Hazel (Corylus avellana L.) leaves as source of antimicrobial and antioxidative compounds

Abstract

Aqueous extracts of leaves of different hazel (Corylus avellana L.) cultivars (Cv. M. Bollwiller, Fertille de Coutard and Daviana), were analysed by reversed-phase HPLC/DAD for the definition of their phenolic composition. Antioxidant potential was assessed by the reducing power assay, and the scavenging effect on DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals and b-carotene linoleate model system. Their antimicrobial capacity was also tested against Gram positive (Bacillus cereus, Bacillus subtilis, Staphylococcus aureus) and Gram negative bacteria (Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae) and fungi (Candida albicans, Cryptococcus neoformans). Eight phenolic compounds were identified: 3-, 4-and 5-caffeoylquinic acids, caffeoyltartaric acid, p-coumaroyltartaric acid, myricetin-rhamnoside, quercetin 3-rhamnoside and kaempferol 3-rhamnoside. A p-coumaric acid, three myricetin and one quercetin derivatives were also detected. The hazel leaves extract presented high antioxidant activity in a concentration-dependent way, in general with similar behaviour of all cultivars. Gram positive bacteria revealed to be very sensitive to hazel leaf extract (MIC 0.1 mg/ml for B. cereus and S. aureus and 1 mg/ml for B. subtilis). However, Gram negative and the fungi displayed much lower sensitivity, being P. aeruginosa and C. albicans resistant at 100 mg/ml. Cv. M. Bollwiller exhibited the most potent antimicrobial activity.

Chemical composition, and antioxidant and antimicrobial activities of three hazelnut (Corylus avellana L.) cultivars

“…Daviana cultivar proved to be the most promissory cultivar, presenting the best results, with higher growth inhibition zones and lower MICs. Fruit extracts had a similar antimicrobial activity to hazel leaf extracts for the same cultivars (Oliveira et al, 2007) which were effective at low concentrations (around 0.1 mg/mL); the present extracts are even better than table olive extracts previously studied by us Sousa et al, 2006). The antimicrobial agents added in food generally present problems related to some inherent toxicity (resistance, mutagenesis and carcinogenesis effects, for example) and natural compounds, such polyphenols have gained increasing importance.…”

“…With this regard the antimicrobial capacity of phenolic compounds has also been reported (Rauha et al, 2000;Puupponen-Pimiä et al, 2001;Proestos et al, 2005;Sousa et al, 2006;Pereira et al, 2006Pereira et al, , 2007. In fact, there are recent reports about the antioxidant and antiradical activities in extracts of Turkish hazelnut kernel, hazelnut green leafy cover (Alasalvar et al, 2006b), and other hazelnut byproducts such as hazelnut tree leaf (Oliveira et al, 2007;Shahidi et al, 2007).…”

“…In a previous study, our research group reported the antioxidant potential and antimicrobial activity of hazel leaves (Oliveira et al, 2007). Besides the few studies on the antioxidant activity of Turkish hazelnut varieties already mentioned, nothing has been reported about the antioxidant activity of hazelnuts produced in other regions and cultivars or about antimicrobial potential of hazelnut in general.…”

Antioxidant properties and UPLC–MS/MS profiling of phenolics in jacquemont’s hazelnut kernels (Corylus jacquemontii) and its byproducts from western Himalaya

“…The prevalent phenolics accumulates in Corylus avellana kernels and its byproducts are catechin, gallic acid, sinapic acid, caffeic acid, p-coumaric acid, ferulic acid, their esters and flavonoids (Shahidi et al 2007;Del Rio et al 2011). Various other bioactive phenols have also been characterized in hazelnut leaves and foliar buds (Oliveira et al 2007). However, literature survey revealed that jacquemont's hazelnut got very less attention than C. avellana.…”

Effect of thermal treatment on phenolic content, antioxidant, and -amylase inhibition activities of Moringa stenopetala leaves

“…Reducing power of the extracts was determined as described by Oliveira et al (2007) with slight modification. Different concentrations (50, 100, 250 and 500 μg/mL) of leaf extracts were mixed with phosphate buffer (2.5 mL, 0.2 M, pH 6.6) and 2.5 mL of 1% potassium ferricyanide.…”