title: Tyramine Pathways in Citrus Plant Defense: Glycoconjugates of Tyramine and Its N-Methylated Derivatives.
abstract: Glucosylated forms of tyramine and some of its N-methylated derivatives are here reported for the first time to occur in Citrus genus plants. The compounds tyramine-O-β-d-glucoside, N-methyltyramine-O-β-d-glucoside, and N,N-dimethyltyramine-O-β-d-glucoside were detected in juice and leaves of sweet orange, bitter orange, bergamot, citron, lemon, mandarin, and pomelo. The compounds were identified by mass spectrometric analysis, enzymatic synthesis, and comparison with extracts of Stapelia hirsuta L., a plant belonging to the Apocynaceae family in which N,N-dimethyltyramine-O-β-d-glucoside was identified by others. Interestingly, in Stapelia hirsuta we discovered also tyramine-O-β-d-glucoside, N-methyltyramine-O-β-d-glucoside, and the tyramine metabolite, N,N,N-trimethyltyramine-O-β-glucoside. However, the latter tyramine metabolite, never described before, was not detected in any of the Citrus plants included in this study. The presence of N-methylated tyramine derivatives and their glucosylated forms in Citrus plants, together with octopamine and synephrine, also deriving from tyramine, supports the hypothesis of specific biosynthetic pathways of adrenergic compounds aimed to defend against biotic stress.
authors.affiliation: Department of Biochemistry, Biophysics and General Pathology, Università degli Studi della Campania "Luigi Vanvitelli" , via L. De Crecchio 7, 80138, Naples, Italy.
authors.forename: Luigi
authors.identifier: http://orcid.org/0000-0002-9728-522X
authors.initials: L
authors.lastname: Servillo
authors.affiliation: Stazione Sperimentale per le Industrie delle Essenze e dei derivati dagli Agrumi, Azienda Speciale della Camera di Commercio di Reggio Calabria , Via Generale Tommasini 2, 89127 Reggio Calabria, Italy.|Ministero dello Sviluppo Economico , Via Molise 2, Roma, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Castaldo
authors.affiliation: Department of Biochemistry, Biophysics and General Pathology, Università degli Studi della Campania "Luigi Vanvitelli" , via L. De Crecchio 7, 80138, Naples, Italy.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Giovane
authors.affiliation: Department of Biochemistry, Biophysics and General Pathology, Università degli Studi della Campania "Luigi Vanvitelli" , via L. De Crecchio 7, 80138, Naples, Italy.
authors.forename: Rosario
authors.initials: R
authors.lastname: Casale
authors.affiliation: Department of Biochemistry, Biophysics and General Pathology, Università degli Studi della Campania "Luigi Vanvitelli" , via L. De Crecchio 7, 80138, Naples, Italy.
authors.forename: Nunzia
authors.initials: N
authors.lastname: D'Onofrio
authors.affiliation: Stazione Sperimentale per le Industrie delle Essenze e dei derivati dagli Agrumi, Azienda Speciale della Camera di Commercio di Reggio Calabria , Via Generale Tommasini 2, 89127 Reggio Calabria, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Cautela
authors.affiliation: Department of Biochemistry, Biophysics and General Pathology, Università degli Studi della Campania "Luigi Vanvitelli" , via L. De Crecchio 7, 80138, Naples, Italy.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Balestrieri
mesh_terms: D029062:Apocynaceae / Q000737:chemistry / Q000276:immunology; D002957:Citrus / Q000737:chemistry* / Q000276:immunology; D005638:Fruit / Q000737:chemistry / Q000276:immunology; D006001:Glycoconjugates / Q000737:chemistry* / Q000276:immunology; D008745:Methylation; D015394:Molecular Structure; D010936:Plant Extracts / Q000737:chemistry* / Q000276:immunology; D014439:Tyramine / Q000737:chemistry* / Q000276:immunology
chemical_list: D006001:Glycoconjugates; D010936:Plant Extracts; D014439:Tyramine
keywords: Citrus plant; N-methyltyramine-glucoside; Stapelia hirsuta; biotic stress; candicine-glucoside; hordenine-glucoside; tyramine-glucoside