Flavonoids enantiomer distribution in different parts of goldenrod (Solidago virgaurea L.), lucerne (Medicago sativa L.) and phacelia (Phacelia tanacetifolia Benth.)

Plant material is a rich source of valuable compounds such as flavanones. Their different forms influence bioavailability and biological activity, causing problems with the selection of plant material for specific purposes. The purpose of this research was to determine selected flavanone (eriodictyol, naringenin, liquiritigenin, and hesperetin) enantiomer contents in free form and bonded to glycosides by an RP‐UHPLC‐ESI‐MS/MS method. Different parts (stems, leaves, and flowers) of goldenrod (Solidago virgaurea L.), lucerne (Medicago sativa L.), and phacelia (Phacelia tanacetifolia Benth.) were used. The highest content of eriodictyol was found in goldenrod flowers (13.1 μg/g), where it occurred mainly as the (S)‐enantiomer, and the greatest proportion of the total amount was bonded to glycosides. The richest source of naringenin was found to be lucerne leaves (4.7 μg/g), where it was mainly bonded to glycosides and with the (S)‐enantiomer as the dominant form. Liquiritigenin was determined only in lucerne, where the flowers contained the highest amount (1.2 μg/g), with the (R)‐enantiomer as dominant aglycone form and the (S)‐enantiomer as the dominant glycosylated form. The highest hesperetin content was determined in phacelia leaves (0.38 μg/g), where it was present in the form of a glycoside and only as the (S)‐enantiomer. A comparison of the different analyte forms occurring in different plant parts was performed for the first time.     

Complex of Rutin with β-Cyclodextrin as Potential Delivery System

This study aimed to obtain and characterize an RU-β-CD complex in the context of investigating the possibility of changes in the solubility, stability, antioxidative and microbiological activity as well as permeability of complexated rutin as against its free form. The formation of the RU-β-CD complex via a co-grinding technique was confirmed by using DSC, SEM, FT-IR and Raman spectroscopy, and its geometry was assessed through molecular modeling. It was found that the stability and solubility of the so-obtained complex were greater compared to the free form; however, a slight decrease was observed inits antibacterial potency. An examination of changes in the EPR spectra of thecomplex excluded any reducing effect of complexation on the antioxidative activity of rutin. Considering the prospect of preformulation studies involving RU-β-CD complexes, of significance is also the observed possibility of prolongedly releasing rutin from the complex at a constant level over along period of 20 h, and the fact that twice as much complexated rutin was able topermeate compared to its free form.     

Neuronal Autophagy: Self-eating or Self-cannibalism in Alzheimer’s Disease

Autophagy is a major intracellular degeneration pathway involved in the elimination and recycling of damaged organelles and long-lived proteins by lysosomes. Many of the pathological factors, which trigger neurodegenerative diseases, can perturb the autophagy activity, which is associated with misfolded protein aggregates accumulation in these disorders. Alzheimer’s disease, the first neurodegenerative disorder between dementias, is characterized by two aggregating proteins, β-amyloid peptide (plaques) and τ-protein (tangles). In Alzheimer’s disease autophagosomes dynamically form along neurites within neuronal cells and in synapses but effective clearance of these structures needs retrograde transportation towards the neuronal soma where there is a major concentration of lysosomes. Maturation of autophago-lysosomes and their retrograde trafficking are perturbed in Alzheimer’s disease, which causes a massive concentration of autophagy elements along degenerating neurites. Transportation system is disturbed along defected microtubules in Alzheimer’s disease brains. τ-protein has been found to control the stability of microtubules, however, phosphorylation of τ-protein or an increase in the total level of τ-protein can cause dysfunction of neuronal cells microtubules. Current evidence has shown that autophagy is developing in Alzheimer’s disease brains because of ineffective degradation of autophagosomes, which hold amyloid precursor protein-rich organelles and secretases important for β-amyloid peptides generation from amyloid precursor. The combination of raised autophagy induction and abnormal clearance of β-amyloid peptide-generating autophagic vacuoles creates circumstances helpful for β-amyloid peptide aggregation and accumulation in Alzheimer’s disease. However, the key role of autophagy in Alzheimer’s disease development is still under consideration today. One point of view suggests that abnormal autophagy induction causes a concentration of autophagic vacuoles rich in amyloid precursor protein, β-amyloid peptide and the elements crucial for its formation, whereas other hypothesis points to marred autophagic clearance or even decrease in autophagic effectiveness playing a role in maturation of Alzheimer’s disease. In this review we present the recent evidence linking autophagy to Alzheimer’s disease and the role of autophagic regulation in the development of full-blown Alzheimer’s disease.     

Interaction of the initiator protein of an IncB plasmid with its origin of DNA replication

The replication initiator protein RepA of the IncB plasmid pMU720 was purified and used in DNase I protection assays in vitro. RepA protected a 68-bp region of the origin of replication of pMU720. This region, which lies immediately downstream of the DnaA box, contains four copies of the sequence motif 5'AANCNGCAA3'. Mutational analyses identified this sequence as the binding site specifically recognized by RepA (the RepA box). Binding of RepA to the RepA boxes was ordered and sequential, with the box closest to the DnaA binding site (box 1) occupied first and the most distant boxes (boxes 3 and 4) occupied last. However, only boxes 1, 2, and 4 were essential for origin activity, with box 3 playing a lesser role. Changing the spacing between box 1 and the other three boxes affected binding of RepA in vitro and origin activity in vivo, indicating that the RepA molecules bound to ori(B) interact with one another.     

Mutations affecting pseudoknot control of the replication of B group plasmids.

The translational initiation region of the mRNA for the replication initiation protein (RepA) of pMU720 is predicted to be sequestered in an inhibitory secondary structure designated stem-loop III. Activation of repA translation requires both the disruption of stem-loop III by ribosomes involved in the translation and termination of the leader peptide RepB and the formation of a pseudoknot, a tertiary RNA structure. Disruption of stem-loop III by site-directed mutagenesis was found to be insufficient to allow high repA expression in the absence of pseudoknot formation, indicating that the pseudoknot acts as an enhancer of repA translation. Furthermore, extending the length of the leader peptide RepB and changing the distance between the pseudoknot and repA Shine-Dalgarno sequence were found to have major effects on the translation of repA.     

Interaction between the antisense and target RNAs involved in the regulation of IncB plasmid replication.

Physical analysis of RNA I, the small antisense RNA which regulates the replication of IncB miniplasmid pMU720, showed that it is a highly structured molecule containing an imperfectly paired stem closed by a 6-base hairpin loop. Mutational studies revealed that a 3-base sequence in the hairpin loop is critical to the interaction between RNA I and its complementary target in the RepA mRNA (RNA II). Furthermore, a 2-base interior loop in the upper stem was found to play an important role in facilitating effective binding between RNA I and RNA II. From these analyses, a model describing the molecular mechanism of binding between RNA I and RNA II is proposed.     

Control of replication in I-complex plasmids

The closely related plasmids that make up the I-complex group and the more distantly related IncL/M plasmids regulate the frequency of initiation of their replication by controlling the efficiency of translation of the rate limiting replication initiator protein, RepA. Translation initiation of repA is dependent on the formation of a pseudoknot immediately upstream of its Shine-Dalgarno sequence. Formation of this pseudoknot involves base pairing between two complementary sequences in the repA mRNA and requires that the secondary structure sequestering the distal sequence be disrupted by movement of the ribosome translating and terminating a leader peptide, whose coding sequence precedes and overlaps that of repA. Expression of repA is controlled by a small antisense RNA, RNAI, which on binding to its complementary target in the repA mRNA not only pre-empts formation of the pseudoknot, but also inhibits translation of the leader peptide. The requirement that translation of the leader peptide be completed for the pseudoknot to form increases the time available for the inhibitory interaction of RNAI with its target, so that at high copy number the frequency of pseudoknot formation is lowered, reducing the proportion of repA mRNA that are translated. At low copy number, when concentration of RNAI is low, repA is translated with increased frequency, leading to increased frequency of plasmid replication.