Phyllodulcin

Phyllodulcin at a Glance

Phyllodulcin is a naturally occurring dihydroisocoumarin — the intensely sweet principle of Japanese sweet-tea, or “amacha,” brewed from the fermented leaves of the sweet-hydrangea (Hydrangea macrophylla var. thunbergii, and the related H. serrata). Weight for weight it is a high-intensity sweetener, reported at roughly 400–800 times the sweetness of sucrose ^{1,2Reference 1Kim MJ et al. · 2016Relative sweetness and sweetness quality of phyllodulcin [(3R)-8-hydroxy-3-(3-hydroxy-4-methoxyphenyl)-3,4-dihydro-1H-isochromen-1-one]View study →Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}.

A quirk of its chemistry defines the plant: the sweetness is not present in the living leaf. Phyllodulcin is stored as a non-sweet glucoside, phyllodulcin-8-O-glucoside, and only when the leaf is bruised, fermented and dried do the plant’s own enzymes cleave off the sugar to release the free, sweet aglycone ^{2Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}. This is why amacha must be made — the fresh leaf is not sweet.

Beyond the kitchen and the temple, the isolated molecule has drawn preclinical interest as an anti-obesity / anti-adipogenic (PPARγ-like) agent, an anti-amyloid neuroprotectant, and a weak antiallergic — but the honest posture is that every one of these signals is cell-culture or rodent work on the isolate; there are no human efficacy trials, and the compound’s real-world footprint is as a flavour, not a drug ^{3,5,6Reference 3Zhang H et al. · 2007In vitroNew type of anti-diabetic compounds from the processed leaves of Hydrangea macrophylla var. thunbergii — in vitro and mouseView study →Reference 5Kim E et al. · 2017AnimalPhyllodulcin regulates obesity-related metabolic changes and fat-browning genes in high-fat-diet-induced obese mice — mouse in vivoView study →Reference 6Cho E et al. · 2023AnimalPhyllodulcin improves hippocampal long-term potentiation in 5XFAD mice — mouse in vivoView study →}.

A High-Intensity Sweetener

The reason anyone isolated phyllodulcin is its taste. It is one of the classic natural high-intensity sweeteners, and it holds a specific place in the chemistry of sweetness because it became a lead compound for structure–sweetness models.

Potency. Reported relative sweetness spans a wide band — often quoted as 400–800× sucrose ^{2Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →} — with a careful sensory study measuring about 435× sucrose against a 3% sucrose reference ^{1Reference 1Kim MJ et al. · 2016Relative sweetness and sweetness quality of phyllodulcin [(3R)-8-hydroxy-3-(3-hydroxy-4-methoxyphenyl)-3,4-dihydro-1H-isochromen-1-one]View study →}. The spread reflects how strongly perceived potency depends on concentration and reference standard for intense sweeteners.

Why it is sweet. Phyllodulcin’s sweetness is carried by an isovanillyl group (the 3-hydroxy-4-methoxyphenyl ring) fused to the dihydroisocoumarin core; medicinal chemists have used this “isovanillyl sweet unit” as a scaffold, and synthetic analogues built around it range from mildly to enormously sweeter than the parent ^{2Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}. Sweetness is also stereospecific: the naturally occurring (3R) form is the sweet one, and the taste is lost or altered in the mirror-image configuration ^{1Reference 1Kim MJ et al. · 2016Relative sweetness and sweetness quality of phyllodulcin [(3R)-8-hydroxy-3-(3-hydroxy-4-methoxyphenyl)-3,4-dihydro-1H-isochromen-1-one]View study →}.

Its catch. Phyllodulcin is not a clean sweetener. Sensory panels describe a slow, sucrose-like onset and lingering sweetness shadowed by bitterness, a cooling sensation, an “alcoholic” note and an astringent aftertaste ^{1Reference 1Kim MJ et al. · 2016Relative sweetness and sweetness quality of phyllodulcin [(3R)-8-hydroxy-3-(3-hydroxy-4-methoxyphenyl)-3,4-dihydro-1H-isochromen-1-one]View study →}, and reviews flag this off-taste as the main barrier to commercial use ^{2Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}. That off-profile — plus the low leaf yield — is why phyllodulcin remains a traditional and research sweetener rather than a mass-market one.

Amacha: Japan’s Ceremonial Sweet Tea

Phyllodulcin’s cultural home is amacha (甘茶, “sweet tea”), the traditional Japanese infusion of processed sweet-hydrangea leaf. Amacha is best known from Kanbutsu-e, popularly Hanamatsuri (“flower festival”) — the celebration of the Buddha’s birthday on 8 April. At temples a small standing statue of the infant Buddha is set in a flower-decked shrine and worshippers ladle sweet amacha over it, echoing the legend that sweet rain fell at the Buddha’s birth; the tea is then shared with visitors to drink ^{1,2Reference 1Kim MJ et al. · 2016Relative sweetness and sweetness quality of phyllodulcin [(3R)-8-hydroxy-3-(3-hydroxy-4-methoxyphenyl)-3,4-dihydro-1H-isochromen-1-one]View study →Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}.

The drink’s sweetness is the phyllodulcin story in miniature: the fresh leaf is not sweet, and only fermentation and drying — the same steps that make the tea — liberate the free sweetener from its glucoside ^{2Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}. Traditionally the processed leaf is also valued as a mild natural sweetener and folk remedy, but as a dilute infusion, which matters for safety (see Toxicity & Safety): brewing the leaf too strong is a recognised cause of food-poisoning-type illness, and Japanese health guidance caps the customary strength at roughly a few grams of leaf per litre of water ^{11Reference 11Tsukioka J et al. · 2023Quantitative analysis of taxiphyllin, a cyanogenic glycoside, in the leaves of Hydrangea macrophylla var. thunbergii — analyticalView study →}.

What It's Used For

Phyllodulcin’s pharmacology is entirely preclinical and mostly comes from the same Japanese and Korean groups that study sweet-hydrangea leaf. Read it as isolate mechanism, not clinical evidence.

Evidence by IndicationStrength of support · Beta

Support is an experimental score — weighted by study type (human > animal > in vitro) and volume. A beta, not a validated metric. Every row here is preclinical isolate work, so scores stay modest by design.

01Anti-obesity / metabolic (PPARγ-like)Shaky38%Cell + high-fat-diet mouse; adipogenesis/adiponectin + fat-browning genes ^{3,4,5Reference 3Zhang H et al. · 2007In vitroNew type of anti-diabetic compounds from the processed leaves of Hydrangea macrophylla var. thunbergii — in vitro and mouseView study →Reference 4Matsuda H et al. · 2014ReviewSearch for a new type of PPARγ agonist-like anti-diabetic compounds from medicinal plants — reviewView study →Reference 5Kim E et al. · 2017AnimalPhyllodulcin regulates obesity-related metabolic changes and fat-browning genes in high-fat-diet-induced obese mice — mouse in vivoView study →}

02Anti-amyloid / neuroprotectiveShaky30%Single 5XFAD mouse study — ↓Aβ, improved LTP ^{6Reference 6Cho E et al. · 2023AnimalPhyllodulcin improves hippocampal long-term potentiation in 5XFAD mice — mouse in vivoView study →}

03AntioxidantShaky26%C. elegans + mechanistic; ↓ROS, ↓lipid accumulation ^{7Reference 7Cho M et al. · 2024AnimalPhyllodulcin from the hexane fraction of Hydrangea macrophylla inhibits glucose-induced lipid accumulation and ROS generation in Caenorhabditis elegans — in vivo (invertebrate)View study →}

04Antiviral (ACE2 binding, in vitro)Shaky22%In-vitro leaf-dihydroisocoumarin screen vs SARS-CoV-2 spike–ACE2 ^{10Reference 10Yano A et al. · 2023In vitroDihydroisocoumarins of Hydrangea macrophylla var. thunbergii inhibit binding of the SARS-CoV-2 spike protein to ACE2 — in vitroView study →}

05Antiallergic (weak)Shaky20%Mast-cell / rat PCA — phyllodulcin the weak member of its class ^{8,9Reference 8Matsuda H et al. · 1999AnimalEffects of phyllodulcin, hydrangenol, their 8-O-glucosides, and thunberginols A and F on the passive cutaneous anaphylaxis reaction in rats — rat in vivoView study →Reference 9Matsuda H et al. · 1999In vitroStructure requirements of isocoumarins, phthalides and stilbenes from Hydrangeae Dulcis Folium for inhibition of histamine release from rat peritoneal mast cells — in vitroView study →}

Mechanisms

The load-bearing caveat: these targets come from isolate cell/rodent studies. The one target with real human consequence is the last — sweet-taste agonism — which is why phyllodulcin is a flavour before it is anything else.

Pharmacokinetics

Phyllodulcin’s human — and even mammalian — pharmacokinetics are essentially uncharacterised: no reliable oral bioavailability, plasma half-life, metabolism or tissue-distribution data for the isolate were located. Two structural facts frame what little can be said. First, in the plant it exists chiefly as the 8-O-glucoside, which is not absorbed or tasted as the aglycone until β-glucosidases (in processing, or gut flora) cleave the sugar ^{2Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}. Second, as a lipophilic phenolic dihydroisocoumarin it would be expected to undergo phase-II conjugation (glucuronidation/sulfation) like its scaffold-mates, but this has not been measured for phyllodulcin specifically. The absence of PK data is itself the headline — it means every in-vitro potency and rodent dose in the sections above lacks a demonstrated bridge to human exposure.

Clinical Trials

There are no clinical trials of phyllodulcin — as an isolate or as a defined amacha extract — for any indication. Its human use is culinary/ceremonial, not therapeutic. The metabolic, neuroprotective, antioxidant and antiviral findings are all preclinical.

Last checked: July 2026.

Isolate vs. Plant Studies

The evidence base is almost entirely the isolated molecule (or a phyllodulcin-rich fraction) in cells and rodents — the adipogenesis/PPARγ-like work ^{3,4Reference 3Zhang H et al. · 2007In vitroNew type of anti-diabetic compounds from the processed leaves of Hydrangea macrophylla var. thunbergii — in vitro and mouseView study →Reference 4Matsuda H et al. · 2014ReviewSearch for a new type of PPARγ agonist-like anti-diabetic compounds from medicinal plants — reviewView study →}, the high-fat-diet fat-browning study ^{5Reference 5Kim E et al. · 2017AnimalPhyllodulcin regulates obesity-related metabolic changes and fat-browning genes in high-fat-diet-induced obese mice — mouse in vivoView study →}, the 5XFAD anti-amyloid study ^{6Reference 6Cho E et al. · 2023AnimalPhyllodulcin improves hippocampal long-term potentiation in 5XFAD mice — mouse in vivoView study →} and the mast-cell/PCA structure–activity work ^{8,9Reference 8Matsuda H et al. · 1999AnimalEffects of phyllodulcin, hydrangenol, their 8-O-glucosides, and thunberginols A and F on the passive cutaneous anaphylaxis reaction in rats — rat in vivoView study →Reference 9Matsuda H et al. · 1999In vitroStructure requirements of isocoumarins, phthalides and stilbenes from Hydrangeae Dulcis Folium for inhibition of histamine release from rat peritoneal mast cells — in vitroView study →} all test phyllodulcin (or defined leaf fractions) directly. That is a mechanistic strength — the effects are attributed to a named molecule — but it comes with the opposite weakness to most herbs here: there is no whole-plant human trial and no isolate human trial, so nothing anchors the mechanisms to a real-world outcome. The C. elegans antioxidant work used a phyllodulcin-rich fraction rather than the pure compound ^{7Reference 7Cho M et al. · 2024AnimalPhyllodulcin from the hexane fraction of Hydrangea macrophylla inhibits glucose-induced lipid accumulation and ROS generation in Caenorhabditis elegans — in vivo (invertebrate)View study →}, and the antiviral finding is an in-vitro leaf-dihydroisocoumarin screen ^{10Reference 10Yano A et al. · 2023In vitroDihydroisocoumarins of Hydrangea macrophylla var. thunbergii inhibit binding of the SARS-CoV-2 spike protein to ACE2 — in vitroView study →} — both a further step removed from “phyllodulcin does X in a person.” The correct framing: solid isolate mechanism, zero clinical translation.

Its Role in Plants

In the sweet-hydrangea leaf, phyllodulcin is stored not as the free sweet compound but as its non-sweet glucoside, phyllodulcin-8-O-glucoside — a β-D-glucose capped onto the phenolic hydroxyl of the dihydroisocoumarin ^{2Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}. This is the ecologically and practically important fact about the molecule: the glycoside is the storage/transport form, and the free aglycone is generated by hydrolysis. When the leaf is damaged, wilted, fermented and dried — the amacha process — endogenous β-glucosidases cleave the sugar and release the intensely sweet aglycone ^{2Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}. Storing a bioactive phenol as an inert glucoside and unmasking it enzymatically on wounding is a common plant strategy; here it also happens to be the entire basis of the sweet tea. Phyllodulcin belongs to the broader dihydroisocoumarin group that chemically marks the Hydrangea genus, alongside the sibling compound hydrangenol.

Prevalence in Nature

Phyllodulcin is a narrowly distributed compound — effectively a signature of the sweet-hydrangeas. Its documented source is the leaf of Hydrangea macrophylla var. thunbergii (the “amacha” sweet-tea plant) and the closely related H. serrata; the fully sweet aglycone is a product of leaf fermentation/drying, formed from the phyllodulcin-8-O-glucoside precursor rather than stored ready-made ^{1,2Reference 1Kim MJ et al. · 2016Relative sweetness and sweetness quality of phyllodulcin [(3R)-8-hydroxy-3-(3-hydroxy-4-methoxyphenyl)-3,4-dihydro-1H-isochromen-1-one]View study →Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}. It is not confirmed in the North American medicinal species H. arborescens (a root/rhizome herb), which shares the genus’s dihydroisocoumarin marker hydrangenol but not phyllodulcin — a distinction worth keeping, since the two plants are easily conflated. Validated quantitative leaf concentrations (as % dry weight) were not found in accessible sources; leaf content depends heavily on cultivar and on how completely the sweet-tea processing hydrolyses the glucoside.

Discovery & Synthesis

Phyllodulcin was first isolated in 1916 by the Japanese chemists Asahina and Ueno from the sweet-hydrangea leaf, as the compound responsible for the plant’s remarkable sweetness. Its structure — a 3,4-dihydroisocoumarin — was established by Yasuhiko Asahina and Juntaro Asano in 1929, in the German journal Berichte der deutschen chemischen Gesellschaft, alongside the related dihydroisocoumarin hydrangenol, and Asahina’s group went on to publish syntheses of the phyllodulcin and hydrangenol skeletons in 1930–31 ^{12Reference 12Asahina Y · 1929Asahina Y, Asano J (1929). Über die Konstitution von Hydrangenol und Phyllodulcin. Berichte der deutschen chemischen Gesellschaft (A and B Series). https://doi.org/10.1002/cber.19290620124View study →}. The (3R) absolute configuration of the naturally sweet form was assigned later, and matters because sweetness is stereospecific ^{1Reference 1Kim MJ et al. · 2016Relative sweetness and sweetness quality of phyllodulcin [(3R)-8-hydroxy-3-(3-hydroxy-4-methoxyphenyl)-3,4-dihydro-1H-isochromen-1-one]View study →}.

Production today is not industrial. Phyllodulcin is obtained by processing the sweet-hydrangea leaf — the same fermentation/drying that makes amacha — optionally with added β-glucosidase to convert the abundant glucoside to the sweet aglycone; the molecule’s off-taste and low leaf yield have kept it a traditional and research sweetener rather than a manufactured one ^{1,2Reference 1Kim MJ et al. · 2016Relative sweetness and sweetness quality of phyllodulcin [(3R)-8-hydroxy-3-(3-hydroxy-4-methoxyphenyl)-3,4-dihydro-1H-isochromen-1-one]View study →Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}. Total and semi-synthetic routes to the dihydroisocoumarin scaffold exist from the early Asahina syntheses onward, chiefly as tools for structure–sweetness studies rather than commercial supply ^{2Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}.

Patents: not yet researched.

Toxicity & Safety

The isolated compound carries a low toxicity flag: it is a natural food sweetener component with no reported acute toxicity in the preclinical literature, and it is consumed traditionally, in trace amounts, in a dilute tea. The one genuine safety point here belongs not to the pure molecule but to the whole amacha leaf.

Safety at a Glance

✅ Low / no toxicity

• A traditional food sweetener. Phyllodulcin is the sweet component of amacha, drunk ceremonially and as a mild folk sweetener; no acute toxicity is reported for the isolate at dietary exposure ^{1,2Reference 1Kim MJ et al. · 2016Relative sweetness and sweetness quality of phyllodulcin [(3R)-8-hydroxy-3-(3-hydroxy-4-methoxyphenyl)-3,4-dihydro-1H-isochromen-1-one]View study →Reference 2Çiçek SS · 2020ReviewStructure-dependent activity of plant-derived sweeteners — reviewView study →}.
• Over-steeped amacha leaf can cause GI food-poisoning-type illness. This is a real, documented caution for the whole sweet-hydrangea leaf tea brewed too strong — Japanese health guidance limits customary strength to roughly a few grams of leaf per litre of water; it is a herb-preparation caution, not a property of purified phyllodulcin ^{11Reference 11Tsukioka J et al. · 2023Quantitative analysis of taxiphyllin, a cyanogenic glycoside, in the leaves of Hydrangea macrophylla var. thunbergii — analyticalView study →}.
• No human safety or pharmacokinetic data for the isolate. Doses used in the mouse and cell studies have no established human equivalent, and interactions/reproductive safety for the pure molecule are unstudied.

The over-concentration caution deserves emphasis because it is easy to misattribute. Reports of vomiting and GI upset after drinking amacha are tied to too-concentrated leaf infusions, and the sweet-hydrangea leaf also contains a cyanogenic glycoside (taxiphyllin); an analytical study found taxiphyllin is largely hydrolysed during normal processing and judged an unlikely cause of the reported poisonings, leaving the illness most consistent with simply brewing the leaf too strong ^{11Reference 11Tsukioka J et al. · 2023Quantitative analysis of taxiphyllin, a cyanogenic glycoside, in the leaves of Hydrangea macrophylla var. thunbergii — analyticalView study →}. Either way, this is a caution about the whole herb and its preparation, not about isolated phyllodulcin — the molecule described here is a trace sweetener, and reproductive/lactation questions belong to the herb page where intake is actually decided.

Dosage

There is no established or recommended human dose of phyllodulcin. It is a sweetener and a preclinical research molecule, not a dosed therapeutic — the anti-obesity, anti-amyloid and antioxidant figures in the literature are rodent and cell-culture doses with no human equivalent, and are not a basis for self-dosing.

The only traditional human “dose” is indirect, as the sweet component of amacha tea, which is drunk dilute: Japanese health guidance recommends brewing no more than roughly 3 g of amacha leaf per litre of water, precisely because over-concentrated leaf tea can cause GI illness ^{11Reference 11Tsukioka J et al. · 2023Quantitative analysis of taxiphyllin, a cyanogenic glycoside, in the leaves of Hydrangea macrophylla var. thunbergii — analyticalView study →}. These are traditional and research figures, not a personal recommendation.

References

1. Kim MJ, et al. (2016). Relative sweetness and sweetness quality of phyllodulcin [(3R)-8-hydroxy-3-(3-hydroxy-4-methoxyphenyl)-3,4-dihydro-1H-isochromen-1-one]. Food Science and Biotechnology. https://pubmed.ncbi.nlm.nih.gov/30263376/
2. Çiçek SS (2020). Structure-dependent activity of plant-derived sweeteners — review. Molecules. https://pubmed.ncbi.nlm.nih.gov/32331403/
3. Zhang H, et al. (2007). New type of anti-diabetic compounds from the processed leaves of Hydrangea macrophylla var. thunbergii — in vitro and mouse. Bioorganic & Medicinal Chemistry Letters. https://pubmed.ncbi.nlm.nih.gov/17609121/
4. Matsuda H, et al. (2014). Search for a new type of PPARγ agonist-like anti-diabetic compounds from medicinal plants — review. Biological & Pharmaceutical Bulletin. https://pubmed.ncbi.nlm.nih.gov/24882400/
5. Kim E, et al. (2017). Phyllodulcin regulates obesity-related metabolic changes and fat-browning genes in high-fat-diet-induced obese mice — mouse in vivo. Nutrients. https://pubmed.ncbi.nlm.nih.gov/28934139/
6. Cho E, et al. (2023). Phyllodulcin improves hippocampal long-term potentiation in 5XFAD mice — mouse in vivo. Biomedicine & Pharmacotherapy. https://pubmed.ncbi.nlm.nih.gov/36913892/
7. Cho M, et al. (2024). Phyllodulcin from the hexane fraction of Hydrangea macrophylla inhibits glucose-induced lipid accumulation and ROS generation in Caenorhabditis elegans — in vivo (invertebrate). Bioscience, Biotechnology, and Biochemistry. https://pubmed.ncbi.nlm.nih.gov/38599627/
8. Matsuda H, et al. (1999). Effects of phyllodulcin, hydrangenol, their 8-O-glucosides, and thunberginols A and F on the passive cutaneous anaphylaxis reaction in rats — rat in vivo. Biological & Pharmaceutical Bulletin. https://pubmed.ncbi.nlm.nih.gov/10480329/
9. Matsuda H, et al. (1999). Structure requirements of isocoumarins, phthalides and stilbenes from Hydrangeae Dulcis Folium for inhibition of histamine release from rat peritoneal mast cells — in vitro. Bioorganic & Medicinal Chemistry. https://pubmed.ncbi.nlm.nih.gov/10465418/
10. Yano A, et al. (2023). Dihydroisocoumarins of Hydrangea macrophylla var. thunbergii inhibit binding of the SARS-CoV-2 spike protein to ACE2 — in vitro. Bioscience, Biotechnology, and Biochemistry. https://pubmed.ncbi.nlm.nih.gov/37296229/
11. Tsukioka J, et al. (2023). Quantitative analysis of taxiphyllin, a cyanogenic glycoside, in the leaves of Hydrangea macrophylla var. thunbergii — analytical. Journal of Natural Medicines. https://pubmed.ncbi.nlm.nih.gov/37517070/
12. Asahina Y, Asano J (1929). Über die Konstitution von Hydrangenol und Phyllodulcin. Berichte der deutschen chemischen Gesellschaft (A and B Series). https://doi.org/10.1002/cber.19290620124

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