title: Inuloxins A-D, phytotoxic bi-and tri-cyclic sesquiterpene lactones produced by Inula viscosa: potential for broomrapes and field dodder management.
abstract: Four phytotoxic bi- and tri-cyclic sesquiterpene lactones, named inuloxins A-D, were isolated together with the known α-costic acid, from the aerial parts of Inula viscosa (family Asteraceae), a widespread Mediterranean plant well known for its content of pharmacologically active metabolites. The structures of inuloxins A-D were established by spectroscopic and chemical methods and determined to be: (4E,7R*,8R*,10S*)-3-oxo-germacra-4,11(13)-dien-8β-12-olide (A), its 11,13-dihydro analogue (B), (5R*,7R*,8R*,10R*)-1,15-methylene-5β-hydroxy-eudesm-1(15),11(13)-dien-8β-12-olide (C), and (7R*,8R*)-1,4-dimethyl-4-hydroxy-secoeudesm-5(10),11(13)-dien-8β-12-olide (D). The S absolute stereochemistry at C-5 of 5-hydroxyhexan-2-yl side chain of inuloxin D was assigned by applying an advanced Mosher's method. The phytotoxic activity of inuloxins A-D, that of the diazo and monoacetyl derivatives (of inuloxin A and C, resply), as well as that of α-costic acid was evaluated against two parasitic plant species, i.e. crenate broomrape (Orobanche crenata) and field dodder (Cuscuta campestris). Inuloxins A, C and D were the most active on both parasites and caused up to 100% inhibition of the seed germination. Inuloxin B was less active on Cuscuta and completely inactive against Orobanche. The main metabolite α-costic acid had a suppressive effect on the dodder seed germination but had a stimulating action on the broomrape seed germination. These preliminary results allowed to suppose some structure-activity relationships.
authors.affiliation: Dipartimento di Scienze del Suolo, della Pianta, dell'Ambiente e delle Produzioni Animali, Università di Napoli Federico II, 80055 Portici, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Andolfi
authors.forename: Nadjia
authors.initials: N
authors.lastname: Zermane
authors.forename: Alessio
authors.initials: A
authors.lastname: Cimmino
authors.forename: Fabiana
authors.initials: F
authors.lastname: Avolio
authors.forename: Angela
authors.initials: A
authors.lastname: Boari
authors.forename: Maurizio
authors.initials: M
authors.lastname: Vurro
authors.forename: Antonio
authors.initials: A
authors.lastname: Evidente
mesh_terms: D018525:Germination; D038143:Inula / Q000737:chemistry*; D007783:Lactones / Q000737:chemistry*; D015394:Molecular Structure; D031672:Orobanche / Q000737:chemistry*; D012717:Sesquiterpenes / Q000737:chemistry*
chemical_list: D007783:Lactones; D012717:Sesquiterpenes