title: Phenolic acids, syringaldehyde, and juglone in fruits of different cultivars of Juglans regia L.
abstract: Phenolic acids (chlorogenic, caffeic, p-coumaric, ferulic, sinapic, ellagic, and syringic acid) as well as syringaldehyde and juglone were identified in ripe fruits of 10 walnut cultivars: Adams, Cisco, Chandler, Franquette, Lara, Fernor, Fernette, Alsoszentivani 117 (A-117), Rasna, and Elit. Analyses were done using a high-performance liquid chromatograph equipped with a diode array detector. Significant differences in the contents of identified phenolics were observed among cultivars. Phenolics were determined separately in the kernel and in the thin skin of the walnut, termed the pellicle. Not only in the kernel but also in the pellicle did syringic acid, juglone, and ellagic acid predominate (average values of 33.83, 11.75, and 5.90 mg/100 g of kernel; and 1003.24, 317.90, and 128.98 mg/100 g of pellicle, respectively), and the contents of ferulic and sinapic acid (average values of 0.06 and 0.05 mg/100 g of kernel and 2.93 and 2.17 mg/100 g of pellicle, respectively) were the lowest in all cultivars. The highest differences in the sum of all identified phenolics were observed between Rasna and Fernette fruits; in Rasna there were >2-fold higher contents of identified phenolics in both kernel and pellicle. It was found that the walnut pellicle is the most important source of walnut phenolics. The ratio between the contents in pellicle and kernel varied by at least 14.8-fold for caffeic acid (cv. Adams) and by up to 752.0-fold for p-coumaric acid (cv. Elit).
authors.affiliation: Department of Agronomy, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia. mateja.colaric@bf.uni-lj.si
authors.forename: Mateja
authors.initials: M
authors.lastname: Colaric
authors.forename: Robert
authors.initials: R
authors.lastname: Veberic
authors.forename: Anita
authors.initials: A
authors.lastname: Solar
authors.forename: Metka
authors.initials: M
authors.lastname: Hudina
authors.forename: Franci
authors.initials: F
authors.lastname: Stampar
mesh_terms: D000146:Acids, Carbocyclic / Q000032:analysis*; D001547:Benzaldehydes / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D005638:Fruit / Q000737:chemistry*; D031324:Juglans / Q000737:chemistry*; D009285:Naphthoquinones / Q000032:analysis*
chemical_list: D000146:Acids, Carbocyclic; D001547:Benzaldehydes; D009285:Naphthoquinones; C069665:syringaldehyde; C005134:juglone