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Chemoenzymatic synthesis of sulfoquinovosylmonoacylglycerols (SQMG) as anti-tumor-promoters
Full text linkDuring our search for new glycoglycerolipids active in cancer chemoprevention, in recent years we have synthesized a number of esters of 2-O-beta-D-glycosylglycerols in which the length, shape, number and position of the acyl chain, and the type of sugar (alphaand beta glucose or galactose) were varied. These compounds were found to be very active in inhibiting the tumor-promoting activity of the phorbol ester TPA both in in vitro and in in vivo tests, being such activities mainly influenced by the changes of the acyl chains length. Sulfoquinovosylacylglycerols are acylated sulfoglycolipids in which sulfoquinovose (6-deoxy-6-sulfo-glucose) is alpha-linked to the sn-3 position of glycerol. These compounds exhibit noteworthy biological activities, that make them very attractive for their use in cancer therapy.
Here we report the synthesis of 6’-sulfo-derivatives (SQMG) based on the skeleton of 2-O-beta-D-glucosylglycerol to which previously synthesized biologically active glucoglycerolipid analogues are related. A chemoenzymatic strategy has been used to selectively insert the proper chemical functionalities (i.e. acyl chain) at the desired position of glucosylglycerol to obtain the target compounds. Their potential as anti-tumor-promoters will be also discussed
Sulfoglycolipids : new molecule for tumor treatment
No full textLarge number of glycoglycerolipids have been found in green, red and brown algae, which have been attracting a surge of interest due to the increased understanding of their wide spectrum of biological and pharmacological activities, including antitumor, anti-HIV, anti-inflammatory etc.
The sulfoglycolipids are abundant sulfur-containing glycerolipids in the biotic world, sulfoquinovosylacylglycerols (SQAGs), occur in higher plants, other photosynthetic organisms and most of the marine water algae2, a sulfonic acid head group, 6-deoxy-6-sulfo-glucose, referred to as sulfoquinovose3 is major characteristic feature of SQAGs. Recent records of SQAGs biological activities, includes inhibitory effects on HIV-reverse transcriptase4, eukaryotic DNA polymerase5, proliferation of some cancer cell lines5, angiogenesis (especially when coupled with tumor radiotherapy)6 and also apoptosis induction5, make these compounds very attractive for their potential in cancer therapy. Also, extractive SQAG mixtures are known to inhibit in vitro TPA induced tumor promotion stage7.
All of these above mentioned biological activities motivate us to synthesize new active compounds for cancer therapy by structural modifications of natural SQAGs. SQAG analogues (SQDG & SQMG) has been synthesized in which the sulfoquinovose moiety is β-linked to the 2 position of glycerol carrying acyl chains of different length with chemoenzymetic approach as well. Similar compounds, carrying a hydroxyl group instead of the sulfonate group (namely some glycoglycerolipid analogues), are known to be active as anti-tumor-promoters in TPA promoted carcinogenesis in vitro and in vivo experiments8,9.
A synthetic strategy has been used to selectively insert the proper chemical functionalities (i.e. sulfonate and acyl chains) at the desired positions of the previously prepared glucosylglycerol skeleton to obtain the target compounds. LPS enzyme played an important role regarding selectivity at glycerol moiety.
Biological evaluation of anti-tumor activities has been done including the anti-tumor-promoting properties of the obtained compounds.
Compared this data of SQDG with the reported activities for glycoglycerolipid analogues8,9 it was possible to ascertain the influence of the sulfonate group on the anti-tumor-promoting activity
2-O-beta-D-glucosylglycerol based analogues of sulfoquinovosylacylglycerols
No full textSulfoquinovosylacylglycerols(SQAG) are sulfoglycoglycerolipids discovered in photosynthetic microorganisms, a large number of marine algae and higher plants by Benson in 1959,1 in which sulfoquinovose (6-deoxy-6-sulfo-glucose) is -linked to the sn-3 position of a diacylglycerol. Recently reported2-3 biological activities of SQAG, including inhibitory effects on HIV-reverse transcriptase, mammalian DNA polymerase, proliferation of some cancer cell lines, angiogenesis and apoptosis induction, make these compounds very attractive for their potential in cancer therapy.
Here we report the synthesis of SQAG analogues based on the skeleton of 2-O-beta-D-glucosylglycerol to which previously prepared biologically active glucoglycerolipid analogues are related.4 A chemoenzymatic strategy has been used to selectively insert the proper chemical functionalities (i.e. acyl chains) at the desired positions of glucosylglycerol to obtain the target compounds. Their potential as anti-tumor-promoters and angiogenesis inhibitors will be also discussed
Sulfoglycolipids analogues as new molecules for tumor treatment
Full text linkThe sulfoglycolipids sulfoquinovosylacylglycerols(SQAG) are abundant sulfur-containing glycerolipids that are associated with photosynthetic organisms especially with a large number of marine algae. Their main structural feature is the anionic head group constituent sulfoquinovose, a derivative of glucose in which the 6-hydroxyl is replaced by a sulfonate group, -linked to the sn-3 position of a diacylglycerol1. Recently reported biological activities of SQAGs, including inhibitory effects on HIV-reverse transcriptase, and mammalian DNA polymerase, proliferation of some cancer cell lines, angiogenesis (especially when coupled with tumor radiotherapy), and apoptosis induction, make these compounds very attractive for their potential in cancer therapy. Also, extractive SQAG mixtures are known to inhibit in vitro TPA induced tumor promotion stage.
To obtain new active compounds for cancer therapy by structural modification of natural SQAGs, SQAG analogues have been synthesized in which the sulfoquinovose moiety is linked to the 2 position of glycerol carrying acyl chains of different length. Similar compounds in fact, with a 6’-hydroxyl instead of a 6’-sulfonate (namely some glycoglycerolipid analogues), are known to be active as anti-tumor-promoters in TPA promoted carcinogenesis in vitro and in vivo experiments.
A synthetic strategy has been used to selectively insert the proper chemical functionalities (i.e. sulfonate and acyl chains) at the desired positions of the previously prepared glucosylglycerol skeleton to obtain the target compounds.
Biological evaluation of anti-tumor activities will be performed including the study of their chemopreventing potential
SQAGs: A stepping stone in the biotic world
No full textMulti-targeting drug discovery research has been driven, medically, commercially and intellectually; this need has often been equated with the identification and exploitation of novel targets. Glycolipids present both potentials and problems, their biological relevance has been recognized, but problems in procuring lipids rendered them a difficult class of compounds to handle in drug discovery efforts. Sulfoquinovosylacylglycerols (SQAGs), which are one of the abundant sulfur-containing glycerolipids in the biotic world, isolated from different phototrophic organisms, particularly plants and algae, have already been identified as bioactive compounds. In addition to their antiviral activity, their influence on the immune response in mammalian cells is the focus of many studies shown to have an important role in several biological activities. The purpose of this contest is to spotlight the longtime untouched topics of availability, historical background synthesis and recent findings of SQAG's as mammalian DNA polymerase inhibitor, antiangiogenesis, radiosensitizer, immunosuppressive quality, HIV-reverse transcriptase inhibitor, not only for optimizing the treatment of cancer but also for developing the therapeutic approaches for various diseases. This is definitely the beginning of the revolution in the biotic world
2-O-β-d-Glucopyranosyl-sn-glycerol based analogues of sulfoquinovosyldiacylglycerols (SQDG) and their role in inhibiting Epstein-Barr virus early antigen activation
No full textNew sulfoquinovosyldiacylglycerols derived from 2-O-beta-d-glucopyranosyl-sn-glycerol, carrying acyl chains of various length on the glycerol moiety, were prepared through a convenient synthetic procedure in which a sulfonate is introduced at the C-6 position of glucose by oxidation of a thioacetate in the presence of the unprotected secondary hydroxyl groups, and tested for their anti-tumor-promoting activity using a short-term in vitro assay for Epstein-Barr virus early antigen (EBV-EA) activation. Our study has allowed to ascertain the role of the 6'-sulfonate group and the need of a free hydroxyl group on the glycerol moiety in inhibiting the EBV activation promoted by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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