HMR lignan

HMR Lignan (7-Hydroxymatairesinol): A Comprehensive Reference

1. Identity: Botanical and Chemical Names, Source, and Preparations

Chemical and Botanical Identity

The lignan 7-hydroxymatairesinol (commercially designated HMR/lignan™, or HMRlignan™) was identified and extracted from the heartwood of the Norway spruce, Picea abies. The compound belongs to the broad class of plant polyphenols known as lignans, a category structurally distinct from isoflavones and other phytoestrogen subclasses. HMR is a lignan — a group of chemical compounds found in plants derived from phenylalanine via dimerization of substituted cinnamic alcohols, known as monolignols, to a dibenzylbutane skeleton.

HMR's chemical structure is similar to matairesinol. The molecule exists as two stereoisomers; HMR isomer 2 has been found to be more biologically active than HMR isomer 1. The commercial supplement form is typically supplied as a potassium acetate complex. Produced by Linnea SA using a special low-environmental-impact process, the product yields an off-white crystalline powder standardized to not less than 90% 7-hydroxymatairesinol (HMR) potassium acetate complex.

Natural Source and Distribution in the Plant

The spruce knots, which are parts of the branches embedded in the stem, consist of 6–16% of lignans, and HMR represents 65–80% of the total lignan content. In spruce, lignan concentration in thick roots is 2–3 percent. Abundance of lignans occurs in the heartwood of branches (5–10 percent) and twists, especially in the knots, where the amount of lignans may be higher than 10 percent. These concentrations are about hundred-fold compared to ground flaxseed powder, a material long known as lignan-rich.

The typical lignans in the heartwood of spruce (Picea abies) are hydroxymatairesinol (HMR), α-conidendrin, conidendric acid, matairesinol, isolariciresinol, secoisolariciresinol, liovil, picearesinol, lariciresinol, and pinoresinol. HMR, however, is by far the dominant component. The far most abundant single component of lignans in spruce is hydroxymatairesinol (HMR), at about 60 percent of total lignans, which occurs mainly in unconjugated free form.

Research has found that 7-hydroxymatairesinol, which had not previously been detected in cereals because of destructive extraction methods, is in fact the dominating lignan in wheat, triticale, barley, corn, amaranth, millet, and oat bran. Nevertheless, Norway spruce (Picea abies) remains the most potent, and hence economically viable, source for manufacture into dietary supplements and functional foods.

Commercial Forms and Preparations

HMRlignan™ is a proprietary and patent-protected product manufactured and marketed worldwide by Linnea, Switzerland. The original developmental work was carried out in Finland in collaboration with the wood production industry, and worldwide patents were obtained both for the organic solvent extraction process and for the use of the lignans. HMRlignan (Linnea SA, Switzerland), an extract derived from this plant, is a pure lignan in the aglycone form.

The ingredient is supplied as an off-white crystalline powder and incorporated into dietary supplement capsules, tablets, softgels, and functional foods. HMRlignan™ is standardized to contain 80,000 mg/100 g of lignans, and the daily dosage to raise enterolactone levels is cited as 10–30 mg. Isolation of HMR can be made from the oversize chip fraction (containing branches, twists, and knots) of compression wood of spruce (Picea abies). Total extract of Picea abies (TEP, containing HMR and its isomer) and HMRlignan™ purified HMR are commercially available from Linnea SA, Riazzino, Switzerland.

2. Traditional and Historical Context

7-hydroxymatairesinol as an isolated compound has no known use in traditional or historical herbal medicine. It was discovered and studied in the context of modern phytochemistry and nutritional science, particularly in the late 20th and early 21st centuries, as researchers began isolating specific lignans from plant sources and exploring their biological effects.

However, the plant source of HMR — the Norway spruce — has been used historically in European folk medicine. Resin, bark, and needles from various spruce species were applied in salves, infusions, and poultices for treating respiratory conditions, wounds, inflammation, and infections. These traditional applications referred to the whole plant material, not to isolated lignans, and no documented traditional practice specifically isolated or concentrated HMR from the wood knots.

HMRlignan as an isolated compound is a modern nutraceutical discovered in the 1990s–2000s with no direct traditional medicine use. However, lignan-rich plants like flaxseed, sesame, and whole grains have been consumed across cultures for reproductive health, digestive balance, and cardiovascular wellness — providing the broader dietary context from which scientific interest in plant lignans first arose.

The earliest systematic extraction of HMR from Picea abies heartwood was documented in laboratory methods by Ekman in 1976 and 1979, and the commercial development of HMRlignan™ as a dietary supplement ingredient proceeded through the 1990s and early 2000s, originally under the pharmaceutical company Hormos Medical before the rights transferred to Linnea SA.

3. Key Constituents, Chemistry, and Mechanisms of Action

The Parent Compound: 7-Hydroxymatairesinol

Lignans are plant polyphenols which may possess anticancer, antioxidant, antimicrobial, anti-inflammatory, and immunomodulatory activities. In particular, the lignan 7-hydroxymatairesinol (HMR/lignan) is a novel precursor of the mammalian lignan enterolactone (EL). HMR itself may exert direct biological effects, but its predominant mechanism of action in the human body is mediated through its conversion by intestinal bacteria to the enterolignan enterolactone (ENL) and, to a lesser extent, 7-hydroxyenterolactone.

Metabolic Conversion: Gut Microbiota Transformation

HMR, the most abundant single component of spruce lignans, was metabolized to enterolactone (ENL) as the major metabolite in rats after oral administration. The amounts of urinary ENL increased with the dose of HMR (from 3 to 50 mg/kg), and only minor amounts of unmetabolized HMR isomers and other lignans were found in urine.

The metabolism of the plant lignans matairesinol, secoisolariciresinol, pinoresinol, syringaresinol, arctigenin, 7-hydroxymatairesinol, isolariciresinol, and lariciresinol by human fecal microflora was investigated to study their properties as mammalian lignan precursors. Quantitative analyses of lignan precursors and the mammalian lignans enterolactone and enterodiol were performed by HPLC with coulometric electrode array detection. The metabolic products were characterized as trimethylsilyl derivatives by gas chromatography–mass spectrometry. Metabolites of 7-hydroxymatairesinol were characterized as enterolactone and 7-hydroxyenterolactone by comparison with authentic reference compounds.

The gut bacterial taxa involved in enterolignan production from plant lignan precursors have been partially characterized in the broader lignan literature. The final step — dehydrogenation of enterodiol to enterolactone and closure of the lactone ring — is catalyzed by subdominant populations of Clostridiales, in particular Lactonifactor longoviformis. The efficiency of this conversion varies significantly between individuals, meaning the same dietary intake can result in different circulating levels depending on the composition of a person's gut flora.

Enterolactone as the Primary Bioactive Metabolite

The enterolignans, enterolactone and enterodiol, the main metabolites produced from plant lignans by the gut microbiota, have enhanced bioavailability and activity compared to their precursors, with beneficial effects on metabolic and cardiovascular health.

Enterolactone acts as a selective estrogen receptor modulator (SERM), binding estrogen receptors with weak agonist or antagonist activity depending on the hormonal environment. Both HMR and its metabolite EL are endowed with estrogenic activity, which is likely to be exerted through the contribution of ER-dependent pathways and to target the same intracellular mechanisms acted upon by estradiol (E2). The estrogenicity of HMR and EL is, however, milder than that of E2, as indicated by the lower potencies and efficacies of both lignans.

Direct Antioxidant Properties

Lignans including 7-hydroxymatairesinol have been shown to inhibit lipid peroxidation and eliminate hydroxyl radicals. HMR has also shown antioxidant properties in vitro. These antioxidant mechanisms are considered relevant both to the compound's chemopreventive and cardiovascular profiles. Through binding the estrogen receptors, enterolignans may inhibit inflammatory response to vascular injury and prevent atherosclerosis. In addition, enterolignans may also act as antioxidants and alleviate DNA damage and lipid peroxidation.

Anti-Inflammatory Mechanisms

In THP-1 cells (an established model of human monocytes), HMR concentration-dependently reduced LPS-stimulated tumor necrosis factor (TNF)-α secretion in the supernatant. HMR at low, sub-µM concentrations also reduced TNF-α mRNA, which was, however, enhanced by supra-µM concentrations of HMR. In human polymorphonuclear leukocytes (PMNs), HMR concentration-dependently reduced reactive oxygen species (ROS) production induced by either N-formyl-Met-Leu-Phe, phorbol myristate acetate, or angiotensin II, as well as interleukin-8 production induced by either N-formyl-Met-Leu-Phe or angiotensin II.

Pharmacokinetics: Absorption and Distribution

Pharmacokinetic data indicate that 7-HMR is rapidly absorbed into the bloodstream and effectively metabolized to ENL in postmenopausal women. Considerable systemic exposure of HMRlignan was verified by dose-related increases in plasma total (conjugated and unconjugated) concentrations of 7-HMR and metabolites enterolactone, 7-hydroxyenterolactone, and matairesinol. Enterolactone appeared to be the major metabolite. Most (>96%) of the circulating 7-HMR and enterolactone was in conjugated form, as measured from low-dose rat plasma samples. A notable pharmacological finding is that determination of 7-HMR and its related metabolites in plasma and brain samples after 5 days of oral HMR/lignan (10 mg/kg daily) proved that both 7-HMR and 7-HMR-glucuronide reach the brain tissue, with a substantial increase in concentration over time for the former.

4. Scientific Evidence by Area of Use

4.1 Menopausal Symptoms (Hot Flashes / Vasomotor Symptoms)

This is the area with the most direct human clinical evidence for HMRlignan™ specifically.

Human clinical trial: A single-blind, parallel, pharmacokinetic and dose-comparison study was conducted on 22 postmenopausal females not receiving hormone replacement therapy. Subjects were enrolled in either a 36 mg/d (low-dose) or 72 mg/d dose (high-dose) regimen for 8 weeks. Primary measured outcomes included plasma levels of 7-HMR and enterolactone (ENL), and single-dose pharmacokinetic analysis was performed on a subset of subjects in the low-dose group. Safety data and adverse event reports were collected, as well as data on hot flash frequency and severity.

Doses up to 72 mg/d HMRlignan for 8 weeks were safe and well tolerated in this population. Clinical efficacy was demonstrated via an overall decrease in hot flash frequency and severity.

Evidence strength: This is a single small-scale (n = 22), single-blinded, non-placebo-controlled trial. While the results are promising, the absence of a placebo arm and the small sample size substantially limit interpretation. The study provides preliminary human evidence and a pharmacokinetic framework but is insufficient to establish definitive clinical efficacy for hot flash reduction.

4.2 Estrogen Metabolism and Hormonal Health

The estrogenicity of HMR and EL was investigated in comparison to estradiol (E2) by measuring their effects on growth and apoptotic markers in the human estrogen-sensitive cell line MCF-7. HMR, EL, and E2 concentration-dependently increased the percentage of MCF-7 cells in the S phase of the cell cycle, with the following relative potencies: E2 ≅ EL >> HMR, and efficacies: E2 > HMR >> EL. The effects of HMR and EL were reduced in the presence of the estrogen receptor (ER) antagonist tamoxifen.

A randomized controlled trial (RCT) investigated the effects of a combination supplement containing HMR lignan (10 mg per capsule) together with indole-3-carbinol (I3C) on estrogen metabolism. The trial was a double-blind, placebo-controlled, parallel study in which 98 subjects were recruited to one of two arms. A lignan source derived from the Norwegian spruce tree, 7-hydroxymatairesinol (HMR lignan), had antitumor effects in rat mammary cancers, and positively influenced the concentration of 2-OHE and the ratio of 2-OHE:16α-OHE1 in human subjects. The ratio of 2-hydroxylated to 16α-hydroxylated estrogens is used as a biomarker of estrogen metabolism favoring reduced breast cancer risk. This study was limited by the use of a multi-ingredient formula, making it impossible to attribute effects specifically to HMR. The present results support the notion that dietary supplementation with HMR may result in a mild estrogenic activity, both directly and by providing a suitable source for endogenous EL.

Evidence strength: The estrogenic/SERM mechanism is well-established mechanistically (in vitro). Human evidence for clinically meaningful effects on estrogen metabolism specifically attributable to HMR remains limited and indirect.

4.3 Breast Cancer Risk

HMR (15 mg/kg body weight, oral) given for 51 days decreased the number of growing tumors and increased the proportion of regressing and stabilized tumors in the rat dimethylbenz[a]anthracene (DMBA)-induced mammary tumor model.

Hydroxymatairesinol (HMR) has antitumor activity either as an unchanged compound and/or after conversion to enterolactone in the DMBA-induced breast cancer model. HMR has therefore a potential to have beneficial effects in humans who are at risk of developing breast cancer (BC).

At the epidemiological level, broader lignan intake and enterolactone levels have been associated with breast cancer outcomes. Epidemiological studies have inconsistently shown that high lignan intake and circulating ENL are associated with reduced risk of breast, prostate, and colorectal cancer as well as cardiovascular disease and total and cause-specific mortality.

Evidence strength: The evidence for HMR's effects on breast cancer is primarily preclinical (animal models and in vitro). Epidemiological data refer to dietary lignans broadly — not to HMRlignan specifically — and the findings are described as inconsistent. No controlled human clinical trials of HMR specifically for breast cancer outcomes have been published.

4.4 Prostate Cancer

Clinical intervention studies and experimental studies with lignan-rich diets suggest that lignans may have inhibitory effects on prostate cancer, but no clinical or experimental studies with purified lignans had previously been published. The purpose of one study was to investigate the effect of a plant lignan 7-hydroxymatairesinol (HMR) on LNCaP human prostate cancer xenografts in athymic mice. Athymic nude male mice were injected subcutaneously with LNCaP cells. Starting 3 days after tumor cell injections, a control diet or a control diet supplemented with 0.15% or 0.30% of HMR was administered to mice and the tumor take rate and growth was observed for 9 weeks.

HMR diet inhibited the growth of LNCaP tumors. Mice treated with HMR had smaller tumor volume, lower tumor take rate, increased proportion of nongrowing tumors, and higher tumor cell apoptotic index compared with controls.

At the epidemiological and clinical level, no unequivocal prostate cancer risk reduction has been found for lignans in epidemiological studies, suggesting that lignan concentrations found in populations consuming a regular non-supplemented diet are not chemopreventive in prostate cancer. To the knowledge of reviewers, HMR is the only dietary lignan tested in an animal model of prostate cancer. Further clinical studies performed with the purified compounds are required to substantiate a health claim.

Evidence strength: Preclinical (animal) evidence is positive but limited to xenograft mouse models. Thus far, HMR is the only dietary lignan tested for its safety in the context of long-term intervention studies. Human clinical data are absent for this specific endpoint.

4.5 Cardiovascular Health

The cardiovascular evidence base relates to enterolactone — the primary metabolite of HMR — rather than to HMR itself as a supplement specifically tested in cardiac endpoint trials.

Three meta-analyses were conducted investigating the association between enterolactone and all-cause and CVD mortality, and non-fatal myocardial infarction. A 30% and 45% reduced all-cause and CVD mortality risk were revealed at higher enterolactone concentrations. There is evidence to suggest that enterolactone is associated with a lower CVD mortality risk. This emphasizes the importance of the role of the microbiota in disease prevention. To strengthen the evidence, more studies are warranted.

Five intervention studies using flaxseed lignan supplements indicated beneficial associations with C-reactive protein, and a meta-analysis that included these studies also suggested lignans have a lowering effect on plasma total and low-density lipoprotein cholesterol. Eleven human observational epidemiological studies examined dietary intakes of lignans in relation to cardiovascular disease risk. Five showed decreased risk with either increasing dietary intakes of lignans or increased levels of serum enterolactone, five studies were of borderline significance, and one was null.

In an animal toxicity study, plasma triglycerides were dose-dependently depressed in males of all test groups and in females of the mid- and high-dose group, while plasma total cholesterol and phospholipids were decreased in high-dose males. These changes, which have also been reported for other (flaxseed) lignans, were not considered to represent adverse effects.

Evidence strength: The cardiovascular evidence is observational and refers to dietary lignans and circulating enterolactone broadly. Intervention trials with HMRlignan specifically targeting cardiovascular endpoints are absent. The lipid-lowering signals come from flaxseed lignan trials and animal studies, not from HMR-specific controlled trials. Overall, evidence for enterolactone elevation is strong; evidence for downstream clinical endpoints such as cardiovascular disease or cancer risk reduction requires larger interventional studies.

4.6 Immunomodulation

The pharmacological profile of the lignan 7-hydroxymatairesinol (HMR/lignan) includes chemopreventive effects, antioxidant properties, and mild proestrogenic activity. Results indicate that HMR is an effective inhibitor of both monocytic THP-1 cells and of human PMNs and warrant further studies to assess their relevance for the prevention and treatment of several conditions characterized by chronic systemic inflammation.

Evidence strength: The immunomodulatory evidence is in vitro only (cell culture studies using THP-1 monocytic cells and human PMNs). No human clinical trials have tested HMR specifically for immune outcomes.

4.7 Neuroprotection and Neurodegenerative Disease

Natural polyphenols, especially lignans, have raised attention for their anti-inflammatory, antioxidant, and estrogenic activity at a peripheral level. One study evaluated the central effects of chronic treatment with lignan 7-hydroxymatairesinol (HMR/lignan) on neurodegenerative, neuroinflammatory processes and motor deficits induced by a unilateral intrastriatal injection of 6-hydroxydopamine (6-OHDA) in rats to evaluate the potential neuroprotective properties of this compound. These results suggest intriguing properties of HMR/lignan at neuroprotective and symptomatic levels in the context of Parkinson's disease.

The gut bacterial metabolite enterolactone, formed through intestinal bacterial metabolism of the lignan 7-hydroxymatairesinol (HMR), was found to attenuate the degeneration of the striatal dopaminergic terminals in Parkinson's disease, in the PD rat models.

Evidence strength: Entirely preclinical (rodent models). There are no human clinical trials evaluating HMR for any neurological condition. These findings are hypothesis-generating.

4.8 Metabolic Health and Type 2 Diabetes

Research into the broader class of lignan metabolites suggests relevance to glucose metabolism. Urinary concentrations of lignan metabolites are reported to be significantly associated with a lower risk of Type 2 diabetes (T2D). Enterolactone dose-dependently increased glucose uptake in L6 myotubes under insulin-absent conditions. This increase by ENL was canceled by compound C, an inhibitor of 5′-adenosine monophosphate-activated protein kinase (AMPK). Activation (phosphorylation) of AMPK and translocation of glucose transporter 4 (GLUT4) to the plasma membrane in L6 myotubes were demonstrated by Western blotting analyses.

Evidence strength: Preclinical (in vitro and mouse models) and epidemiological (urinary lignan metabolite biomarkers). No human intervention trials specifically testing HMRlignan for metabolic disease endpoints are available.

5. Body Systems and Health Areas

• Endocrine / Reproductive System: SERM activity via estrogen receptor modulation; potential relevance to menopausal symptoms, estrogen metabolism, and hormone-sensitive tissues.
• Cardiovascular System: Observational associations between enterolactone levels and reduced CVD mortality; possible lipid and inflammatory modulation.
• Oncology (Chemopreventive): Preclinical antitumor activity in breast and prostate cancer models; epidemiological associations with lignan intake and cancer risk reduction (inconsistent).
• Immune System: In vitro inhibition of pro-inflammatory cytokines (TNF-α, IL-8) and reduction of ROS production in immune cell models.
• Nervous System: Preclinical neuroprotective effects in Parkinson's disease rodent models; penetration of the blood-brain barrier demonstrated in animal studies.
• Metabolic System: Epidemiological inverse associations between enterolactone and T2D risk; AMPK activation by enterolactone in cell studies.
• Gastrointestinal System: HMR acts as a substrate for gut microbiota-mediated biotransformation; its clinical effects are therefore partially a function of gut microbiome composition.

6. Dosage Forms and Dosages Reported in Studies

A single-blind, parallel, pharmacokinetic and dose-comparison study was conducted on 22 postmenopausal females. Subjects were enrolled in either a 36 mg/d (low-dose) or 72 mg/d dose (high-dose) regimen for 8 weeks.

The daily dosage to raise enterolactone levels is cited at 10–30 mg in product documentation, with HMRlignan™ standardized to contain 80,000 mg/100 g of lignans.

In the multi-ingredient combination RCT study of estrogen metabolism, each treatment capsule contained 200 mg I3C and 10 mg HMR lignans, in accordance with previous research. The daily dosage was 2 capsules (one with breakfast and one with dinner).

In the 13-week animal safety study, dietary levels of 0, 0.25, 1, and 4% (w/w) of potassium acetate complex of 7-HMR were used, resulting in average daily intakes of 160, 640, and 2,600 mg HMRlignan/kg body weight/day, respectively.

In rodent Parkinson's disease neuroprotection work, the study evaluated the central effects of chronic treatment with lignan 7-hydroxymatairesinol (HMR/lignan), with Sprague-Dawley male rats receiving lignan (10 mg/kg) or vehicle treatment (oral) for 4 weeks starting from the day of 6-OHDA injection.

In animal mammary tumor experiments, HMR (15 mg/kg body weight, oral) was given for 51 days. In the prostate cancer xenograft study, control diet or control diet supplemented with 0.15% or 0.30% of HMR was administered to mice for 9 weeks.

7. Safety Considerations and Interactions

Formal Toxicology Studies

A 13-week toxicity study at dietary levels of 0, 0.25, 1, and 4% (w/w) of potassium acetate complex of 7-HMR (HMRlignan) was conducted in the Wistar rat. HMRlignan exposure did not significantly affect clinical signs, ophthalmoscopy, neurobehavioral observations, or motor activity.

At high doses in the rat toxicology study, some organ-weight and endocrine signals were detected: the relative weight of the kidneys was increased in males of the high-dose group. The weight of the full and empty cecum showed dose-related increases in males of all treatment groups and in females of the high-dose group. Absolute ovary weights were decreased in all treatment groups, while decreases in relative ovary weights were confined to the mid- and high-dose group. In addition, a marginal lengthening of the estrus cycle was noted in high-dose females.

Human Safety Data

Doses up to 72 mg/d HMRlignan for 8 weeks were safe and well tolerated in postmenopausal women.

Estrogenic Activity and Hormone-Sensitive Conditions

At high concentrations, HMR has estrogenic properties, which are considerably weaker than those of estradiol. The results support the notion that dietary supplementation with HMR may result in a mild estrogenic activity, both directly and by providing a suitable source for endogenous EL. This mild SERM activity implies that caution in populations with hormone-sensitive conditions (e.g., estrogen receptor-positive cancers) is scientifically rational, though formal drug interaction studies in such populations have not been published for HMR specifically.

HMR (50 mg/kg body weight) did not exert estrogenic or antiestrogenic activity in the uterine growth test in immature rats — a standard in vivo assay for estrogenic potency — suggesting the compound is a very weak estrogen by classical measures.

Gut Microbiome Dependency

Inconsistencies in observed effects can be due to interpersonal variation of ENL formation or responses. Because the biological activity of HMR depends substantially on its microbial conversion to enterolactone, individuals with impaired gut microbiota diversity (e.g., following antibiotic use) may experience significantly reduced conversion and thus diminished biological effect.

Interaction with Drug-Metabolizing Enzymes

Broader lignan research notes that the effects of lignan consumption are influenced by enzyme genotypes, specifically catechol-O-methyltransferase (COMT), required for the conversion of 4-OHE1 to its proliferative form, and cytochrome P450 enzyme CYP1B1, needed in the conversion of estrogens to 16α-OHE1. No dedicated pharmacokinetic drug interaction studies for HMR with specific pharmaceutical agents have been published in the peer-reviewed literature identified. The phytoestrogenic nature of HMR and its metabolite enterolactone raises theoretical considerations regarding concurrent use with estrogenic or antiestrogenic drugs (e.g., tamoxifen, aromatase inhibitors), but formal interaction data are unavailable.

Aromatase Inhibition

HMR is metabolized to enterolactone, which inhibits aromatization in vitro. HMR may, as a precursor of an aromatase inhibitor, also prevent the development of lower urinary tract symptoms (LUTS), bladder instability, bladder outlet obstruction, urethral dyssynergia, and gynecomastia. These claims are mechanistic and preclinical; no human clinical trials have substantiated these specific effects.

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