Mannosylxylarinols A and B, Two New 3,4-Seco-ergostane-type Steroidal Saponins From the Fungus Xylaria necrophora SZSS1-2-2.

Two new 3,4-seco-ergostane-type steroidal saponins (1 and 2) were isolated from the fermentation products of the fungus Xylaria necrophora SZSS1-2-2, together with four known compounds: 2-hexylidene-3-methylsuccinic acid (3), xylcarpin C (4), (24R)-22,23-dihydroxy-ergosta-4,6,8(14)-trien-3-one 23-β-D-glucopyranoside (5), and 5-carboxymellein (6). The structures and absolute configurations of the new compounds were elucidated by comprehensive spectroscopic analyses, electronic circular dichroism (ECD), and GIAO 1 3C NMR computational methods, and chemical hydrolysis followed by derivatization to determine the D‑mannose configuration of the sugar moiety. All isolated compounds (1-6) were evaluated for their biological activities. Only compound 5 showed selective inhibitory activity, inhibiting BV2 microglial cells with an IC50 value of 17.10 ± 4.18 µM. Additionally, none of the compounds exhibited antimicrobial activity against the tested microorganisms.