Agnuside

Agnuside: A Comprehensive Reference

1. Identity

1.1 Chemical Identity

Agnuside (AGN) is an iridoid glycoside and the principal active phytoconstituent and a chemotaxonomic marker of the genus Vitex. Its CAS registry number is 11027-63-7 and its molecular formula is C₂₂H₂₆O₁₁. It is isolated from V. agnus-castus, V. negundo, and V. cymosa, and is composed of aucubin and p-hydroxybenzoic acid (PHBA).

Agnuside is composed of aucubin and p-hydroxybenzoic acid. Aucubin itself is an iridoid glycoside; iridoids are commonly found in plants and function as defensive compounds. Aucubin is a monoterpenoid-based compound. Structurally, agnuside is characterized by a glucose moiety linked to an aglycone, specifically an iridoid compound. The full IUPAC synonym recognized in chemical databases is (1S,4aR,5S,7aS)-tetrahydro-5-hydroxy-7-[[(4-hydroxybenzoyl)oxy]methyl]cyclopenta[c]pyran-1-yl β-D-glucopyranoside.

Agnuside is an iridoid glycoside originally isolated from Vitex rotundifolia fruit and has diverse biological activities. Experimental data cites the iridoid glycoside agnuside and the flavonol casticin as the two quality control markers for standardized Vitex agnus-castus extracts. In terms of solubility, agnuside is generally soluble in water and organic solvents, which facilitates its extraction and incorporation into various therapeutic preparations.

1.2 Natural Sources and Botanical Taxonomy

Agnuside is a key iridoid glycoside found in the fruit of Vitex agnus-castus (chaste tree), a plant with a long history of use in traditional medicine, particularly for women's reproductive health. Commonly known as chaste tree, chasteberry, or monk's pepper, Vitex agnus-castus is a deciduous shrub or small tree in the Lamiaceae family, native to the Mediterranean region, western Asia, and parts of Africa.

Vitex is one of the largest genera in the Lamiaceae family (formerly under the family Verbenaceae), consisting of 217 species in total. Some of the most well recognized and researched species of Vitex are Vitex negundo L., Vitex agnus-castus L., Vitex trifolia L., Vitex rotundifolia, Vitex cymosa Bertero ex Spreng, and Vitex peduncularis Wall.

The compound is typically extracted from the fruits or leaves of the chaste tree and is often used in herbal medicine formulations. In Vitex agnus-castus, the iridoid glycosides aucubin, agnuside, and eurostoside are found both in the leaf drug and in the fruit drug. Agnuside has also been isolated from additional plant genera: iridoid compounds such as agnuside, adoxosidic acid, and monotropein were successfully extracted from Odontites luteus, indicating that the compound is not exclusive to the Vitex genus.

The plant typically grows 8 to 20 feet tall with an upright, rounded form, featuring aromatic, palmately compound leaves composed of five to seven leaflets that are grayish-green above and gray beneath. It produces spikes of small, fragrant lavender to violet flowers in summer, followed by small, pepper-like berries that are the primary medicinal part. The black spherical berries are lignified ovaries of two carpels each containing one seed, roughly ovoid about three by four millimetres, dark-grey in colour, yielding when crushed a dark powder of characteristic aroma and fragrant, slightly acrid and bitter peppery taste.

1.3 Common Forms and Preparations

Dried, ripened, or fresh ripe fruits (berries) can be used to produce phytotherapeutic medications in the form of liquid extract, dried fruit, or as a tablet or capsule. Fluid extract (40 drops daily) and tincture (35 to 45 drops, three times a day) have also been used. VAC-enriched food supplements are also available.

The primary preparations in which agnuside functions as a standardization marker include:

• Standardized dry extracts: Each tablet of one commercial preparation (MonoSelect® Agnus) contains 40 mg of high-quality extract from Vitex agnus-castus berries standardized to contain 0.5% of key compound agnuside.
• Agnucaston / Agnolyt formulations: Agnolyt, 1 capsule per day, dried extract 3.5–4.2 mg/day, extraction ratio 9.58–11.5:1, was used in a PMS trial; Monoselect Agnus, a fast-release VAC extract standardised for 0.5% in agnuside, was used in another PMS trial.
• Tinctures: Preparations include tincture (1:5) with extraction solvent ethanol 58–60% m/m, and tincture (1:5) with ethanol 70% V/V.
• HPLC-standardized quality control extracts: A high-performance liquid chromatography method coupled with photodiode array detection has been developed for the identification and quantification of p-hydroxybenzoic acid and agnuside in the extracts of Vitex negundo and Vitex trifolia.

2. Traditional and Historical Use

2.1 Ancient Greek and Roman Medicine

Historically, Vitex agnus-castus has been used in traditional medicine for over 2,000 years, particularly for women's reproductive health issues, including menstrual irregularities, premenstrual syndrome (PMS), and to suppress libido—earning its "chaste tree" designation. Hippocrates, in the 5th century BCE, documented its use to facilitate the expulsion of the placenta after childbirth and to address uterine tumors or inflammations.

Historical documents reference Vitex agnus-castus as early as the 1st century CE in Dioscorides' "De Materia Medica," where it was noted for promoting chastity among convent nuns (hence the common name "chaste tree"). In ancient Greece, women chewed leaves or made wine infusions of the berries during festivals to reduce libido and enhance focus. Roman physicians, including Pliny the Elder, recommended it for menstrual irregularities and mastitis, and medieval herbalists in Europe kept the tradition going, calling it "monk's pepper" (Monkpepper).

The ancient Romans dedicated the vitex tree to the goddess Hera, the protector of motherhood and marriage, who was said to have been born under one. Roman wives were also said to use the leaves to reduce the libido of their husbands. Its macaronic specific name agnus-castus repeats "chaste" in both Greek and Latin; the small tree was considered to be sacred to the virginal goddess Hestia/Vesta.

2.2 Medieval European Use

In the late Middle Ages in Europe, the use of VAC was introduced also to celibate clerics for its supposed usefulness in reducing undesired sexual libido. Throughout European folk traditions, the dried berries of Vitex agnus-castus have been utilized to manage premenstrual syndrome (PMS) symptoms such as breast tenderness and mood swings, to regulate irregular menstrual cycles, and to suppress lactation.

2.3 Ayurvedic and Asian Traditional Medicine

In traditional Ayurvedic texts, Vitex agnus-castus appears more subtly under regional names, often blended in ghritas (medicated ghee) for balancing Vata-Pitta doshas tied to reproductive health. The Vitex species are used in the Indian system of medicine for the treatment of a range of diseases; V. negundo and V. trifolia are prescribed as major herbal plants among Vitex species.

Records note that chasteberry was used in many cultures to support gynecological health, skin health, digestive comfort, and overall well-being.

3. Phytochemistry: Key Constituents and Context

3.1 The Broader Phytochemical Profile of Vitex

The chemical composition of Vitex agnus-castus L. includes many different chemical compounds, among which are: vitexilactone, rotundifuran, ketosteroids, diterpenoids (vitexlactam, vitexilactone, viteagnusin I, and rotundifuran), flavonoids (orientin, kaempferol, penduletin, luteolin, artemetin, vitexin, and casticin), and iridoids (agnuside, agnusoside, agnucastosid A/B, and aucubin).

V. agnus-castus contains iridoids, flavonoids, diterpenoids, progestins, essential oils, and ketosteroids. Agnuside is one member of the iridoid glycoside class, and within the Vitex genus it co-occurs with the closely related glycosides aucubin (its aglycone precursor), agnusoside, and eurostoside. The flavonoid casticin and the diterpene rotundifuran are among the other pharmacologically investigated co-constituents.

3.2 Agnuside as a Quality Marker

Experimental data cites the iridoid glycoside agnuside and the flavonol casticin as the two quality control markers for preparations of Vitex agnus-castus. This standardization role means that agnuside content is routinely measured by HPLC to verify extract identity and potency. Mean retention times of standard p-hydroxybenzoic acid and agnuside in validated HPLC methods were 6.14 and 11.90 minutes, respectively.

4. Mechanisms of Action

4.1 Dopaminergic Activity and Prolactin Inhibition

Women suffering from premenstrual mastodynia often respond to stimuli of prolactin release with a hypersecretion of this hormone. Pharmacological reduction of prolactin release by dopamine agonists or treatment with extracts of Agnus castus improve the clinical situation of patients with such premenstrual symptoms.

To assess whether the prolactin-inhibitory effect of AC preparations is due to compounds acting as dopamine agonists, the corpus striatum membrane dopamine receptor binding assay was used. Results demonstrated for the first time that AC extract contains an active principle that binds to the D2 receptor. Thus, it is very likely that it is this dopaminergic principle which inhibits prolactin release in vitro from rat pituitary cells.

Both extracts from Vitex agnus castus as well as synthetic dopamine agonists (Lisuride) significantly inhibit basal as well as TRH-stimulated prolactin secretion of rat pituitary cells in vitro, and as a consequence inhibition of prolactin secretion could be blocked by adding a dopamine receptor blocker. Therefore, because of its dopaminergic effect, Agnus castus could be considered as an efficient alternative phytotherapeutic drug in the treatment of slight hyperprolactinaemia.

More recent work has refined which compound classes carry the dopaminergic signal. Pre-clinical studies suggest that extracts prepared from the fruits of Vitex agnus castus interact with dopamine D2 receptors, leading to reduced prolactin secretion. Diterpenes featuring a clerodadienol scaffold were identified as major active compounds in this mechanism, alongside the iridoid fraction. It has been postulated that the diterpenes contained in VAC extract may interact with dopamine D2 receptors and inhibit prolactin release via dopamine D2R activation in the anterior pituitary.

4.2 Anti-Inflammatory Mechanisms: COX-2 and NLRP3 Inhibition

Agnuside is an iridoid glycoside originally isolated from V. rotundifolia fruit that has diverse biological activities. It inhibits COX-2 with an IC₅₀ value of 0.026 mg/ml but exhibits less than 10% inhibition of COX-1 at this concentration. This selectivity for COX-2 over COX-1 is pharmacologically significant because it suggests an anti-inflammatory effect with potentially less impact on COX-1-mediated gastric protection compared to non-selective inhibitors.

Agnuside also interacts with the NLRP3 inflammasome pathway. Agnuside exhibits the strongest binding affinity observed in one study with NLRP3 (−9.5 kcal/mol), dramatically exceeding the comparator compound Pramipexole's interaction (−6.3 kcal/mol) by 51%. This highlights Agnuside's exceptional anti-inflammatory potential.

In a rat model of knee osteoarthritis, agnuside (AGN), a nontoxic, natural small molecule isolated from the extract of Vitex negundo L. (Verbenaceae), has been demonstrated to have antioxidation, anti-inflammatory, analgesia, and many other properties as an iridoid glycoside. A MIA-induced KOA model was established, and it was found that AGN at the oral dose of 6.25 mg/kg can effectively relieve local hypoxia in synovial tissue. The content of proinflammatory factors IL-1β and IL-18 in the fibroblast-like synoviocyte supernatant was also reduced by AGN. Additionally, both mRNA and protein levels of fibrotic markers were significantly decreased after AGN management. This study demonstrates that AGN alleviates synovitis and fibrosis in experimental KOA through the inhibition of HIF-1α accumulation and NLRP3 inflammasome activation.

4.3 Anti-Arthritic Activity

Pandey et al. investigated the anti-arthritic activity of agnuside mediated through the down-regulation of inflammatory mediators and cytokines (published in Inflamm Res. 2012). This represented preclinical, in vitro and in vivo work demonstrating agnuside's capacity to modulate multiple mediators of the inflammatory cascade relevant to arthritic conditions.

4.4 Phytoestrogenic and Opioidergic Actions

VAC is rich in diverse bioactive constituents, including flavonoids, iridoids, diterpenes, and essential oils, which collectively contribute to its complex pharmacological profile. Emerging evidence from in vitro, in vivo, and clinical studies suggests that VAC may modulate key neuroendocrine pathways involved in menopause through dopaminergic, phytoestrogenic, opioidergic, and indirect serotonergic mechanisms. These actions are proposed to influence prolactin regulation, estrogen receptor activity, mood stability, vasomotor symptoms, and overall hormonal balance during the menopausal transition.

The flavonoid apigenin can be isolated from Vitex and has selective binding affinity for the beta-estrogen receptor subtype. Apigenin also shows regulatory effects on fat tissue homeostasis, but estrogenic effects on uterine weight or bone density were not noted in animal studies. While apigenin is a flavonoid co-constituent rather than agnuside itself, this illustrates the multiplicity of mechanisms within the whole plant extract.

4.5 Neuroprotective Potential

Agnuside's dopaminergic and anti-inflammatory effects complement Vitexin's anti-aggregation and anti-inflammatory properties within the broader neuroprotective profile of Vitex preparations. V. agnus-castus extract was administered to a mouse model of permanent middle cerebral artery occlusion for 30 days, and it was observed that the anti-inflammatory and estrogenic activities reduced stroke injuries. This study also reported neuroprotective activity by reducing matrix metalloproteinase-9 (MMP-9) and increasing interleukin-10. These findings, however, are from animal models and have not yet been confirmed in human clinical studies.

4.6 Pharmacokinetics

The pharmacokinetics of iridoid glycosides, including agnuside, have been summarized based on several active compounds. In general, glycosides do not work directly in the blood; in the digestive system, enzymes, stomach acid, intestinal bacteria, and intestinal membrane enzymes convert them into another structure, which then plays a pharmacological role. The specific pharmacokinetic profile of isolated agnuside in humans has not been characterized in detail in published clinical literature; much of what is known derives from studies on the parent glycoside class.

5. Scientific Evidence by Area of Use

5.1 Premenstrual Syndrome (PMS)

The strongest and most consistent clinical evidence for agnuside-containing preparations concerns premenstrual syndrome. The European Medicines Agency's (EMA) Committee on Herbal Medicinal Products (HMPC) monograph designates the herbal medicinal product as having well-established use for the treatment of premenstrual syndrome.

In a multicenter, double-blind, placebo-controlled, parallel-group study, 162 female patients with PMS (18–45 years) were randomized to either placebo or different doses of Ze 440 (8, 20, and 30 mg) over three menstrual cycles. PMS symptoms' severity was assessed by patients using visual analog scales (VAS) for the symptoms irritability, mood alteration, anger, headache, bloating, and breast fullness. Each of the treatments was well tolerated.

The effect of Vitex agnus-castus extract in women with premenstrual syndrome was investigated. The plant was shown to be effective, safe, and well tolerated. In a study in Germany, cases of PMS/PMDD were investigated in which the plant extract was used as a complementary method to heal PMS/PMDD. In another study, patients with PMDD were treated with fluoxetine and Vitex agnus-castus. The fluoxetine helped to treat psychological symptoms while the VAC extract reduced the physical symptoms.

Vitex appears to decrease many symptoms of PMS, especially edema, mood alterations, and mastalgia. Vitex may not be as effective for bloating or for symptoms of sweet craving, palpitations, and dizziness.

Evidence strength: The evidence for PMS is moderate-to-good, with multiple randomized controlled trials supporting efficacy, and institutional recognition by the EMA HMPC. However, limitations include heterogeneity in extract preparation, dosing, and outcome measures across trials.

5.2 Mastalgia (Cyclical Breast Pain)

Women suffering from premenstrual mastodynia often respond to stimuli of prolactin release with a hypersecretion of this hormone. Pharmacological reduction of prolactin release by dopamine agonists or treatment with extracts of Agnus castus improve the clinical situation of patients with such premenstrual symptoms.

The VAC extract was shown to be efficient in the treatment of hyperprolactinemia, menstrual disorders, PMS, and mastalgia. For isolated mastalgia, a low VAC dosage could be appropriate.

Evidence strength: Evidence for cyclical mastalgia is moderate, supported by mechanistic data (prolactin inhibition via D2 receptor binding) and clinical observational and controlled studies, though the number of high-quality RCTs is limited.

5.3 Hyperprolactinaemia

Due to its action on D2 receptors, VAC could have a role in the treatment of mild hyperprolactinaemia, including patients with idiopathic hyperprolactinaemia, microprolactinoma, drug-induced hyperprolactinaemia, or polycystic ovary syndrome. These potential indications remain investigational; clinical trial data in these populations is preliminary.

Evidence strength: Preliminary; largely supported by mechanistic/in vitro and small clinical observations. Large RCTs specifically for agnuside in hyperprolactinaemia are lacking.

5.4 Menstrual Irregularity and Fertility

In patients with accompanying menstrual abnormalities, such as secondary amenorrhea, oligomenorrhea (scant menstruation), and menorrhagia (excessive and prolonged menstruation), vitex may normalize bleeding patterns. Vitex agnus-castus is effective in reducing symptoms of many gynecological problems. It is clinically used in abnormal uterine bleeding disorders and mastodynia.

Evidence strength: Moderate for menstrual irregularity based on clinical evidence, though studies vary in design and extract standardization.

5.5 Musculoskeletal and Anti-Arthritic Applications

Agnuside alleviates synovitis and fibrosis in experimental knee osteoarthritis through the inhibition of HIF-1α accumulation and NLRP3 inflammasome activation. It reveals novel targets for anti-inflammatory and antioxidant effects of AGN and announces its potential value in treating KOA in humans.

Evidence strength: Preclinical only. These findings come from animal (rat) models and in vitro studies. No human clinical trials have yet been published specifically testing agnuside for osteoarthritis.

5.6 Neuroprotection and Neurodegeneration

Results indicated that Vitex agnus-castus and/or pramipexole markedly ameliorated rotenone-induced striatal neurodegeneration, evidenced by their abilities to mitigate neurobehavioral alterations, and modulate dopamine, oxidative stress (MDA), antioxidant (GPX and catalase), and inflammatory markers. These findings were from an animal model and molecular docking study.

The superior binding profile of agnuside suggests enhanced potential for GSDMD inhibition, which could translate to improved neuroprotection through reduced pyroptotic cell death. This mechanism represents a novel therapeutic approach that complements traditional dopaminergic strategies, potentially offering enhanced neuroprotective effects in neurodegenerative disorders.

Evidence strength: Preclinical and in silico only. Human data are absent. These findings require clinical validation before any conclusions about human neuroprotective benefit can be drawn.

5.7 Cytotoxic Activity

Agnuside showed a cytotoxic effect (76%) to COLO 320 cancer cells at 24 hours. These in vitro findings are preliminary and have not been translated into clinical cancer research. The significance of this in vitro result for any human oncological application is currently unknown.

Evidence strength: In vitro only. No clinical evidence is available for any oncological application of agnuside.

6. Body Systems and Health Areas of Association

• Female reproductive system / endocrine system: Primary area of use; supported by clinical evidence for PMS, mastalgia, menstrual irregularity, and exploratory evidence for hyperprolactinaemia.
• Neuroendocrine system: Dopamine D2 receptor modulation; inhibition of pituitary prolactin secretion.
• Musculoskeletal system: Anti-inflammatory and anti-fibrotic activity in preclinical arthritis and osteoarthritis models.
• Central nervous system: Preclinical evidence for dopaminergic and neuroprotective effects; neurodegeneration models.
• Immune/inflammatory system: Reported data on different beneficial health-promoting potentials of this plant include antioxidant, immunomodulatory, cytotoxic, antimutagenic, antimicrobial, antifungal, antinociceptive, opioidergic, antiepileptic, and anti-inflammatory properties.

7. Dosage Forms and Reported Dosages

The variability in preparation and dosage was noted in the different clinical studies. The dosage of VAC dry extract is often 20 to 40 mg per day; in some cases, higher doses (up to 1800 mg per day) were used.

The prescription of 4 mg/day of an extract standardized to 6% of the constituent agnuside is one of the formulations sold in the USA and this dose has been used in some studies.

The EMA HMPC monograph specifies for well-established use: daily dose: once daily 20 mg dry extract for female adults.

Dosages and dosing regimens in clinical studies varied from 40 drops (approximately 2 mL) of VAC extract/tincture for 6 days before menses to 1800 mg/day.

Regarding dose-response behavior, an open, placebo-controlled trial in men, using chaste tree extract (120–480 mg per day for 14 days or placebo) demonstrated dose-dependent effects: at lower doses, vitex increases prolactin production, but at higher doses, prolactin production was decreased.

The Canadian Health Products monograph cites a dried fruit dosage range of 30–2000 milligrams per day, referencing WHO (2009), Bradley (2006), and ESCOP (2003). Use for at least 3 months to see beneficial effects is cited by Bradley (2006), ESCOP (2003), and Hoffmann (2003).

For the osteoarthritis preclinical study, agnuside at the oral dose of 6.25 mg/kg was shown to effectively relieve local hypoxia in synovial tissue in rat models — a figure not directly translatable to human dosing.

8. Safety Considerations and Drug Interactions

8.1 General Safety Profile

Chaste tree administration is generally regarded as safe for use because it has not been associated with any major adverse reactions. Minor and reversible adverse effects reported in clinical trials and surveillance include GI reactions, pruritus, rash, headache, fatigue, acne, and menstrual disturbances.

Vitex has been used safely in studies lasting from three months up to 1.5 years. The VAC benefits include high tolerability, with no severe side effects and no documented major drug interactions in clinical surveillance.

8.2 Drug Interactions

An interaction with dopamine agonists (e.g., bromocriptine, levodopa), dopamine receptor antagonists, and fertility and contraceptive drugs may be theoretically possible. This theoretical interaction follows directly from the established mechanism of action: because VAC/agnuside-containing preparations exert dopaminergic activity at D2 receptors, concurrent use with dopamine antagonists (including many antipsychotic medications) could produce pharmacodynamically opposing effects.

The Canadian natural health products monograph advises asking a health care practitioner before use if taking hormone-containing medications such as progesterone preparations, oral contraceptives, or hormone replacement therapy.

8.3 Contraindications and At-Risk Populations

The EMA HMPC monograph specifies there is no relevant indication in prepubertal children, and use in pubertal children and adolescents under 18 years of age is not recommended.

The EMA monograph and other regulatory references consistently flag use during pregnancy as contraindicated for well-established use preparations, given the plant's hormonal effects and the lack of safety data in pregnancy. The Canadian monograph similarly reflects guidance from ESCOP (2003) and WHO (2009) on these restrictions.

8.4 Dose-Dependent Biphasic Prolactin Effects

A pharmacologically significant safety consideration is the dose-dependent biphasic effect on prolactin. At lower doses, vitex increases prolactin production (linked to increases in milk production in lactating females), but at higher doses, prolactin production was decreased. This biphasic response means that self-directed low-dose supplementation could paradoxically elevate prolactin rather than suppress it, with implications for conditions in which hyperprolactinaemia is a concern.

References

• PMC: Traditional Medicinal Uses, Phytochemistry, Biological Properties, and Health Applications of Vitex sp.
• PMC: Iridoids: Research Advances in Their Phytochemistry, Biological Activities, and Pharmacokinetics
• PMC: Systematic Review of Premenstrual, Postmenstrual and Infertility Disorders of Vitex Agnus Castus
• PMC / PubMed: Agnuside Alleviates Synovitis and Fibrosis in Knee Osteoarthritis through the Inhibition of HIF-1α and NLRP3 Inflammasome
• PubMed: In vitro prolactin but not LH and FSH release is inhibited by compounds in extracts of Agnus castus — Jarry et al.
• PubMed: Agnus castus extracts inhibit prolactin secretion of rat pituitary cells
• Frontiers in Endocrinology: Vitex agnus castus effects on hyperprolactinaemia
• PMC: Vitex agnus castus Extract Ze 440: Diterpene and Triterpene's Interactions with Dopamine D2 Receptor
• PMC: Deciphering the Role of NLRP-3/Caspase-1/GSDMD Pyroptotic Signal in Striatal Neurodegeneration by Vitex agnus-castus Leaf Extract
• ScienceDirect: Dose-dependent efficacy of the Vitex agnus castus extract Ze 440 in patients suffering from premenstrual syndrome
• EMA HMPC: European Union Herbal Monograph on Vitex agnus-castus L., fructus — Revision 1 (2018)
• EMA: Agni casti fructus — Herbal Medicinal Product
• Health Canada Natural Health Products Ingredients Database: Chaste Tree — Vitex agnus-castus
• Alternative Medicine Review: Vitex agnus-castus Monograph
• NCATS Inxight Drugs: Agnuside
• PMC: Validated HPLC method for identification and quantification of p-hydroxybenzoic acid and agnuside in Vitex negundo and Vitex trifolia
• PMC: Compounds from the Fruits of Vitex agnus-castus in Chemoprevention via NADP(H):Quinone Oxidoreductase Type 1 Induction
• ScienceDirect: Plant iridoids: Chemistry, dietary sources and potential health benefits
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• Drugs.com / Natural Patient Package: Chaste Tree Uses, Benefits & Dosage
• Wikipedia: Aucubin (chemistry, relationship to agnuside)