Fragmentation study of clerodane diterpenes from <i>Casearia</i> species by tandem mass spectrometry (quadrupole time‐of‐flight and ion trap)
Why this work is in the frame
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Bibliographic record
Abstract
Rationale Clerodane‐type diterpenes from Casearia species show important pharmacological activites such as antitumor, antimicrobial and anti‐inflamatory. There are several mass spectrometry (MS)‐based methods for identification of diterpenes; however, there is still a lack of MS procedures capable of providing characteristic fragmentation pathways for a rapid and unambiguous elucidation of casearin‐like compounds. Methods Casearin‐like compounds were investigated by electrospray ionization tandem mass spectrometry (ESI‐MS/MS). The fragmentation studies were carried out by tandem mass spectrometry in space (quadrupole time‐of‐flight (QTOF)) using different collision energies and also by tandem mass spectrometry in time (QIT) by selective isolation of product ions. Results Casearin‐like compounds presented a predominance of sodium‐ and potassium‐cationized precursor ions. Both QIT and QTOF techniques provided sequential neutral losses of esters related to the R 1 to R 5 substituents linked to the nucleus of the clerodane diterpenes. The fragmentation pathway is initiated with a cleavage of the ester moieties R 2 followed by the elimination of the ester groups R 3 , both losing neutral carboxylic acids. Using QIT, it was also possible to observe the cleavage of the ester groups R 1 or R 5 by MS 4 experiments. Conclusions Through a rational analysis of the fragmentation mechanisms of Casearia diterpenes it was possible to suggest an annotation strategy based on the sequential cleavages of the ester groups related to the R 2 , R 3 and R 5 substituents. These results will assist studies of the dereplication and metabolomics involving casearin‐like compounds present in complex extracts of Casearia species.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it