Bayleaf

Other Names

allorobay laurelbay leafbay treebay-leaf laureldafinadafinëdafinov listdafnidaphnedapnidefnedhafnedəfnə yarpağıereinotzerramuFolia LauriFructus Laurigekkei-jugekkeijuGrecian laurelHab-ul-gharHabb-ul-GharHub-ul-gharlaakerilagerlaurlaurbærlaurellaurel treelauriellolaurierlaurier d'apollonlaurolaurovy listLaurus nobilislavrlavrovo durvollorllorerlorbeerLorbeerstrauchloreloureirolourolouro-comumlouro-de-apolôniolouro-europeulovorRandRoman laurelsweet bagsweet baysweet laurelteejh patteejpattatree laureltrue laurelTurkish laurelwaraq al-lauriwaraq ghaaryue guiyue gui shu yeyue gui ziyueh kueiyuht gwai

Synopsis

Bay Leaf (Laurus nobilis L.): A Comprehensive Reference

1. Identity, Botanical Classification, and Common Forms

1.1 Botanical and Taxonomic Identity

Bay leaf (Laurus nobilis) is an evergreen perennial shrub belonging to the family Lauraceae. It is an evergreen tree growing up to ten meters high, widespread in the Mediterranean area, and widely cultivated in many countries with moderate and subtropical climate. The name Laurus nobilis comes from the Latin laurus, meaning "to praise," and nobilis, meaning "noble."

Known as bay, sweet bay, bay laurel, Roman laurel, or daphne, it is an evergreen shrub of the Lauraceae family, which includes 2,500–3,500 plant species that grow in the subtropics and tropics of East Asia, and South and North America. This plant is native to the Mediterranean region and is cultivated in other warm climates of the southern United States, Central America, Europe, the Middle East, and Asia. Other members of the Lauraceae family include sassafras, avocado, and cinnamon.

The genus Laurus has a range of 2,400 to 2,500 species, and their varieties are native to the Southern Mediterranean region, the subtropics and tropics of Eastern Asia, South and North America, the Balkans, and Asia Minor.

1.2 Common Forms and Preparations

Bay leaf has been used for thousands of years for food flavoring, essential oil applications, and in traditional medicine. The leaves are commercially available and medicinally employed in several preparations:

Dried whole leaves: Dried leaves and the essential oil deriving from leaves are used as a valuable spice and flavoring agent in culinary and food industry.
Ground/powdered leaves: Used in capsule form in clinical trials investigating metabolic effects (discussed below).
Essential oil: The leaves contain volatile oils that accumulate in the palisade and mesophyll cells, present in a percentage of 1–3% on a fresh weight basis. The main constituent out of approximately 150 identified by GC-MS in the essential oil is usually 1,8-cineole, with content ranging up to 50%, or even 70%.
Aqueous infusion/decoction: Laurus nobilis L. is commonly used in folk medicine in the form of infusion or decoction to treat gastrointestinal diseases and flatulence as a carminative, antiseptic, and anti-inflammatory agent.
Polyphenol extracts: Laurel leaves comprise essential oils, alkaloids, polysaccharides, sugars, norisoprenoids, tocopherols, organic acids, and a variety of polyphenols comprising flavonoids and non-flavonoids (phenolic acids and lignans) whose structure varies in complexity.

2. Traditional and Historical Use

2.1 Ancient Greece and Rome

In ancient times, bay laurel had decorative uses as a symbol for prosperity, fame, and victory. Ancient Mediterranean cultures also believed this tree had the power to keep them from misfortune, so trees were often planted near houses to deter lightning strikes. In Greek mythology, it was considered sacred, which is why in ancient Greece, receiving a wreath made of bay leaves was considered an honor bestowed on Olympic winners, poets, victors, and heroes.

The Greek gods of healing and medicine, Apollo and Aesculapius, held the bay laurel sacred. Dioscorides, a Greek physician and botanist in the first century A.D., recommended bay laurel bark for fortifying the liver and dissolving kidney stones. Ancient Greeks and Romans used an infusion of the leaves to warm and tonify the stomach and bladder, and made a paste from the leaves to relieve the pain of bee stings.

Bay laurels have been used to treat uterine problems, rheumatism, and for nerves. The leaves and extracts are used to suppress high blood sugar, fungal and bacterial infections, and the plant has been used to treat eructation, flatulence, and gastrointestinal problems.

2.2 Mediterranean and Middle Eastern Folk Medicine

Laurus nobilis Linn. (Lauraceae), commonly known as bay, has been used as a traditional medicine in the Mediterranean and Europe to treat diverse immunological disorders.

The aqueous extract of the leaves has been traditionally employed in Turkish folk medicine as an anti-hemorrhoidal, anti-rheumatic, diuretic, as well as an antidote for snakebites. The leaves are traditionally used as a carminative, stomachic, and nervine, as well as in the treatment of amenorrhea, colic, condylomata, hysteria, polyps, sclerosis, and spasms. In Iranian folk medicine, the leaves are used to treat epilepsy, neuralgia, and parkinsonism.

L. nobilis leaves have traditionally been used in Mediterranean cuisine for seasoning, as well as in folk medicine along with L. nobilis fruits for treating viral infections, cough, rheumatism, impaired digestion, diarrhea, and other health conditions.

2.3 Other Cultural Traditions

In Chinese folk tradition and Taoism, the bay leaf symbolized healing and strength. The Romans spread this plant to parts of Europe from which the first settlers introduced it to colonies in the New World.

In ancient Egypt, bay leaves were used in perfumes and were also believed to have medicinal properties; the ancient Egyptians used bay leaves to treat a variety of ailments including headaches and fever. Bay leaves were also used in ancient India, where they were believed to have medicinal properties and were used in Ayurvedic medicine.

In herbal medicine, aqueous extracts of bay laurel have been used as an astringent and salve for open wounds, and it is also used in massage therapy and aromatherapy.

3. Key Constituents and Active Compounds

3.1 Essential Oil (Volatile Fraction)

The essential oil content in Laurus nobilis leaves ranges from 1% to 3%, depending on geographic origin and harvest period, and contains sesquiterpene lactones, with predominant compounds being 1,8-cineole (eucalyptol), α-pinene, β-pinene, α-terpinyl acetate, sabinene, linalool, and, in relatively low concentrations, eugenol and methyl-eugenol.

Across multiple GC-MS analyses from different geographic origins, 1,8-cineole consistently dominates. The major oil components have been reported as 1,8-cineol (43.52–31.31%), methyl-eugenol (14.96–4.07%), α-terpinyl acetate (13.00–8.51%), linalool (11.72–1.08%), sabinene (10.57–4.85%), α-pinene (7.41–3.61%), eugenol (4.12–1.97%), and terpinen-4-ol (2.33–1.25%).

The oxygenated compounds are the principal fraction in all analyzed oils, consisting primarily of oxygenated monoterpenes. A high content of methyl eugenol and α-terpinyl acetate was found in commercial food items, whereas 1,8-cineole (51%) and α-terpinyl acetate (10%) were the main compounds in commercial pharmaceutical items.

3.2 Non-Volatile Phenolic Compounds

The biological activities of L. nobilis can be attributed to its phenolic compounds, such as flavonoids, phenolic acids, tannins, and lignans.

Flavonoids present the main constituents of alcoholic leaf extracts. Flavonols are present in the highest amount, with kaempferol and its glycosides being the main representatives (almost 50%), followed by quercetin and isorhamnetin and their glycosides, which are also present in significant amounts.

Among polyphenols in pressurized liquid extracts, flavonols (rutin and quercetin-3-glucoside) were the most abundant identified compounds. A wide range of secondary metabolites, such as flavonoids (quercetin and kaempferol), phenolic acids (ferulic and caffeic acid), tannins, alkaloids, and saponins, are present in L. nobilis in addition to essential oils.

The plant mostly contains tannins, flavones, flavonoids, alkaloids, eugenol, linalool, methyl chavicol, and anthocyanins. The extent of each of these chemical constituents varies depending on the type of species or cultivars as well as cultivation conditions such as soil type, weather, irrigation, pruning, and other horticultural practices.

3.3 Sesquiterpene Lactones

Sesquiterpene lactones are found in the roots and leaves of bay trees, and two distinct chemical types were discovered with laurenobiolide and costunolide as major compounds. Sesquiterpene lactones found in bay leaf have been discovered to have a variety of pharmacological properties such as inhibitory effects on NO production (anti-inflammatory), inhibitory effects on alcohol absorption, and enhancement of liver glutathione S-transferase (GST) activity.

3.4 Summary of Key Compound Classes

Monoterpenes: 1,8-cineole (eucalyptol), sabinene, α-pinene, β-pinene, linalool, α-terpineol, terpinen-4-ol, α-terpinyl acetate
Phenylpropanoids: Eugenol, methyl eugenol
Sesquiterpene lactones: Costunolide, laurenobiolide, parthenolide
Flavonols: Kaempferol and glycosides, quercetin and glycosides, rutin, isorhamnetin
Phenolic acids: Ferulic acid, caffeic acid
Alkaloids, tannins, anthocyanins, saponins, tocopherols

4. Mechanisms of Action

4.1 Anti-inflammatory Mechanisms

To elucidate the anti-inflammatory mechanism of L. nobilis, its leaf extract was examined for its effect on inflammasome activation in mouse bone marrow-derived macrophages. L. nobilis leaf extract inhibited NOD-like receptor pyrin domain-containing 3 (NLRP3) inflammasome activation, which was associated with caspase-1 activation, interleukin-1β secretion, and apoptosis-associated speck-like protein containing a CARD (ASC) pyroptosome complex formation. The major component 1,8-cineole consistently suppressed NLRP3 inflammasome activation.

In macrophage models, L. nobilis extracts suppress activation of the NLRP3 inflammasome, reducing caspase-1 activity and interleukin-1β production. In vivo, bay leaf extracts significantly attenuated inflammatory cytokine release and lung tissue damage in murine models of acute lung injury, with 1,8-cineole identified as a key mediator.

4.2 Smooth Muscle Relaxation

Essential oil constituents such as 1,8-cineole and eugenol exhibit smooth muscle relaxant effects, possibly via calcium channel blockade or muscarinic receptor modulation, supporting traditional use for cramps and colic.

4.3 Antioxidant Mechanisms

Polyphenols can be considered largely responsible for the laurel leaf extracts' antioxidant activity, since they possess redox properties which allow them to act as antioxidant agents. Recent research has demonstrated that bay leaf extracts can modulate oxidative stress pathways and inhibit lipid peroxidation, making them promising agents in the prevention of chronic diseases like cancer, neurodegeneration, and cardiovascular disorders.

4.4 Anticonvulsant/Neurological Mechanisms

Many components of the essential oil of bay leaf such as eugenol, methyl eugenol, and pinene have anticonvulsant activity, while eugenol, methyl eugenol, and cineole produce sedation and motor impairment. Eugenol and methyleugenol exhibited anesthetic and muscle relaxant effects, and the observed sedation and motor impairment appear to be related in part to these components of laurel essential oil.

4.5 Antidiabetic Mechanisms

Bay leaves (Laurus nobilis) have been shown to improve insulin function in vitro. The precise intracellular mechanism in humans has not been fully characterized, but animal studies have pointed to reductions in serum glucose and lipid levels at multiple dose levels.

4.6 Cytotoxic/Anticancer Mechanisms

Using bioassay-directed isolation studies, different cytotoxic and apoptosis-inducing compounds have been identified in bay leaf. Hot water-soluble sesquiterpenes isolated from laurel (Laurus nobilis L.) induce cell death and morphological change indicative of apoptotic chromatin condensation in leukemia cells.

5. Scientific Evidence by Area of Use

5.1 Glycemic and Lipid Control (Diabetes and Metabolic Health)

This is the area with the most directly available human clinical evidence for bay leaf as a dietary supplement.

The objective of one key study was to determine if bay leaves may be important in the prevention and/or alleviation of type 2 diabetes. Forty people with type 2 diabetes were divided into 4 groups and given capsules containing 1, 2, or 3 g of ground bay leaves per day for 30 days or a placebo, followed by a 10-day washout period. All three levels of bay leaves reduced serum glucose with significant decreases ranging from 21 to 26% after 30 days.

Total cholesterol decreased 20 to 24% after 30 days, with larger decreases in low-density lipoprotein (LDL) cholesterol of 32 to 40%. High-density lipoprotein (HDL) cholesterol increased 29 and 20% in the groups taking bay leaves.

This study demonstrated that consumption of bay leaves, 1 to 3 g/day for 30 days, decreases risk factors for diabetes and cardiovascular diseases and suggests that bay leaves may be beneficial for people with type 2 diabetes.

Cookies containing bay leaf powder (not less than 6% w/w) exhibited significant benefit on postprandial glucose level in healthy human subjects.

Evidence strength: The 2009 Khan et al. human trial is small (40 participants), short-term (30 days), and to date has not been replicated in a larger, independently conducted randomized controlled trial. Supporting animal data are extensive but do not substitute for human evidence. This area is considered promising but preliminary.

5.2 Anti-inflammatory Activity

The great number of phytochemicals in L. nobilis essential oils exerts physiological effects and therapeutic potential, including analgesic and anti-inflammatory activities. The essential oil of bay leaf also has analgesic and many anti-inflammatory activities.

Evidence strength: Predominantly in vitro (cell culture) and animal model data. The NLRP3 inflammasome inhibition finding is from mouse macrophage models. No controlled human clinical trials specifically measuring anti-inflammatory endpoints have been published to date.

5.3 Antimicrobial and Antifungal Activity

Antimicrobial and antifungal activities of the essential oil and 1,8-cineole were determined in vitro. The essential oil showed significant antimicrobial activity against all microorganisms tested, giving inhibition zones between 6.33 and 8.66 mm.

Numerous scientific studies highlight the antimicrobial, antifungal, anticonvulsant, antioxidant, anti-inflammatory, antidiabetic, anticancer, neuroprotective, and anticholinergic activities of L. nobilis.

Evidence strength: Antimicrobial effects are well-demonstrated in vitro against both Gram-positive and Gram-negative bacteria, as well as fungi. No human clinical trials for infectious disease indications have been conducted. These findings remain at the laboratory level.

5.4 Antioxidant Activity

High DPPH radical scavenging activity (IC₅₀ values as low as 10.9 µg/mL), along with elevated total phenolic (198 mg GAE/g) and flavonoid contents (628 mg QE/g), has been reported for L. nobilis extracts.

The phenolic compounds of L. nobilis possess enormous potential for the treatment or prevention of systemic diseases including metabolic, allergic, and age-related diseases.

Evidence strength: Strong in vitro evidence for antioxidant capacity. No standalone human trials measuring antioxidant biomarkers as primary endpoints have been published.

5.5 Neurological and Neuroprotective Effects

The essential oil and extracts of L. nobilis exhibit multiple neuropharmacological activities, including anticonvulsant, neuroprotective, anticholinesterase, anxiolytic, and cognitive-enhancing effects.

One study investigated whether bay leaf incense (BL) elicits memory formation via the action on the cholinergic system using a scopolamine-induced rat model. Rats were exposed to BL for 5 minutes in a smoking chamber apparatus once daily for 22 days, while memory impairment was induced by scopolamine (0.7 mg/kg), a muscarinic receptor antagonist.

The plant's leaves have been utilized in Iranian folk medicine to alleviate symptoms associated with epilepsy, neuralgia, and Parkinsonism. The extract from the leaves has been found to possess anticonvulsant and antiepileptic properties.

Animal study data found that laurel essential oil produced sedation and motor deficits at the anticonvulsant doses, and eucalyptol was shown to have an inhibitory effect on locomotion and potentiate pentobarbital sleep time in mice.

Evidence strength: Exclusively preclinical (animal models and in vitro). No human clinical trials for neurological or cognitive endpoints have been identified. Findings are exploratory.

5.6 Anticancer Activity

One study demonstrated selective activity of L. nobilis ethanolic leaf extract against multiple cancer cell lines, including SAS head and neck cancer cells, while confirming safety on normal fibroblasts and revealing mechanisms such as apoptosis and cell cycle arrest. The study evaluated the anticancer and antioxidant activities of the ethanolic leaf extracts and identified main phytochemical constituents using UPLC-QTOF/MS. The study is preliminary and seeks to establish the potential use of L. nobilis extract components in the future.

Evidence strength: All current anticancer data are in vitro (cell line) studies. There are no human clinical trials. This area remains entirely preliminary.

5.7 Gastrointestinal Effects

The leaves and essential oil of L. nobilis have been historically used in traditional medicine to alleviate gastrointestinal issues such as bloating and flatulence in the upper abdomen. This is attributed to their capacity to stimulate the secretion of gastric fluids.

Evidence strength: Traditional use is well-documented across cultures. Mechanism (gastric secretion stimulation) is plausible but not confirmed by controlled human trials. No rigorous clinical data exist.

5.8 Lipid Profile in Healthy Subjects

One study investigated the effects of daily Laurus nobilis tea consumption on lipid profile biomarkers in healthy volunteers (Chbili et al., 2020, J Am Coll Nutr 39(8):733–738), though the full results of this trial are not extractable from available sources. The citation appears in multiple review articles in the literature.

6. Body Systems and Health Areas

It has been reported to have antioxidant, antibacterial, antifungal, antiviral, biocidal, antidiabetic, antiulcerogenic, neuroprotective, analgesic, anti-inflammatory, and anticholinergic properties, making this plant of great clinical importance. The principal body systems with documented scientific or traditional relevance are:

Metabolic / Endocrine System: Antidiabetic effects, glycemic and lipid profile modulation (human data available)
Gastrointestinal System: Carminative, antispasmodic, stimulation of gastric secretion, antidiarrheal
Immune / Inflammatory System: NLRP3 inflammasome inhibition, cytokine suppression, general immunomodulation
Central Nervous System: Anticonvulsant, neuroprotective, anticholinesterase, anxiolytic (preclinical only)
Cardiovascular System: LDL reduction, HDL elevation, triglyceride lowering (human data available in diabetic context)
Microbiological / Antimicrobial: Antibacterial, antifungal activity (in vitro)
Oncological: Pro-apoptotic activity in cancer cell lines (in vitro only)
Dermatological / Topical: Traditional use as wound salve and astringent; essential oil used in massage

7. Dosage Forms and Reported Dosages

Dosages documented in published scientific studies are as follows:

Oral capsules of ground bay leaf powder — diabetes trial (Khan et al., 2009): Forty people with type 2 diabetes were given capsules containing 1, 2, or 3 g of ground bay leaves per day for 30 days, followed by a 10-day washout period.
Bay leaf powder in food — postprandial glycemia (Khan et al., 2017): Cookies containing bay leaf powder (not less than 6% w/w) exhibited significant benefit on postprandial glucose level in healthy human subjects.
Animal model dosages — high-fat diet study: Animals were administered bay leaves aqueous (AQ) extracts at 50, 100, and 250 mg/kg of body weight, and bay leaves methanol/acetone (MeAc) extract at 50, 100, and 250 mg/kg of body weight.
Animal model — rabbit supplementation: Rabbits fed with fat-enriched diet supplemented with dried bay leaves at 1 g/kg body weight for 56 days showed a significant decrease in blood lipid and glycemic profiles as well as a reduction in serum levels of ALT and AST.
Essential oil — antimicrobial testing (in vitro): The essential oil showed significant antimicrobial activity against all microorganisms tested starting at the lowest amount used (0.4 µL), giving inhibition zones between 6.33 and 8.66 mm.

No standardized human dosage has been established by any regulatory or pharmacopeial authority for bay leaf as a dietary supplement. The existing clinical evidence is limited to a single small human trial at 1–3 g/day of powdered leaf in capsule form.

8. Safety Considerations and Interactions

8.1 Physical Obstruction Risk

Whole dried bay leaves, if swallowed, present a documented physical hazard. The stiff, rigid leaves do not soften sufficiently during digestion and have been associated with gastrointestinal tract perforation in case reports in the medical literature (Lingenfelser et al., J Clin Gastroenterol, 1992;14(2):174–176). Bay leaves used in cooking are conventionally removed before the dish is consumed. Ground, powdered, or extracted forms do not carry this physical risk.

8.2 Methyl Eugenol — Genotoxicity and Hepatotoxicity Concerns

Among the constituents of bay leaf essential oil, methyl-eugenol is considered the primary potentially hepatotoxic agent. This aromatic compound undergoes hepatic metabolism via cytochrome P450 enzymes, yielding reactive intermediates such as 1′-hydroxymethyleugenol, which is genotoxic: it forms DNA adducts, induces oxidative stress, and triggers mitochondrial dysfunction, leading to cell necrosis and apoptosis via a p53-dependent pathway.

As of 2023, despite limited human epidemiological evidence, methyleugenol is classified by IARC as a potential carcinogen based on animal data. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety and efficacy of an essential oil from the leaves of Laurus nobilis L. (laurel leaf oil) when used as a sensory additive for all animal species; the additive contains up to 4% methyleugenol.

A published case report assessed a 55-year-old female patient with substantially elevated liver transaminase levels. It was concluded through thorough medical history that the patient regularly consumed herbal infusions, specifically Laurus nobilis leaves, commonly known as bay laurel. This case, assessed using the updated RUCAM causality assessment tool, suggests that regular high-dose consumption of bay leaf herbal tea may pose a hepatotoxic risk, attributed to cumulative methyl-eugenol exposure.

8.3 Allergic Contact Dermatitis

Allergic contact dermatitis with laurel essential oil has been observed in rare cases. Cases of allergic contact dermatitis caused by laurel leaf oil are documented in the dermatological literature (Brás et al., Contact Dermatitis, 2015;72:417–419).

8.4 Central Nervous System Effects at High Doses

Animal study data found that laurel essential oil produced sedation and motor deficits at the anticonvulsant doses. Eucalyptol was shown to have an inhibitory effect on locomotion and potentiate pentobarbital sleep time in mice. These findings have not been replicated in human pharmacokinetic studies, but they suggest that very high doses of bay leaf essential oil could potentiate CNS depressant drugs.

8.5 Variability in Phytochemical Content

The extent of each chemical constituent varies depending on the type of species or cultivars as well as cultivation conditions such as soil type, weather, irrigation, pruning, and other horticultural practices. This variability complicates dose standardization and makes it difficult to extrapolate results from one preparation to another.

8.6 Note on Topical Essential Oil Use

Due to its toxicity, bay laurel oil should not be ingested. The essential oil is generally used diluted in carrier oils for topical application or in aromatherapy, and ingestion is not a recognized route for therapeutic use in evidence-based sources.

References

Health Conditions

Health conditions that Bayleaf may help support.

No conditions available.

Body Systems

Body systems that Bayleaf may help support.

No body systems available.