Gardenia (Gardenia jasminoides Ellis): A Comprehensive Reference
1. Identity and Botanical Classification
1.1 Nomenclature
Gardenia jasminoides Ellis, also named gardenia, cape jasmine, or cape jessamine, is a popular evergreen shrub. Also known as "Cape Jasmine," it is an East Asian blooming species indigenous to East Asia. In traditional Chinese medicine (TCM), it is known by the Chinese names Zhizi (栀子) or Zhi Zi; in Japan it is called Sanshishi. It belongs to the Rubiaceae family.
1.2 Botanical Description and Geographic Distribution
G. jasminoides is distributed in the tropical and subtropical regions of the world, especially south of the Yangtze River in China. It naturally grows in the laurel forests of China, Japan, Taiwan, and Vietnam. The plant produces extremely scented and often double flowers with large white petals; depending on the variety, the white flowers have a scent similar to that of jasmine. The fruit is an ovoid, yellow or yellow-orange berry containing slightly bent seeds.
1.3 Medicinal Plant Part and Common Preparations
Gardenia jasminoides Ellis (G. jasminoides) is a popular shrub in the Rubiaceae family. The desiccative ripe fruits of this plant have long been applied in China for centuries as both a food and medicinal substance. The fruit is harvested when mature and dried, developing its characteristic deep yellow-orange color.
As a traditional Chinese medicine, G. jasminoides has been used for thousands of years in prescriptions with the preparation of decoction, liniment, and concentrated preparations. Gardenia flowers can be eaten raw, pickled, or preserved in honey. In China, the petals are used in tea for their aroma, while a yellow-red dye used in textiles and sweets has been extracted from the pulp of the fruit. In modern contexts, the fruit appears in standardized extracts, capsules, tablets, and topical preparations.
Gardenia yellow pigment has also been widely used as an excellent natural dye-stuff. Hence, Gardenia jasminoides Ellis has been applied to many fields, including the food industry, textile industry, and chemical industry, in addition to its predominant medicinal uses. Gardenia blue is a dark blue food colorant widely used in Japan and is made from naturally derived raw materials obtained from the fruit of Gardenia jasminoides.
2. Traditional and Historical Use
2.1 Traditional Chinese Medicine (TCM)
Gardenia jasminoides is an ancient herbal medicine listed in Shen Nong's Herbal, the earliest pharmacological book in China, for its medicinal properties, and is commonly used in traditional Chinese medicine. Its dried fruits used as a traditional herbal medicine were first recorded in the book named Shennong Ben Cao Jing, the Classic of Herbal Medicine in China.
It is classified as a "Middle grade" drug and is recorded in the Chinese pharmacopoeia with various effects, such as eliminating vexation, reducing fever, and cooling blood. Gardenia jasminoides fructus (fruit) is used in traditional Chinese medicine to "drain fire" and treat certain febrile conditions. Zhi Zi (Gardenia jasminoides), commonly known as Gardenia Fruit, is a widely used heat-clearing herb in traditional Chinese medicine. For centuries, it has been valued for its ability to drain fire, eliminate irritability, clear heat, and cool the blood.
Zhi Zi has been recorded in Chinese medical texts for over two thousand years and appears in classical formulas such as Zhi Zi Chi Tang, traditionally used to address irritability and restlessness caused by heat. In classical Chinese herbal medicine, Zhi Zi is frequently included in formulas designed to clear heat from the heart, liver, and lungs, relieve restlessness, and eliminate toxic heat from the body.
In Chinese medical theory, Gardenia jasminoides could reach meridians of the heart, lung, and triple burner and suppress the evil fire, relieve internal heat, and cool blood in the body. The Ministry of Health of China has listed it as one of the first pharmaceutical or food resources. In ethnic, traditional, and folk medicine, G. jasminoides Ellis has been used to treat fever and cold and relieve nervous anxiety.
The herb has also been processed in China according to records in the Treatise on Febrile Diseases, and it is considered a medicine-food homology by the National Health Commission of the People's Republic of China.
A notable classical formula containing gardenia fruit is Yinchenghao Tang (YCHT), used historically for jaundice-related conditions. YCHT as recorded in Shanghanlun accurately consists of 18.0 g of the flos of Artemisia capillaries Thunb, 9.0 g of the fruit of Gardenia jasminoides Ellis, and 6.0 g of the root of Rheum officinale Baill. Huang-Lian-Jie-Du-Tang is another prescription formulation that contains Coptix chinensis, Scutellaria baicalensis, Phellodendron amurense, and Gardenia jasminoides, and is used to treat various inflammatory diseases, such as gastritis, dermatitis, and aphthous stomatitis.
2.2 Traditional Use in Japan and Korea
In addition to its use in traditional Chinese medicine, G. jasminoides has been widely used in folk medicine in Japan and Korea for hundreds of years to treat fever, gastrointestinal issues, and inflammation. Shishihakuhito is a Chinese herbal medicine mainly composed of gardenia fruit that is used to treat atopic dermatitis. It inhibits immunoglobulin E (IgE)-mediated histamine release.
2.3 Traditional Preparations and Applications
Revered in ancient China, gardenia fruit was lauded for its cooling properties and was often used to clear heat and eliminate irritability. Its applications included remedies for fever, jaundice, headaches, and urinary tract difficulties. People also used it to address swelling, trauma, and inflammation, relying on its reputed ability to promote calm and balance within the body. The fruit of gardenia is a traditional Chinese folk medicine used in the treatment of an array of illnesses including jaundice, headaches, fever, inflammation, hepatic disorders, and hypertension.
Gardenia yellow pigment has been the most important source of a natural colorant for food, cloth, and paint for thousands of years. Gardenia jasminoides is used in traditional Chinese medicine for various properties including emollient, emetic, diuretic, vermifuge, antispasmodic, antiseptic, and analgesic actions.
3. Phytochemistry: Key Constituents and Active Compounds
3.1 Overall Chemical Complexity
Approximately 162 chemical compounds have been isolated and identified from this herb. Among them, iridoid glycosides and yellow pigment are generally considered the main bioactive and characteristic ingredients. An examination uncovers a variety of bioactive phytoconstituents, such as flavonoids, iridoid glycosides, gardenia's yellow pigment, monoterpenoids, sesquiterpenoids, triterpenoids, organic acids and their derivatives, along with other compounds.
3.2 Iridoid Glycosides
The major constituents of Gardenia jasminoides are iridoid glycosides, such as geniposide, gardenoside, shanzhiside, scandoside methyl ester, deacetyl-asperulosidic acid methyl ester, and genipin-1-β-D-gentiobioside.
Geniposide is the most abundant and best-studied iridoid glycoside. As a major active iridoid glycoside from Gardenia jasminoides J. Ellis (Rubiaceae), geniposide possesses various pharmacological activities, including anti-platelet aggregation and anti-inflammatory action. Geniposide, the glycoside form of genipin, is a bioactive iridoid glycoside found in Gardenia jasminoides (fruits). Geniposide shows several pharmacological effects (in vitro and in vivo) including neuroprotective, antidiabetic, hepatoprotective, anti-inflammatory, analgesic, antidepressant-like, cardioprotective, antioxidant, immune-regulatory, antithrombotic, and antitumoral activity.
Genipin is the aglycone of geniposide, formed by enzymatic hydrolysis. Geniposide, one of the major glycosides in gardenia fruit extract, is hydrolyzed to the aglycone genipin by β-D-glucosidases in the human liver and intestines. Geniposide and genipin are the most important iridoid compounds isolated from Gardenia jasminoides Ellis, and genipin is the aglycone of geniposide. As the predominant active ingredient with a distinct pharmacological activity, genipin is also an outstanding biological crosslinking agent. The hydrolysis of geniposide and gardenoside by β-glucosidase results in the production of genipin, a water-soluble iridoid monoterpenoid. Genipin can react with amino acids such as glycine, lysine, or phenylalanine to obtain the blue dye gardenia blue.
3.3 Carotenoids (Crocin and Crocetin)
It has been reported that G. jasminoides possesses multiple biological activities, such as antioxidant properties, hypoglycemic effect, inhibition of inflammation, antidepression activity, and improved sleeping quality. The two major phytochemicals, genipin and crocin, possess potent medicinal properties. Crocin I is a diterpenoid compound of Gardenia jasminoides Ellis, which is one of its main active components. Crocin, the primary bioactive component of gardenia yellow (comprising approximately 44.96% of it), exhibited approximately 4.68% oral bioavailability and was biotransformed to crocetin (approximately 30.47%) in the colon.
3.4 Additional Phytochemical Classes
Four new iridoids and one new phenylpropanoid glucoside, together with sixteen known compounds, have been isolated from the edible flowers of wild Gardenia jasminoides J. Ellis. The chemical components that have been reported so far include iridoid glycosides, monoterpenes, diterpenes, triterpenes, flavonoids, organic acids, and other compounds.
4. Mechanisms of Action
4.1 Anti-inflammatory Pathways
Geniposide performs anti-inflammatory and neuroprotective activities via modulating mitogen-activated protein kinase (MAPK)/nuclear factor kappa-B (NF-κB) and phosphatidylinositide 3-kinases-protein kinase B (PI3K-Akt) signalling pathways. Geniposide, a major component of Gardenia jasminoides fruit, is used in the treatment of chronic inflammation as well as to combat oxidative stress; IL-1β and TNF-α levels were significantly reduced by geniposide, which likewise prevented pneumonia in mice via blocking the NF-κB signaling pathway.
Importantly, Gardenia jasminoides inhibits tumor necrosis factor-alpha (TNF-α)-induced vascular inflammation in human umbilical vein endothelial cells.
4.2 Neuroprotective and Antidepressant Mechanisms
A growing body of evidence shows that the neuroprotective benefit of geniposide probably arises from its agonist action on the glucagon-like peptide-1 receptor (GLP-1R). When this receptor is activated, neurotrophic effects are induced in cells, such as neurite outgrowth, reducing amyloid plaques, inhibiting tau phosphorylation, preventing memory impairment.
In a depressive state, serum levels of adrenocorticotropic hormone and cortisol are increased, as well as hypothalamic corticotropin-releasing hormone gene expression. The dysfunction of the HPA axis plays an important role in the serotonergic system. Geniposide is proposed to modulate this pathway. Crocin has been demonstrated to harbor anti-inflammatory, antioxidant, and neuroprotective properties, as well as to act on AMPK and inhibit the influence of the AMPK-ULK-1 complex on autophagy, thus protecting brain regions.
Microglia are the prime effectors in immune and inflammatory responses of the central nervous system (CNS). Under pathological conditions, the activation of these cells helps restore CNS homeostasis. However, chronic microglial activation endangers neuronal survival through the release of various proinflammatory and neurotoxic factors. Negative regulators of microglial activation have been considered as potential therapeutic candidates to target neurodegeneration, such as that in Alzheimer's and Parkinson's diseases. The effect of certain gardenia constituents has been found to be due to inhibition of the NLRP3 inflammasome and NF-κB and their promotion of M1 to M2 phenotypic conversion of microglia.
4.3 Hepatoprotective Mechanisms
Geniposide exerts protective effects against hepatic steatosis in rats fed a high-fat diet; the underlying mechanism may be associated with its antioxidant actions or regulation of adipocytokine release and expression of PPARα. Previous in vitro and in vivo studies have shown that geniposide attenuates oxidative stress and inflammatory response via the modulation of Nrf2/AMPK/mTOR signaling in non-alcoholic fatty liver disease and increases DNA binding activities of hepatocyte nuclear factor-4α and peroxisome proliferator-activated receptor-α in alcoholic steatosis.
4.4 Antidiabetic Mechanisms
The pharmacological action of genipin has been shown to include the rapid inhibition of uncoupling protein 2, a negative regulator of insulin secretion in pancreatic tissues. Based on numerous pharmacological studies, Gardenia jasminoides Ellis (Zhi-zi) and its ingredients, mainly including iridoid glycosides and carotenoids (crocins), possess potent antioxidant and anti-inflammatory properties, and can promote insulin secretion and sensitization, stimulate GLP-1 pathway activity, and protect islet β cells and the macro- and microvascular systems. These properties are the primary reasons why Zhi-zi and its ingredients are effective in reducing glucose levels, treating diabetes, and preventing its complications.
4.5 Crosslinking and Industrial Mechanism of Genipin
Several lines of evidence suggest that genipin is a potent inhibitor of UCP2, which functions as a tumor promoter in a variety of cancers, attenuates generation of reactive oxygen species and the expression of matrix metalloproteinase 2, and induces caspase-dependent apoptosis in vitro and in vivo. Gardenia jasminoides fruit contains geniposide that, following reaction with beta-glucosidase, forms genipin that can then react with peptides, amino acids, or proteins to form a blue pigment.
5. Scientific Evidence by Area of Use
5.1 Inflammation and Oxidative Stress
The anti-inflammatory effects of gardenia constituents have been examined primarily in preclinical (in vitro and animal) models. The traditional use of Gardenia jasminoides as an anti-inflammatory agent has been confirmed in mouse models and in vitro, through the attenuation of inflammatory mediators.
Gardenia jasminoides fruit extract inhibited IL-4/IL-13-induced inflammatory response and phosphorylation of STAT6 in keratinocytes and a 3D skin model. The extract repaired tight junctions in keratinocytes and in the 3D skin model. Gardenia jasminoides fruit extract treatment also ameliorated atopic dermatitis-like skin lesions in MC903-induced mice. These findings are at the preclinical stage; no large-scale human clinical trials in this indication have been reported in the available literature.
5.2 Liver Health and Hepatoprotection
Several lines of preclinical evidence support hepatoprotective properties. Crude water extracts of G. jasminoides (10–100 mg/kg in rats) reduced liver fibrosis and resulted in a decrease in the levels of the liver injury markers ALT and AST, hydroxyproline, and smooth muscle actin, a marker of active hepatic stellate cells.
Geniposide, a major constituent of the Gardenia jasminoides extract, enhances the activities of glutathione (GSH) peroxidase and decreases malondialdehyde (MDA) levels in liver. Geniposide treatment was found to reduce levels of IL-6, IL-1β, and TNF-α in a mouse model of liver fibrosis.
A 2025 animal study using a NASH model investigated dosing specifics: This study investigated the therapeutic potential of Gardenia jasminoides fruit extract (GJE) in a rat model of NASH with fibrosis induced by a high-fat, high-fructose (HFHF) diet. Male Sprague-Dawley rats were assigned to groups treated with 0.119 g/kg BW or 0.239 g/kg BW of GJE, administered via intragastric gavage once daily from weeks 13–20. Serum ALT and AST levels were significantly increased in the NASH/fibrosis group, which also showed the highest histopathology scores and collagen deposition. GJE treatment significantly reduced ALT and AST levels in both low- and high-dose groups. The low-dose GJE group showed marked improvement in NASH histopathology, while both treatment groups exhibited reduced hepatic collagen deposition. GJE treatment significantly suppressed NF-κB p65 and Col1a1 expression, along with downregulation of MMP-12, α-SMA, IL-13, and TGF-β1 protein levels. These results are animal-based only, and human clinical trial data in NASH are not yet available in the peer-reviewed literature.
G. jasminoides Ellis polysaccharide (GPS) was evaluated in an alpha-naphthylisothiocyanate (ANIT)-induced cholestatic mouse model. GPS administration dose-dependently ameliorated impaired hepatic function, including a 2–7-fold decrease in aminotransferase levels, ameliorating tissue damage, upregulating the expression of farnesoid X receptor (FXR) and pregnane X receptor (PXR) and their downstream efflux transporters, and decreasing the levels of 12 bile acids in cholestatic mice. Furthermore, GPS ameliorated gut microbiota dysbiosis, improved intestinal barrier function, and reduced serum and hepatic lipopolysaccharide levels 1.5-fold. Again, this evidence is preclinical.
5.3 Diabetes and Metabolic Conditions
Preclinical data on antidiabetic effects are extensive. Modern studies have indicated Gardenia jasminoides Ellis shows a positive effect in treating type 2 diabetes mellitus (T2DM). In one study, 60 streptozotocin-induced T2DM rats were divided into four groups: type 2 diabetes control group, geniposide-treated group, total iridoid glycosides-treated group, and crude extraction of gardeniae fructus-treated group, along with ten healthy control rats.
Treatment with low and high doses (200 and 400 mg/kg) of gardenia polysaccharides significantly reduced the fasting blood glucose level of T2DM mice by 44.8% and 33.0%, respectively. GPS intervention also upregulated the liver expression of peroxisome proliferator-activated receptor gamma (PPARγ) by 1.7-fold, improved insulin resistance, and increased glycogen synthesis in T2DM mice compared with untreated controls. All available evidence for diabetes management from gardenia is preclinical; the absence of controlled human clinical trials represents a critical gap.
5.4 Neurological Conditions: Depression, Anxiety, and Cognitive Function
Recent studies have confirmed the significant efficacy of G. jasminoides Ellis for treating central nervous system (CNS) disorders, including Alzheimer's disease, Parkinson's disease, and major depressive disorder; however, G. jasminoides Ellis has not been systematically evaluated.
Studies have shown that gardenia extract has a significant improvement effect on neurological diseases, including anxiety, depression, Alzheimer's disease, and Parkinson's disease. However, most of this evidence is from animal and cell studies.
Fructus gardeniae (FG) is a traditional Chinese medicine and health food for thousands of years of application throughout Chinese history and is still widely used in clinical Chinese medicine. FG has a beneficial impact on anxiety, depression, insomnia, and psychiatric disorders; however, its mechanism of action requires further investigation.
One notable human randomized controlled trial examined crocin — the carotenoid pigment shared between gardenia and saffron. Methadone maintenance treatment (MMT) may be associated with symptoms of depression and anxiety, sleep disturbances, and sexual dysfunctions. This study was designed to determine the effects of crocin on psychological parameters in patients under MMT. Patients under MMT were randomly allocated to receive either 30 mg/day crocin (15 mg twice daily) (n = 25) or placebo (n = 25) for 8 weeks. The findings documented that crocin in patients under MMT significantly improved their depression, anxiety, general health, sleep quality, and erectile functions. Based on these findings, crocin may be recommended as an adjunct therapy for opioid-dependent patients under treatment with MMT. This is a small, single-center trial in a specific clinical population; generalizability is limited.
Gardenia jasminoides Ellis (GJ) is one of the five constituents of Yueju pill, a traditional Chinese medicine for treatment of syndromes associated with mood disorders. Preclinical and clinical studies suggest that Yueju pill confers rapid antidepressant effects. Gardenia's specific individual contribution within these multi-herb formulas cannot be isolated from the available data.
Short-term memory assays on an Abeta transgenic drosophila model showed that certain iridoid glucosides isolated from gardenia can improve short-term memory capacity to varying degrees, with some being the most active, suggesting that these compounds may have potential antagonism against Alzheimer's-related pathology. This is in-vivo invertebrate data only.
5.5 Atopic Dermatitis and Skin Conditions
Ethnopharmacological relevance: Gardenia jasminoides Ellis has been used in traditional medicine for treatment of inflammation, edema, and dermatitis. The aim of one key study was to investigate the mechanism by which Gardenia jasminoides extract (GJE) elicits anti-allergic effects in mast cells and in mice with atopic dermatitis (AD).
GJE and its ethyl acetate fraction inhibited compound 48/80-induced histamine release from MC/9 mast cells. Topical application of GJE or GJE-EA to Dermatophagoides farinae-exposed NC/Nga mice reduced the symptoms of AD, inhibited the infiltration of inflammatory cells, and lowered the serum levels of immunoglobulin E and histamine. These results suggest that GJE and GJE-EA can suppress mast cell degranulation-induced histamine release, and geniposide may be a potential therapeutic candidate for AD. These findings are preclinical; human clinical trials for atopic dermatitis using gardenia fruit extract specifically are not yet reported in the accessible peer-reviewed literature.
5.6 Cardiovascular Effects
Pharmacological studies have shown that Gardenia has certain liver- and gallbladder-protecting, blood sugar-lowering, pancreatic secretion-promoting, gastric function-protective, blood pressure-lowering, lipid-regulating, neuroprotective, anti-inflammatory, antioxidant, anti-fatigue, and anti-thrombotic activities. The anti-hypertensive effect and the anti-allergic activity of G. jasminoides were associated with the active component, geniposide. These are primarily preclinical observations, and human clinical evidence for gardenia's cardiovascular effects is limited.
5.7 Skin Aging and Blue-Light Protection
One published study investigated the topical cosmetic application of gardenia fruit extract: "A melatonin-like ingredient" was discovered in the extract of Gardenia jasminoides, which acts as a filter against blue light and as a melatonin-like ingredient to prevent and stop premature aging. The extract showed significant protective effects on the mitochondrial network of primary fibroblasts, a significant decrease of −86% in oxidized proteins on skin explants, and preservation of the natural melatonin cycle in co-cultures of sensory neurons and keratinocytes. Upon analysis using in silico methods, only the crocetin form, released through skin microbiota activation, was found to act as a melatonin-like molecule by interacting with the MT1-receptor. Clinical studies revealed a significant decrease in wrinkle number of −21% in comparison to placebo. The extract showed strong protection against blue light damage and the prevention of premature aging through its melatonin-like properties. This was a small, industry-sponsored clinical evaluation; independent large-scale replication has not been established.
6. Body Systems and Health Areas Associated with Gardenia
Various pharmacological properties, such as a beneficial effect on the nervous, cardiovascular, and digestive systems, hepatoprotective activity, antidepressant activity, and anti-inflammatory activity, were validated in preclinical studies. These components are associated with wide-ranging pharmacological applications, which encompass antioxidant, anti-inflammatory, anti-diabetic, cardiovascular disorders, neurodisorders, anti-tumor, treatment of liver injury, anti-hepatic injury, gastrocellular activity, improvement of gut microbiota, atopic dermatitis, anti-viral, improvement of the quality of sleep, protection from blue light and ultraviolet rays, vitiligo, inhibition of retinal damage, antibacterial activity, anti-senescence activity, anti-thrombosis, osteoporosis protection, and postmenopausal syndrome treatment. It must be emphasized that the majority of these associations derive from in vitro, animal, or small-scale studies rather than well-powered human clinical trials.
7. Dosage Forms and Reported Dosages
Dosages vary substantially across the literature, depending on the extract type, the specific constituent being studied, and the indication. The following are dosages as specifically reported in source studies:
- Crude extract in rats (liver fibrosis model): 10–100 mg/kg in rats, shown to reduce liver fibrosis and decrease liver injury markers ALT and AST.
- Geniposide in diabetic wound rats: A diabetic rodent model was induced by streptozotocin combined with high-fat feed. Geniposide subgroups received 200, 400, and 500 mg/kg orally administered once daily.
- Gardenia polysaccharides in T2DM mice: Treatment with low and high doses (200 and 400 mg/kg) of GPS significantly reduced the fasting blood glucose level of T2DM mice by 44.8% and 33.0%, respectively.
- NASH model in rats: Male Sprague-Dawley rats were treated with 0.119 g/kg BW (low dose) or 0.239 g/kg BW (high dose) of GJE once daily for 8 weeks.
- Crocin in human RCT (methadone maintenance patients): Patients received either 30 mg/day crocin (2 tablets, 15 mg twice daily) or placebo for 8 weeks.
- Geniposide (CYP inhibition study in rats): Rats were treated orally with the iridoid glycoside at 0.1 g/kg body weight/day or the crude extract of its fruits at 2 g/kg/day for 4 days.
- Gardenia yellow (subchronic toxicology, rats): In the subchronic study, gardenia yellow was orally administered to rats by gavage at doses of 0, 0.50, 1.50, and 4.50 g/kg·bw/day for 90 days followed by a recovery period of 28 days.
No standardized human therapeutic dosage range for whole gardenia fruit extract or its isolated constituents has been established in the peer-reviewed literature reviewed for this article.
8. Safety Considerations and Interactions
8.1 General Toxicity Profile
Researchers have not found any significant side effects resulting from G. jasminoides, and the median lethal dose (LD50) of the ethanol extract of G. jasminoides is 17.1 g/kg and 107.48 g/kg for intraperitoneal injection and oral administration in animals, respectively.
8.2 Dose-Dependent Hepatotoxicity
A critical safety concern is dose-dependent liver and kidney toxicity. Close attention must be paid to the dosage of Fructus Gardeniae in order to achieve a therapeutic effect and avoid adverse reactions, including hepatotoxicity and nephrotoxicity. There are reports of liver toxicity from Gardenia jasminoides fruit, and possible hepatotoxic effects of genipin were observed in both in vitro and in vivo studies.
No appreciable toxic-related changes were observed in rats at 0.50 g/kg·bw/day of gardenia yellow. When animals received gardenia yellow at 1.50 g/kg·bw/day or more, body weight loss was observed, and pigments began to deposit in several vital organs, resulting in significant changes of several hematological and biochemical indicators related to nutritional status and liver and kidney function, more severe in the high-dose group. In the recovery period, the alterations of clinical symptoms and parameters were relieved substantially. Based on the results of this study, the no-observed-adverse-effect level (NOAEL) of gardenia yellow E500 in rats was set at 0.50 g/kg·bw/day.
Gardenia jasminoides Ellis is a key ingredient in the Zhi-Zi-Hou-Po decoction (ZZHPD), which is a commonly used clinically combined prescription of TCM that may induce hepatotoxicity. However, the underlying toxicity mechanism of ZZHPD is not fully understood.
8.3 Skin Discoloration
In 2020, a case of someone who had developed blue-gray discoloration of the skin as a result of chronic intake of gardenia fruit extract was published. This is consistent with genipin's well-known reactivity with amino acids to form blue chromophores, as described in the phytochemistry section. In animal studies, the only treatment-related change with gardenia blue was grossly observed blue discoloration of the stomach, intestines, and mesenteric lymph nodes, as well as reversible dark discoloration of the kidneys, all without associated histopathology.
8.4 Gardenia Blue: Regulatory Safety Review
The study was performed in anticipation of the worldwide marketing of gardenia blue as a food colorant after authorization by the U.S. Food and Drug Administration (FDA) and the European Union, and a positive safety opinion from JECFA, the FAO/WHO Joint Expert Committee on Food Additives. No adverse effects were identified in Sprague-Dawley rats following 12 and 24 months of dietary exposures up to 5% gardenia blue.
No evidence of mutagenicity of gardenia blue was detected in a 5-strain bacterial reverse mutation assay, with or without metabolic activation. In in vitro micronucleus and chromosome aberration assays, genipin tested positive under some test conditions; however, gardenia blue tested negative in both assays.
Regulatory review found no evidence that reproductive toxicity hazards existed from petitioned use levels of gardenia (genipin) blue. The chronic/carcinogenicity study adhered to Redbook 2000 guidelines and reported no adverse effects up to a nominal concentration of 5% gardenia (genipin) blue in feed for rats. No results from this study suggest that gardenia (genipin) blue is a reproductive or developmental toxicant.
8.5 Drug Interactions: CYP450 Enzyme Inhibition
A pharmacologically significant concern is the interaction of gardenia constituents with drug-metabolizing enzymes. G. jasminoides decreased CYP450 content, benzo[a]pyrene hydroxylation, 7-ethoxycoumarin O-deethylation (CYP1A and CYP2B), and erythromycin N-demethylation activities in liver microsomes. Geniposide and crude extract of G. jasminoides fruits were administered orally (geniposide at 0.1 g/kg body weight/day; crude extract at 2 g/kg/day) for 4 days. G. jasminoides demonstrated that geniposide from G. jasminoides has the ability to inhibit a CYP3A monooxygenase and increase glutathione content in rat liver. Inhibition of CYP3A4 enzymes in humans could theoretically alter the metabolism of numerous co-administered drugs, though direct human interaction studies are limited.
8.6 Herb-Drug Interactions
Herb-drug interaction is a rising public health concern along with the growing prevalence of herbal medicines worldwide. It is increasingly recognized that the disease status may also participate in herb/drug-drug interactions. One preclinical study examined the co-administration of simvastatin and G. jasminoides in the context of NASH, finding that disease-state-dependent factors can alter the pharmacokinetics and hepatotoxicity profile of both agents in combination. These interactions have not been characterized in clinical pharmacokinetic studies in humans.
8.7 Genotoxicity of Genipin
In in vitro micronucleus and chromosome aberration assays, genipin tested positive under some test conditions. However, in combined micronucleus/comet assays conducted in male and female mice, exposure to genipin at doses reaching maximal toxicity (74 and 222 mg/kg bw/day for males and females, respectively) did not induce micronuclei in peripheral blood or DNA damage. The in vivo genotoxicity of genipin at high concentrations was not replicated in the in vivo assays, but the in vitro signal warrants caution and further study.
9. Summary of Evidence Strength
- Anti-inflammatory / antioxidant: Robust preclinical evidence (in vitro, animal models); no large-scale human RCTs specific to isolated gardenia extract.
- Hepatoprotection: Consistent preclinical findings across multiple animal models; human clinical trial data are absent from the current literature.
- Antidiabetic / metabolic: Multiple animal studies show glucose-lowering, insulin-sensitizing effects; no human clinical trials identified for gardenia extract alone.
- CNS effects (depression, anxiety, cognition): Promising preclinical data; one small human RCT on crocin in a specific patient population (MMT); gardenia's constituent is shared with saffron (Crocus sativus), where a larger clinical evidence base exists separately.
- Atopic dermatitis: Preclinical evidence only; one historical TCM formula (Shishihakuhito) used clinically in Japan but not rigorously evaluated in modern RCTs.
- Cardiovascular: Mechanistic and animal data; insufficient human evidence.
- Skin aging / blue light: Preliminary cosmetic clinical study with methodological limitations; evidence is early-stage.
Pharmacological investigations support the traditional use of this herb and may validate the folk medicinal use of Gardenia jasminoides Ellis to treat different diseases. Despite its considerable therapeutic promise, it is essential to take its toxicity into account, especially at elevated doses. Additional research is necessary to evaluate its safety profile and enhance its medicinal uses.
References
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