Monoamine reuptake inhibition and mood-enhancing potential of a specified oregano extract.

A healthy, balanced diet is essential for both physical and mental well-being. Such a diet must include an adequate intake of micronutrients, essential fatty acids, amino acids and antioxidants. The monoamine neurotransmitters, serotonin, dopamine and noradrenaline, are derived from dietary amino acids and are involved in the modulation of mood, anxiety, cognition, sleep regulation and appetite. The capacity of nutritional interventions to elevate brain monoamine concentrations and, as a consequence, with the potential for mood enhancement, has not been extensively evaluated. The present study investigated an extract from oregano leaves, with a specified range of active constituents, identified via an unbiased, high-throughput screening programme. The oregano extract was demonstrated to inhibit the reuptake and degradation of the monoamine neurotransmitters in a dose-dependent manner, and microdialysis experiments in rats revealed an elevation of extracellular serotonin levels in the brain. Furthermore, following administration of oregano extract, behavioural responses were observed in mice that parallel the beneficial effects exhibited by monoamine-enhancing compounds when used in human subjects. In conclusion, these data show that an extract prepared from leaves of oregano, a major constituent of the Mediterranean diet, is brain-active, with moderate triple reuptake inhibitory activity, and exhibits positive behavioural effects in animal models. We postulate that such an extract may be effective in enhancing mental well-being in humans.

Flavone synthase II (CYP93B16) from soybean (Glycine max L.).

Flavonoids are a very diverse group of plant secondary metabolites with a wide array of activities in plants, as well as in nutrition and health. All flavonoids are derived from a limited number of flavanone intermediates, which serve as substrates for a variety of enzyme activities, enabling the generation of diversity in flavonoid structures. Flavonoids can be characteristic metabolites, like isoflavonoids for legumes. Others, like flavones, occur in nearly all plants. Interestingly, there exist two fundamentally different enzymatic systems able to directly generate flavones from flavanones, flavone synthase (FNS) I and II. We describe an inducible flavone synthase activity from soybean (Glycine max) cell cultures, generating 7,4'-dihydroxyflavone (DHF), which we classified as FNS II. The corresponding full-length cDNA (CYP93B16) was isolated using known FNS II sequences from other plants. Functional expression in yeast allowed the detailed biochemical characterization of the catalytic activity of FNS II. A direct conversion of flavanones such as liquiritigenin, naringenin, and eriodictyol into the corresponding flavones DHF, apigenin and luteolin, respectively, was demonstrated. The enzymatic reaction of FNSII was stereoselective, favouring the (S)- over the (R)-enantiomer. Phylogenetic analyses of the subfamily of plant CYP93B enzymes indicate the evolution of a gene encoding a flavone synthase which originally catalyzed the direct conversion of flavanones into flavones, via early gene duplication into a less efficient enzyme with an altered catalytic mechanism. Ultimately, this allowed the evolution of the legume-specific isoflavonoid synthase activity.

Coronalon: a powerful tool in plant stress physiology.

Coronalon, a synthetic 6-ethyl indanoyl isoleucine conjugate, has been designed as a highly active mimic of octadecanoid phytohormones that are involved in insect and disease resistance. The spectrum of biological activities that is affected by coronalon was investigated in nine different plant systems specifically responding to jasmonates and/or 12-oxo-phytodienoic acid. In all bioassays analyzed, coronalon demonstrated a general strong activity at low micromolar concentrations. The results obtained showed the induction of (i) defense-related secondary metabolite accumulation in both cell cultures and plant tissues, (ii) specific abiotic and biotic stress-related gene expression, and (iii) root growth retardation. The general activity of coronalon in the induction of plant stress responses together with its simple and efficient synthesis suggests that this compound might serve as a valuable tool in the examination of various aspects in plant stress physiology. Moreover, coronalon might become employed in agriculture to elicit plant resistance against various aggressors.

The role of octadecanoids and functional mimics in soybean defense responses.

Oxylipins of the jasmonate pathway and synthetic functional analogs have been analyzed for their elicitor-like activities in an assay based on the induced accumulation of glyceollins, the phytoalexins of soybean (Glycine max L.), in cell suspension cultures of this plant. Jasmonic acid (JA) and its methyl ester showed weak phytoalexin-inducing activity when compared to an early jasmonate biosynthetic precursor, 12-oxo-phytodienoic acid (OPDA), as well as to the bacterial phytotoxin coronatine and certain 6-substituted indanoyl-L-isoleucine methyl esters, which all were highly active. Interestingly, different octadecanoids and indanoyl conjugates induced the accumulation of transcripts of various defense-related genes to different degrees, indicating distinct induction competencies. Therefore, these signaling compounds and mimics were further analyzed for their effects on signal transduction elements, such as the transient enhancement of the cytosolic Ca2+ concentration and MAP kinase activation, which are known to be initiated by a soybean pathogen-derived beta-glucan elicitor. In contrast to the beta-glucan elicitor, none of the other compounds tested triggered these early signaling elements. Moreover, endogenous levels of OPDA and JA in soybean cells were shown to be unaffected after treatment with beta-glucans. Thus, OPDA and JA, which are functionally mimicked by coronatine and a variety of 6-substituted derivatives of indanoyl-L-isoleucine methyl ester, represent highly efficient signaling compounds of a lipid-based pathway not deployed in the beta-glucan elicitor-initiated signal transduction.

Selective induction of secondary metabolism in Phaseolus lunatus by 6-substituted indanoyl isoleucine conjugates.

A novel and highly efficient route to new indanoyl isoleucine conjugates is described, which allows a wide range of substituents to be attached to the 6-position of the indanoyl moiety. We report the synthesis of conjugates with methyl, methoxy, propoxy, allyloxy, pentoxy, and 2-(2-methoxy-ethoxy)-ethoxy 6-position substituents. Preliminary biological activities of the novel compounds with significantly enhanced water solubility were determined using the Lima bean (Phaseolus lunatus) volatile bioassay. The compounds induce variable volatile patterns, and structure-activity relationships show an ability to differentially induce separate pathways leading to secondary metabolites.