Orthogonal Method for Double-Bond Placement via Ozone-Induced Dissociation Mass Spectrometry (OzID-MS)

Abstract

Most often, the structures of secondary metabolites are solved using a suite of NMR techniques. However, there are times when it can be challenging to position double bonds, particularly those that are fully substituted or when there are multiple double bonds in similar chemical environments. Ozone-induced dissociation mass spectrometry (OzID-MS) serves as an orthogonal structure elucidation tool, using predictable fragmentation patterns that are generated after ozonolysis across a carbon-carbon double bond. This technique is finding growing use in the lipidomics community, suggestive of its potential value for secondary metabolites. This methodology was evaluated by confirming the double-bond positions in five fungal secondary metabolites, specifically, ent-sartorypyrone E (1), sartorypyrone A (2), sorbicillin (3), trichodermic acid A (4), and AA03390 (5). This demonstrated its potential with a variety of chemotypes, ranging from polyketides to terpenoids and including those in both conjugated and nonconjugated polyenes. In addition, the potential of using this methodology in the context of a mixture was piloted by studying Aspergillus fischeri, first examining a traditional extract and then sampling a live fungal culture in situ. While the intensity of signals varied from pure compound to extract to in situ, the utility of the technique was preserved.

Comoclathrin, a novel potent skin-whitening agent produced by endophytic Comoclathris strains associated with Andalusia desert plants

“…The remaining four signals in the 13 C NMR spectrum were deduced as quaternary, corresponding to the carbonyl carbon C-1’ at δ C 192.4, to the oxygenated aromatic carbons C-1 and C-5 at δ C 165.1 and 167.0, and to the quaternary carbon C-2 ( δ C 113.2). Comparison of HRMS, 1 H- and 13 C-NMR spectra (Table 3 ) with literature data suggested compound 2 as a polyketide analogue of sorbicillin and 6-demethylsorbicillin, showing a common sorbyl group but with no aromatic methyl protons 26 , 31 . This hypothesis was further confirmed by 2D NMR (Fig.…”

Drug Leads from Endophytic Fungi: Lessons Learned via Scaled Production

“…The droplet probe has been used to monitor the production of secondary metabolites in fungal cultures [25][26][27][28][29][30][31][32][33][34][35], with several notable examples highlighted in a recent review [16]. One benefit of this technique for this application was the ability to generate heat maps, showing in a relative manner where secondary metabolites are concentrated.…”

Review of Recent Advances in Lipid Analysis of Biological Samples via Ambient Ionization Mass Spectrometry

“…Generally, tandem mass spectrometry (MS/MS) via the collision-induced desorption (CID) method can provide a lipid head group and fatty acyl chain composition, but has limited application in directly locating the C=C positions, because low energy CID cannot obtain informative fragment ions to assign the C=C location [15][16][17]. Hence, emerging MS-based dissociation methods, including ozone-induced dissociation (OzID) [18,19], electron-induced dissociation (EID) [20], ultraviolet photodissociation (UVPD) [1,21], and selective C=C bond derivatization methods (e.g., the Paternò-Büchi (PB) reaction [22,23], meta-chloroperoxybenzoic acid (m-CPBA) epoxidation [24,25], and peracetic acid (PAA) epoxidation [5]), have been developed to elucidate the lipid structure. Traditionally, MS coupled with chromatographic approaches (such as liquid chromatography (LC)) are effective tools for the characterization of lipid isomers [26][27][28], but these methods usually require tedious sample preparations prior to MS analysis.…”