Tetrahydro-1,8-naphthyridinol Analogues of α-Tocopherol as Antioxidants in Lipid Membranes and Low-Density Lipoproteins
Why this work is in the frame
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Bibliographic record
Abstract
Recently we demonstrated that the C(7)-unsubstituted tetrahydro-1,8-naphthyridin-3-ol has more than an order of magnitude better peroxyl radical trapping activity than alpha-tocopherol (alpha-TOH) in inhibited autoxidations in benzene. In order to prepare analogues more structurally related to alpha-TOH for further studies in vitro and in vivo, we developed synthetic approaches to C(7)-monoalkyl and C(7)-dialkyl analogues using a sequence involving (1) AgNO3-mediated hydroxymethyl radical addition to 1,8-naphthyridine, (2) regioselective alkyllithium addition by cyclic chelation in a nonpolar solvent, (3) iodination of the naphthyridine at C(3), and (4) CuI-medidated benzyloxylation of the aryl iodide followed by catalytic hydrogenolysis. An alpha-TOH isostere was prepared by a Wittig coupling of a C16 side chain identical to that of alpha-TOH to the naphthyridinols. The C(7)-mono- and dialkyl analogues exhibited more than an order of magnitude higher antioxidant activity (k(inh) = (5.3-6.1) x 10(7) M(-1) s(-1)) than alpha-TOH (k(inh) = 0.35 x 10(7) M(-) s(-1)) in benzene, as determined by a newly developed peroxyl radical clock. In addition to the strong antioxidant activity in benzene, the closest alpha-TOH analogue (naphthyridinol-based tocopherol, N-TOH) showed excellent inhibition of the oxidation of cholesteryl esters in human low-density lipoprotein and spared endogenous alpha-TOH in these experiments. Lateral diffusion of N-TOH in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine liposomes was comparable to that of alpha-TOH, suggesting that it will have good antioxidant characteristics in both membranes and lipoproteins. Furthermore, a binding assay using a fluorescent tocopherol analogue showed that N-TOH binds to recombinant human tocopherol transfer protein better than alpha-TOH itself, suggesting that distribution of unnatural antioxidants such as N-TOH in vivo is possible.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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