Alkaloids from single skins of the Argentinian toad Melanophryniscus rubriventris (ANURA, BUFONIDAE): An unexpected variability in alkaloid profiles and a profusion of new structures

GC-MS analysis of single-skins of ten Melanophryniscus rubriventris toads (five collections of two toads each) captured during their breeding season in NW Argentina has revealed a total of 127 alkaloids of which 56 had not been previously detected in any frog or toad. Included among these new alkaloids are 23 new diastereomers of previously reported alkaloids. What is particularly distinguishing about the alkaloid profiles of these ten collections is the occurrence of many of the alkaloids, whether known or new to us, in only one of the ten skins sampled, despite two skins being obtained from each breeding site of the five populations. Many of the alkaloids are of classes known to have structures with branched-chains (e.g. pumiliotoxins and tricyclic structures) that are considered to derive from dietary mites. A large number of previously reported and new alkaloids are also of unclassified structures. Only a very few 3,5-disubstituted-indolizidine or -pyrrolizidine alkaloids are observed that have a straight-chain carbon skeleton and are likely derived from ant prey. The possible relationship of these collections made during the toad’s brief breeding episodes to sequestration of dietary arthropods and individual alkaloid profiles is discussed.Fil: Garraffo, H. Martin. Laboratorio de Bioorganic Chemistry; Estados UnidosFil: Andriamaharavo, Nirina R.. Laboratorio de Bioorganic Chemistry; Estados UnidosFil: Vaira, Marcos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentina. Universidad Nacional de Jujuy. Facultad de Ingeniería; ArgentinaFil: Quiroga, Maria Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Jujuy. Universidad Nacional de Jujuy. Centro de Investigaciones y Transferencia de Jujuy; ArgentinaFil: Heit, Cecilia Inés. Laboratorio de Análisis de Residuos y Trazas; ArgentinaFil: Spande, Thomas F.. Laboratorio de Bioorganic Chemistry; Estados Unido

62(P-39) Total Synthesis of Dart-Poison Frog Alkaloids 223A, 205B, 207I, 223I

A remarkably diverse array of biologically active alkaloids, for example, blockers of neuromuscular-type, ganglionic-type, and nicotinic receptor channels, occurs in amphibian skin, and over 500 alkaloids have been isolated to date. The structural diversity and pharmacological activity associated with these alkaloids have stimulated research in numerous synthetic groups. Among them, we achieved the first synthesis of the alkaloids 223A has been accomplished, the proposed structure has been revised, and the relative stereostructure of natural 223A was determined. We have demonstrated the first enantioselective total synthesis of the antipode of structurally unique alkaloid 205B, and the absolute stereochemistry of natural 205B has been determined to be 2aR, 5aR, 6S, 8S, 8aR. Furthermore, we achieved the chiral synthesis of quinolizidine 207I and its absolute stereochemistry was determined to be 1S, 4S, 10S by the GC-coinjection analysis of racemic compound and natural product. Finally, we also achieved the synthesis of both stereoisomers for the alkaloid 223I, and the determination of the ralative stereochemistry of natural 223I using GC-coinjection analysis of these isomers and natural product is now under investigations

The chemical defense of the Texas cave harvestman Chinquipellobunus madlae: first report on the family Stygnopsidae and on a North American troglobiont harvestman (Opilones: Gonyleptoidea)

Volume: 38Start Page: 126End Page: 12

Heteroresistance to Fluconazole in Cryptococcus neoformans Is Intrinsic and Associated with Virulence▿ †

In 1999, heteroresistance to triazoles was reported in Cryptococcus neoformans strains isolated from an azole therapy failure case of cryptococcosis in an AIDS patient and in a diagnostic strain from a non-AIDS patient. In this study, we analyzed 130 strains of C. neoformans isolated from clinical and environmental sources before 1979, prior to the advent of triazoles, and 16 fluconazole (FLC)-resistant strains isolated from AIDS patients undergoing FLC maintenance therapy during 1990 to 2000. All strains isolated prior to 1979 manifested heteroresistance (subset of a population that grows in the presence of FLC) at concentrations between 4 and 64 μg/ml, and all 16 FLC-resistant AIDS isolates manifested heteroresistance at concentrations between 16 and 128 μg/ml. Upon exposure to stepwise increases in the concentration of FLC, subpopulations that could grow at higher concentrations emerged. Repeated transfer on drug-free media caused the highly resistant subpopulations to revert to the original level of heteroresistance. The reversion pattern fell into four categories based on the number of transfers required. The strains heteroresistant at ≥32 μg/ml were significantly more resistant to other xenobiotics and were also more virulent in mice than were those heteroresistant at ≤8 μg/ml. During FLC treatment of mice infected by strains with low levels of heteroresistance, subpopulations exhibiting higher levels of heteroresistance emerged after a certain period of time. The ABC transporter AFR1, known to efflux FLC, was unrelated to the heteroresistance mechanism. Our study showed that heteroresistance to azole is universal and suggests that heteroresistance contributes to relapse of cryptococcosis during azole maintenance therapy

Widespread sucralose exposure in a randomized clinical trial in healthy young adults.

Background: Low-calorie sweeteners (LCSs) are found in many foods and beverages, but consumers may not realize their presence, and their role in appetite, weight, and health is controversial. Although consumption limits based on toxicologic safety are well established, the threshold required to exert clinically relevant metabolic effects is unknown. Objectives: This study aimed to determine whether individuals who do not report consumption of LCSs can be correctly characterized as “unexposed” and to investigate whether instructions to avoid LCSs are effective in minimizing exposure. Design: Eighteen healthy 18- to 35-y-old “nonconsumers” (<1 food or beverage with LCSs/mo) enrolled in a 2-wk trial designed to evaluate the effects of LCSs on the gut microbiota. The trial consisted of 3 visits. At baseline, participants were counseled extensively about avoiding LCSs. After the run-in, participants were randomly assigned to consume diet soda containing sucralose or carbonated water (control) 3 times/d for 1 wk. Food diaries were maintained throughout the study, and a spot urine sample was collected at each visit. Results: At baseline, 8 participants had sucralose in their urine (29.9–239.0 ng/mL; mean ± SD: 111.4 ± 91.5 ng/mL). After the run-in, sucralose was found in 8 individuals (2 of whom did not have detectable sucralose at baseline) and ranged from 25.0 to 1062.0 ng/mL (mean ± SD: 191.7 ± 354.2 ng/mL). Only 1 participant reported consumption of an LCS-containing food before her visit. After the intervention, sucralose was detected in 3 individuals randomly assigned to receive carbonated water (26–121 ng/mL; mean ± SD: 60.7 ± 52.4 ng/mL). Conclusions: Despite the selection of healthy volunteers with minimal reported LCS consumption, more than one-third were exposed to sucralose at baseline and/or before randomization, and nearly half were exposed after assignment to the control. This shows that instructions to avoid LCSs are not effective and that nondietary sources (e.g., personal care products) may be important contributors to overall exposure. This trial was registered at clinicaltrials.gov as NCT02877186

Discovery of the Costa Rican poison frog Dendrobates granuliferus in sympatry with Dendrobates pumilio, and comments on taxonomic use of skin alkaloids. American Museum novitates ; no. 3144

21 p. : ill. (some col.) ; 26 cm.Includes bibliographical references (p. 19-21)."Dendrobates granuliferus, previously thought to be a characteristic endemic of Pacific-side rain forest in the Golfo Dulce region, was found in sympatry with Dendrobates pumilio on the Caribbean coast of southeastern Costa Rica, near the Panamanian border. The sympatric frogs were easily separated by features of coloration and skin texture. Relative abundance in microsympatry was about 100 pumilio:4 granuliferus. Inasmuch as Dendrobates pumilio is sometimes strikingly polymorphic within populations, the initial identifications were tested with bioacoustical, skin-alkaloid, and allozyme data. These comparisons negate the possibility of intrapopulational polymorphism and are consistent with the determination of the rare species as D. granuliferus. Previous inferences that D. granuliferus and D. pumilio are sister species are neither supported nor repudiated by present data. Interpopulational and even individual variation in the skin toxins of these species is extraordinary and probably reflect dietary differences as well as genetic factors. Current knowledge of the dendrobatid alkaloids is briefly reviewed in a systematic context. With a few exceptions, skin chemistry has not been useful in supporting taxonomic differentiation of closely related species. But underlying genetic mechanisms for alkaloid sequestering (and synthesis?) support the monophyly of a suprageneric group of aposematic dendrobatids (tropical poison frogs). Within this group, the monophyly of Phyllobates (true dart-poison frogs) and of Phyllobates + Dendrobates is supported by alkaloid data. The monophyly of Minyobates (dwarf poison frogs) also is corroborated, although in this case the alkaloid character is one of loss and especially in need of further study"--P. [1]-2