GARDINERIN, A BIOLOGICALLY ACTIVE ACETOGENIN FROM THE SRI LANKAN GONIOTHALAMUS GARDINERI HOOK. F. AND THOMSON

Objective: The study was undertaken to isolate biologically active compounds from Goniothalamus gardineri, a plant endemic to Sri Lanka. Methods: Roots and flowers of Goniothalamus gardineri were extracted into dichloromethane and methanol. A new acetogenin, gardinerin isolated by column chromatography of the dichloromethane extract was structurally characterized using NMR and Mass spectroscopies. It was found to be mosquito larvicidal (against 2nd instar larvae of Aedes aegypti), cytotoxic (in the brine shrimp assay) and antioxidant (DPPH assay). Results: Gardinerin exhibited potent mosquitolarvicidal activity (LC50 = 0.0744±0.37 ppm.), cytotoxicity (LC50 = 1.5±0.37 ppm) and antioxidant activity (IC50 =10.02±0.01 ppm). The same extract furnished (5R)-goniothalamin. The hexane extract of the flowers of G. gardineri yielded poriferesterol and stigmast-4, 22-dien-3-one.Conclusion: The endemic plant G. gardineri has yielded an acetogenin possessing highly potent antioxidant, cytotoxic and mosquitolarvicidal activity. Â

Synthesis, Characterization, and Evaluation of Rhodamine Based Sensors For Nerve Gas Mimics

Six new rhodamine-B based compounds were synthesized (1-6) and used as fluorescent turn-ON sensors for diethyl chlorophosphate (DCP) in aqueous media at pH 7.0. Compound 1 and 3 gave high fluorescent enhancement with DCP compared to the other compounds. Very high selectivity and sensitivity were observed as these compounds did not show significant fluorescent enhancement with dimethyl methylphosphonate (DMMP), HCl, and metal ions, such as Na +, K +, Ca 2+, Cr 3+, Mn 2+, Fe 2+, Co 2+, Ni 2+, Cu 2+, Zn 2+, Cd 2+, Hg 2+, Pb 2+. Depending on the way the sensor is presented, results are instantaneous or observed over some minutes. © 2011 Elsevier Ltd. All rights reserved

Highly Sensitive and Selective Reversible Sensor for the Detection of Cr³⁺

A new fluorescent sensor capable of sensing Cr3+ has been synthesized. Complexing with Cr3+ triggers the formation of a highly fluorescent ring-open form which is pink in color. The sensor shows extremely high fluorescence enhancement upon complexation with Cr3+ and it can be used as a “naked eye” sensor. Binding of Cr3+ was found to be reversible as the pink color disappears with excess EDTA. © 2009 Elsevier Ltd. All rights reserved

Rhodamine Based Turn-ON Dual Sensor For Fe³⁺ and Cu²⁺

A new rhodamine-based dual sensor selectively detects Cu 2+ and Fe 3+. Complexation with Fe 3+ triggers the formation of a highly fluorescent ring-open form, while Cu 2+ forms a nonfluorescent complex detectable by its UV-vis spectrum. Both Cu 2+ and Fe 3+ give an immediate color change and the sensing mechanism is reversible, as indicated by disappearance of the color with the addition of excess EDTA. © 2011 Elsevier Ltd. All rights reserved

Single- and Multiphoton Turn-on Fluorescent Fe³⁺ Sensors Based on Bis(rhodamine)

Selective and sensitive turn-on fluorescent Fe 3+ sensors based on novel bis(rhodamine) dye molecules are reported. The compounds are synthesized with very high yields and characterized with NMR, ESI mass spectrometry, and elemental analysis. Single- and two-photon fluorescence enhancement is observed for both molecules in the presence of Fe 3+. High selectivity and sensitivity is observed over other metal ions and is shown to be due mainly to the spirolactam ring-opening power of Fe 3+. All measurements are made in buffer environments simulating biological conditions to facilitate single- and multiphoton fluorescence imaging of Fe 3+ in vivo and in vitro. Larger enhancement of fluorescence for both one- and two-photon excitation makes them suitable candidates for fluorescent labeling of biological systems. Two photon cross-section and time-resolved fluorescence measurements are utilized to understand the selectivity of the present sensors for Fe 3+-sensing. © 2010 American Chemical Society

Bordetella pertussis FbpA Binds Both Unchelated Iron and Iron Siderophore Complexes

Bordetella pertussis is the causative agent of whooping cough. This pathogenic bacterium can obtain the essential nutrient iron using its native alcaligin siderophore and by utilizing xeno-siderophores such as desferrioxamine B, ferrichrome, and enterobactin. Previous genome-wide expression profiling identified an iron repressible B. pertussis gene encoding a periplasmic protein (FbpA_Bp). A previously reported crystal structure shows significant similarity between FbpA_Bp and previously characterized bacterial iron binding proteins, and established its iron-binding ability. Bordetella growth studies determined that FbpA_Bp was required for utilization of not only unchelated iron, but also utilization of iron bound to both native and xeno-siderophores. In this <i>in vitro</i> solution study, we quantified the binding of unchelated ferric iron to FbpA_Bp in the presence of various anions and importantly, we demonstrated that FbpA_Bp binds all the ferric siderophores tested (native and xeno) with μM affinity. <i>In silico</i> modeling augmented solution data. FbpA_Bp was incapable of iron removal from ferric xeno-siderophores <i>in vitro</i>. However, when FbpA_Bp was reacted with native ferric-alcaligin, it elicited a pronounced change in the iron coordination environment, which may signify an early step in FbpA_Bp-mediated iron removal from the native siderophore. To our knowledge, this is the first time the periplasmic component of an iron uptake system has been shown to bind iron directly as Fe³⁺ and indirectly as a ferric siderophore complex

Borate as a Synergistic Anion for <i>Marinobacter algicola</i> Ferric Binding Protein, FbpA: A Role for Boron in Iron Transport in Marine Life

Boron in the ocean is generally considered a nonbiological element due to its relatively high concentration (0.4 mM) and depth independent concentration profile. Here we report an unexpected role for boron in the iron transport system of the marine bacterium <i>Marinobacter algicola</i>. Proteome analysis under varying boron concentrations revealed that the periplasmic ferric binding protein (Mb-FbpA) was among the proteins whose expression was most affected, strongly implicating the involvement of boron in iron utilization. Here we show that boron facilitates Fe³⁺ sequestration by Mb-FbpA at pH 8 (oceanic pH) by acting as a synergistic anion (B­(OH)₄^1–). Fe³⁺ sequestration does not occur at pH 6.5 where boric acid (B­(OH)₃; p<i>K</i>_a = 8.55) is the predominant species. Borate anion is also shown to bind to apo-Mb-FbpA with mM affinity at pH 8, consistent with the biological relevance implied from boron’s oceanic concentration (0.4 mM). Borate is among those synergistic anions tested which support the strongest Fe³⁺ binding to Mb-FbpA, where the range of anion dependent affinity constants is log <i>K′</i>_eff = 21–22. Since the p<i>K</i>_a of boric acid (8.55) lies near the pH of ocean water, changes in oceanic pH, as a consequence of fluctuations in atmospheric CO₂, may perturb iron uptake in many marine heterotrophic bacteria due to a decrease in oceanic borate anion concentration

Correction: Outcomes among children and adults at risk of severe dengue in Sri Lanka: Opportunity for outpatient case management in countries with high disease burden.

[This corrects the article DOI: 10.1371/journal.pntd.0010091.]