A new phthalide derivative from Peperomia nivalis

One new phthalide (1) was isolated from aerial parts of Peperomia nivalis, along with known compounds (2 and 3), reported in this species for the first time. The structure of the new compound was characterised on the basis of 1D (H-1 and C-13 NMR), 2D (COSY, HMQC, HMBC and NOESY) NMR and high-resolution mass spectral (HRMS) data. Compound 2 was isolated from a natural source for the first time but previously synthesised. Compounds 1-3 were evaluated for their anti-Helicobacter pylori and anti-Plasmodium falciparum activities. Compound 1 showed moderate activities against H. pylori (MIC 47.5 mu M) and the F32-Tanzania strain of P. falciparum (IC50 8.5 mu M). Compounds 2 and 3 exhibited weak anti-H. pylori activity (MIC 241.3 and 237.6 mu M, respectively) and were inactive against P. falciparum. [GRAPHICS]

Lichen-associated bacteria transform antibacterial usnic acid to products of lower antibiotic activity

International audienceLichens are specific symbiotic organisms harboring various microorganisms in addition to the two classic partners (algae or cyanobacterium and fungus). Although lichens produce many antibiotic compounds such as (+)-usnic acid, their associated microorganisms possess the ability to colonize an environment where antibiosis exists. Here, we have studied the behavior of several lichen-associated bacterial strains in the presence of (+)-usnic acid, a known antibiotic lichen compound. The effect of this compound was firstly evaluated on the growth and metabolism of three bacteria, thus showing its ability to inhibit Gram-positive bacteria. This inhibition was not thwarted with the usnic acid producer strain Streptomyces cyaneofuscatus. The biotransformation of this lichen metabolite was also studied. An ethanolamine derivative of (+)-usnic acid with low antibiotic activity was highlighted with chemical profiling, using HPLC-UV combined with low resolution mass spectrometry. These findings highlight the way in which some strains develop resistance mechanisms. A methylated derivative of (+)-usnic acid was annotated using the molecular networking method, thus showing the interest of this computer-based approach in biotransformation studies

A new 5-alkylresorcinol glucoside derivative from Cybianthus magnus

One new 5-alkylresorcinol glucoside (1) was isolated from leaves of Cybianthus magnus, along with 12 known compounds, isolated from four plants belonging to Myrsinaceae family (2, 3 isolated from C. magnus; 4-7, 10 and 11 isolated from Myrsine latifolia; 4, 8 and 9 isolated from Myrsine sessiflora; 6, 7, 10, 12 and 13 isolated from Myrsine congesta). Their structures were determined on the basis of spectroscopic analysis and by comparison of their spectral data with those reported in the literature. So far, only nine 5-alkylresorcinol glucosides were isolated from leaves of Grevillea robusta. Since resorcinols are known to exhibit strong cytotoxic activity, compounds 1 and 2 were tested against cell lines 3T3, H460, DU145 and MCF-7 for cytotoxicity in vitro and compounds 3-13 were tested for their antileishmanial activity. Compound 2 displayed a strong cytotoxic activity with IC50 values ranging between 22 and 100M for all tested cell lines. Compounds 3-13 were not active against Leishmania amazonensis amastigotes