Thermally Assisted Hydrolysis and Methylation of Purified Tannins from Plants
Why this work is in the frame
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Bibliographic record
Abstract
A collection of tannins extracted from various plant species was subjected to thermally assisted hydrolysis and methylation (THM) using tetramethylammonium hydroxide. The products obtained included 1,3,5-trimethoxybenzenes, derived from A rings of condensed tannins (CTs), and 1,2-dimethoxybenzene, 1,2,3-trimethoxybenzene, and derivatives as major products from the B ring. 1,2,4-Tri- and two tetramethoxybenzenes were also detected in most analyses. Correlation analyses revealed that they were derived from the B ring, with 1,2,4-trimethoxybenzene being derived from a procyanidin (PC) B ring and 1,2,3,5-tetramethoxybenzene from a prodelphinidin (PD) ring. Tannins from species that contained both CT and hydrolyzable tannin (HT) produced mainly permethylated gallic acid moieties upon THM, and the products derived from CTs were less abundant. Most likely, the ester-bound HTs are more easily transmethylated than the cleavage and methylation of the C-C and C-O linked CTs. Statistical analyses of the THM products and 13C NMR data of the tannins showed good correlations between the B ring hydroxylation and the di- and trimethoxybenzenes observed. Using the ratio of the methyl esters of 3,4-dimethoxybenzoic acid and 3,4,5-trimethoxybenzoic acid only provided good correlations of the percent PC as well. Furthermore, the 1,3,5-trimethoxybenzenes may serve as good markers of tannins in plant, soil, sediment or other samples as analyzed by THM.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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