Quinoline and para-aminobenzoic acid derivatives with anti-osteoclastic activity from a marine mesophotic zone Demosponge sponge-associated fungus Xylaria sp. NBUF245.

One undescribed quinoline derivative, xylaminoquin A (1), one new p-aminobenzoic acid derivative, xylamidate B (2), and methyl 4-(butanoylamino)-3-hydroxybenzoate, reported for the first time as a natural product and named xylamidate C (3), together with known alkaloids and diketopiperazines, methyl 4-acetylamino-3-hydroxybenzoate (4), methyl 4-[(1-oxobutyl)amino]benzoate (5), pseurotin A (6), azaspirofuran A (7), cyclo(l-Tyr-l-Leu) (8), and cyclo-(l-Tyr-l-Val) (9) were isolated from Xylaria sp. NBUF245, a fungus associated with a Demosponge sp. collected from the marine mesophotic zone. Structurally, compound 1 is the first example of 3,7-dissubstitented quinoline derivative isolated from fungi. The structures of all compounds were elucidated by combined analysis of spectroscopic data and X-ray crystallography. Bioassay results showed that compound 5 effectively prevented prednisolone-induced bone loss in zebrafish at a concentration of 30 μM, suggesting potential osteoprotective activity.