Therapeutic potential of genipin in various acute liver injury, fulminant hepatitis, NAFLD and other non-cancer liver diseases: More friend than foe.

Genipin is an aglycone derived from the geniposide, the most abundant iridoid glucoside constituent of Gardenia jasminoides Ellis. For decades, genipin is the focus of studies as a versatile compound in the treatment of various pathogenic conditions. In particularly, Gardenia jasminoides Ellis has long been used in traditional Chinese medicine for the prevention and treatment of liver disease. Mounting experimental data has proved genipin possesses therapeutic potential for cholestatic, septic, ischemia/reperfusion-triggered acute liver injury, fulminant hepatitis and NAFLD. This critical review is a reflection on the valuable lessons from decades of research regarding pharmacological activities of genipin. Of note, genipin represents choleretic effect by potentiating bilirubin disposal and enhancement of genes in charge of the efflux of a number of organic anions. The anti-inflammatory capability of genipin is mediated by suppression of the production and function of pro-inflammatory cytokines and inflammasome. Moreover, genipin modulates various transcription factor and signal transduction pathway. Genipin appears to trigger the upregulation of several key genes encoding antioxidant and xenobiotic-metabolizing enzymes. Furthermore, the medicinal impact of genipin extends to modulation of regulated cell death, including autophagic cell death, apoptosis, necroptosis and pyroptosis, and modulation of quality of cellular organelle. Another crucial effect of genipin appears to be linked to dual role in targeting uncoupling protein 2 (UCP2). As a typical UCP2-inhibiting compound, genipin could inhibit AMP-activated protein kinase or NF-κB in circumstance. On the contrary, reactive oxygen species production and cellular lipid deposits mediated by genipin through the upregulation of UCP2 is observed in liver steatosis, suggesting the precise role of genipin is disease-specific. Collectively, we comprehensively summarize the mechanisms and pathways associated with the hepatoprotective activity of genipin and discuss potential toxic impact. Notably, our focus is the direct medicinal effect of genipin itself, whereas its utility as a crosslinking agent in tissue engineering is out of scope for the current review. Further studies are therefore required to disentangle these complicated pharmacological properties to confer this natural agent a far greater potency.

Role of intestinal microbiota-mediated genipin dialdehyde intermediate formation in geniposide-induced hepatotoxicity in rats.

Geniposide is a natural hepatotoxic iridoid glycoside. Its hydrolysate of intestinal microbiota, genipin, is thought to be responsible for the hepatotoxicity. However, the underlying mechanism that genipin contributes to the hepatotoxicity of geniposide is not well understood. In this study, we found that genipin spontaneously converted into a reactive dialdehyde intermediate and covalently bond to the primary amine group of free amino acids in both of the phosphate buffers and geniposide-treated rats. Furthermore, genipin dialdehyde can form the covalent linkage to the primary amino group (ε) of lysine side chains of the hepatic proteins in geniposide-treated rats. Pretreatment with ß-glucosidase or antibiotics significantly modulated the genipin dialdehyde formation and protein modification, revealing the essential role of microbial glycosidases. The levels of protein adduct were that mapped onto the hepatotoxicity of geniposide. In summary, this study demonstrates that the intestinal microbiota mediated covalent modification of the hepatic protein by genipin dialdehyde may play a crucial role in the liver injury of geniposide. The study is also helpful for understanding the contribution of intestinal microbiota to the metabolic activation of xenobiotics.

The Short-Term Safety Evaluation of Corneal Crosslinking Agent-Genipin.

BACKGROUND: Genipin (GP) is a safe method for corneal crosslinking, even for very thin corneas. However, there have been no reports on the optimal GP concentration range to use in vivo for corneal crosslinking. OBJECTIVES: To investigate the safety of corneal crosslinking after a 24-h incubation with different concentrations of GP. METHODS: Twenty New Zealand white rabbits were divided into a phosphate-buffered saline (PBS) group, 0.2% GP crosslinking (GP-CXL) group, 0.25% GP-CXL group, and 0.3% GP-CXL group. Before and after surgery, the operated eyes of each group were characterized by confocal microscopy, and corneal buttons were excised for endothelium staining and electron microscopy. RESULTS: The keratocyte structures in each GP group appeared to be similar to those in the PBS group. Through the confocal microscopy, the changes in corneal endothelial cell density also did not significantly differ among groups. There was a significant difference in apoptosis between the 0.3% GP-CXL and PBS groups (p < 0.05) and between the 0.3% GP-CXL and 0.25% GP-CXL groups (p < 0.05), but there were no significant differences between the 0.2 and 0.25% GP-CXL groups compared to the PBS group. Transmission electron microscopy showed endothelial cell damage in the 0.3% GP-CXL group, with minimal endothelial cell damage in the other groups. CONCLUSIONS: Treatment of rabbit corneas with ≤0.25% GP resulted in minimal toxicity to keratocytes and endothelial cells, suggesting that it is a safe crosslinking agent at those concentrations.

The Effects of Different Varieties of Aurantii Fructus Immaturus on the Potential Toxicity of Zhi-Zi-Hou-Po Decoction Based on Spectrum-Toxicity Correlation Analysis.

In accordance with the provision in China Pharmacopoeia, Citrus aurantium L. (Sour orange-SZS) and Citrus sinensis Osbeck (Sweet orange-TZS) are all in line with the requirements of Aurantii Fructus Immaturus (ZS). Both kinds of ZS are also marketed in the market. With the frequent occurrence of depression, Zhi-Zi-Hou-Po decoction (ZZHPD) has attracted wide attention. Currently, studies have shown that ZZHPD has a potential toxicity risk, but the effect of two commercial varieties of ZS on ZZHPD has not been reported. In this study, the toxicity differences of ZZHPD prepared by SZS and TZS were revealed through repeated administration experiments in rats. This indicated that different varieties of ZS could affect the toxicity of the prescription. In order to further study the chemical material basis of the toxicity difference, the fingerprints of ZZHPD prepared by different varieties of ZS were established by high-performance liquid chromatography (HPLC). Five different characteristic peaks were screened by non-target chemometrics. They were identified as geniposide, neoeriocitrin, naringin, hesperidin, and neohesperidin using an HPLC-time-of-flight mass spectrometry analyzer (TOF/MS) and an HPLC-triple stage quadrupole mass spectrometry analyzer (QqQ-MS/MS). Combined with a quantitative analysis and previous studies on promoting the intestinal absorption of geniposide, it is speculated that the synergistic effects of the components may be the main reason for the difference of toxicity among the different medicinal materials. This study provides a reference for the clinical, safe use of ZZHPD, and also provides a new perspective for the study of the potential toxic substances of traditional Chinese medicine compound preparations.

[Marker genes of geniposide-induced hepatotoxicity based on genomic strategy].

The aim of this paper was to screen out relevant genes of geniposide-induced hepatotoxicity based on genomics,in order to provide a scientific basis for the non-clinical evaluation of drugs containing Gardeniae Fructus and geniposide. Fifty-five SD rats were randomly divided into normal control group,24 h group and 72 h group. The changes of appearance,behavior and weight of rats were observed after administration by gavage for 3 days. The activities of ALT and AST were detected. Molecular mechanism of geniposideinduced hepatotoxicity was investigated by Affymetrix miRNA 4. 0 and Affymetrix Rat Gene 2. 0 to examine the gene expression levels in Sprague-Dawley rat livers at 24 h and 72 h after administration of overdose-geniposide( 300 mg·kg-1 daily),and then verified by Realtime quantitative PCR. Compared with the normal control group,the activities of ALT and AST were markedly increased. In addition,experimental results indicated that 324 genes were differentially expressed,among which 259 were up-regulated and 65 down-regulated.Nine candidate genes were verified by qRT-PCR,including Bcl2,Il1 b,Tpm3,MMP2,Col1α1,Ifit1,Aldob,Nr0 b2,Cyp2 c23. And Bcl2,Col1α1,Aldob,Nr0 b2 and Cyp2 c23 were found to be correlated with geniposide-induced hepatotoxicity. This study provides an important clue for mechanism of geniposide-induced hepatotoxicity.

A New Iridoid Dimer and Other Constituents from the Traditional Kurdish Plant Pterocephalus nestorianus Nábelek.

Accompanied by other rare compounds, a new iridoid dimer, named kurdnestorianoside (1), showing an unprecedented secologanol configuration, has been isolated for the first time from the Kurdish medicinal plant Pterocephalus nestorianus, which is used in Kurdistan for treating oral diseases and inflammation. The structure of 1 was established from 1D- and 2D-NMR spectroscopic data. Kaempferol 3-O-[3,6-di-O-(E)-p-coumaroyl]-ß-d-glucopyranoside (7) showed a remarkable antiproliferative activity against several human tumor cell lines.

Anti-mycobacterial activity of plumericin and isoplumericin against MDR Mycobacterium tuberculosis.

BACKGROUND AND OBJECTIVES: Because of the developing resistance of Mycobacterium species against currently available anti-mycobacterial drugs, there is an urgent need for new drug development. In this study, we have evaluated the in vitro anti-mycobacterial activity of Plumeria bicolor extract and its phytoconstituents - plumericin and isoplumericin against multi-drug resistance Mycobacterium tuberculosis. METHODS: The in vitro anti-mycobacterial activity of chloroform extract of P. bicolor, plumericin and isoplumericin were tested against M. tuberculosis (H37Rv) and four multi-drug resistant (MDR) clinical isolates by measuring the minimum inhibitory concentration (MIC) using MTT (Tetrazolium bromide [3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide]) assay. The extract and both compounds were further evaluated by standard assay procedures to determine their minimum bactericidal concentration (MBC). Cytotoxicity of these compounds was performed against J774G8 murine macrophage cell lines. The activity was represented in the mean (±SD) of duplicate samples from three independent assays. RESULTS: Plumericin showed better activity against pan sensitive as well as four MDR strains of M. tuberculosis with MIC values of 2.1 ± 0.12, 1.3 ± 0.15, 2.0 ± 0.07, 1.5 ± 0.13 & 2.0 ± 0.14 µg/mL and MBC values of 3.6 ± 0.22, 2.5 ± 0.18, 3.8 ± 0.27, 2.9 ± 0.20 & 3.7 ± 0.32 µg/mL than isoplumericin, respectively. Interestingly, both isolated active compounds showed an advantage over rifampicin (80 times) and isoniazid (8 times) by being highly active against the MDR strains. The extract and both compounds were found to be non-toxic against J774G8 macrophages up to the used concentrations. CONCLUSION: Plumericin showed more potent activity than isoplumericin. The excellent activity of these compounds against MDR strains opens a possibility of obtaining new anti-mycobacterial drug candidate in near future.

Leaf chemistry and foliage avoidance by the thrips Frankliniella occidentalis and Heliothrips haemorrhoidalis in glasshouse collections.

Observational studies on foliage avoidance by the polyphagous thrips species Frankliniella occidentalis (Pergande) and Heliothrips haemorrhoidalis (Bouché) (Thysanoptera: Thripidae) identified six non-host species (Allagopappus dichotomus (Asteraceae), Gardenia posoquerioides (Rubiaceae), Plectranthus aff. barbatus, Plectranthus strigosus, Plectranthus zuluensis (Lamiaceae), and Sclerochiton harveyanus (Acanthaceae) among plants growing within a major glasshouse botanical collection. The effects of sequentially obtained acetone and aqueous methanol leaf extracts on mortality in first instar Frankliniella occidentalis were assessed. The acetone leaf extract of Sclerochiton harveyanus, which had the highest activity against the thrips, yielded four new iridoids, sclerochitonosides A-C, and sclerochitonoside B 4'-methyl ether. Mortality of F. occidentalis was increased on exposure to all four iridoids, and the most active iridoid was sclerochitonoside A (8-epiloganic acid 4'-hydroxyphenylethyl ester). Choice experiments demonstrated that this compound did not significantly deter H. haemorrhoidalis from treated leaf surfaces. The significance of iridoids in the defense mechanism of plants against thrips is discussed.

Metabolomics based comprehensive investigation of Gardeniae Fructus induced hepatotoxicity.

Gardeniae Fructus (Zhizi in Chinese, ZZ in brief), a commonly used herbal medicine, has aroused wide concern for hepatotoxicity, but the mechanism remains to be investigated. This study was aimed at investigating the mechanism of ZZ-induced liver injury in vivo and in vitro based on metabolomics and evaluating the hepatotoxicity prediction ability of the in vitro model. SD rats were administered with extracted ZZ and HepG2 cells were treated with genipin, the major hepatotoxic metabolite of ZZ. Liver, plasma, intracellular and extracellular samples were obtained for metabolomics analysis. As a result, ZZ caused plasma biochemical and liver histopathological alterations in rats, and induced purine and amino acid metabolism disorder in the liver and pyrimidine, primary bile acids, amino acid metabolism and pantothenate and CoA biosynthesis disorder in the plasma. Pyrimidine, purine, amino acid metabolism and pantothenate and CoA biosynthesis were also found to be disturbed in the genipin-treated HepG2 cells, which exhibited similarity with the result in vivo. This study comprehensively illustrates the underlying mechanism involved in ZZ-related hepatotoxicity from the aspect of metabolome, and provides evidence that identifying hepatotoxicity can be achieved in cells, representing a non-animal alternative for systemic toxicology.

Genipin induces developmental toxicity through oxidative stress and apoptosis in zebrafish.

Genipin, an iridoid substance, is mainly derived from Gardenia jasminoides Ellis of the traditional Chinese medicine and is widely used in raw materials for the food additive gardenia blue and biological materials. The developmental toxicity of genipin has not been investigated, and its underlying mechanism is unclear. Therefore, in this study we attempt to investigate the potential developmental toxicity of genipin in zebrafish embryos/larvae. The results showed zebrafish embryos treated with 50 µg/ml dose of genipin display inhibited hatching rates and body length. The pericardial edema was observed. It was also found that genipin could induce cardio-toxicity, hepatotoxicity and nephrotoxicity in zebrafish larvae. After genipin treatment, the suppression of antioxidant capacity and increase of oxidative stress were showed for the triggered generation of ROS and MDA, and decreased activity of SOD. Compared with the 0.5% DMSO group, a number of apoptotic cells in zebrafish were increased after genipin exposure. By measuring marker gene expression with the using of qRT-PCR, we proposed that developmental toxicity after genipin treatment might be associated with oxidative stress and apoptosis increase. Our research offers a better understanding for developmental toxicity of genipin.

New anti-malarial phenylpropanoid conjugated iridoids from Morinda morindoides.

A new phenylpropanoid conjugated iridoid together with four known congeners was isolated from Morinda morindoides, used for the therapy of malaria traditionally in some African countries, as anti-malarial principles through bioassay-guided separation. Furthermore, their absolute stereostructures were unambiguously established by a combination of modified Mosher's method and chemical correlation.

Iridoid and acyclic monoterpene glycosides, kankanosides L, M, N, O, and P from Cistanche tubulosa.

Three iridoid glycosides, kankanosides L, M, and N, and two acyclic monoterpene glycosides, kankanosides O and P, were isolated from fresh stems of Cistanche tubulosa (Orobanchaceae) together with eight iridoid glycosides, five acyclic monoterpene glycosides, three phenylpropanoid glycosides, and four lignan glycosides. Their structures were elucidated on the basis of chemical and physicochemical evidence.

Safety Evaluations of Single Dose of the Olive Secoiridoid S-(-)-Oleocanthal in Swiss Albino Mice.

Epidemiological and clinical studies compellingly showed the ability of Mediterranean diet rich in extra-virgin olive oil (EVOO) to reduce multiple diseases such as cancer, cardiovascular diseases, and aging cognitive functions decline. The S-(-)-Oleocanthal (OC) is a minor phenolic secoiridoid exclusively found in extra-virgin olive oil (EVOO). OC recently gained notable research attention due to its excellent in vitro and in vivo biological effects against multiple cancers, inflammations, and Alzheimer's disease. However, OC safety has not been comprehensively studied yet. This study reports for the first time the detailed safety of oral single OC dose in Swiss albino mice, applying the OECD 420 procedure. Male and female Swiss albino mice (n = 10) were orally treated with a single OC dose of either 10, 250, or 500 mg/kg bodyweight or equivalent volumes of distilled water. Mice fed a regular diet, and carefully observed for 14 days. Further, mice were then sacrificed, blood samples, and organs were collected and subjected to hematological, biochemical, and histological examinations. OC 10 mg/kg oral dose appears to be without adverse effects. Further, 250 mg/kg OC, p.o., is suggested as a possible upper dose for preclinical studies in the future.

Sustained scleral stiffening in rats after a single genipin treatment.

Scleral stiffening has been proposed as a therapy for glaucoma and myopia. Previous in vivo studies have evaluated the efficacy of scleral stiffening after multiple treatments with a natural collagen crosslinker, genipin. However, multiple injections limit clinical translatability. Here, we examined whether scleral stiffening was maintained after four weeks following a single genipin treatment. Eyes from brown Norway rats were treated in vivo with a single 15 mM genipin retrobulbar injection, sham retrobulbar injection, or were left naive. Eyes were enucleated either 1 day or four weeks post-injection and underwent whole globe inflation testing. We assessed first principal Lagrange strain of the posterior sclera using digital image correlation as a proxy for scleral stiffness. Four weeks post-injection, genipin treatment resulted in a 58% reduction in scleral strain as compared to controls (p = 0.005). We conclude that a single in vivo injection of genipin effectively stiffened rat sclera for at least four weeks which motivates further functional studies and possible clinical translation of genipin-induced scleral stiffening.

Oral Acute and Repeated-Doses Toxicity Study of Valepotriates from Valeriana glechomifolia (Meyer) in Mice.

BACKGROUND: Species of Valeriana show sedative, hypnotic, anxiolytic, antidepressant and anti-inflammatory properties, which are associated with valepotriates. However, data about toxicity and safety of these compounds are still limited. The aim of this study was to investigate the toxicity of a valepotriate-enriched fraction (VAL) from Valeriana glechomifolia Meyer based on the Organization for Economic Cooperation and Development (OECD) guidelines 423 and 407. METHODS: In the acute study, CF1 mice were treated with a single dose of VAL (2000 mg/kg, p.o.) and observed for 14 days. In the repeated dose study, CF1 mice received single daily doses of VAL (30, 150 or 300 mg/kg, p.o.) or vehicle for 28 days. These doses were chosen based on previous results by our group and according to Guideline 407- OECD. RESULTS: The acute study allowed to classify VAL in the hazard category 5. The repeat-dose study has shown that VAL 300 mg/kg delayed weight gain and reduced food consumption in the first week, probably due to transient sedative effects. The other doses had no effect on animals' ponderal evolution. At the end of the treatment, all groups had equal body weight and food consumption. None of the doses altered any behavioral, urinary, biochemical, hematological, anatomic or histological parameters. CONCLUSION: A valepotriate-enriched fraction from Valeriana glechomifolia presents relatively low oral acute toxicity and does not induce evident toxicity after oral repeated treatment (at least up to 300 mg/kg) in mice.

Verminoside- and verbascoside-induced genotoxicity on human lymphocytes: involvement of PARP-1 and p53 proteins.

Verminoside and verbascoside are natural compounds present in plants used in traditional medicine. They exhibit several biological activities including anti-inflammatory, anti-bacterial and anti-tumor properties. The potential applications of these compounds as ingredients in pharmaceutical formulations and cosmetics prompted us to investigate on cytotoxic and genotoxic activity of verminoside and verbascoside on human lymphocytes using genetic toxicity assays recommended in preclinical studies by the US Food and Drug Administration (FDA). We analyzed chromosome aberrations (CAs) and sister chromatid exchanges (SCEs) as well as the mitotic index (MI) and cell viability after the treatments with verminoside and verbascoside. This report is the first to clearly demonstrate a significant increase of structural CAs and SCEs on normal human lymphocytes associated with a reduction of the MI in both verminoside- and verbascoside-treated cells. Moreover, we observed enhanced protein expression levels of PARP-1 and p53 that are key regulatory proteins involved in cell proliferation and DNA repair. Interestingly, mass spectrometric analysis of the compounds in the culture supernatants also showed that verminoside remained unchanged during the culture period while verbascoside was hydrolyzed to its derivative, caffeic acid and the last one seems to be responsible for the observed biological activity.

Metabolism and pharmacokinetics of genipin and geniposide in rats.

Geniposide, an iridoid glucoside, is a major constituent in the fruits of Gardenia jasminoides (Gardenia fruits), a popular Chinese herb. Genipin, the aglycone of geniposide, is used to prepare blue colorants in food industry and also a crosslinking reagent for biological tissue fixation. In this study, we investigated the metabolism and pharmacokinetics of genipin and geniposide in rats. Blood samples were withdrawn via cardiopuncture and the plasma samples were assayed by HPLC method before and after hydrolysis with sulfatase and beta-glucuronidase. The results indicated that after oral administration of genipin or Gardenia fruit decoction, genipin sulfate was a major metabolite in the bloodstream, whereas the parent forms of genipin and geniposide were not detected. Importantly, oral administration of 200mg/kg of genipin resulted in a mortality of 78% (7/9) in rats.

[Study on the temporal change of properties of genipin crosslinked gelatin].

Investigated the changes of crosslinking index, swelling ratio, degradation rate and cytotoxicity of genipin crosslinked gelatin accompany with crosslinking time. 1% genipin crosslinked gelatin were divided into 7 groups by crosslinking time: 10 min group, 30 min group, 1 h group, 2 h group, 12 h group, 24 h group, 72 h group. The results proved that genipin could crosslink gelatin effectively. Accompany with increasing of crosslinking time, crosslinking index increased, and swelling ratio, degradation rate decreased. In 10 min group, crosslinking index was low(26.7%), swelling ratio was high, (265%), completely degraded within 1 week. This indicated that biomaterials of 10 min group was instable and degraded easily. Compared with 10 min group, biomaterials of 30 min group changed significantly with crosslinking index(45.7%), swelling ratio (206%) and degration rate (completely degraded between 4 weeks and 8 weeks). This indicated that genipin could change the properties of gelatin within 30 min. Biomaterials after 30 min, crosslinking index increased, and swelling ratio, degradation rate decreased gradually accompanied with increasing of crosslinking time. Biomaterials of 72 h, crosslinking index was 73.1%, swelling ratio was 152%, and degradated 18.9% after 12 weeks. RGR (relative cell growth rate) of every group measured by MTT assay changed between 87.9% and 105.4%, indicated that the cytotoxicity of genipin crosslinked gelatin was very low.

Oral chronic toxicity study of geniposide in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Geniposide, the major active constituent of Fructus Gardeniae (FG), has been widely used to treat various diseases in China. AIM OF THE STUDY: This chronic toxicity study was conducted to investigate the safety of geniposide. MATERIALS AND METHODS: Geniposide was administered to Sprague-Dawley (SD) rats of both sexes by oral gavage at dosages of 25, 50, or 100mg/kg in a volume of 10mL/kg once daily for 26 weeks. Endpoints included clinical observations, food consumption, body weights, blood biochemistry, haematology, and histomorphological observations. RESULTS: The administration of geniposide did not influence animal mortality, the general conditions of the animals, body weights or food consumption. After 4 weeks of administration, significant toxicity was not observed. However, in the 13th week of the toxicity study, a few haematological parameters and some relative organ weights of male rats in the 50 and 100mg/kg geniposide groups were significantly increased. The percentage of reticulocytes (Retic %) was significantly increased in male and female rats administered 100mg/kg geniposide. In addition, two female rats in the 100mg/kg geniposide group showed slight pathological changes in hepatic and renal tissues. Furthermore, in a chronic (26 weeks) toxicity study, differences were detected in alanine aminotransferase (ALT), aspartate aminotransferase (AST), sodium (Na+), potassium (K+), white blood cell (WBC), red blood cell (RBC), and haemoglobin (HGB) levels and the relative weights of the liver and spleen in male rats administered 100mg/kg geniposide. In addition, differences were detected in Retic % and the relative weights of the liver, thymus, and kidneys in female rats administered 100mg/kg geniposide. Urinalysis results from male and female rats in the 100mg/kg geniposide group revealed noticeable changes. The histopathological structures of hepatic and renal tissues in the high-dose geniposide group exhibited serious abnormalities and pigment deposition. CONCLUSION: Geniposide affected serum biochemistry, urinalysis, and haematological parameters as well as relative organ weights. The treatment also caused noticeable pathological abnormalities in liver and kidney tissues. Therefore, administration of a high dose of geniposide (100mg/kg) for 26 weeks could induced obvious liver and kidney damage.

Genotoxicity evaluation of the naturally-derived food colorant, gardenia blue, and its precursor, genipin.

Gardenia blue is widely used in Eastern Asia as a natural food colorant. To evaluate the genotoxic potential of gardenia blue, as well as genipin, the natural starting material from which it is produced, a GLP-compliant test battery was conducted according to OECD guidelines. No evidence of mutagenicity of gardenia blue was detected in a 5-strain bacterial reverse mutation assay, with or without metabolic activation; an equivocal response for genipin occurred in S. typhimurium TA97a 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. In combined micronucleus/comet assays conducted in male and female B6C3F1 mice, exposure to genipin at doses reaching maximal toxicity (74 and 222 mg/kg bw/day for males and females, respectively) or gardenia blue tested up to the limit dose (2000 mg/kg bw/day) did not induce micronuclei in peripheral blood or DNA damage in several examined tissues. Modified ("reverse") comet assays showed no evidence of DNA crosslinking potential of either genipin, known to form crosslinks with other macromolecules, or gardenia blue. Our results indicate that consumption of gardenia blue in food products does not pose a significant genotoxic concern for humans.