Marine Natural Meroterpenes: Synthesis and Antiproliferative Activity

Meroterpenes are compounds of mixed biogenesis, isolated from plants, microorganisms and marine invertebrates. We have previously isolated and determined the structure for a series of meroterpenes extracted from the ascidian Aplidium aff. densum. Here, we demonstrate the chemical synthesis of three of them and their derivatives, and evaluate their biological activity on two bacterial strains, on sea urchin eggs, and on cancerous and healthy human cells

Structures and activities of tiahuramides A–C, cyclic depsipeptides from a tahitian collection of the marine cyanobacterium Lyngbya majuscula

The structures of three new cyclic depsipeptides, tiahuramides A (1), B (2), and C (3), from a French Polynesian collection of the marine cyanobacterium Lyngbya majuscula are described. The planar structures of these compounds were established by a combination of mass spectrometry and 1D and 2D NMR experiments. Absolute configurations of natural and nonproteinogenic amino acids were determined through a combination of acid hydrolysis, derivitization with Marfey’s reagent, and HPLC. The absolute configuration of hydroxy acids was confirmed by Mosher’s method. The antibacterial activities of tiahuramides against three marine bacteria were evaluated. Compound 3 was the most active compound of the series, with an MIC of 6.7 μM on one of the three tested bacteria. The three peptides inhibit the first cell division of sea urchin fertilized eggs with IC50 values in the range from 3.9 to 11 μM. Tiahuramide B (2), the most potent compound, causes cellular alteration characteristics of apoptotic cells, blebbing, DNA condensation, and fragmentation, already at the first egg cleavage. The cytotoxic activity of compounds 1–3 was tested in SH-SY5Y human neuroblastoma cells. Compounds 2 and 3 showed an IC50 of 14 and 6.0 μM, respectively, whereas compound 1 displayed no toxicity in this cell line at 100 μM. To determine the type of cell death induced by tiahuramide C (3), SH-SY5Y cells were costained with annexin V–FITC and propidium iodide and analyzed by flow cytometry. The double staining indicated that the cytotoxicity of compound 3 in this cell line is produced by necrosis

Free Online Training and Value Perception in France

International audienceDigital training has taken on a major place in our society with the health crisis. Among the many online training offers available, some are free of charge, so that the user does not have to pay for his or her learning, and we can sometimes wonder about the value of these training courses: do they offer the same quality as the paid ones? After collecting data from 245 people, our study shows that the price of an e-learning course does not necessarily influence the value that the user attributes to it, and that a free course can have the same value and interest as a paid course. Moreover, free training is a significant marker in the decision-making process: it gives the training an additional benefit, which goes beyond the mere monetary savings made, compared to the same paid offer. Therefore, free training can give the user the perception of a greater general benefit than paid training

Effect of Online Training Price and Price Perception on Quality and Benefit Perception in France

International audienceWith the health problem, digital training has assumed a major role in our society. Some of the numerous online trainingopportunities are free, allowing the user to learn without having to pay, but occasionally we may question about the worth ofthese training opportunities—do they provide the same quality as the paid ones? Our two studies, which gathered informationfrom 245 and 114 individuals, demonstrates that a free course can have the same value and interest as a paid course and thatthe cost of an e-learning course does not always affect the value that the user attributes to it. We found that free training is animportant deciding factor because it provides the training with an advantage over the identical paid service that goes beyondsimple cost savings. As a result, free training may appear to the user to offer more overall benefits than expensive training.We also found that a price perceived as “a fair price” appear to the user as giving more benefits that an “expensive one”

Antifouling Activity of Meroterpenes Isolated from the Ascidian Aplidium aff. densum

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Antibacterial activity of carob (Ceratonia siliqua L.) extracts against phytopathogenic bacteria Pectobacterium atrosepticum

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Structures and Activities of Tiahuramides A–C, Cyclic Depsipeptides from a Tahitian Collection of the Marine Cyanobacterium <i>Lyngbya majuscula</i>

The structures of three new cyclic depsipeptides, tiahuramides A (<b>1</b>), B (<b>2</b>), and C (<b>3</b>), from a French Polynesian collection of the marine cyanobacterium <i>Lyngbya majuscula</i> are described. The planar structures of these compounds were established by a combination of mass spectrometry and 1D and 2D NMR experiments. Absolute configurations of natural and nonproteinogenic amino acids were determined through a combination of acid hydrolysis, derivitization with Marfey’s reagent, and HPLC. The absolute configuration of hydroxy acids was confirmed by Mosher’s method. The antibacterial activities of tiahuramides against three marine bacteria were evaluated. Compound <b>3</b> was the most active compound of the series, with an MIC of 6.7 μM on one of the three tested bacteria. The three peptides inhibit the first cell division of sea urchin fertilized eggs with IC₅₀ values in the range from 3.9 to 11 μM. Tiahuramide B (<b>2</b>), the most potent compound, causes cellular alteration characteristics of apoptotic cells, blebbing, DNA condensation, and fragmentation, already at the first egg cleavage. The cytotoxic activity of compounds <b>1</b>–<b>3</b> was tested in SH-SY5Y human neuroblastoma cells. Compounds <b>2</b> and <b>3</b> showed an IC₅₀ of 14 and 6.0 μM, respectively, whereas compound <b>1</b> displayed no toxicity in this cell line at 100 μM. To determine the type of cell death induced by tiahuramide C (<b>3</b>), SH-SY5Y cells were costained with annexin V–FITC and propidium iodide and analyzed by flow cytometry. The double staining indicated that the cytotoxicity of compound <b>3</b> in this cell line is produced by necrosis