title: Walnut (Juglans regia L.) leaves: phenolic compounds, antibacterial activity and antioxidant potential of different cultivars.
abstract: Different cultivars of walnut (Juglans regia L.) leaves (Cv. Lara, Franquette, Mayette, Marbot, Mellanaise and Parisienne) grown in Portugal, were investigated in what concerns phenolic compounds and antimicrobial and antioxidant properties. Phenolics analysis was performed by reversed-phase HPLC/DAD and 10 compounds were identified and quantified: 3- and 5-caffeoylquinic acids, 3- and 4-p-coumaroylquinic acids, p-coumaric acid, quercetin 3-galactoside, quercetin 3-pentoside derivative, quercetin 3-arabinoside, quercetin 3-xyloside and quercetin 3-rhamnoside. The antimicrobial capacity was screened against Gram positive (Bacillus cereus, B. subtilis, Staphylococcus aureus) and Gram negative bacteria (Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae) and fungi (Candida albicans, Cryptococcus neoformans). Walnut leaves selectively inhibited the growth of Gram positive bacteria, being B. cereus the most susceptible one (MIC 0.1mg/mL). Gram negative bacteria and fungi were resistant to the extracts at 100mg/mL. Lara walnut leaves were also submitted to antibacterial assays using 18 clinical isolates of Staphylococcus sp. Antioxidant activity was accessed by the reducing power assay, the scavenging effect on DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals and beta-carotene linoleate model system. In a general way, all of the studied walnut leaves cultivars presented high antioxidant activity (EC(50) values lower than 1mg/mL), being Cv. Lara the most effective one.
authors.affiliation: CIMO/Escola Superior Agrária, Instituto Politécnico de Bragança, Campus Sta Apolónia, Apt. 1172, 5301-855 Bragança, Portugal. jpereira@ipb.pt
authors.forename: José Alberto
authors.initials: JA
authors.lastname: Pereira
authors.forename: Ivo
authors.initials: I
authors.lastname: Oliveira
authors.forename: Anabela
authors.initials: A
authors.lastname: Sousa
authors.forename: Patrícia
authors.initials: P
authors.lastname: Valentão
authors.forename: Paula B
authors.initials: PB
authors.lastname: Andrade
authors.forename: Isabel C F R
authors.initials: IC
authors.lastname: Ferreira
authors.forename: Federico
authors.initials: F
authors.lastname: Ferreres
authors.forename: Albino
authors.initials: A
authors.lastname: Bento
authors.forename: Rosa
authors.initials: R
authors.lastname: Seabra
authors.forename: Letícia
authors.initials: L
authors.lastname: Estevinho
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D000935:Antifungal Agents / Q000737:chemistry / Q000494:pharmacology*; D000975:Antioxidants / Q000737:chemistry / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects; D001713:Biphenyl Compounds / Q000737:chemistry; D002176:Candida albicans / Q000187:drug effects; D003455:Cryptococcus neoformans / Q000187:drug effects; D006834:Hydrazines / Q000737:chemistry; D031324:Juglans / Q000737:chemistry* / Q000145:classification; D008967:Molecular Biology; D010084:Oxidation-Reduction; D010636:Phenols / Q000032:analysis; D010851:Picrates; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; D000975:Antioxidants; D001713:Biphenyl Compounds; D006834:Hydrazines; D010636:Phenols; D010851:Picrates; D010936:Plant Extracts; C004931:1,1-diphenyl-2-picrylhydrazyl