Antimicrobial Dialkylresorcins from Marine-Derived Microorganisms: Insights into Their Mode of Action and Putative Ecological Relevance.

Zobellia galactanivorans has been reported as a seaweed-associated or marine-derived species with largely unknown secondary metabolites. The combination of bioinformatic analysis and MS- and bioactivity guided separation led to the isolation of a new antibiotically active dialkylresorcin from the marine bacterium Z. galactanivorans. The antibiotic profile of the new dialkylresorcin zobelliphol (1: ) was investigated and compared with related and naturally occurring dialkyresorcins (i.e., stemphol (2: ) and 4-butyl-3,5-dihydroxybenzoic acid (3: )) from the marine-derived fungus Stemphylium globuliferum. Bacterial reporter strain assays provided insights into the mode of action of this antibiotic compound class. We identified an interference with bacterial DNA biosynthesis for the dialkylresorcin derivative 1: . In addition, the putative biosynthetic gene cluster corresponding to production of 1: was identified and a biosynthetic hypothesis was deduced.

The dialkyl resorcinol stemphol disrupts calcium homeostasis to trigger programmed immunogenic necrosis in cancer.

Stemphol (STP) is a novel druggable phytotoxin triggering mixed apoptotic and non-apoptotic necrotic-like cell death in human acute myeloid leukemia (AML). Use of several chemical inhibitors highlighted that STP-induced non-canonical programmed cell death was Ca2+-dependent but independent of caspases, poly (ADP-ribose) polymerase-1, cathepsin, or calpains. Similar to thapsigargin, STP led to increased cytosolic Ca2+ levels and computational docking confirmed binding of STP within the thapsigargin binding pocket of the sarco/endoplasmic reticulum (ER) Ca2+-ATPase (SERCA). Moreover, the inositol 1,4,5-trisphosphate receptor is implicated in STP-modulated cytosolic Ca2+ accumulation leading to ER stress and mitochondrial swelling associated with collapsed cristae as observed by electron microscopy. Confocal fluorescent microscopy allowed identifying mitochondrial Ca2+ overload as initiator of STP-induced cell death insensitive to necrostatin-1 or cycloheximide. Finally, we observed that STP-induced necrosis is dependent of mitochondrial permeability transition pore (mPTP) opening. Importantly, the translational immunogenic potential of STP was validated by HMGB1 release of STP-treated AML patient cells. STP reduced colony and in vivo tumor forming potential and impaired the development of AML patient-derived xenografts in zebrafish.

Twilight zone sponges from Guam yield theonellin isocyanate and psammaplysins I and J.

From the organic extracts of two Guam sponges, Rhaphoxya sp. and Suberea sp., determined to have cytotoxic and chemopreventive activities, three new compounds, theonellin isocyanate (1) and psammaplysins I and J (5, 6), and six previously reported compounds (2-4, 7-9) were isolated and characterized spectroscopically ((1)H and (13)C NMR, MS, IR, UV, [α](D)). The two new metabolites (5 and 6) isolated from the Suberea sp. sponge are rare examples of compounds containing a bromotyramine moiety rather than the more usual dibromo analogue. For the compounds isolated from the Rhaphoxya sp., this is the first report of the known compounds 2-4 being found in a single sponge. For previously reported compounds 2-4 complete unambiguous (1)H and (13)C NMR data are provided.