Delphinidin

Delphinidin: A Comprehensive Reference

1. Identity and Chemical Characterization

Names and Classification

Delphinidin (also delphinidine) is an anthocyanidin, a primary plant pigment, and also an antioxidant. Delphinidin is a polyphenolic compound with its basic structure based on the flavylium cation, which consists of a three-ring system (C6-C3-C6), otherwise called the anthocyanidin skeleton. Its systematic IUPAC-related name is 3,3′,4′,5,5′,7-hexahydroxyflavylium; it is also designated in the literature as 3,3′,4′,5,5′,7-hexa-hydroxy-flavylium. Dp (3,3',4',5,5',7-hexa-hydroxy-flavylium), one of the major anthocyanidins, is a polyphenolic compound with oxygen in the 1st position and is linked to the sugar moiety in 3-O-β-position of the C ring. Dp (PubChem CID: 68245) is made up of three rings: A (resorcinol), B (catechol), and C (3-O-substituted-pyrylium). The chloride salt form carries CAS number 528-53-0, while the free base has CAS 13270-61-6. The molecular formula of the aglycone (free base) is C₁₅H₁₁O₇⁺.

Structural Features

Anthocyanins are naturally occurring water-soluble flavonoids abundantly present in fruits and vegetables. They are polymethoxy derivatives of 2-phenyl-benzopyrylium or flavylium salts. Delphinidin has hydroxyl groups (–OH) at the 3, 5, 7, 3′, 4′, and 5′ positions of the anthocyanidin skeleton. Dp has 6 hydrogen bond donor and 6 hydrogen bond acceptor atoms. Because of the presence of numerous electron donor atoms, Dp acts as a potent antioxidant by scavenging reactive oxygen species (ROS). The presence of a 3-hydroxyl group in ring B of Dp distinguishes it from other anthocyanins. This additional hydroxyl group on the B-ring, compared to related anthocyanidins such as cyanidin or malvidin, is considered a key structural determinant of delphinidin's particularly strong antioxidant activity.

Delphinidin, like nearly all other anthocyanidins, is pH-sensitive, i.e. a natural pH indicator, and changes from blue in basic solution to red in acidic solution. Additionally, delphinidin is prone to degradation under high pH conditions, leading to reduced bioactivity.

Nomenclature Origin

The word "anthocyanins" derives from the Greek anthos (meaning flower) and kyanos (meaning blue). Delphinidin itself takes its name from the genus Delphinium, the larkspur flower, from which early blue anthocyanin pigments were isolated. The first classical report on the isolation of a blue anthocyanin, from Centaurea cyanus (cornflower), was published in 1913 by Willstätter and Everest. The first isolation of delphinidin as a defined compound dates back to the 1930s when chemists investigated anthocyan pigments in flowers of the genus Delphinium, which gave it its name.

Glycosidic (Anthocyanin) Forms

When delphinidin occurs naturally in plants, it is almost invariably conjugated to one or more sugar molecules, forming what are called anthocyanins (the glycosidic forms), as opposed to the free aglycone anthocyanidin. Delphinidin is found in different glycosidic forms, such as delphinidin-3-glucoside, delphinidin-3-rutinoside, delphinidin-3-galactoside, delphinidin-3-sambubioside, and delphinidin-3-arabinoside. Glycosidic moieties are present as mono-, di-, or triglycerides bonded by α or β glycosidic linkages. The glycosidic linkage is present in the C-3 position of the anthocyanidin (aglycone). Commonly present sugar moieties include glucose, galactose, rhamnose, arabinose, and xylose.

Several glycosides derived from delphinidin are known: myrtillin (delphinidin-3-O-glucoside) and tulipanin (delphinidin-3-O-rutinoside) can be found in blackcurrant pomace. Dp is highly active in its aglycone form, but the presence of a sugar moiety is vital for its bioavailability.

2. Natural Sources

Botanical Distribution

Delphinidin (Dp) is a purple-colored plant pigment which occurs in a variety of berries, eggplant, roselle, and wine. Anthocyanins are commonly found in higher plants and are mainly accountable for the blue, purple, and red colors of fruits like berries, grapes, currants (gooseberries), some tropical fruits, vegetables, roots, and cereals. Delphinidin gives blue hues to flowers in the genera Viola and Delphinium. It also gives the blue-red color of the grape variety Cabernet Sauvignon, and can be found in cranberries and Concord grapes as well as pomegranates and bilberries.

Key dietary botanical sources include:

• Blueberries and bilberries (Vaccinium spp.): among the richest sources of delphinidin glycosides in the diet.
• Blackcurrants (Ribes nigrum): myrtillin (delphinidin-3-O-glucoside) and tulipanin (delphinidin-3-O-rutinoside) can be found in blackcurrant pomace.
• Eggplant (Solanum melongena): the dark skin is a characteristic source of delphinidin glycosides.
• Grapes (Vitis vinifera) and red wine: one of the important anthocyanidin components of red wine and berries is delphinidin.
• Roselle (Hibiscus sabdariffa): delphinidin-3-sambubioside (Dp3-Sam), a Hibiscus anthocyanin, was isolated from the dried calyces of Hibiscus sabdariffa L., which has been used for folk beverages and herbal medicine.
• Pomegranates, cranberries, plums, and black rice: additional documented dietary sources in the peer-reviewed literature.

Acyl glycosides of anthocyanidin are biosynthesized via the phenylpropanoid pathway. In plant tissues, delphinidin predominantly accumulates in the epidermal cells of fruits, flowers, and leaves, where it plays an ecophysiological role in pollinator attraction and UV photoprotection.

3. Traditional and Historical Use

Delphinidin as an isolated, chemically defined molecule is exclusively a product of modern analytical chemistry; its formal isolation and characterization date only to the early-to-mid twentieth century. Traditional use therefore refers to use of the whole plant foods and preparations that contain delphinidin as a naturally occurring constituent, rather than to knowingly targeted use of delphinidin itself.

Hibiscus sabdariffa dried calyces, which are rich in delphinidin-3-sambubioside, have been used in folk beverages and herbal medicine across the Middle East, West Africa, and Southeast Asia for centuries, where aqueous infusions (commonly known as bissap, karkade, or agua de jamaica) were consumed as cooling beverages and used in traditional medicine for a range of purposes. Dietary sources of anthocyanins including red and purple berries, grapes, apples, plums, and cabbage have been consumed across diverse food cultures for millennia, with their distinctive pigmentation recognized long before the chemistry was understood.

In East Asian traditional medicine systems, fruits and plant parts containing what we now know to be anthocyanins — particularly dark-colored berries — were used empirically. Blueberries and bilberries have been used in northern European and North American folk medicine, bilberry leaf and fruit preparations appearing in European traditional medicine contexts related to vision and vascular support. Purple corn (Zea mays var.), which contains anthocyanins including delphinidin glycosides, has been used in Andean traditional food culture, notably in the Peruvian beverage chicha morada. None of these traditional uses were attributed to delphinidin specifically, as this compound was not characterized until the twentieth century.

In ancient times, medicines were primarily derived from natural sources due to their perceived safety, availability, and affordability. Today, most drugs are synthetic and are derived from scaffolds or plant-based molecules with known health benefits such as sterols, carotenoids, polyphenols, and anthocyanins. The modern scientific interest in delphinidin is thus a continuation of traditional use of its source plants, now pursued with molecular and clinical investigational tools.

4. Key Chemical Constituents and Active Compounds

Delphinidin as the Primary Bioactive

Cyanidin, delphinidin, malvidin, peonidin, petunidin, and pelargonidin are the six common anthocyanidins. Among these, delphinidin is distinguished by its three free hydroxyl groups on the B-ring (at positions 3′, 4′, and 5′), making it the most hydroxylated of the common anthocyanidins. A recent study has demonstrated that delphinidin is the most potent antioxidant monomer in anthocyanins.

Metabolic Degradation Products

Delphinidin does not circulate intact for prolonged periods. In tissue culture medium, Dp degrades rapidly with a half-life of approximately 30 min into gallic acid and phloroglucinol aldehyde. The antioxidant protection conferred by delphinidin is partly mediated by modulation of endogenous antioxidant defences driven by its degradation product, gallic acid. Delphinidin was found to degrade rapidly (t_1/2 ~30 min), generating gallic acid as a major degradation product. These metabolites — particularly gallic acid — are themselves biologically active and may account for a portion of the observed health effects attributed to delphinidin consumption.

5. Mechanisms of Action

Antioxidant Activity

As a potent antioxidant, delphinidin scavenges reactive oxygen species (ROS) and upregulates endogenous defenses via the Nrf2 pathway, mitigating oxidative stress in chronic diseases. Three mechanisms have been proposed for anthocyanin antioxidant activity: donating a hydrogen atom, transferring electrons to free radicals, and breaking through the structure. Delphinidin has more hydroxyl groups in its structure and consequently has higher activity as an antioxidant. Dp promotes Nrf2 nuclear translocation and leads to increased expression of antioxidant protein HO-1, which is an Nrf2-related phase II enzyme (heme oxygenase-1) present in HepG2 cells. This confirms the hepatoprotective effect of Dp and its role in regulation of the expression of Nrf2/HO-1 to protect HepG2 cells.

In a cultured human umbilical vein endothelial cell model of oxidative stress, the antioxidant protective effects of both delphinidin and gallic acid displayed a hormesic profile; 100 µM concentrations of both were cytotoxic, but relatively low concentrations (100 nM–1 µM) protected the cells and were associated with increased intracellular glutathione. This finding is directly relevant to the bioavailability challenge: the concentrations that appear protective in cellular studies are closer to physiologically achievable levels than the cytotoxic concentrations, suggesting that low in-vivo concentrations may still exert meaningful cellular effects.

Anti-inflammatory Mechanisms

Delphinidin suppresses inflammation by inhibiting NF-κB and MAPK signaling, reducing pro-inflammatory cytokines like TNF-α and IL-6. In cell models, Dp3-Sam and delphinidin reduced the levels of inflammatory mediators including iNOS, NO, IL-6, MCP-1, and TNF-α induced by LPS. Cellular signaling analysis revealed that they downregulated the NF-κB pathway and MEK1/2-ERK1/2 signaling. In human airway epithelial cells, Dp inhibits the expression of MUC8 and MUC5B by acting through toll-like receptor (TLR4)-mediated ERK1/2 and p38 MAPK signaling pathways. The data support the effectiveness of Dp in inflammatory airway diseases; therefore, Dp can be considered a promising lead for future research.

Dp has been demonstrated to decrease hepatic inflammatory markers such as TNF-α, IL-6, and INF. It also decreased the immunopositivity of nuclear factor kappa-B (NF-κB) and CYP2E1 in liver tissues and restored altered hepatic architecture.

Anticancer and Antiproliferative Mechanisms

Its anti-cancer effects include apoptosis induction, cell cycle arrest, and inhibition of angiogenesis and metastasis through modulation of VEGF, MMPs, and PI3K/Akt pathways. DP can exert an effect on signaling pathways involved in inflammation and cell proliferation, suppressing tumor growth and metastasis. DP can also inhibit angiogenesis (the process of new blood vessel formation), which is essential for tumor growth and metastasis. This is partly achieved by downregulating pro-angiogenic factors like VEGF.

The epigenetic modulatory effect of DP and its derivatives are reportedly crucial in inhibiting tumor progression. The molecules modulate the expression of genes involved in cancer progression through epigenetic mechanisms, such as histone modification and DNA methylation. Delphinidin blocks VEGF-induced VEGFR-2 phosphorylation and the subsequent activation of ERK1/2 signaling.

Cardiovascular Mechanisms

Delphinidin demonstrates cardioprotective effects by enhancing endothelial function and reducing LDL oxidation. The vasculoprotective properties of delphinidin are driven mainly by its action on endothelial cells. Delphinidin-3-glucoside (Dp-3-g) significantly inhibited human and murine platelet aggregation in both platelet-rich plasma and purified platelets. It also markedly reduced thrombus growth in human and murine blood in perfusion chambers at both low and high shear rates.

Neuroprotective Mechanisms

Delphinidin's neuroprotective actions involve attenuating neuroinflammation and amyloid-β aggregation in neurodegenerative disorders. Dp exhibits neuroprotective activity against hypoxia. It has the ability to attenuate the oxidative stress of H₂O₂ in SK-N-SH cells by inactivation of the ASK-JNK/p38 signaling pathway. Dp also showed an effective response by abrogating intracellular calcium influx and tau phosphorylation against cytotoxicity induced by Aβ25−35.

Metabolic and Antidiabetic Mechanisms

Anthocyanins potentially modulate carbohydrate metabolism and blood glycemic levels and help reduce many cardiovascular risk factors. Delphinidin-3-rutinoside (Dp-3-R) has the ability to increase glucagon-like peptide-1 (GLP-1) secretion in GLUTag cells mediated through the Ca²⁺/calmodulin-dependent Ca²⁺-CaMKII pathway. The presence of 3 hydroxyl groups or two methoxyl moieties in the aromatic ring of Dp-3-R is important to stimulate GLP-1 secretion.

6. Bioavailability, Absorption, and Metabolism

Anthocyanins, including delphinidin, exhibit very low oral bioavailability due to their poor absorption in the gastrointestinal tract and extensive intestinal and hepatic first-pass metabolism, resulting in limited plasma concentration. The absorption of delphinidin is complex, and its bioavailability — the proportion that enters circulation to have an active effect — is relatively low. When consumed, delphinidin is attached to a sugar molecule, and only a small fraction is absorbed in its intact form in the stomach and small intestine.

Lactobacillus bacteria are primarily involved in the metabolism of Dp in the colon. They use intestinal gut enzymes — like glucosidase, glucuronidase, galactosidase, and rhamnosidase — to cleave the glycosidic bond of Dp glycosides (anthocyanin) and to set the aglycone (anthocyanidin) part free. Gut microbiota allow the absorption of Dp and other flavonoids, and enhance their bioavailability. Pharmacokinetic information on Dp indicated that it reaches peak plasma value after 2 h of ingestion, and that the phase II metabolite of Dp glucuronide reaches peak level after 6.3 h.

Human tracer studies show that plasma concentrations of parent anthocyanins are typically in the low nanomolar range and short-lived. For instance, a study reported that after human volunteers ingested a mixture of black currant anthocyanins (BCA) at a dose of 6.24 µmol/kg body weight, the plasma C_max of delphinidin-3-rutinoside was only 73.4 ± 35.0 nmol/L.

Human primary hepatocytes and liver microsomal enzymes like CYP2C6, CYP2A6, CYP2B6, and CYP3A4 have been used for evaluation of metabolic characteristics of anthocyanins and anthocyanidins. Delphinidin faces a fundamental challenge posed by the substantial gap between its effective in vitro concentrations and actual in vivo exposure levels. This gap is a critically important limitation when interpreting the large body of in vitro data.

7. Scientific Evidence by Area of Use

7.1 Antioxidant and Oxidative Stress

Evidence level: Predominantly in vitro and animal models; limited direct human data on delphinidin specifically.

A recent study has demonstrated that delphinidin is the most potent antioxidant monomer in anthocyanins and can regulate the oxidation-antioxidant system, protect photoreceptor cells from apoptosis and pyroptosis, and play a role in iron metabolism. In cell culture systems, relatively low concentrations (100 nM–1 µM) of delphinidin protected cultured human umbilical vein endothelial cells from oxidative stress and were associated with increased intracellular glutathione, supporting a mechanism of indirect antioxidant protection via glutathione upregulation at physiologically plausible concentrations. Most evidence on the antioxidant effects of delphinidin as an isolated compound remains at the in vitro level. Human data are primarily indirect, drawn from intervention trials using anthocyanin-rich extracts where delphinidin is one of multiple active constituents rather than the sole agent.

7.2 Cardiovascular Health

Evidence level: Mechanistic and preclinical; some supportive indirect human evidence from broader anthocyanin trials.

Anthocyanins potentially modulate carbohydrate metabolism and blood glycemic levels, and help reduce many cardiovascular risk factors. Specifically regarding delphinidin, delphinidin-3-glucoside (Dp-3-g) significantly inhibited human and murine platelet aggregation in both platelet-rich plasma and purified platelets and markedly reduced thrombus growth in human and murine blood in perfusion chambers at both low and high shear rates. Using intravital microscopy, Dp-3-g was observed to decrease platelet deposition, destabilize thrombi, and prolong the time required for vessel occlusion. These are preclinical findings from ex vivo human blood and animal models, not from human clinical trials.

The vasculoprotective properties of delphinidin are driven mainly by its action on endothelial cells. Moreover, delphinidin displays anti-angiogenic properties in both in vitro and in vivo angiogenesis models. While no large clinical trials have examined isolated delphinidin supplementation for cardiovascular endpoints, broader anthocyanin clinical trials involving foods high in delphinidin glycosides (e.g., bilberry, blackcurrant) have reported modest favorable effects on endothelial function and platelet reactivity in healthy and at-risk populations. These results cannot be attributed solely to delphinidin.

7.3 Cancer Biology

Evidence level: Extensive preclinical (in vitro and animal) evidence; no completed human clinical trials specifically for delphinidin as an anticancer agent. This area remains investigational.

The antiproliferative effects of delphinidin have been identified in various types of cancer cells, involving the regulation of intracellular signaling pathways. DP has anti-proliferative and pro-apoptotic effects in various cancer cell lines such as lung, breast, and ovarian cancer cells. In hepatocellular carcinoma, delphinidin induces apoptotic cell death through the induction of B-cell lymphoma-2 (Bcl-2) associated X protein and the reduction of Bcl-2.

In non-small cell lung cancer (NSCLC) in vitro, radiosensitising effects were assessed by treating cells with a sub-cytotoxic dose of delphinidin (5 µM) before exposure to γ-ionising radiation. Treatment with delphinidin or radiation alone induced NSCLC cell death; however, the combination of delphinidin pre-treatment and radiation was more effective than either agent alone, yielding a radiation enhancement ratio of 1.54 at the 50% lethal dose.

Delphinidin is a potent EMT inhibitor that inhibits cell migration in human U-87 MG glioblastoma cells, as evidenced by reduced TGF/Smad2 and TGF/ERK signaling pathways, as well as decreased expression of EMT markers fibronectin and Snail, among all anthocyanidins studied.

Due to the limited number of clinical trials related to delphinidin's anti-cancer properties, its safety and long-term effects in clinical applications cannot be verified, thus requiring large-scale clinical trials for research. Poor solubility of DP in water poses challenges for formulation and delivery. Such low solubilities lead to poor absorption in the gastrointestinal tract, which can limit its bioavailability and efficacy when administered orally. The transition from preclinical to clinical evidence remains an unmet need in this field.

7.4 Anti-inflammatory Effects

Evidence level: Robust in vitro and animal evidence; limited direct human trials on isolated delphinidin.

In an animal model, Dp3-Sam and Dp reduced the production of IL-6, MCP-1, and TNF-α and attenuated mouse paw edema induced by LPS. Both in vitro and in vivo data demonstrated that Hibiscus Dp3-Sam possesses potential anti-inflammatory properties. Results from a spinal cord injury rat model suggest that the anti-inflammatory effect of delphinidin alleviated inflammation via alleviation of intramedullary spinal pressure through the NF-κB and p38-MAPK signaling pathways. These are animal model findings and have not been replicated in clinical populations.

Topically, application of delphinidin to flaky mouse skin decreases the level of pathological markers of psoriasis lesions. Anthocyanin niosomes were prepared and in vivo anti-inflammatory activity was evaluated on croton oil-induced inflamed ears of rats with niosomes at 0.5 and 5 mg/cm²; niosomes improved permeation rate and prolonged the anti-inflammatory effect, with percent ear edema inhibition of the 5 mg/cm² niosome group greater than the 0.5 mg/cm² group.

7.5 Neurological and Neuroprotective Effects

Evidence level: Preclinical and mechanistic; no completed human trials specific to delphinidin.

Dp exhibits neuroprotective activity against hypoxia. It has the ability to attenuate the oxidative stress of H₂O₂ in SK-N-SH cells by inactivation of the ASK-JNK/p38 signaling pathway. Dp also showed an effective response by abrogating intracellular calcium influx and tau phosphorylation against cytotoxicity induced by Aβ₂₅₋₃₅. Regarding brain penetration, the 3-O-β-galactoside of Dp has the ability to cross the blood-brain barrier (BBB) and its presence was detected in various regions of the brain in experimental animals, indicating its potential in treatment of various brain-related disorders. All evidence in this area is preclinical.

7.6 Metabolic Health and Diabetes

Evidence level: Animal models and some mechanistic human cell data; no adequately powered human clinical trials on isolated delphinidin.

Streptozotocin (STZ)-induced diabetes in mice, upon treatment with Dp (100 mg/ml) in free and liposomal forms for 8 weeks, displayed a reduction in albumin glycosylation rate; the data revealed that the liposomal form of Dp could be developed as an effective treatment modality to control diabetes. Dp-3-rutinoside (Dp-3-R) has the ability to increase glucagon-like peptide-1 (GLP-1) secretion in GLUTag cells mediated through the Ca²⁺/calmodulin-dependent Ca²⁺-CaMKII pathway. The presence of 3 hydroxyl groups or two methoxyl moieties in the aromatic ring of Dp-3-R is important to stimulate GLP-1 secretion. GLP-1 stimulation in a cell model is a mechanistic finding and does not directly translate to clinical efficacy.

7.7 Gut Microbiota

Evidence level: Animal and limited human studies; currently characterized as preliminary.

Several animal and human clinical studies have shown that delphinidin exerts beneficial effects on gut microbiota. Lactobacillus bacteria are primarily involved in the metabolism of Dp in the colon, where they use intestinal gut enzymes to cleave the glycosidic bond of Dp glycosides and release the aglycone. However, only a limited number of in vitro, in vivo, and human studies have been conducted so far; thus, it cannot be generalized that consumption of fruits and vegetables rich in Dp or supplementation with Dp leads to a favorable effect. More detailed animal and human studies are needed to confirm the beneficial effects of consumption of anthocyanin/anthocyanidin-rich food including Dp on proliferation of healthy anaerobic gut microbiota.

7.8 Ocular Health

Evidence level: Cell-based and animal models; no clinical trials on delphinidin specifically for vision.

Delphinidin can regulate the oxidation-antioxidant system, protect photoreceptor cells from apoptosis and pyroptosis, and play a role in iron metabolism. Light-damaged mice showed iron overload in the neurosensory retina and retinal pigment epithelium, leading to abnormal lipid oxide metabolism, accumulation of lipid ROS, and ferroptosis induction — conditions against which delphinidin has shown protective effects in animal models.

8. Body Systems Associated with Delphinidin Research

• Cardiovascular system: endothelial function, platelet aggregation, LDL oxidation, anti-angiogenic effects, vasculoprotection.
• Gastrointestinal / gut microbiota: modulation of colonic microbiota composition, prebiotic-like interactions.
• Nervous system: neuroprotection against hypoxia, oxidative neuronal stress, amyloid-β cytotoxicity, tau phosphorylation.
• Metabolic / endocrine: GLP-1 secretion, glycemic regulation, insulin sensitivity in animal models.
• Oncology: multi-pathway anticancer action across multiple tumor types in preclinical models.
• Skin / integument: topical anti-inflammatory activity, reduction of psoriasis markers in animal models.
• Ocular: protection of retinal cells against light-induced ferroptosis and oxidative damage.
• Hepatic: hepatoprotection via Nrf2/HO-1 pathway activation and reduction of hepatic inflammatory markers.

9. Dosage Forms and Reported Dosages

There are no established recommended dietary allowances (RDAs), tolerable upper intake levels (ULs), or standardized clinical dosing protocols for isolated delphinidin from any major regulatory or pharmacopeial body. The dosages below are those reported within individual research studies and should not be interpreted as endorsed therapeutic doses.

• In vitro (cell culture): a sub-cytotoxic dose of delphinidin at 5 µM was used before exposure to γ-ionising radiation in NSCLC cell experiments. Concentrations of 100 nM–1 µM were protective in human endothelial cells, while 100 µM concentrations were cytotoxic.
• Animal studies (oral): STZ-induced diabetic mice were treated with Dp at 100 mg/ml in free and liposomal forms for 8 weeks.
• Human pharmacokinetic (oral, as part of anthocyanin mixture): human volunteers ingested a mixture of black currant anthocyanins at a dose of 6.24 µmol/kg body weight, producing a plasma C_max of delphinidin-3-rutinoside of only 73.4 ± 35.0 nmol/L.
• Topical (animal model): anthocyanin niosomes were applied at 0.5 and 5 mg/cm² to croton oil-induced inflamed rat ears; the higher concentration produced greater percent ear edema inhibition.

Forms available as supplements: anthocyanins are commonly used in food supplements and nutraceuticals because of their beneficial effects on humans. Delphinidin-containing supplements are typically standardized extracts of bilberry, blackcurrant, maqui berry (Aristotelia chilensis), or roselle, where the content of delphinidin glycosides is measured by HPLC but rarely represents pure isolated delphinidin. Delphinidin is a promising bioactive compound that can be used for the development of nutraceuticals and food products for human health.

10. Safety Considerations and Interactions

General Safety Profile

Natural compounds such as cyanidin, delphinidin, malvidin, and pelargonidin have been used as therapeutics for several diseases; these natural compounds promote the function of modern drug treatments, with few side effects. However, formal toxicology data for isolated delphinidin at supplemental doses in humans are limited. The absence of reported significant adverse events in anthocyanin-rich food consumption does not automatically establish the safety of high-dose isolated delphinidin supplementation.

Both delphinidin and gallic acid generated oxygen-centred radicals at high (100 µM) concentrations in vitro. In a cultured human umbilical vein endothelial cell model, 100 µM concentrations of both were cytotoxic. This concentration-dependent toxicity observed in vitro underscores that very high doses may have pro-oxidant rather than antioxidant effects, although these concentrations far exceed typical physiological exposure.

Metabolic Stability and Degradation

Delphinidin is prone to degradation under high pH conditions, leading to reduced bioactivity. Formulation conditions, the pH of the gastrointestinal tract, and food matrix interactions all influence the amount of intact delphinidin reaching systemic circulation.

Drug Interactions

Human primary hepatocytes and liver microsomal enzymes like CYP2C6, CYP2A6, CYP2B6, and CYP3A4 have been involved in the evaluation of metabolic characteristics of anthocyanins and anthocyanidins. The involvement of CYP3A4 in delphinidin metabolism raises the theoretical possibility of pharmacokinetic interactions with drugs that are substrates, inducers, or inhibitors of these enzymes, although this has not been systematically characterized in human clinical studies. The interaction between simultaneously administered drugs and high doses of anthocyanidin dietary supplements should be studied in greater detail to decide on a pharmacotherapeutic treatment plan. Although many reports have defined potential interactions between drugs and anthocyanin supplements, their deep molecular metabolic reactions and safety concerns are not well-described; hence further research is warranted.

Bioavailability-Related Considerations

Variability in anthocyanin bioavailability may be produced by lack of homogeneity introduced at three different levels: food matrix and food processing, enzymes involved in anthocyanin metabolism and transport, and anthocyanin-metabolizing gut microbiota. The literature on anthocyanin bioavailability considering inter- or intra-individual variability is still very scarce, which makes it difficult to reach any firm conclusion on the main metabolizing enzymes or bacteria responsible for the variability. This variability means that plasma exposure to delphinidin can differ substantially across individuals consuming equivalent doses.

Overall Assessment of the Evidence Base

Delphinidin, a bioactive anthocyanidin found in pigmented fruits and vegetables, exhibits remarkable therapeutic potential due to its antioxidant, anti-inflammatory, and anti-cancer properties. Current knowledge on delphinidin's structure, dietary sources, stability challenges, and mechanisms of action continues to be synthesized. However, the weight of current evidence is heavily concentrated in cell-based and animal experimental models. Delphinidin faces a fundamental challenge posed by the substantial gap between its effective in vitro concentrations and actual in vivo exposure levels. The compound's low and variable oral bioavailability, rapid degradation, and the resultant low nanomolar plasma concentrations observed in human studies substantially limit direct translation of in vitro findings to clinical practice. Future research should focus on delineating its mode of action in various cancers to facilitate clinical translation. Additionally, it is necessary to further explore the optimal dosage, administration route, and the best combination of delphinidin with other drugs. Novel delivery strategies — including liposomal encapsulation and cyclodextrin complexation — are being investigated in preclinical settings to address bioavailability limitations.

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