Further Investigation into Maple Syrup Yields 3 New Lignans, a New Phenylpropanoid, and 26 Other Phytochemicals
Bibliographic record
Abstract
Maple syrup is made by boiling the sap collected from certain maple ( Acer ) species. During this process, phytochemicals naturally present in tree sap are concentrated in maple syrup. Twenty-three phytochemicals from a butanol extract of Canadian maple syrup (MS-BuOH) had previously been reported; this paper reports the isolation and identification of 30 additional compounds (1-30) from its ethyl acetate extract (MS-EtOAc) not previously reported from MS-BuOH. Of these, 4 compounds are new (1-3, 18) and 20 compounds (4-7, 10-12, 14-17, 19, 20, 22-24, 26, and 28-30) are being reported from maple syrup for the first time. The new compounds include 3 lignans and 1 phenylpropanoid: 5-(3″,4″-dimethoxyphenyl)-3-hydroxy-3-(4'-hydroxy-3'-methoxybenzyl)-4-(hydroxymethyl)dihydrofuran-2-one (1), (erythro,erythro)-1-[4-[2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl)ethoxy]-3,5-dimethoxyphenyl]-1,2,3-propanetriol (2), (erythro,threo)-1-[4-[2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl)ethoxy]-3,5-dimethoxyphenyl]-1,2,3-propanetriol (3), and 2,3-dihydroxy-1-(3,4- dihydroxyphenyl)-1-propanone (18), respectively. In addition, 25 other phenolic compounds were isolated including (threo,erythro)-1-[4-[(2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl)ethoxy]-3-methoxyphenyl]-1,2,3-propanetriol (4), (threo,threo)-1-[4-[(2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl)ethoxy]-3-methoxyphenyl]-1,2,3-propanetriol (5), threo-guaiacylglycerol-β-O-4'-dihydroconiferyl alcohol (6), erythro-1-(4-hydroxy-3-methoxyphenyl)-2-[4-(3-hydroxypropyl)-2,6-dimethoxyphenoxy]-1,3-propanediol (7), 2-[4-[2,3-dihydro-3-(hydroxymethyl)-5-(3-hydroxypropyl)-7-methoxy-2-benzofuranyl]-2,6-dimethoxyphenoxy]-1-(4-hydroxy-3-methoxyphenyl)-1,3-propanediol (8), acernikol (9), leptolepisol D (10), buddlenol E (11), (1S,2R)-2-[2,6-dimethoxy-4-[(1S,3aR,4S,6aR)-tetrahydro-4-(4-hydroxy-3,5-dimethoxyphenyl)-1H,3H-furo[3,4-c]furan-1-yl]phenoxy]-1-(4-hydroxy-3-methoxyphenyl)-1,3-propanediol (12), syringaresinol (13), isolariciresinol (14), icariside E4 (15), sakuraresinol (16), 1,2-diguaiacyl-1,3-propanediol (17), 2,3-dihydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)-1-propanone (19), 3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)propan-1-one (20), dihydroconiferyl alcohol (21), 4-acetylcatechol (22), 3',4',5'-trihydroxyacetophenone (23), 3,4-dihydroxy-2-methylbenzaldehyde (24), protocatechuic acid (25), 4-(dimethoxymethyl)pyrocatechol (26), tyrosol (27), isofraxidin (28), and 4-hydroxycatechol (29). One sesquiterpene, phaseic acid (30), which is a known metabolite of the phytohormone abscisic acid, was also isolated from MS-EtOAc. The antioxidant activities of MS-EtOAc (IC(50) = 75.5 μg/mL) and the pure isolates (IC(50) ca. 68-3000 μM) were comparable to that of vitamin C (IC(50) = 40 μM) and the synthetic commercial antioxidant butylated hydroxytoluene (IC(50) = 3000 μM), in the diphenylpicrylhydrazyl radical scavenging assay. The current study advances scientific knowledge of maple syrup constituents and suggests that these diverse phytochemicals may impart potential health benefits to this natural sweetener.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.003 | 0.001 |
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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".