Herein, I will review our efforts to develop a comprehensive and robust model for the estimation of the first oxidation potential,
, and antioxidant activity, AA, of flavonoids that would, besides ...enabling fast and cheap prediction of
and AA for a flavonoid of interest, help us explain the relationship between
, AA and electronic structure. The model development went forward with enlarging the set of flavonoids and, that way, we had to learn how to deal with the structural peculiarities of some of the 35 flavonoids from the final calibration set, for which the
measurements were all made in our laboratory. The developed models were simple quadratic models based either on atomic spin densities or differences in the atomic charges of the species involved in any of the three main oxidation mechanisms. The best model takes into account all three mechanisms of oxidation, single electron transfer-proton transfer (SET-PT), sequential proton loss electron transfer (SPLET) and hydrogen atom transfer (HAT), yielding excellent statistics (
= 0.970, S.E. = 0.043).
(ProQuest: ... denotes formulae omitted.) Dear Editor, In Volume 70 (pages 134-139) of Arhiv za higijenu rada i toksikologiju - Archives of Industrial Hygiene and Toxicology I published a paper ...entitled "The relationship between antioxidant activity, first electrochemical oxidation potential, and spin population of flavonoid radicals" (1). ...in my paper (1), I detected hesperetin as an outlier in regression models for the estimation of both oxidation potential (E ) and antioxidant activities (AA), on a set of 14 flavonoids. Later, in our paper on E models for 29 flavonoids (2), we succeeded in resolving a problem with hesperetin and its glycosides, hesperidin and neohesperidin, thanks to studies on the electron donation potential of the ortho-methoxy group in quinones (3, 4).
In this paper, I tested our quadratic regression models for the estimation of flavonoid oxidation potentials based on spin populations, the differences in the net atomic charges between a cation and ...a neutral flavonoid, between a radical and an anion of a flavonoid, and between a radical and a neutral flavonoid on a larger set of flavonoids (
= 35). By including six new flavonoids (5,6,7-trihydroxyflavone, 3,3’,4’,7-tetrahydroxyflavone, 3,7-dihydroxyflavone, 4’,7-dihydroxyflavone, 4’,5,7-trihydroxyisoflavone, and 6-hydroxyflavone), we created a respectable calibration set of 35 flavonoids with their oxidation potentials all measured at the same conditions by the same experimentalist. The best model was based on the mean values of the three variables using differences in the net atomic charges (
= 0.970, S.E. = 0.043), which are connected with the three different mechanisms of electrochemical oxidation, SET-PT, SPLET, and HAT.
In this study, we developed several QSAR models based on simple descriptors (such as topological and constitutional) to estimate butyrylcholinesterase (BChE) inhibition potency, pKi (or pIC50), of a ...set of 297 (289 after exclusion of outliers) structurally different compounds. The models were similar to the best model that we obtained previously for acetylcholinesterase AChE and were based on the valence molecular connectivity indices of second and third order (2χv and 3χv), the number of aliphatic hydroxyl groups (nOH), AlogP Ghose–Crippen octanol–water partition coeff. (logP), and O-060–atom-centred fragments (Al-O-Ar, Ar-O-Ar, R..O..R and R-O-C=X). The best models with two and three descriptors yielded r = 0.787 and S.E. = 0.89, and r = 0.827 and S.E. = 0.81, respectively. We also correlated nine scoring functions, calculated for 20 ligands whose complexes with BChE we found in the Protein Data Bank as crystal structures to pKi (or pIC50). The best correlations yielded PLP1 and PLP2 (Piecewise Linear Pairwise potential functions) with r = 0.619 and 0.689, respectively. Correlation with certain simple topological and constitutional descriptors yielded better results, e.g., 3χv (r = 0.730), on the same set of compounds (N = 20).
Acetylcholinesterase (AChE) has proven to be an effective drug target in the treatment of neurodegenerative diseases such as Alzheimer’s, Parkinson’s and dementia. We developed a novel QSAR ...regression model for estimating potency to inhibit AChE, pKi, on a set of 75 structurally different compounds including oximes, N-hydroxyiminoacetamides, 4-aminoquinolines and flavonoids. Although the model included only three simple descriptors, the valence molecular connectivity index of the zero-order, 0χv, the number of 10-membered rings (nR10) and the number of hydroxyl groups (nOH), it yielded excellent statistics (r = 0.937, S.E. = 0.51). The stability of the model was evaluated when an initial set of 75 compounds was broadened to 165 compounds in total, with the increase of the range of pKi (exp) from 6.0 to 10.2, yielding r = 0.882 and S.E. = 0.89. The predictive power of the model was evaluated by calculating pKi values for 55 randomly chosen compounds (S.E.test = 0.90) from the calibration model created on other 110 compounds (S.E. = 0.89), all taken from the pool of 165 compounds.
The bifid mandibular canal (BMC) is an anatomical variation with reported prevalence ranging from 0.08 to 65%. Identifying anatomical variations of mandibular canal is very important in order to ...prevent possible complications during oral surgical and other dental procedures.
The aim of this study was to determine the prevalence and to classify the morphology of BMCs using digital panoramic radiographs.
A retrospective study was conducted that included 1008 digital panoramic radiographs (412 female and 596 male) used to identify the type of BMC. Panoramic radiographs were analyzed by three oral surgeons and one dentist, and BMCs were classified into six different types, 4 types according to Langlais et al. (types 1-4), and two new types (types 5 and 6) described by authors.
The prevalence of BMC was 4.66% (n=47), with no significant differences in gender between BMC types (
=0.947
0.74). The prevalence of type 1 BMC was 0.79% (n=8), type 2 2.08% (n=21), type 3 0.30% (n=3), type 4 0% (n=0), type 5 0.89% (n=9) and type 6 0.60% (n=6).
This study revealed a relatively high prevalence of BMCs among Zagreb citizens. Furthermore, two new types of BMCs were described. These results stress the importance of a careful and thorough radiographic analysis prior to each invasive procedure in the mandible.
I have shown that by averaging antioxidant activity (AA) values measured by different methods it is possible to obtain an excellent correlation (
=0.960) between the first electrochemical oxidation ...potential,
, and AA. Separate correlations using the AA values obtained with each of the four methods
were 0.561 for diphenyl-1-picrylhydrazyl (DPPH), 0.849 for Folin Ciocalteu reagent (FCR), 0.848 for the ferric-reducing ability of plasma (FRAP), and 0.668 for the Trolox equivalent antioxidant capacity (TEAC) were all worse, and in some cases not useful at all, such as the one for DPPH. Also, the sum of atomic orbital spin populations on the carbon atoms in the skeleton of radicals ( s(C) Σ AOSP
), calculated with the semi-empirical parameterisation method 6 (PM6) in water, was used to correlate both
and AA, yielding R2=0.926 and 0.950, respectively. This showed to be a much better variable for the estimation of
and AA than the bond dissociation energy (BDE),
=0.854 and 0.901 for
and AA, respectively, and especially the ionisation potential (IP),
=0.445 and 0.435 for
and AA, respectively.
We developed a model for the stability (log β(ZnLB)) of Zn(2+) mixed complexes (N = 16) with 2-aminobenzamide (L) and four amino acids (B) glycine, alanine, valine, and phenylalanine at 300, 310, ...320, and 330 K. The model was based on the quadratic regression function of the molecular valence connectivity index of the third order, (3)χ(v), yielded S.E. = 0.02. We also developed an overall model for K(1), K(2) and β(ZnLB) of the same system at all of the four temperatures (N= 48). This model yielded S.E. = 0.05.
PDF
