2,5-diketopiperazines mitigate the amount of advanced glycation end products accumulated with age in human dermal fibroblasts.

OBJECTIVE: Glycation is a common non-enzymatic reaction between proteins and sugars, resulting in the formation of advanced glycation end products (AGEs) in the human body. As can be seen in diabetic patients, the accumulation of AGEs in the skin has aesthetic consequences (wrinkles, brown spots and yellowish complexion). Therefore, the objective of this work was to find compounds isolated from natural sources that could eliminate the final AGEs accumulated in the skin with ageing. METHODS AND RESULTS: A preliminary screening performed on a bank of microbial extracts and pure compounds showed that 2,5-Diketopiperazines (DKPs), as well as the extract of Sphingobacterium sp (SNB-CN13), reduced the presence of AGEs in fibroblasts by -28% and -23%, respectively. In this article, we present the dereplication approach used to reveal the presence of 26 different DKPs in the crude extract of Sphingobacterium sp. Bioguided fractionation has led to the isolation of 12 of them, whose identity has been confirmed by HRMS and NMR. A green synthesis approach has been developed to synthesize 3 symmetrical DKPs. The biological activity of all DKPs was evaluated by the development of an in vitro test using immunocytochemistry to reveal the presence of AGE carboxymethyl-lysine in human dermal fibroblasts. CONCLUSION: Our work shows for the first time that DKPs decrease the amount of carboxymethyl-lysine AGE in elderly human dermal fibroblasts grown in vitro. Therefore, diketopiperazines can be considered as compounds of interest for dermatological and cosmetic applications with an anti-ageing aim.

OBJECTIF: La glycation est une réaction non enzymatique courante entre les protéines et les sucres, qui entraîne la formation de produits finaux de glycation avancée (AGE) dans le corps humain. Comme on peut le voir chez les patients diabétiques, l'accumulation d'AGE dans la peau a des conséquences esthétiques (rides, taches brunes, teint jaunâtre). Par conséquent, l'objectif de ce travail était de trouver des composés isolés de sources naturelles qui pourraient éliminer les AGE finaux accumulés dans la peau avec le vieillissement. MÉTHODES & RÉSULTATS: Un examen préliminaire effectué sur une banque d'extraits microbiens et de composés purs a montré que les 2,5-dicétopipérazines (DKP), ainsi que l'extrait de Sphingobacterium sp. (SNB-CN13), réduisaient la présence d'AGE dans les fibroblastes de - 28% et - 23% respectivement. Dans cet article, nous présentons l'approche de déréplication utilisée pour révéler la présence de 26 DKP différentes dans l'extrait brut de Sphingobacterium sp. Le fractionnement bioguidé a conduit à l'isolement de 12 d'entre elles, dont l'identité a été confirmée par HRMS et RMN. Une approche de synthèse verte a été développée pour synthétiser 3 DKP symétriques. L'activité biologique de toutes les DKP a été évaluée par le développement d'un test in vitro utilisant l'immunocytochimie pour révéler la présence de carboxyméthyl-lysine AGE dans les fibroblastes dermiques humains. CONCLUSION: Nos travaux montrent pour la première fois que les DKP diminuent la quantité de carboxyméthyl-lysine AGE dans les fibroblastes dermiques humains âgés cultivés in vitro. Par conséquent, les dicétopipérazines peuvent être considérées comme des composés intéressants pour des applications dermatologiques et cosmétiques à visée anti-âge.

In vitro antidermatophytic activity of Otacanthus azureus (Linden) Ronse essential oil alone and in combination with azoles.

AIMS: We determined the chemical composition and investigated the antifungal activity of Otacanthus azureus (Linden) Ronse essential oil (EO) against a range of dermatophytes alone or in combination with azole antifungals. METHODS AND RESULTS: Aerial parts of the plant were steam-distilled and the obtained oil was analysed by gas chromatography/mass spectrometry and (1) H-NMR. It was shown to be largely composed of sesquiterpenes, with the main component being ß-copaen-4-α-ol. Using broth microdilution techniques, this oil was found to have remarkable in vitro antifungal activities. Minimum inhibitory concentrations as low as 4 µg ml(-1) were recorded. The analysis of the combined effect of the O. azureus EO with azoles using chequerboard assays revealed a synergism between the EO and ketoconazole, fluconazole or itraconazole against Trichophyton mentagrophytes. Notably, the O. azureus essential oil showed low cytotoxicity to VERO cells. CONCLUSIONS: The O. azureus essential oil alone or in combination with azoles is a promising antifungal agent in the treatment for human dermatomycoses caused by filamentous fungi. SIGNIFICANCE AND IMPACT OF THE STUDY: There is much interest in the study of essential oils for the discovery of new antimicrobial drugs. This study has highlighted the antidermatophytic activity of the O. azureus EO.

Antileishmanial sesquiterpene lactones from Pseudelephantopus spicatus, a traditional remedy from the Chayahuita Amerindians (Peru). Part III.

ETHNOPHARMACOLOGICAL RELEVANCE: The study of traditional remedies used by the Chayahuita, an ethnic group from the Peruvian Amazonia, has prompted us to investigate in detail the ethanolic extract of Pseudelephantopus spicatus (Juss. ex Aubl.) C.F. Baker, which has demonstrated strong biological activity towards Leishmania amazonensis. Our goal was to discover the active compound of this plant-based remedy. MATERIALS AND METHODS: A bioguided fractionation of the crude extract was undertaken based on the biological activity recorded against Leishmania amazonensis axenic amastigotes in in vitro bioassays. RESULTS: Three strongly to moderately active compounds were isolated: two hirsutinolides (the 8,13-diacetyl-piptocarphol and the 8-acetyl-13-O-ethyl-piptocarphol) and ursolic acid. IC(50) against Leishmania amazonensis axenic amastigotes are respectively 0.2, 0.37 and 0.99 µM (while IC(50) of amphotericin B is 0.41 µM). These compounds have never been isolated from this plant species, and germacranolides have never been identified as potential antileishmanial agents. CONCLUSIONS: The compounds isolated from Pseudelephantopus spicatus account for the antileishmanial activity of the plant, thus giving support to its use by the Chayahuita in Peru.