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The Genus Blumea
Published in Namrita Lall, Medicinal Plants for Cosmetics, Health and Diseases, 2022
In further studies, a very rare halogenated xanthene was reported by Huang et al. (2010) from ethyl acetate fraction of B. riperia and was named Blumeaxanthene II (67). Compound 67 was found to be weakly cytotoxic against Bel-7404 liver cancer cells tested in vitro based on concentration (Huang et al., 2010). Saewan et al. (2011) isolated nine flavonoids from B. balsamifera and evaluated them for cytotoxicity against KB (oral cancer), MCF-7 (breast cancer) and NCI-H187 (lung cancer) cell lines, whereby most of the flavonoids were found to be active. Luteolin-7-methyl ether (3) showed strong cytotoxicity against human lung cancer (NCI-H187) cell lines with an IC50 value of 1.29 μg/mL and moderate toxicity against oral cavity cancer (KB) cell lines with an IC50 of 17.83 μg/mL. The isolated flavonoids—Quercetin (17), Rhamnetin (20), Tamarixetin (21), Dihydroquercetin-4’-methylether (44) and Dihydroquercetin-7,4’-dimethylether (45)—showed significantly higher anti-tyrosinase activity than Arbutin (positive control) on mushroom tyrosinase using levodopa (L-DOPA) as the substrate (Saewan et al., 2011).
New Chemical Scaffolds to Selectively Target the Trypanothione Metabolism
Published in Venkatesan Jayaprakash, Daniele Castagnolo, Yusuf Özkay, Medicinal Chemistry of Neglected and Tropical Diseases, 2019
Chibale et al. (2003) showed that some compounds including mepacrine, promazine and clomipramine display the ability to both reverse the chloroquine resistance in Plasmodium and to inhibit TR. Based on this observation, they designed and developed a series of xanthene derivatives with intrinsic antimalarial activity, as potential TR inhibitor. Among all the derivatives of xanthenes, compound 16 showed the highest inhibitory activity (IC50 of 35.7 μM), conserving an antimalarial activity (IC50 = 1.75 μM). Chibale et al. also synthesized a series of sulfonamide and urea derivatives of quinacrine with varying methylene spacer lengths, tested for inhibition of TR and for activity in vitro against strains of the parasitic protozoa Trypanosoma, Leishmania and Plasmodium (Chibale et al. 2001, 2000). They succeeded in finding inhibitors with higher activity against TR with respect to quinacrine, with the best compound with an IC50 of 3.3 μM, 40 times better than that of quinacrine (IC50 = 133 μM). Their studies revealed that sulfonamide derivatives were more active than urea in inhibiting TR but this trend of activity did not correlate with the in vitro activities against L. donovani, T. cruzi, and T. brucei.
Molecular Imaging of Viable Cancer Cells
Published in Shoogo Ueno, Bioimaging, 2020
PeT is a widely accepted mechanism for fluorescence quenching of fluorophores. However, it had been believed that PeT quenching was applicable only to UV-excitable fluorophores such as anthracene, but not to long-wavelength fluorophores in the visible to NIR range. In this context, our research group demonstrated that the fluorescence properties of probes could be precisely controlled by means of intramolecular PeT, and we developed various kinds of fluorescence probes. We considered that the structure of fluorescein, widely used as the fluorescent core of fluorescence probes, could be divided into two parts, i.e., the benzoic acid moiety as the potential PeT donor and the xanthene ring as the fluorophore. The basis for this idea was that only small alterations in absorbance are observed among fluorescein derivatives, and the dihedral angle between the benzoic acid moiety and the xanthene ring is almost 90°, which strongly suggests that there would be little ground-state interaction between these two parts. We also found that fluorescence emission from the xanthene fluorophore can be modulated by varying the Highest Occupied Molecular Orbital (HOMO) level of the benzoic acid moiety; when the HOMO level is higher than a certain threshold, the molecule shows little fluorescence, which suggests the occurrence of PeT quenching. On the other hand, when the HOMO level is lower than the threshold, as in the original fluorescein molecule for example, strong fluorescence emission is observed. The occurrence of PeT is clearly evidenced by transient absorption spectroscopy, which showed bands of the radical cation of the electron donor moiety and the radical anion of the xanthene moiety.11 The PeT rates and the rates of back electron transfer follow the Marcus parabolic dependence of electron transfer rate on the driving force. These observations provided a quantitative basis for modulating the fluorescence properties of fluorescein derivatives, and thus a clear rationale for designing fluorescein-based probes was established for the first time. This strategy has been proved to be applicable not only to fluorescein, but also to a wide range of long-wavelength excitable fluorophores such as BODIPYs,12 rhodamines,13 silicon rhodamines,14 and cyanines.15 Further, the opposite direction of electron transfer also works in visible light-excitable fluorophores: the fluorescence properties can be modulated via PeT from the excited fluorophore to a reducible benzene moiety (donor-excited PeT; d-PeT).16 In other words, when the Lowest Unoccupied Molecular Orbital (LUMO) energy of the benzoic acid moiety is lower than a certain threshold, the rate of d-PeT is quite fast and hence the derivative will be non-fluorescent. This finding also provided the basis for a new and practical strategy for rational design of novel functional fluorescence probes.
Antimicrobial sonodynamic and photodynamic therapies against Candida albicans
Published in Biofouling, 2018
Fernanda Alves, Ana Cláudia Pavarina, Ewerton Garcia de Oliveira Mima, Anthony P. McHale, John Francis Callan
The present investigation also demonstrated that the treatments mediated by the sensitizer PDZ were more effective on both planktonic and biofilm phase growths in comparison with the RB treatments. These results obtained may be attributed to the different characteristics of each sensitizer. The sensitizer PDZ, classified as a second-generation PS, is obtained from the cyanobacterium Spirulina platensis as a noncovalent complex of N-methyl-D-glucosamine chlorine e6 salt on basis of chlorophyll a derivatives. PDZ has an absorption peak in the red region of the spectrum (660 nm) and it is known to produce a high amount of singlet oxygen (Ferreira et al. 2008). On the other hand, the xanthene dye RB is an anionic water-soluble synthetic fluorescein derivative, which has an absorption peak in the green region of the spectrum (450–600 nm) and a low rate of photodegradation (Spagnul et al. 2015). This PS is capable of photo-catalytic conversion of an oxygen molecule to singlet oxygen under 532 nm light irradiation, with a singlet oxygen quantum yield of ~76% (Encinas et al. 2009). Moreover, the higher efficacy of the aPDT treatment mediated by PDZ in comparison with RB may also be attributed to the wavelength of the LED device used. PDZ was excited by a LED device with the appropriated wavelength for this sensitizer (660 nm) and RB was not, and this may influence the efficacy of the treatment.
Neuropharmacological and molecular docking studies of xanthones from Swertia corymbosa
Published in Journal of Receptors and Signal Transduction, 2018
Ganesan Mahendran, Ramachandran Vijayan
Despite this apparent medicinal value, the psychopharmacological effects of xanthones from S. corymbosa have not been extensively characterized. Thus, the goal of the present study was to screen the psychopharmacological activities of xanthones through established animal models. Rates were given xanthenes compounds and then were subjected to evaluate the psychomotor, sedative-hypnotic, anxiolytic and anticonvulsant effects of a substance. Finally, molecular modeling study [12,13] was employed to understand the structural features and the key active site residues involved in the molecular interactions with the anti-epileptic and anxiolytic receptors. We also observed the structural changes of the receptors active sites upon drug binding provides insights into the biological interactions may help in the development of potential drugs against psychiatric disorders.
Recent advances in electrochemical and optical sensing of the organophosphate chlorpyrifos: a review
Published in Critical Reviews in Toxicology, 2022
Athira Sradha S, Louis George, Keerthana P, Anitha Varghese
Fluorescence detection based-sensors are the most commonly explored area in optical sensing. FBS exploits the property of conditional fluorescence of naturally fluorescent molecules. This implies that based on the interaction with the analyte molecules, molecules can be either be fluorescent or non-fluorescent. Since most analytes are not fluorescent materials, FBS involves the attachment of fluorescent labels or probes onto the analytes via chemical linkages. The labels/probes must have suitable functional groups for easy attachment, high quantum yield, high molar absorption coefficient and must be easily excitable. Mostly organic dyes like xanthene dyes satisfy these conditions and serve as excellent candidates for fluorescent label/probe (Sharma et al. 2018).