Terpendole A

Structures of terpendoles A, B, C and D, novel acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors, were determined by spectroscopic studies. All terpendoles consist of diterpene and indole moieties in common. Terpendoles A, C and D possess an additional isoprenyl unit via oxygen atom(s) of their diterpene moieties. The relative stereochemistries of terpendoles C and D were confirmed by NOE experiments and X-ray crystallographic analysis.

A novel 1(2), 2(18)-diseco indole diterpenoid, drechmerin H (1), was isolated from the fermentation broth of Drechmeria sp. together with a new indole diterpenoid, 2'-epi terpendole A (3), and a known analogue, terpendole A (2). Their structures were determined by HRESIMS, 1D and 2D NMR, ECD, and X-ray single crystal diffraction analyses as well as quantum chemical calculation. The abosulte configuration of terpendole A (2) was determined for the first time. Compound 1 displayed the significant agonistic effect on pregnane X receptor (PXR) with EC50 value of 134.91 ± 2.01 nM, and its interaction with PXR was investigated by molecular docking. Meantime, a plausible biosynthetic pathway for compounds 1-3 is also discussed in the present work.

Six new compounds [ascherlactones A (1) and B (2), ascherchromanone A (3), phenethyl 4'-O-methylglucoside (8), 4'-O-methylpleoside (10), and 4'-O-methyltorachrysone 8-O-glucoside (11)] and one naturally new compound [4'-O-methyl-β-d-benzylglucoside (9)] together with fourteen known compounds, including paecilodepsipeptides A (5), B (7), and D (4), conoideocrellide A (6), eugenin (12), 5-hydroxy-2,3-dimethyl-7-methoxychromone (13), (S)-1-phenyl-1,2-ethanediol (14), (2S)-l-3-phenyllactic acid (15), papuline [or (2S)-l-3-phenyllactic acid methyl ester, 16], 2'-epi terpendole A (17), terpendoles C (18) and D (19), cholic acid, and zeorin were isolated from the entomopathogenic fungus Aschersonia confluens BCC53152. Their chemical structures were elucidated on the basis of NMR spectroscopic and mass spectrometric analyses. The absolute configurations were determined by using the evidence from NOESY correlations, chemical means, optical rotation values together with comparison of ECD spectroscopic data with the calculated ECD spectra. The plausible biosynthetic pathway of compounds 1-3 was also proposed. Moreover, antimicrobial activity such as antimalarial, antitubercular, antifungal, and antibacterial activities and cytotoxicity against cancerous (MCF-7, KB, and NCI-H187) and non-cancerous (Vero) cells of the isolated compounds were evaluated.