Seven new orsellinic acid esters, 1–7, and four known compounds were isolated from the solid, fermented rice culture of Chaetomium globosporum (cib-132). Their structures were elucidated by 1D- and 2D-NMR spectra, and the relative configuration of compound 1 was determined by X-ray crystallographic analysis.

Three new eudesmanolactones (=eudesmanolides), loloanolide A (1), loloanolide B (2), and 1-O-acetylloloanolide B (3), together with five known compounds, were isolated from the CHCl₃ extract of the aerial parts of Camchaya loloana. Their structures were elucidated on the basis of spectroscopic analysis. This type of eudesmanolactones bearing a 2-(hydroxymethyl)acryloyloxy group at C(8) was discovered for the first time. Compounds 1–3 exhibited cytotoxicity against the HepG2 cell line, with GI₅₀ values of 22.9, 18.1, and 12.8 nmol/ml, respectively.

Introduction – Biosynthesis of terretonin was studied due to the interesting skeleton of this series of sesterterpenoids. Very recently, López-Gresa reported two new sesterterpenoids (terretonins E and F) which are inhibitors of the mammalian mitochondrial respiratory chain. Mass spectrometry (MS), especially tandem mass spectrometry, has been one of the most important physicochemical methods for the identification of trace natural products due to it rapidity, sensitivity and low levels of sample consumption. The potential application prospect and unique skeleton prompted us to study structural characterisation using MS.

Objective – To obtain sufficient information for rapid structural elucidation of this class of compounds using MS.

Methodology – The elemental composition of the product ions was confirmed by low-energy ESI-CID-QTOF-MS/MS analyses. The fragmentation pathways were postulated on the basis of ESI-QTOF-MS/MS/MS and ESI-IT-MSⁿ spectra. Common features and major differences between ESI-QTOF-MS/MS and IT-MSⁿ spectra were compared. For ESI-QTOF-MS/MS/MS experiments, capillary exit voltage was raised to induce in-source dissociation. Ammonium acetate or acetic acid were added into solutions to improve the intensity of [M + H]⁺. The collision energy was optimised to achieve sufficient fragmentation. Some fragmentation pathways were unambiguously proposed by the variety of abundance of fragment ions at different collision energies even without MSⁿ spectra.

Results – Fragmentation pathways of five representative sesterterpenoids were elucidated using ESI-QTOF-MS/MS/MS and ESI-IT-MSⁿ in both positive- and negative-ion mode. The key group of characterising fragmentation profiles was ring B, and these fragmentation patterns are helpful to identify different types of sestertepenoids.

Conclusion – Complementary information obtained from fragmentation experiments of [M + H]⁺ (or [M + NH₄]⁺) and [M − H]⁻ precursor ions is especially valuable for rapid identification of this kind of sesterterpenoid.