Indonesian plants with potential as an anti-diabetes mellitus agent

Diabetes Mellitus (DM) is a degenerative disease that continues to increase in numberin Indonesia and is a disease that is spread throughout the world due to unbalancednutritional conditions. Treatment of diabetes mellitus is a chronic and lifelongtreatment. Treatment of diabetes mellitus, such as the use of insulin and oralantihyperglycemia drugs, is relatively expensive, is used for a long time and can causeunwanted side effects. There are many plants that have potential as antihyperglycemiadrugs. One of the active compounds that act as antihyperglycemia isflavonoids.Flavonoids derived from various types of plants studied are thought to actas antihyperglycemic agents. Flavonoids are known to have the ability to scavenge freeradicals or act as natural antioxidants. The antioxidant activity of flavonoids is relatedto phenolic –OH groups which can capture or neutralize free radicals (such as ROS orRNS). Flavonoids can play a role in pancreatic tissue damage caused by DNA alkylationdue to alloxan induction as a result of improving the morphology of the rat pancreas(Prameswari and Widjanarko, 2014).

Synthesis and Characterization of New Palladium(II) Schiff Base Complexes Derived from β-Diketones and Diamines

A new series of heterocyclic Schiff bases were prepared from condensation of 1-phenyl-3-methyl-4-acetyl/benzoyl-pyrazolone with 4,4′-diaminodiphenylmethane and 4,4′-diaminodiphenyl ether, resulting in the formation of four novel Schiff base ligands. These ligands were then treated with ethanolic solution of PdCl2, to form corresponding palladium(II) complexes. These complexes were characterized by elemental analysis, IR, 1H NMR, TGA, magnetic susceptibility measurements and UV-visible absorption spectroscopy. All the Pd(II) complexes were found to have one coordinated water molecule. Schiff base ligands chelated with the metal atom through two donor sites N and O of azomethine (-C=N-) and phenolic (-OH) groups, respectively.

Mild and controlled lignin methylation with trimethyl phosphate: towards a precise control of lignin functionality

A novel protocol for a mild, controlled and selective methylation of lignin phenolic OH groups with trimethylphosphate has been developed.

Statistical Analysis of the Relationship Between Antioxidant Activity and the Structure of Flavonoid Compounds

Using different methods of statistics, this paper aims to highlight the potential link between the antioxidant activity of flavonoids and the corresponding molecular descriptors. By calculating the descriptors (van der Waals surface (A), molar volume (V), partition coefficient (LogP), refractivity (R), polarizability (a), forming heat (Hformation), hydration energy (Ehidr), the dipole moment (mt)), together with antioxidant activities (RSA) calculated or taken from the literature, number of phenolic -OH groups and the presence (2) or absence (1) of C2=C3 double bond) for 29 flavonoid compounds and by intercorrelation between the studied parameters, the link between the number of phenolic groups grafted to the basic structure of flavonoids and their antioxidant activity was confirmed. Simultaneously, by using the chi-squared test and the intercorrelations matrix, a satisfactorily correlation coefficient (r2=0.5678; r=0.7536) between the structure of the flavonoids and their activity was obtained, fact that confirms the correlation of the antioxidant activity with the number of -OH phenolic groups.

Synthesis and Crystal Structure of Calix[4]arene Derivative Containing 1,3-Diketo Moieties

The synthesis of the calix[4]arene derivative containing 1,3-diketo moieties via direct Claisen condensation without protection of the unsubstituted phenolic OH groups is reported. Single crystal X-ray diffraction analysis reveals that the calix unit to be in a cone conformation incorporating two 1,3-diketo subunits disposed in alternate position at the lower rim. And the crystal packing reveals that the overall packing of the complex is staggered anti-parallelly.

Lignin Modification Supported by DFT-Based Theoretical Study as a Way to Produce Competitive Natural Antioxidants

The valorization of lignins as renewable aromatic feedstock is of utmost importance in terms of the use of sustainable resources. This study provides a deductive approach towards market-oriented lignin-derived antioxidants by ascertaining the direct effect of different structural features of lignin on the reactivity of its phenolic OH groups in the radical scavenging reactions. The antioxidant activity of a series of compounds, modeling lignin structural units, was experimentally characterized and rationalized, using thermodynamic descriptors. The calculated O–H bond dissociation enthalpies (BDE) of characteristic lignin subunits were used to predict the modification pathways of technical lignins. The last ones were isolated by soda delignification from different biomass sources and their oligomeric fractions were studied as a raw material for modification and production of optimized antioxidants. These were characterized in terms of chemical structure, molecular weight distribution, content of the functional groups, and the antioxidant activity. The developed approach for the targeted modification of lignins allowed the products competitive with two commercial synthetic phenolic antioxidants in both free radical scavenging and stabilization of thermooxidative destruction of polyurethane films.

Ion-exchange properties and swelling capacity of leaf cell wall of Arctic plants

Ion-exchange (number of functional group) properties and swelling capacity of leaf cell walls of plant species Betula nana, Salix polaris, Dryas octopetala and Cassiope tetragona from Western Spitsbergen Island were investigated. It was found out that cell wall of Arctic plants is cation exchanger which has similar functional groups (amine groups, carboxyl groups and phenolic OH-groups) with cell wall of boreal plants. In all investigated species, the highest percentage in the structure of the cell wall was recorded for the carboxyl groups of hydroxycinnamic acids and phenolic OH-groups, which are part of phenolic compounds. In comparison with species from other climatic zones leaf cell wall of arctic plants has in 2–3 times higher amount of ion exchange groups of all types as well as the higher values of swelling coefficients. It was proposed that the high values of the ion-exchange capacity and swelling coefficient of the cell wall of all studied species contribute to greater water flow system by the apoplast and enhance the metabolic processes in the cell wall of plants at high latitudes.

Synthesis of Monofunctionalized Calix[5]arenes

Seven OH-free and O-permethylated monofunctionalized calix[5]arenes carrying either additional methyl or tert-butyl groups are prepared following fragment condensation protocols. This strategy proves to be superior to previous approaches. Calix[5]arenes with free OH groups all adopt a cone conformation stabilized by a seam of hydrogen bonds at the lower rim. Post-condensation modifications, i.e., methylation of phenolic OH groups or functional group interconversions can also be achieved. Bulky tert-butyl groups are also found to stabilize the cone conformations of O-methylated compounds. These compounds offer versatile functional groups that make these concave molecules interesting building blocks for the synthesis of more sophisticated molecular architectures.