New acyclic sesquiterpenoid derivatives and a monoterpene disaccharide from Dichondra repens Forst.

A new highly oxygenated acyclic sesquiterpenoid (2E, 6E)-8,10,11-trihydroxyl-7,11-dimethyl-3-hydroxymethyl-2,6-dodecadienoic acid (1) and its glucoside (2), together with a new pinane monoterpene disaccharide glucoside 6,6-dimethyl-2-methlenebicyclo [3.1.1]hept-3-O-(6-O-apiofuranosyl)-β-d-glucopyranoside (3) were isolated from hydrophilic extract of Dichondra repens. Their structures were elucidated on the basis of spectroscopic analyses and chemical methods. The three compounds did not show any cytotoxic activity (IC50 > 20 μM) against two human lung cancer cell lines (NCI-H661 and A549).     

Human metabolism of dietary flavonoids: Identification of plasma metabolites of quercetin

The position of conjugation of the flavonoid quercetin dramatically affects biological activity in vitro, therefore it is important to determine the exact nature of the plasma metabolites. In the present study, we have used various methods (HPLC with diode array detection, LCMS, chemical and enzymic synthesis of authentic conjugates and specific enzymic hydrolysis) to show that quercetin glucosides are not present in plasma of human subjects 1.5 h after consumption of onions (a rich source of flavonoid glucosides). All four individuals had similar qualitative profiles of metabolites. The major circulating compounds in the plasma after 1.5 h are identified as quercetin-3-glucuronide, 3′-methyl-quercetin-3-glucuronide and quercetin-3′-sulfate. The existence of substitutions in the B and/or C ring of plasma quercetin metabolites suggests that these conjugates will each have very different biological activities.     

Protective effect of tetrahydroxystilbene glucoside against d-galactose induced aging process in mice

Tetrahydroxystilbene glucoside (TSG) is a strong antioxidant and free radical scavenger derived from Polygonum multiflorum Thunb. The present study aims to evaluate the protective effect of TSG against d-galactose induced aging process in mice and its possible mechanisms of action. Our study revealed that administration of TSG improved the memory ability and regulated the body weight of mice. TSG also reduced the levels of ROS, NO and IGF-1 and increased the levels of SOD, Ca²⁺ and Klotho protein in the serum. Furthermore, TSG up-regulated the expression of Klotho protein in cerebrum, heart, kidney, testis and epididymis tissues of d-galactose induced aging mice. These results suggested that TSG had a promising anti-aging effect by regulating Klotho gene.     

Characterization of a New (R)-Hydroxynitrile Lyase from the Japanese Apricot Prunus mume and cDNA Cloning and Secretory Expression of One of the Isozymes in Pichia pastoris

PmHNL, a hydroxynitrile lyase from Japanese apricot ume (Prunus mume) seed was purified to homogeneity by ammonium sulfate fractionation and chromatographic steps. The purified enzyme was a monomer with molecular mass of 58 kDa. It was a flavoprotein similar to other hydroxynitrile lyases of the Rosaceae family. It was active over a broad temperature, and pH range. The N-terminal amino acid sequence (20 amino acids) was identical with that of the enzyme from almond (Prunus dulcis). Based on the N-terminal sequence of the purified enzyme and the conserved amino acid sequences of the enzymes from Pr. dulcis, inverse PCR method was used for cloning of a putative PmHNL (PmHNL2) gene from a Pr. mume seedling. Then the cDNA for the enzyme was cloned. The deduced amino acid sequence was found to be highly similar (95%) to that of an enzyme from Pr. serotina, isozyme 2. The recombinant Pichia pastoris transformed with the PmHNL2 gene secreted an active enzyme in glycosylated form.     

Neutral Sugar Fragments from Antibiotic K-52B

The neutral constituent sugars of antibiotic K-52B and their glycosidic linkages were examined by methylation analysis and Smith degradation. After partial acid hydrolysis of K-52B, neutral oligosaccharides I, II and III were isolated, and the constituent sugars of each oligosaccharide and their glycosidic linkages were similarly examined. K-52B was found to contain α-d-glc_p-(l → 4)-d-gal_p-(l → 4)-l-fuc and l-ara_f-(1 → 4)-d-gal-(l → as neutral sugar fragments.     

Volatile Components of Roasted Shrimp

The components of the strong and favorable aroma obtained from roasted shrimp were investigated. The aroma concentrate of roasted shrimp was isolated by combining the dichloromethane extract and carbon dioxide distillation methods. The concentrate was fractionated into acidic, basic and neutral fractions. Each fraction was analyzed by combined gas chromatography-mass spectrometry. Seventy-seven compounds were identified, among which isovaleric acid, alkyl pyrazines, isovaleramide, ketones and some sulfur-containing compounds were the main and characteristic constituents of the roasted shrimp aroma.

These constituents were compared with those of the volatiles of boiled shrimp, which was prepared by using simultaneous distillation and extraction methods in a modified Likens and Nickerson’s apparatus.     

Relationship between Gelation and Aggregation of Alkali-treated Soybean 7S and 11S Globulins

Gel was obtained when alkaline dope solutions of the 7S and 11S globulins (8% protein concentration) prepared at pH above 11 were dialyzed against phosphate buffer, pH 7.6, µ= 0.3. To make clear the mechanism of gelation, the relationship between changes in viscosity and aggregation phenomena of the neutralized dope solutions was investigated by means of viscosity measurement, disc electrophoresis and gel filtration, comparing the 7S and 11S fractions. In conclusion, it is revealed that the gel is constituted with macromolecule aggregates, and to form the aggregates which are suitable for gelation, all of the following conditions must be satisfied at least : 1); Unfolding and dissociation into subunits once (above pH 11), 2); High ionic strength in the media (µ=0.3), 3); Formation of hydrogen, hydrophobic and disulfide bonds, 4); High protein concentration (above 8%).     

Plant P450s as versatile drivers for evolution of species-specific chemical diversity

The irreversible nature of reactions catalysed by P450s makes these enzymes landmarks in the evolution of plant metabolic pathways. Founding members of P450 families are often associated with general (i.e. primary) metabolic pathways, restricted to single copy or very few representatives, indicative of purifying selection. Recruitment of those and subsequent blooms into multi-member gene families generates genetic raw material for functional diversification, which is an inherent characteristic of specialized (i.e. secondary) metabolism. However, a growing number of highly specialized P450s from not only the CYP71 clan indicate substantial contribution of convergent and divergent evolution to the observed general and specialized metabolite diversity. We will discuss examples of how the genetic and functional diversification of plant P450s drives chemical diversity in light of plant evolution. Even though it is difficult to predict the function or substrate of a P450 based on sequence similarity, grouping with a family or subfamily in phylogenetic trees can indicate association with metabolism of particular classes of compounds. Examples will be given that focus on multi-member gene families of P450s involved in the metabolic routes of four classes of specialized metabolites: cyanogenic glucosides, glucosinolates, mono- to triterpenoids and phenylpropanoids.