SUMMARY Many secondary metabolites found in plants have a role in defence against herbivores, pests and pathogens. In this review, a few examples are described and discussed, and some of the problems in determining the precise role(s) of such metabolites highlighted. The role of secondary metabolites in defence may involve deterrence/anti‐feedant activity, toxicity or acting as precursors to physical defence systems. Many specialist herbivores and pathogens do not merely circumvent the deterrent or toxic effects of secondary metabolites but actually utilize these compounds as either host recognition cues or nutrients (or both). This is true of both cyanogenic glucosides and glucosinolates, which art discussed in detail as examples of defensive compounds. Their biochemistry is compared and contrasted. An enormous variety of secondary metabolites are derived from shikimic acid or aromatic amino acids, many of which have important roles in defence mechanisms. Several classes of secondary products are ‘induced’ by infection, wounding or herbivory, and examples of these are given. Genetic variation in the speed and extent of such induction may account, at least in part, for the difference between resistant and susceptible varieties. Both salicylates and jasmonates have been implicated as signals in such responses and in many other physiological processes, though their prescise roles and interactions in signalling and development are not fully understood.

Moringa species are important multi-purpose tropical crops, as human foods and for medicine and oil production. There has been no previous comprehensive analysis of the secondary metabolites in Moringa species. Tissues of M. oleifera from a wide variety of sources and M. stenopetala from a single source were analyzed for glucosinolates and phenolics (flavonoids, anthocyanins, proanthocyanidins, and cinnamates). M. oleifera and M. stenopetala seeds only contained 4-(alpha-l-rhamnopyranosyloxy)-benzylglucosinolate at high concentrations. Roots of M. oleifera and M. stenopetala had high concentrations of both 4-(alpha-l-rhamnopyranosyloxy)-benzylglucosinolate and benzyl glucosinolate. Leaves from both species contained 4-(alpha-l-rhamnopyranosyloxy)-benzylglucosinolate and three monoacetyl isomers of this glucosinolate. Only 4-(alpha-l-rhamnopyranosyloxy)-benzylglucosinolate was detected in M. oleifera bark tissue. M. oleifera leaves contained quercetin-3-O-glucoside and quercetin-3-O-(6' '-malonyl-glucoside), and lower amounts of kaempferol-3-O-glucoside and kaempferol-3-O-(6' '-malonyl-glucoside). M. oleifera leaves also contained 3-caffeoylquinic acid and 5-caffeoylquinic acid. Leaves of M. stenopetala contained quercetin 3-O-rhamnoglucoside (rutin) and 5-caffeoylquinic acid. Neither proanthocyanidins nor anthocyanins were detected in any of the tissues of either species.

No abstract

No abstract

Aims:  To evaluate the antimicrobial properties of flavonoid‐rich fractions derived from bergamot peel, a byproduct from the Citrus fruit processing industry and the influence of enzymatic deglycosylation on their activity against different bacteria and yeast. Methods and Results:  Bergamot ethanolic fractions were tested against Gram‐negative bacteria (Escherichia coli, Pseudomonas putida, Salmonella enterica), Gram‐positive bacteria (Listeria innocua, Bacillus subtilis, Staphylococcus aureus, Lactococcus lactis) and the yeast Saccharomyces cerevisiae. Bergamot fractions were found to be active against all the Gram‐negative bacteria tested, and their antimicrobial potency increased after enzymatic deglycosylation. The minimum inhibitory concentrations of the fractions and the pure flavonoids, neohesperidin, hesperetin (aglycone), neoeriocitrin, eriodictyol (aglycone), naringin and naringenin (aglycone), were found to be in the range 200 to 800 μg ml−1. The interactions between three bergamot flavonoids were also evaluated. Conclusion:  The enzyme preparation Pectinase 62L efficiently converted common glycosides into their aglycones from bergamot extracts, and this deglycosylation increased the antimicrobial potency of Citrus flavonoids. Pairwise combinations of eriodictyol, naringenin and hesperetin showed both synergistic and indifferent interactions that were dependent on the test indicator organism. Significance and Impact of the Study:  Bergamot peel is a potential source of natural antimicrobials that are active against Gram‐negative bacteria.

The results suggest that most ingested procyanidins reach the small intestine intact and are available for absorption or metabolism.

Hydroxycinnamic acids are a group of phenolic compounds that exhibit a wide range of in vitro chemoprotective and antioxidant properties. Cereals containing a high proportion of the bran layers are rich in ester-linked hydroxycinnamic acids, such as ferulic and diferulic acids. The present work investigated the absorption in humans of hydroxycinnamic acids from high-bran breakfast cereal (wheat). Plasma and urine samples from six volunteers were collected before and after cereal consumption and analyzed for total hydroxycinnamic acids content after beta-glucuronidase/sulfatase treatment both by HPLC-DAD and by LC-MS (SIM monitoring). High-bran cereal administration resulted in increased plasma ferulic and sinapic acid concentrations (maximum levels detected of approximately 200 and approximately 40 nM, respectively) with absorption peaks between 1 and 3 h. Increases of approximately 4-fold in ferulic acid and approximately 5-fold in feruloylglycine were detected in 24-h urine after consumption of the cereal. Most of the ferulic acid detected in urine and plasma was present as conjugates (feruloylglycine and/or glucuronides). Diferulic acids were undetectable. The data show that ferulic and sinapic acids are taken up in humans from dietary high bran wheat but that absorption is limited and may originate only from the free and soluble portions present in the cereal.

Chestnut fruits are highly regarded and widely consumed throughout Europe, America and Asia. Various commercial forms are available, e.g. fresh and industrially processed. There have been various reviews on the composition of chestnut fruits but there has not been a comprehensive review of the different health benefits that this fruit can provide. This review is focused on the composition and associated health effects of European fresh chestnut (Castanea sativa Mill.) fruits and their home-processed and industrial products, e.g. boiled, roasted, frozen, and 'marron glacées'. We also expand the knowledge of chestnut uses by presenting data for other chestnut materials that have potential applications as new foods, as sources of antioxidants, and as sources of other useful bioactives. There is considerable literature data on nutrients in fresh chestnut fruits but less information on bioactive non-nutrients such as phenolics. Chestnuts are mostly consumed as processed forms, and the different types of processing clearly affect the nutrient and non-nutrient composition of the fruits. The benefits that this fruit can provide for human and animal health are numerous, but it is clear that improvements can be made for both production and quality of chestnut products, e.g. genetic selection and optimizing industrial processing.