Four undescribed ergostane-type steroids from Lasiodiplodia pseudotheobromae and their neuroprotective activity

Four undescribed ergostane-type steroids, (22E,24R)-4α,5α-epoxyergosta-9α,14β-dihydroxy-7,22-diene-3,6-dione, (22E,24R)-4α,5α-epoxyergosta-9α,14α-dihydroxy-7,22-diene-3,6-dione, 12α-hydroxyergosta-7,22,24(28)-triene-3-one, and 3β,12α-dihydroxyergosta-7,24(28)-diene, along with a known congener (22E,24R)-9α,14β-dihydroxyergosta-4,7,22-triene-3,6-dione, were isolated from the fungus Lasiodiplodia pseudotheobromae. Their structures were elucidated using NMR, HRESIMS, ECD calculation, and X-ray diffraction analyses. (22E,24R)-4α,5α-epoxyergosta-9α,14β-dihydroxy-7,22-diene-3,6-dione and (22E,24R)-4α,5α-epoxyergosta-9α,14α-dihydroxy-7,22-diene-3,6-dione are a pair of C-14 epimers possessing an unusual epoxy group between C-4 and C-5, which was demonstrated using single-crystal X-ray diffraction analyses. The absolute configurations of 12α-hydroxyergosta-7,22,24(28)-triene-3-one and 3β,12α-dihydroxyergosta-7,24(28)-diene were determined by ECD calculations. Moreover, 3β,12α-dihydroxyergosta-7,24(28)-diene exhibited neuroprotective activity in vitro in glutamate-treated SH-SY5Y cell lines.