Development of models for prediction of the antioxidant activity of derivatives of natural compounds

Antioxidants are important for maintaining the appropriate balance between oxidizing and reducing species in the body and thus preventing oxidative stress. Many natural compounds are being screened for their possible antioxidant activity. It was found that a mushroom pigment Norbadione A, which is a pulvinic acid derivative, shows an antioxidant activity; the same was found for other pulvinic acid derivatives and structurally related coumarines. Based on the results of in vitro studies performed on these compounds as a part of this study quantitative structure–activity relationship (QSAR) predictive models were constructed using multiple linear regression, counter-propagation artificial neural networks and support vector regression (SVR). The models have been developed in accordance with current QSAR guidelines, including the assessment of the models applicability domains. A new approach for the graphical evaluation of the applicability domain for SVR models is suggested. The developed models show sufficient predictive abilities for the screening of virtual libraries for new potential antioxidants.     

New Synthetic Approaches to Naturally Occurring and Unnatural Pyranoflavones

Total synthesis of biologically interesting natural and unnatural pyranoflavones has been accomplished starting from readily available 2,4‐dihydroxyacetophenone or 2,4‐dihydroxy‐6‐methoxyacetophenone in three steps, i.e., benzopyran formation, condensation, and cyclization reaction.     

Thermographic imaging as alternative method in allergy diagnosis

Allergen sensitization is being diagnosed by commonly available methods in clinical practice—skin prick tests (SPTs) and specific immunoglobulin E test (sIgE). Recently, a new thermographic (TH) method for the assessment of SPT was developed, and it was demonstrated that the TH measurements of forearm temperature distribution during SPT, supported by a mathematical model, offer a new quantification method of allergen-induced skin reactions. The aim of this study is a comprehensive comparison of the TH method with SPT and sIgE techniques. The studies were performed for a group of 51 patients. The SPT and sIgE examinations were done in a routine way. For TH analyses, set of thermograms of both forearms were acquired after prick and analyzed with the use of developed software. All results were converted into categorized scale for comparison. The collected results indicate high correlation coefficients between methods equal to 0.76–0.99. Sensitivity and accuracy of TH assessment in respect of both SPT and sIgE methods is at good level (0.72–0.93). Acceptable level of specificity 0.60–0.88 was also achieved for most allergic responses. Excellent agreement between SPT and sIgE methods was observed which makes the TH assessment competitive. Due to higher precision and sensitivity of digital infrared technology, possibility of making error in diagnosis is significantly reduced. Additional advantage of the TH method relies on an estimation of the skin reactivity which allows highlighting the hypersensitivity patients and automatic correction of the diagnosis.     

Response signal in a femtosecond pump-probe experiment in a condensed medium with account of the memory induced by the relaxation medium

For a model molecular system with one vibrational degree of freedom and three electronic states coupled by pump and probe laser pulses in a condensed medium, the response signal in a femtosecond pump-probe experiment is calculated. The potential curves of all three states are described by the Morse potential. Calculations are performed using two qualitatively different approaches to describing the medium-induced relaxation: with memory of the relaxation process and without memory (Markovian approximation). The temporal evolution of the vibrational wave packet in the intermediate electronically excited state is described using a master equation for the density matrix of the molecular system, which is derived within the framework of the Nakajima-Zwanzig formalism. It is demonstrated that, at short delay times, when the proposed approach is applicable, taking into account memory effects can substantially change the form of the pump-probe experiment signal in comparison with the signal calculated in the Markovian approximation.     

Simultaneous determination of five coumarins in Angelicae dahuricae Radix by HPLC/UV and LC‐ESI‐MS/MS

Rapid, simple and reliable HPLC/UV and LC‐ESI‐MS/MS methods for the simultaneous determination of five active coumarins of Angelicae dahuricae Radix, byakangelicol (1), oxypeucedanin (2), imperatorin (3), phellopterin (4) and isoimperatorin (5) were developed and validated. The separation condition for HPLC/UV was optimized using a Develosil RPAQUEOUS C₃₀ column using 70% acetonitrile in water as the mobile phase. This HPLC/UV method was successful for providing the baseline separation of the five coumarins with no interfering peaks detected in the 70% ethanol extract of Angelicae dahuricae Radix. The specific determination of the five coumarins was also accomplished by a triple quadrupole tandem mass spectrometer equipped with an electrospray ionization source (LC‐ESI‐MS/MS). Multiple reaction monitoring (MRM) in the positive mode was used to enhance the selectivity of detection. The LC‐ESI‐MS/MS methods were successfully applied for the determination of the five major coumarins in Angelicae dahuricae Radix. These HPLC/UV and LC‐ESI‐MS/MS methods were validated in terms of recovery, linearity, accuracy and precision (intra‐ and inter‐day validation). Taken together, the shorter analysis time involved makes these HPLC/UV and LC‐ESI‐MS/MS methods valuable for the commercial quality control of Angelicae dahuricae Radix extracts and its pharmaceutical preparations. Copyright © 2009 John Wiley & Sons, Ltd.     

Efficient and general method for the synthesis of benzopyrans by ethylenediamine diacetate-catalyzed reactions of resorcinols with α,β-unsaturated aldehydes. One step synthesis of biologically active (±)-confluentin and (±)-daurichromenic acid

An efficient and general synthesis of benzopyrans is achieved by ethylenediamine diacetate-catalyzed reactions of resorcinols with α,β-unsaturated aldehydes in moderated yields. As an application of this methodology, biologically interesting confluentin, which was known to have an inhibitory effect on histamine release is synthesized in one step. Also, natural daurichromenic acid, which has highly potent anti-HIV activity, is successfully synthesized in one step.     

Cerium oxide-catalyzed multicomponent condensation approach to spirooxindoles in water

An efficient and facile green synthesis of spirooxindole derivatives bearing pyrano[2,3-c]pyrazole moiety has been achieved via a \(\mathrm{CeO}_{2}\)-NPs catalyzed four-component reaction in water. The protocol offers an environmentally benign and effective approach to highly functionalized and biologically interesting spiro[indoline-3,4\(^\prime \)-pyrano[2,3-c]pyrazole] derivatives. The synthesized compounds exhibit potent antioxidant and antibacterial activities.     

Improved induced matchings in sparse graphs

An induced matching in a graph G=(V,E) is a matching M such that (V,M) is an induced subgraph of G. Clearly, among two vertices with the same neighbourhood (called twins) at most one is matched in any induced matching, and if one of them is matched then there is another matching of the same size that matches the other vertex. Motivated by this, Kanj et al. [10] studied induced matchings in twinless graphs. They showed that any twinless planar graph contains an induced matching of size at least and that there are twinless planar graphs that do not contain an induced matching of size greater than . We improve both these bounds to , which is tight up to an additive constant. This implies that the problem of deciding whether a planar graph has an induced matching of size k has a kernel of size at most 28k. We also show for the first time that this problem is fixed parameter tractable for graphs of bounded arboricity.Kanj et al. also presented an algorithm which decides in -time whether an n-vertex planar graph contains an induced matching of size k. Our results improve the time complexity analysis of their algorithm. However, we also show a more efficient -time algorithm. Its main ingredient is a new, O^∗(4^l)-time algorithm for finding a maximum induced matching in a graph of branch width at most l.