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Victória Luswarghi Souza Costa,João Paulo Mendes Tribst,Eduardo Shigueyuki Uemura,Dayana Campanelli de Morais,Alexandre Luiz Souto Borges 대한치과보존학회 2018 Restorative Dentistry & Endodontics Vol.43 No.4
Objectives: To analyze the influence of thickness and incisal extension of indirect veneers on the stress and strain generated in maxillary canine teeth. Materials and Methods: A 3-dimensional maxillary canine model was validated with an in vitro strain gauge and exported to computer-assisted engineering software. Materials were considered homogeneous, isotropic, and elastic. Each canine tooth was then subjected to a 0.3 and 0.8 mm reduction on the facial surface, in preparations with and without incisal covering, and restored with a lithium disilicate veneer. A 50 N load was applied at 45° to the long axis of the tooth, on the incisal third of the palatal surface of the crown. Results: The results showed a mean of 218.16 µstrain of stress in the in vitro experiment, and 210.63 µstrain in finite element analysis (FEA). The stress concentration on prepared teeth was higher at the palatal root surface, with a mean value of 11.02 MPa and varying less than 3% between the preparation designs. The veneers concentrated higher stresses at the incisal third of the facial surface, with a mean of 3.88 MPa and a 40% increase in less-thick veneers. The incisal cover generated a new stress concentration area, with values over 48.18 MPa. Conclusions: The mathematical model for a maxillary canine tooth was validated using FEA. The thickness (0.3 or 0.8 mm) and the incisal covering showed no difference for the tooth structure. However, the incisal covering was harmful for the veneer, of which the greatest thickness was beneficial.
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Olive M. F. Demgne,Judith Flore Tchuissang Mbougnia,Armel Jackson Seukep,Armelle Tsafack Mbaveng,Mathieu Tene,Paul Nayim,Brice E. N. Wamba,Michel-Gael F. Guefack,Veronique Penlap Beng,Pierre Tane,Vict 경희대학교 융합한의과학연구소 2022 Oriental Pharmacy and Experimental Medicine Vol.22 No.4
In this study, we examined the antibacterial and antibiotic-resistance reversal properties of methanol (MeOH) and ethyl acetate (EtOAc) extracts and compounds from Psychotria sycophylla aerial parts against drug-resistant bacteria. The tests were performed using the microdilution method. The mechanisms of action were investigated on growth kinetic and proton pumps of Escherichia coli. The structures of isolated compounds including oleanolic acid (1), ursolic acid (2), lupeol (3), betulinic acid (4), β-sitosterol glucoside (5), and stigmasterol (6), were established based on nuclear magnetic resonance (NMR) and electrospray ionization-mass spectrometry (ESI–MS). The extracts displayed noteworthy antibacterial activities, with recorded minimal inhibitory concentrations (MIC) ranging from 4 to 1024 μg/mL. Significant activities (MIC < 100 μg/ mL) were obtained with the MeOH extract against Providencia stuartii PS2636 and Staphylococcus aureus MRSA9 (MIC of 16 μg/mL) as well as the EtOAc extract against S. aureus MRSA3 (MIC of 32 μg/mL) and Enterobacter aerogenes EA27 (MIC of 4 μg/mL). MeOH extract displayed a broad-spectrum antibacterial activity, acting against 21 out of 22 studied bacteria. The MICs of compounds (1–6) varied from 16 to 256 μg/mL. Oleanolic acid (1) appeared to be the most effective, preventing the growth of 100% of studied bacteria. The MeOH extract significantly enhanced the efficacy of conventional antibiotics against selected multidrug-resistant Gram-negative bacteria. The mechanistic investigations showed interference of MeOH with bacterial growth kinetic (by extending the lag phase) and inhibition of proton pumps. The current study provides a strong experimental baseline to consider P. sycophylla extracts and compounds as potent antibacterial natural products.
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Rö,nsberg, David,Debbab, Abdessamad,Má,ndi, Attila,Vasylyeva, Vera,Bö,hler, Philip,Stork, Bjö,rn,Engelke, Laura,Hamacher, Alexandra,Sawadogo, Richard,Diederich, Marc,Wray, Vict American Chemical Society 2013 Journal of organic chemistry Vol.78 No.24
<P>Four tetrahydroxanthone dimers (<B>1</B>–<B>4</B>) and four biogenetically related monomers (<B>5</B>–<B>8</B>), including the new derivatives <B>4</B>–<B>6</B>, were isolated from the endophyte Phomopsis longicolla. The absolute configurations of <B>2</B>–<B>4</B> were established for the first time by TDDFT electronic circular dichroism calculations, and that of phomoxanthone A (<B>1</B>) was revised by X-ray crystallography. Phomoxanthone A (<B>1</B>) showed the strongest pro-apoptotic activity when tested against a panel of human cancer cell lines, including cisplatin-resistant cells, whereas it was up to 100-fold less active against healthy blood cells. It was also the most potent activator of murine T lymphocytes, NK cells, and macrophages, suggesting an activation of the immune system in parallel to its pro-apoptotic activity. This dual effect in combating cancer cells could help in fighting resistance during chemotherapy. Preliminary structure–activity studies of isolated compounds and derivatives obtained by semisynthesis (<B>9a</B>–<B>11</B>) hinted at the location of the biaryl axis and the presence of acetyl groups as important structural elements for the biological activity of the studied tetrahydroxanthones.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/joceah/2013/joceah.2013.78.issue-24/jo402066b/production/images/medium/jo-2013-02066b_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jo402066b'>ACS Electronic Supporting Info</A></P>
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