17 research outputs found
Antibacterial activity and mode of action of selected glucosinolate hydrolysis products against bacterial pathogens
Plants contain numerous components that are important sources of new bioactive molecules with antimicrobial properties. Isothiocyanates (ITCs) are plant secondary metabolites found in cruciferous vegetables that are arising as promising antimicrobial agents in food industry. The aim of this study was to assess the antibacterial activity of two isothiocyanates (ITCs), allylisothiocyanate (AITC) and 2-phenylethylisothiocyanate (PEITC) against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes. The antibacterial mode of action was also characterized by the assessment of different physiological indices: membrane integrity, intracellular potassium release, physicochemical surface properties and surface charge. The minimum inhibitory concentration (MIC) of AITC and PEITC was 100 g/mL for all bacteria. The minimum bactericidal concentration (MBC) of the ITCs was at least 10 times higher than the MIC. Both AITC and PEITC changed the membrane properties of the bacteria decreasing their surface charge and compromising the integrity of the cytoplasmatic membrane with consequent potassium leakage and propidium iodide uptake. The surface hydrophobicity was also non-specifically altered (E. coli and L. monocytogenes become less hydrophilic; P. aeruginosa and S. aureus become more hydrophilic). This study shows that AITC and PEITC have strong antimicrobial potential against the bacteria tested, through the disruption of the bacterial cell membranes. Moreover, phytochemicals are highlighted as a valuable sustainable source of new bioactive products.This work was supported by the Operational Programme for Competitiveness Factors - COMPETE and by the Portuguese Foundation for Science and Technology through Project Phytodisinfectants - PTDC/DTP-SAP/1078/2012 (COMPETE: FCOMP-01-0124-FEDER-028765), the PhD grant awarded to Ana Abreu (SFRH/BD/84393/2012), and the post-doctoral grants awarded to Anabela Borges (SFRH/BPD/98684/2013) and Lucia C. Simoes (SFRH/BPD/81982/2011). Also, this work was undertaken as part of the European Research Project SUSCLEAN (Contract no FP7-KBBE-2011-5, project number: 287514) and the COST Action FA1202. The authors are solely responsible for this work. It does not represent the opinion of the European Community, and the Community is not responsible for any use that might be made of data appearing herein
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Oxidative discolouration in whole-head and cut lettuce: biochemical and environmental influences on a complex phenotype and potential breeding strategies to improve shelf-life
Lettuce discolouration is a key post-harvest trait. The major enzyme controlling oxidative discolouration
has long been considered to be polyphenol oxidase (PPO) however, levels of PPO and subsequent development of discolouration symptoms have not always correlated. The predominance of a latent state of the enzyme in plant tissues combined with substrate activation and contemporaneous suicide inactivation
mechanisms are considered as potential explanations for
this phenomenon. Leaf tissue physical properties have
been associated with subsequent discolouration and
these may be influenced by variation in nutrient
availability, especially excess nitrogen and head maturity at harvest. Mild calcium and irrigation stress has
also been associated with a reduction in subsequent
discolouration, although excess irrigation has been
linked to increased discolouration potentially through
leaf physical properties. These environmental factors,
including high temperature and UV light intensities,
often have impacts on levels of phenolic compounds
linking the environmental responses to the biochemistry
of the PPO pathway. Breeding strategies targeting the
PALand PPOpathway biochemistry and environmental
response genes are discussed as a more cost-effective
method of mitigating oxidative discolouration then
either modified atmosphere packaging or post-harvest
treatments, although current understanding of the
biochemistry means that such programs are likely to
be limited in nature and it is likely that they will need to be deployed alongside other methods for the foreseeable future
Evaluation of phenolics and cysteine sulfoxides in local onion and shallot germplasm from Italy and Ukraine
Onions (Allium cepa L.) are the most important Allium vegetables whose increasing popu-
larity is related to their pungent taste and richness in
non-nutrient bioactive compounds. Many diverse local
types are present and valued in several areas, although
still poorly characterized. In the present study, fresh
edible parts from Italian and Ukrainian bulb onion,
potato onion, and shallot populations were analyzed for
their phenolic and cysteine sulfoxide content and
antioxidant capacity. Fifteen phenolic compounds,
belonging to flavonols and anthocyanins, and two
cysteine sulfoxides, methiin and isoalliin, were quan-
tified. Total phenolics and cysteine sulfoxides were in
the range 2595\u20139840 and 6777\u201318,916 mg kg-1 d.m.,
respectively. On average, potato onion phenolic con-
tent was 55 and 59 % higher than in bulb onion and
shallot accessions, respectively. Bulb and potato
onions showed a similar cysteine sulfoxide content,
whereas in shallots sulfoxide level was about 17 %
lower. Flavonols were related to antioxidant capacity
in both low and high anthocyanin types; however
anthocyanins gave a prominent contribution to total
antioxidant capacity in red onions. Quantitative vari-
ations of some components allowed a clear discrimi-
nation among the three groups of onions, highlighting
the possibility of selection for both low or high content
of specific components