HMR (7-hydroxymatairesinol)

HMR (7-Hydroxymatairesinol): A Comprehensive Reference

1. Identity: Chemical and Botanical Classification

Chemical Names and Structure

7-Hydroxymatairesinol (abbreviated HMR or 7-HMR) is a naturally occurring plant lignan. 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. 7-HMR differs from the natural plant lignan matairesinol only by one hydroxyl group attached to carbon number seven. The compound exists primarily as the (−)-7(S) enantiomer in nature. It is classified under the dibenzylbutyrolactol structural subclass of lignans. Lignans are one of the major classes of phytoestrogens, which are estrogen-like chemicals that also act as antioxidants.

In commercial dietary supplement form, HMR is most commonly encountered as its potassium acetate co-crystal, marketed under the proprietary name HMRlignan™ (also written HMR/lignan™ or HMRlignan®). Linnea's HMRlignan® is characterized as 7-hydroxymatairesinol in aglycone form, co-crystallized with potassium acetate.

Natural Botanical Sources

HMR was identified and extracted from the heartwood of the Norway spruce, Picea abies. 7-Hydroxymatairesinol represents about 60% of total lignans in the heartwood knots of spruce (Picea abies [L.] H. Karst.) In spruce, HMR is the most abundant single component of lignans in spruce extracts, reaching a concentration of about 60% w/w of total lignans. Lignan concentration in thick roots is 2–3 percent, while 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 a hundred-fold compared to ground flaxseeds powder, known as a lignan-rich material.

While Norway spruce remains the primary commercial source, research has extended the known distribution of 7-HMR. New Finnish research has uncovered the naturally occurring existence of 7-hydroxymatairesinol as the dominant lignan in wheat, triticale, barley, corn, amaranth, millet, and oat bran. Prior to the results of this research, the lignan was known to be found in Norway spruce (Picea abies), which still remains the most potent, and hence, economically viable source for manufacture into dietary supplements and functional foods.

Isolation and Commercial Preparations

Since 7-HMR appears mainly in aglyconic free form, it can be isolated in relatively large amounts by simple extraction methods. Isolation of HMR for use in dietary supplements 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 the isomer) and HMRlignan™ purified HMR (containing mainly HMR) are commercially available from Linnea SA, Riazzino, Switzerland. It is a proprietary and patent-protected product manufactured and marketed worldwide by Linnea, Switzerland.

HMR is sold in several forms for human consumption, including oral capsules, tablets, and as an ingredient in functional foods. HMRlignan™ is standardized to contain 80,000 mg/100 g of lignans.

2. Traditional and Historical Use

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.

The consumption of lignan-rich foods — such as flaxseeds, whole grains, legumes, and vegetables — has a long history in global dietary traditions. While these foods were not specifically valued for their lignan content in antiquity, modern research has revealed that traditional diets high in such plant foods often result in higher levels of beneficial enterolignans in the body, including those derived from HMR.

Today, the scientific isolation and targeted use of 7-hydroxymatairesinol reflect a broader evolution in plant-based health strategies, moving from general dietary and botanical use to precise, compound-specific supplementation. The earliest published scientific identification of HMR as a distinct enterolactone precursor with antitumor properties from Picea abies dates to the work of Saarinen et al. in 2000, with the first human pharmacokinetic and safety data emerging in the early 2000s.

3. Key Constituents, Related Compounds, and Mechanisms of Action

HMR as an Enterolactone Precursor

7-Hydroxymatairesinol is a novel precursor of the mammalian lignan enterolactone (EL). Plant lignans such as matairesinol and secoisolariciresinol are converted in mammals by way of the gut microflora into mammalian lignans, enterolactone, and enterodiol. Gut bacterial metabolism is able to convert dietary lignans into therapeutically relevant polyphenols (i.e., enterolignans), such as enterolactone and enterodiol. In the case of HMR, the conversion pathway is notably direct and efficient. A considerable systemic exposure to HMRlignan is 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. Enterolignans are characterized by various biological activities, including tissue-specific estrogen receptor activation, together with anti-inflammatory and apoptotic effects.

Phytoestrogenic / Estrogenic Receptor Modulation

Both HMR and its metabolite EL are endowed with estrogenic activity, which is likely to be exerted through the contribution of estrogen receptor-dependent pathways and targets 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. These 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.

Treatment of MCF-7 cells with either HMR, EL, or E2 also increased the Bcl-2/Bax mRNA ratio. The effects of HMR and EL were reduced in the presence of the estrogen receptor antagonist tamoxifen. This confirms that at least part of HMR's estrogenic activity is mediated through classical estrogen receptor pathways.

Antioxidant Properties

The antioxidant properties of hydroxymatairesinol (HM-3000) were studied in vitro in lipid peroxidation, superoxide and peroxyl radical scavenging, and LDL-oxidation models in comparison with the known synthetic antioxidants Trolox, butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT). On a molar basis, HM-3000 was a more effective antioxidant than Trolox in all assays and more effective than BHT or BHA in lipid peroxidation and superoxide scavenging tests. The in vivo antioxidative effect (evaluated as the weight gain of C57BL/6J mice fed an alpha-tocopherol-deficient diet) of HM-3000 (500 mg/kg per day) was comparable to that of DL-alpha-tocopherol (766 mg/kg per day).

Anti-inflammatory Mechanisms

The pharmacological profile of HMR includes chemopreventive effects, antioxidant properties, and mild proestrogenic activity. In vitro studies have illuminated multiple anti-inflammatory pathways. In THP-1 cells (a model of human monocytes), HMR concentration-dependently reduced LPS-stimulated tumor necrosis factor (TNF)-alpha secretion in the supernatant. HMR at low, sub-μM concentrations also reduced TNF-alpha mRNA. In human polymorphonuclear neutrophils (PMNs), HMR concentration-dependently reduced reactive oxygen species (ROS) production induced by several stimuli, as well as interleukin-8 production.

HMR and its major isomer HMR2, dominant in cereals such as wheat, triticale, oat, barley, millet, corn bran, and in amaranth whole grain, exhibit strong anti-inflammatory properties in endothelial cells, at least in part through attenuation of nuclear factor-κB (NF-κB) and extracellular signal-regulated kinase (ERK) phosphorylation. A separate study confirmed this vascular mechanism: (-)-7(S)-hydroxymatairesinol possesses both antioxidant and anti-cancer properties that could be a strategy to suppress TNF-α–mediated inflammation in vascular endothelial cells.

Metabolic Mechanisms

In a murine model, administration of HMR to high-fat diet-fed C57BL/6J mice demonstrated effects on lipid and glucose metabolism. Cholesterol (−11%), LDL (−23%), and triglycerides (−15%) were reduced, and sugar metabolism was ameliorated by both lignan preparations, as shown by a more than 70% decrease in insulin secretion and insulin resistance. The expression of several metabolic genes was modulated by the high-fat diet with an effect that was reversed by lignan. In 3T3-L1 cells, the 7-HMR metabolites enterolactone and enterodiol showed a 40% inhibition of cell differentiation accompanied by the inhibited expression of the adipogenic genes PPARγ, C/EBPα, and aP2. These findings are preclinical and require confirmation in human studies.

4. Scientific Evidence by Area of Use

4.1 Menopause: Vasomotor Symptoms and Hormonal Modulation

This is the best-studied clinical application of HMR specifically as an isolated supplement in humans.

Key human pharmacokinetic and clinical study (2013): 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 (high-dose) regimen for 8 weeks. Primary measured outcomes included plasma levels of 7-HMR and enterolactone, 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. The findings indicate that HMRlignan is quickly absorbed into the plasma and is metabolized to ENL in healthy postmenopausal women. Clinically, the data demonstrate a statistically significant improvement in hot flash frequency. Doses up to 72 mg/d HMRlignan for 8 weeks were safe and well tolerated in this population.

Limitations: This study was single-blind (not placebo-controlled) and enrolled only 22 participants. It lacked a true randomized, double-blind, placebo-controlled design, limiting conclusions about efficacy. Further controlled studies are needed to corroborate these findings.

Pharmacokinetic evidence in healthy subjects: Earlier human pharmacokinetic data showed that HM-3000 (HMR) has been given in single doses up to 1,350 mg to healthy male volunteers without treatment-related adverse events. Rapid absorption from the gastrointestinal tract and partial metabolism to enterolactone in humans was demonstrated.

A separate single-dose study in postmenopausal women further confirmed rapid absorption. In a study of 12 postmenopausal women who received a single dose of 25 mg/day of 7-hydroxymatairesinol aglycone (7-HMR), levels of 7-HMR and its metabolite ENL were measured in blood samples over 72 hours.

Evidence strength for menopause/hot flashes: Preliminary. Human evidence exists but is confined to small, single-blind, non-placebo-controlled trials. Observed clinical improvements in hot flash frequency require confirmation from adequately powered, randomized, double-blind, placebo-controlled trials.

4.2 Cancer: Chemoprevention (Preclinical and Epidemiological)

The oncological evidence for HMR is substantial in animal models but absent from human clinical trials with HMR as an isolated supplement.

Mammary cancer (animal models): 7-Hydroxymatairesinol (HMR) is converted to ENL, and both HMR and ENL inhibit the growth of 7,12-dimethylbenz[a]-anthracene (DMBA)-induced mammary cancer in rats. The chemopreventive effects of HMR, a lignan extracted from Norway spruce (Picea abies), on the development of mammary carcinoma induced by DMBA were studied in rats. HMR administered via diet in an average daily dose of 4.7 mg/kg body weight, starting before DMBA induction, reduced tumor volume and tumor growth, but no significant reduction in tumor multiplicity (number of tumors/rat) was observed.

Prostate cancer (animal model): Anticancer effects of a plant lignan 7-hydroxymatairesinol on a prostate cancer model in vivo have been published. 7-Hydroxymatairesinol (HMR) is converted to ENL, and both HMR and ENL inhibit the growth of DMBA-induced mammary cancer. In contrast, life-long exposure to HMR had no effects on uterine or prostate weights at any age.

Antitumor/anticolorectal evidence (animal): The antitumor activity of HMR was studied in DMBA-induced rat mammary cancer; HMR had a statistically significant inhibitory effect on tumor growth. HMR was given in diet at 30 mg/kg per day and decreased the formation of polyps and prevented beta-catenin accumulation into the nucleus, the pathophysiological hallmark of polyp formation in this mouse model.

Epidemiological context: A lignan source derived from the Norwegian spruce tree, 7-hydroxymatairesinol, had antitumor effects in rat mammary cancers. However, 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. Presumably, the main obstacles in assessing the efficacy of food lignans is limited knowledge of the serum and tissue lignan concentrations required for the putative prevention.

Evidence strength for cancer: Preclinical only for HMR specifically. Animal studies and in vitro data are suggestive of chemopreventive potential, but no human intervention trials have been conducted with HMR as an isolated agent to evaluate cancer incidence or tumor outcomes.

4.3 Cardiovascular Health

The rationale for using HMR lignan to support cardiovascular health stems from observation-based studies where higher dietary intake of plant lignans, or higher serum levels of enterolactone, correlate with reduced cardiovascular risk factors and lower incidence of cardiovascular events. In humans, higher circulating concentrations of enterolactone have been associated with lower risk of coronary heart disease (CHD) in several prospective cohort studies, although the findings are not entirely consistent. Observational studies have also shown an inverse association between plant lignan intake and ameliorated lipid profile, increased insulin sensitivity, higher flow-mediated dilation, and reduced aortic stiffness.

Increased concentrations of enterolactone have been associated with a decreased risk of cardiovascular disease. Among the lignans studied in TNF-α–treated human aortic endothelial cells, HMR and HMR2 significantly reduced intracellular adhesion molecule-1 and vascular cell adhesion molecule-1 levels as well as the adhesion of U937 monocytes to endothelial cells. These adhesion molecules are mechanistically relevant to atherosclerosis.

In the 13-week rat toxicity study, which also reported biological effects, 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 for cardiovascular: Indirect and preliminary. Evidence derives principally from observational epidemiology linking enterolactone levels (not HMR supplementation per se) with cardiovascular outcomes, plus mechanistic in vitro and animal data. The evidence specifically for HMR lignan supplementation (as opposed to general dietary lignans) in cardiovascular disease is limited and mostly preclinical.

4.4 Immunomodulation

Results from in vitro studies 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. These are cell-culture findings; no human clinical trials specifically targeting inflammatory or immune conditions with HMR supplementation have been reported in the peer-reviewed literature.

Evidence strength for immunomodulation: In vitro only. Mechanistically plausible, but no clinical translation has yet been demonstrated.

4.5 Metabolic Syndrome, Obesity, and Glucose Metabolism

This invention relates to the use of 7-hydroxymatairesinol (HMR) for preventing, alleviating, or treating the metabolic syndrome conditions. Relevant patents describe potential benefits across components of metabolic syndrome, including visceral obesity, steatosis, inflammation, dyslipidemia, and insulin resistance. The mechanistic rationale is supported by animal data showing significant improvements in lipid and glucose parameters, and by in vitro evidence of inhibition of adipogenesis-related gene expression. However, these findings have not been confirmed in human randomized trials specifically with HMR.

Evidence strength for metabolic syndrome: Primarily preclinical (animal and in vitro). Human evidence is absent.

4.6 Neuroprotection

HMR was found to attenuate the degeneration of the striatal dopaminergic terminals in the context of Parkinson's disease research. Parkinson's disease (PD) is a neurodegenerative disease characterized by loss of dopaminergic neurons in the Substantia Nigra pars compacta. The proinflammatory response can occur early in the disease, contributing to nigrostriatal degeneration. Identification of new molecules able to slow down the degenerative process associated with PD represents a key area of interest. Natural polyphenols, especially lignans, have raised attention for their anti-inflammatory and antioxidant properties in this context.

Evidence strength for neuroprotection: Very preliminary; based on mechanistic reasoning and isolated preclinical observations. No human clinical evidence for any neurological application.

5. Pharmacokinetics and Bioavailability

7-HMR is rapidly absorbed into the bloodstream and effectively metabolized to enterolactone (ENL) in postmenopausal women. Because HMR exists mainly in aglycone (non-glycosylated) free form in Norway spruce extracts, it does not require the same degree of pre-absorptive microbial processing that glycosylated lignans (e.g., secoisolariciresinol diglucoside from flaxseed) require before absorption. This contributes to its relatively high and rapid bioavailability as a supplement.

As a unique source of lignans, HMRlignan™ (7-hydroxymatairesinol) is a highly bioavailable and efficient precursor of enterolactone. In short-term toxicity studies (up to 28 days), HMR was essentially non-toxic when given orally to rats and dogs (daily doses up to 2,000 and 665 mg/kg, respectively); HMR was shown to be well absorbed (>50% of the dose) and rapidly eliminated.

The main factors that may interfere with enterolignans production include genetics, sex, age, food transit time, intestinal redox state, smoking habit, antibiotic uptake, and gut microbiota composition and function. Lignan bioavailability is characterized by marked inter-individual differences. Since the bioconversion of HMR to enterolactone is dependent on the intestinal microbiota, individuals whose microbiome lacks or is depleted of the key bacterial species responsible for this conversion (for example, following antibiotic use) may achieve lower circulating enterolactone levels.

Conversion of HMR to ENL has been demonstrated in vitro in fermentation studies with human fecal microbiota.

6. Dosage Forms and Reported Dosages

The following dosages are drawn directly from published studies and are reported here as observed in those sources, not as recommendations.

• 10–30 mg/day of HMRlignan™ is the daily dosage reported to raise enterolactone levels in human pharmacokinetic studies.
• 36 mg/day (low dose) or 72 mg/day (high dose) were the regimens used in the single-blind, parallel, dose-comparison study conducted on 22 postmenopausal females for 8 weeks.
• Single doses up to 1,350 mg were administered to healthy male volunteers without treatment-related adverse events in early human studies.
• 25 mg/day (single dose) of 7-HMR aglycone was used in a pharmacokinetic study of 12 postmenopausal women.
• In the rat mammary cancer model, HMR was administered via diet in an average daily dose of 4.7 mg/kg body weight; this is an animal dose and is not directly translatable to human dosing.

HMRlignan™ is formulated primarily as an oral supplement (capsules or tablets) and as a functional food ingredient. Only a small dose is needed — between 10 to 40 mg — to elevate the enterolactone level to the same degree as three tablespoons of lignans from unground flaxseed, and with higher bioavailability.

7. Body Systems and Health Areas of Association

• Endocrine/Reproductive System: Mild phytoestrogenic activity via estrogen receptor modulation; studied in the context of menopausal vasomotor symptoms and hormonal balance.
• Oncology/Chemoprevention: Lignans have shown potential in alleviating menopausal symptoms and preventing estrogen-dependent cancers. For HMR specifically, evidence is preclinical.
• Cardiovascular System: Association of its primary metabolite, enterolactone, with reduced coronary heart disease risk; anti-inflammatory effects in human aortic endothelial cells.
• Immune System: In vitro inhibition of inflammatory cytokine secretion and ROS production in human monocytes and PMNs.
• Metabolic Health: Lignans have been shown to exert antioxidant, anti-inflammatory, and hormone-modulating actions. These properties contribute to their potential role in supporting cardiovascular and metabolic health, improving lipid metabolism, enhancing insulin sensitivity, and lowering risk factors associated with conditions such as diabetes and metabolic syndrome. Direct evidence for HMR is animal-based.
• Neurological System: Preliminary animal/mechanistic data on dopaminergic neuroprotection in Parkinson's disease models.
• Gastrointestinal System: As a substrate for the intestinal microbiota, HMR interacts with and potentially modulates the gut microbial environment. Caecal enlargement was noted in high-dose rat studies, suggesting prebiotic-like effects at extreme doses.

8. Safety Considerations and Interactions

Toxicological Safety Data

A 13-week toxicity study at dietary levels of 0, 0.25, 1, and 4% (w/w) of the potassium acetate complex of 7-HMR (HMRlignan) was conducted in the Wistar rat. These dietary levels resulted in an average daily intake of 160, 640, and 2,600 mg HMRlignan/kg body weight/day, respectively.

HMRlignan exposure did not significantly affect clinical signs, ophthalmoscopy, or neurobehavioural observations, and motor activity. However, reproductive endpoints were affected at higher doses: absolute ovary weights were decreased in all treatment groups, while decreases in relative ovary weights were confined to the mid- and high-dose groups. In addition, a marginal lengthening of the estrus cycle was noted in high-dose females. It was concluded that HMRlignan showed weak antiestrogen-like activity which may be mediated through the enterolactone metabolite. Based on declined ovary weight, the no-observed-adverse-effect level (NOAEL) of HMRlignan was set at 0.25% in feed, corresponding to 160 mg/kg body weight/day.

Apart from prevention of hyaline droplet nephropathy in all high-dose male rats, there were no treatment-related histopathological alterations at lower doses.

Human Safety Data

No significant safety issues were identified in the clinical pharmacokinetics study. HMRlignan is quickly absorbed into the plasma and is metabolized to ENL in healthy postmenopausal women. Clinically, the data demonstrate a statistically significant improvement in hot flash frequency. Doses up to 72 mg/d HMRlignan for 8 weeks were safe and well tolerated in this population.

Estrogenic Activity and Hormone-Sensitive Conditions

Because HMR exerts mild estrogenic activity through estrogen receptor-dependent mechanisms, it is relevant to consider its use in individuals with hormone-sensitive conditions. Both HMR and enterolactone are endowed with estrogenic activity, though the estrogenicity of HMR and EL is milder than that of estradiol, as indicated by the lower potencies and efficacies of both lignans. The relevance of this mild activity to conditions such as estrogen receptor-positive breast cancer, endometriosis, or uterine fibroids has not been formally evaluated in clinical trials with HMR.

Gut Microbiota Dependence and Antibiotic Interactions

The conversion of HMR to its primary active metabolite, enterolactone, is entirely dependent on gut microbiota activity. The main factors that may interfere with enterolignan production include genetics, sex, age, food transit time, intestinal redox state, smoking habit, antibiotic uptake, and gut microbiota composition and function. Antibiotic use can substantially reduce or eliminate the intestinal bacteria responsible for converting HMR to enterolactone, potentially abolishing the primary bioactive output of supplementation.

Inter-individual Variability

The two-way interaction between polyphenols and gut microbiota — specifically modulation of the microbiota by polyphenols and metabolism of polyphenols by the microbiota — has been proposed as the main driver of inter-individual variation, assuming the existence of different gut microbiota-associated metabotypes. This means that serum enterolactone levels achieved from a given oral dose of HMR can vary substantially between individuals depending on their microbiome composition.

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