Tier 4 — mechanistic

Fisetin, a major component derived from mulberry (Morus australis Poir.) leaves, prevents vascular abnormal contraction

Natsuko Tsurudome, Yuji Minami, Katsuko Kajiya
BioFactors 2022 48(1):56–66

Bibliography

PubMed
PMID 34687255
PubMed Central
PMC9298084
DOI
10.1002/biof.1798
Funding
Japan Society for the Promotion of Science JSPS KAKENHI grant 20H02936. Wiley record notes funding-section correction November 2021.
Competing interests
Authors stated no potential conflicts of interest.

Study snapshot

DesignAnalytical HPLC/LC-MS/NMR characterization of mulberry leaves and selected fruit samples, plus in-vitro human coronary artery smooth-muscle cell contraction experiments.
ModelMulberry tea/leaf/fruit preparations, dried strawberry and apple samples and cultured human coronary artery smooth-muscle cells.
SampleSample chemistry reported as replicate measurements (n=4 for some assays); no human subjects.
InterventionSamples extracted and analyzed for fisetin content; isolated fisetin tested in stimulated cultured vascular smooth-muscle cells.
DurationShort-term analytical and in-vitro experiments; no participants or clinical follow-up. Assay duration varied by experimental procedure.
EndpointsFisetin concentration μg/g dry weight in sampled plant material; In-vitro vascular smooth-muscle contraction inhibition

What the study showed, in plain terms

The study identified fisetin in mulberry leaves and compared selected plant samples. The reported sample-specific fisetin concentrations per gram dry material differed markedly from a heavily cited 1998 food-composition dataset: strawberry fruit was 0.02 ± 0.01 µg/g dry weight and apple fruit/peel were not detected under this paper's assay conditions. Mulberry leaves exceeded 280 µg/g dry powder in older-tree samples and 600 µg/g in younger-tree samples. These results are not validated general food-table values or a human fisetin intake study.

The large difference between sample-specific studies illustrates why 160 µg/g from the earlier freeze-dried, acid-hydrolyzed data must not automatically be called a fresh-strawberry concentration or used to calculate exact mg in a retail punnet. The vascular-cell findings were mechanistic and cannot establish that consuming leaves treats hypertension.

Key findings

Reported dried sample fisetin: strawberry fruit 0.02 ± 0.01 µg/g; apple fruit and peel below detection under this method.

Mulberry leaves from trees younger than 20 years: 606.21 ± 9.26 µg/g dry weight; older than 20 years: 283.61 ± 1.97 µg/g.

In-vitro coronary smooth-muscle contraction experiments showed an effect of isolated fisetin; no human clinical outcome measured.

What this study can and cannot tell us

Plant variety, age, preparation and assay technique are not interchangeable with the 1998 freeze-dried, acid-hydrolyzed food dataset. The observed discrepancy does not, on its own, prove an error in either paper.

Limited analyzed market samples; no nationally representative food composition database and no validated fresh-strawberry serving estimate.

Cell model, not human vascular or dietary outcome study.

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Dr. Khaled Mahmoud, MBBChCritical Care Medicine, Longevity Science & Editorial Direction Dr. Amr Yasser, PhDCardiometabolic, Musculoskeletal, Gut & Bioavailability Dr. Abdulla Mostafa, PhDCellular Senescence, Neurological, Mitochondrial & Brain-Ageing Biology