Stachybotrolide

Plasma cholesteryl ester transfer protein (CETP), which mediates the transfer and exchange of neutral lipids (cholesteryl esters (CE) and triglycerides (TG) and phospholipids between plasma lipoproteins, plays an essential role in reverse cholesterol transport system. We have found that a fungal metabolite, stachybotramide, modulates the activity of CETP. Stachybotramide stimulated the [14C]CE transfer from high density lipoprotein (HDL) to very low density lipoprotein (VLDL) and low density lipoprotein (LDL) by 1.3- to 1.5-fold at 0.2-0.5 mM. This stimulation was abolished in the presence of anti-CETP antibody. On the other hand, the transfer of [14C]CE from LDL and VLDL to HDL was slightly reduced by stachybotramide at 0.5 mM. Unlike the transfer of [14C]CE, the transfer of [3H]TG from HDL was not significantly affected by stachybotramide. These results suggest that stachybotramide preferentially stimulate the CETP-mediated transfer of CE from HDL to both VLDL and LDL.

A novel spirocyclic drimane coupled by two drimane fragment building blocks 2 and a new drimane 1 were identified in mycelia and culture broth of Stachybotrys sp. MF347. Their structures were established by spectroscopic means. This is the first example of spirocyclic drimane coupled by a spirodihydrobenzofuranlactam unit and a spirodihydroisobenzofuran unit; and the connecting position being N-C instead of an N and N connecting unit. Strain MF347 produced also the known spirocyclic drimanes stachybocin A (12) and stachybocin B (11) featured by two sesquiterpene-spirobenzofuran structural units connected by a lysine residue; the known spirocyclic drimanes chartarlactam O (5); chartarlactam K (6); F1839A (7); stachybotrylactam (8); stachybotramide (9); and 2α-acetoxystachybotrylactam acetate (10); as well as ilicicolin B (13), a known sesquiterpene. The relative configuration of two known spirobenzofuranlactams (3 and 4) was determined. All compounds were subjected to biological activity tests. The spirocyclic drimane 2, 11, and 12, as well as the sesquiterpene 13, exhibited antibacterial activity against the clinically relevant methicillin-resistant Staphylococcus aureus (MRSA).