupin

Abstract

Barley (Hordeum vulgare) is one of the most widely cultivated crops for feedstock and beer production, whereas lupins (Lupinus spp.) are grown as fodder and their seeds are a source of protein. Both species produce the allelopathic alkaloids gramine and hordenine. These plant-specialized metabolites may be of economic interest for crop protection, depending on their tissue distribution. However, in high concentrations they pose a health risk to humans and animals that feed on them. This study was carried out to develop and validate a new method for monitoring these alkaloids and their related metabolites using fluorescence detection. Separation was performed on an HSS T3 column using slightly acidified water-acetonitrile eluents. Calibration plots expressed linearity over the range 0.09–100 pmol/µL for gramine. The accuracy and precision ranged from 97.8 to 123.4%, <7% RSD. The method was successfully applied in a study of the natural range of abundance of gramine, hordenine and their related metabolites, AMI, tryptophan and tyramine, in 22 barley accessions and 10 lupin species. This method provides accurate and highly sensitive chromatographic separation and detection of tryptophan- and tyrosine-derived allelochemicals and is an accessible alternative to LC-MS techniques for routine screening.

Biosynthesis of the allelopathic alkaloid gramine in barley by a cryptic oxidative rearrangement

“…Among the 20 barley lines included in the pan-genome v1 ( 13 ), six do not contain gramine ( 1 ) or contain only traces, whereas the others produce gramine ( 1 ) in the range of 700 to 6600 pmol/mg fresh weight (FW) in the leaves ( 15 ) (Fig. 2B).…”

“…We chose the model plant A. thaliana because of the ease of the genetic transformation system that is available. After stable transformation, selected T1 plants constitutively expressing the genes AMIS , NMT , or a combination of both were tested for the presence of AMI ( 3 ) and gramine ( 1 ) by reversed-phase ultraperformance liquid chromatography fluorescence detection (RP-UPLC-FLD) ( 15 ). More than 88% ( N = 82) of the herbicide-resistant progeny of all plants transformed with the AMIS construct ( N = 92) exhibited AMI ( 3 ) concentrations above the limit of quantification.…”

Metabolic Activation and Cytotoxicity of Gramine Mediated by CYP3A in Rats

“…Plant-derived allelopathic compounds have become new generation pesticides, thereby reducing the environmental stress caused by synthetic chemicals. , As a result, the secondary metabolites produced by plants are widely distributed in aquatic environments and land. , Some are toxic and have harmful effects on organisms in the environment. , GRM, a natural alkaloid obtained from Gramineae plants, has a wide application for pest control and drug development. , The alkaloid has been reported to be extensively present in agricultural land and groundwater. , Acute mortality of domestic animals has occurred through consumption of plants containing this compound. , The resistance of GRM to degradation has a negative impact on human health. Elucidation of the mechanism of hepatotoxicity caused by exposure to GRM is of great significance.…”

“…Gramine (GRM), an indole alkaloid occurring in Gramineae plants, also exhibits various pharmacological effects such as anti-inflammatory, antibacterial, antitumor, vasodilator, and bronchial smooth muscle modulator. − Its derivatives have a great potential to be developed to varieties of pharmaceutical agents. − In particular, GRM is a new biopesticide used to prevent brown planthoppers . Although the biopesticide has less impact on crop production than conventional pesticides, its environmental distribution has drawn public attention, due to potential environmental safety issues concerned . A survey by Swiss academics showed that GRM has been detected in the surface water around agricultural fields and grasslands, with a maximum concentration of 55 ng/mL and an average concentration of 15 ng/mL .…”