Walnut (Juglans regia L.) leaves: phenolic compounds, antibacterial activity and antioxidant potential of different cultivars.
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.
Pereira
José Alberto
JA
CIMO/Escola Superior Agrária, Instituto Politécnico de Bragança, Campus Sta Apolónia, Apt. 1172, 5301-855 Bragança, Portugal. jpereira@ipb.pt
Oliveira
Ivo
I
Sousa
Anabela
A
Valentão
Patrícia
P
Andrade
Paula B
PB
Ferreira
Isabel C F R
IC
Ferreres
Federico
F
Bento
Albino
A
Seabra
Rosa
R
Estevinho
Letícia
L
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*
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