NMR Fingerprints as a Predictive Model to Monitor Punaglandins in the Soft Coral Carijoa (Telesto) riisei (Duchassaing & Michelotti, 1860)

Abstract

Analysis of NMR data reported for constituents found in the invasive soft coral Carijoa (Telesto) riisei has been used to develop a model that can identify punaglandins in C. riisei extracts. Principal component analysis of 1H and 13C NMR data showed that the model can be used to identify the presence of various subclasses of punaglandins that possess different oxidations states of the cyclopentane ring. The application of this model through analysis of covariant HMBC data obtained from dichloromethane extracts showed that C. riisei has significant variability in punaglandin concentration, with many colonies being completely devoid of punaglandins. To verify the identity of compounds predicted by the model, purification of an extract obtained from C. riisei collected from an artificial reef in southeast Queensland led to the isolation of one new compound, 7Z-punaglandin 4-epoxide (1), a series of known punaglandins (2–6), and the known pregnanes 7–9. The absolute configurations of 7Z-punaglandin 4 epoxide (1), punaglandin 6 (4), and carijenone (6) were determined for the first time by comparison of experimental and TDDFT calculated ECD data. All the isolated punaglandins reported herein were predicted to be present using the NMR fingerprint model.

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