- Laurus is a genus of evergreen trees or shrubs belonging to the laurel family, Lauraceae. The genus has three or more species, including bay laurel or sweet bay (Laurus nobilis) widely cultivated as a ornamental plant and culinary herb. Other species include Laurus azorica (Azores laurel) and Laurus novocanariensis. (23)
Bay laurel's symbolism decorates many pages of Roman and Greek mythologies. Many version of the Bay Laurel legend are profusely colored with name-dropping of Apollo, Cupid, Daphne,
Laurel wreath: Bay laurel was used to fashion the laurel wreath of ancient Greece, a symbol of highest status. A wreath of bay laurel was used as the prize at the Pythian Games in honor of Apollo.
- Pythia the priestess of Apollo was reputed to chew laurel leaves from a sacred tree to induce a trance from which she uttered oracular prophecies.
- In Roman culture, the laurel was a symbol of victory and immortality.
- In the language of achievement, it provided roots to words like baccalaureate and poet laureate, along with expressions like "assuming the laurel"and resting on one's laurels." (7)
Laurus nobilis is an evergreen shrub or small tree, variable in size, growing 7 to 18 meters high. Leaves are glabrous, 6 to 12 centimeters long and 2 to 4 centimeters wide, with entire margins, some with undulate. Flowers are dioecious. Each flower is pale yellow-green, about 1 centimeters in diameter, born in pairs beside a leaf. Fruit is a small, shiny berry-like drupe, about 1 centimeter long and containing one seed. (7)
- GC and GC-MS study of leaves for essential oil yielded29 compounds representing 99.18% of total oil. The three main components were 1,8-cineole (68.82%), 1-(S)-α-pinene (6.94%) and R-(+)-limonene (3.04%). (see study below) (2)
- GC and GC-MS study of leaves collected in Southern Italy for essential oil
identified 55 compounds, accounting for 91.6% of total EO. Main components were 1-8-cineole (31.9%), sabinene 12.2%), and linalool (102%). (see study below) (4)
- Phytochemical screening of leaves yielded: (water extract) tannins+++, alkaloids_, saponins++; (ethanol) anthracenosides+, flavonoids+++;
(ether diethylique) alkaloids+, volatile oil++; (petroleum ether) sterols and steroids+. free quinones++. (10)
- Semipreparative HPLC from laurel leaf infusion isolated 10 flavonoid O-glycosides, one flavonoid C- glycoside, catechin, and cinnamtannin B1. (see study below)
- GC-MS and GC-FID study of flowers for essential oil yielded 25 volatile compounds making up 92.07% of total essential oil content. EO yield was 1.06% and most abundant compounds were 1,,8-cineole (45.01%), α-caryophyllene (7.54%), germacradienol (6.13%), limonene (4.69%), α-pinene (3.04%). and germacrene-D (3.14%). )see study below) (34)
- Whole bay leaves have a shelf-life of abut a year, under normal temperature and humidity.
- Considered carminative, stomachic.
- Studies have suggested antioxidant,, antimicrobial, anti-inflammatory, anticancer, antidiabetic, antidyslipidemic, alpha-glucosidase inhibitory properties.
- Laurel leaves from Laurus nobilis are not toxic. It is a spice used for soups, stews and braised meats. Toxicity concerns come from species sharing the common name 'laurel' — more than 30 and many tagged with the country of origin— or 'bay', some of which may be poisonous. One such species is laurel (Prunus laurocerasus), a potentially toxic cyanogenic plant.
- Study done in Swiss albino mice showed significant weight loss at amounts of 0.3 to 3 mg/g. No mortality was observed. (see study below) (5)
Edibility / Culinary
- A source of a spice used in a wide variety of recipes.
- Whole bay leaves used as flavoring agent in food preparation. Aromatic leaves are a popular spice of pasta sauces. (7)
- Ground bay leaves used for soups, stews, fish, vegetables, and stocks; used as additive to a Bloody Mary. Dried berries and pressed leaf oil used as spices. (7)
- Dried leaves used for brewing herbal tea. (see study below 27)
- Essential oils used in the flavoring industry.
- In Iranian folk medicine, leaves used to treat epilepsy, neuralgia and Parkinsonism. (4)
- Leaves used to treat stomach bloating and flatulence.
- Used as salve for open wounds.
- Used to treat muscle and joint pains.
- Poultice of boiled bay leaves used as remedy for rashes of poison ivy, poison oak, and stinging nettle.
- Leaf oil used in preparation of anti dandruff lotion; oil used externally for treatment of psoriasis.
- In Iranian traditional medicine, leaf essential oil used as antiepileptic remedy. (32)
- Wood as flavoring: Wood burned for strong smoke flavoring. (7)
- Ornamental: Cultivated as an ornamental plant.
- Aromatherapy: Used in massage therapy and aromatherapy.
- Oil: Fruit essential oil used in soap making.
- Repellent: Aromatic leaves can be used as insect repellent. (8) (41)
- Sleep-aid: Bay leaf tea or a few drops of leaf essence in water at bedtime used as sleep-aid. Sachet of crushed leaves inside the pillow case reported to be helpful.
• Antidiabetic / Antioxidant / α-Glucosidase Inhibition / Essential Oil / Leaves: Study of essential oil yielded 29 compounds, with three main constituents consisting of 1,8-cineole (68.82%), 1-(S)-α-pinene (6.94%) and R-(+)-limonene (3.04%). On antioxidant evaluation using DPPH, hydroxyl, superoxide radicals, H2O2 scavenging assays, the EO exhibited greater activities than the positive control and three main components when tested independently. On α-glucosidase inhibition assay to evaluate for in-vitro antidiabetic activity, laurel essential oil and 1,8-cineole inhibited α-glucosidase competitively while (S)-α-pinene and R-(+)-limonene were uncompetitive inhibitors. Results suggest potential for treatment of diabetes by scavenging reactive oxygen species and inhibiting α-glucosidase. (see constituents above) (2)
• Antimicrobial / Cytotoxicity / Possible CNS Effects / Essential Oil of Leaves: Study of leaves for essential oil
identified 55 compounds, accounting for 91.6% of total EO. Main components were 1-8-cineole (31.9%), sabinene 12.2%), and linalool (102%). Tested against Gram-positive (S. aureus, B. cereus) and gram-negative (E. coli, P. aeruginosa) bacteria, the EO showed significant antimicrobial activity against all microorganisms tested. The EO and various components also exhibited activity against A. niger, A. versicolor, P. citrinum and P. expansum. IC50s against human neuroblastoma cell line (SH-SY5Y) were ≥400 µg/mL indicating substances were non-cytotoxic. Study investigated the influence of EO and its components on ADCY1 expression. Treatment reduced ADCY! expression in SHSY5Y cells and intracellular production of cAMP. The EO effect may be due to the presence of linalool (10.2%). Study has shown linalool possesses dose-dependent sedative effects in the CNS. (4)
• Antibacterial / Toxicity / Oxidative Stress Effects: Study evaluated the antimicrobial activist and toxicity on Swiss albino mice. Plasmatic markers and enzymes were assessed and histological alterations were evaluated. Study also investigated the effect of the spice on metabolic markers, stress biomarkers and clinical parameters. The study confirmed the antibacterial effect and the toxicity of laurel at 0.3 mg/g, which induced inflammation in the liver, oxidative stress and cell necrosis in the heart. No changes were observed with the amounts of 0.003 and 0.03 mg/g. during seven days of treatment. At 0.3 and 3 mg/g of treatment there was significant decrease in weight. There was no mortality observed. Results suggest the use of L. nobilis as spice should not exceed 0.003 mg/g as no negative effects were observed at this amount. (5)
• Cytotoxic / No Genotoxic Potential: Study evaluated the genotoxic potential of an aqueous extract of leaves using the Allium cepa assay and mouse peripheral blood cell micronucleus test. Results showed no genotoxicity, but cytotoxic activity was observed in two experimental models used. The extract exhibited an antiproliferative effect, suggested by reduction of mitotic index and the polychromatic/ normochromatic erythrocyte (PCE/NCE) ratio. Tests also showed large number of cells undergoing apoptosis with nuclear abnormalities related to cell death processes. Results may be attributed to phenolic compounds, saponins, flavonoids, and alkaloids in the extract. Results suggest L. nobilis used by the general population does not have genotoxic potential. and contains components with apoptotic and antigenotoxic potential. (6)
• Anti-Inflammatory / Leaves: Study evaluated the anti-inflammatory of bay leaf. Studies have previously documented its ability to inhibit protein denaturation. The anti-inflammatory effect was comparable to reference analgesics and non-steroidal anti-inflammatory drugs. (9)
• Herb-Drug Interactions: Major interaction: (1) Narcotic drugs- sweet bay may decrease how fast the body gets rid of pain medications, thereby potentially increasing effects and side effects; for ex: demerol, morphine, hydrocodone, etc; (2) Sedatives/CNS depressants: Sweet bay may cause sleepiness and drowsiness, and taking it with sedating medications may cause too much sleepiness; for ex: Klonopin, Ativan, Ambien, etc. (11)
• Antioxidant / Antimicrobial / Essential Oil / Leaves: Study evaluated leaf essential oils for antioxidant and antimicrobial activity obtained by hydrodistillation and SFME (solvent-free microwave extraction). The EO exhibited antimicrobial activity against S. aureus, E. coli, S. typhimurium. Antioxidant activity was assessed various assays. Strongest antioxidant activity against DPPH radical was found in EO obtained by SFME at 100% power level. Antioxidant activity obtained by HD showed greatest TEAC value which indicated strongest antioxidant activity. (13)
• Cytotoxic Effect Against Different Cancer Cell Lines: Study evaluated the effect of L. nobilis on three different cancer cell lines. Cell viability and proliferation were assessed against different concentrations of a hexane extract and showed remarkable inhibition of AMN (mouse mammary adenocarcinoma), REF (rat embryo fibroblast) and HeLa (cervical human carcinoma cell line in a dose dependent manner. (14)
• Effect of Post Harvest Storage on Oil Constituents: Study evaluated the best ways to store essential oil. The EO was analyzed by GC/MS every four months for one year. Fresh EO yielded approximately 56.83% 1,8-cineole, 13.47% α-terpenyl acetate, 4.96% trans-beta-terpineol, and 3.19 terpinen-4-ol, 4.09% α-pinene, and 6.94% sabinene. Changes in EO content depended on storage conditions. Largest change in EO constituents of the dry herb was observed after storage of one year., with less change after four months of storage. Oil compounds were more stable during the first eight months of herb storage. (15)
• Antidiabetic Effect / Leaves / Trial: Study evaluated the preventive or alleviative effect of bay leaves on 65 patients with type 2 diabetes, 50 given capsules containing 2 g of bay leaves per day for 30 days and 15 given placebo capsules. All patients who consumed bay leaves reduced plasma glucose with significant decreases of 30% after 30 days. Lipid profile showed decreases in TC, LDL, and triglycerides, with increase in HDL. No change was seen in the placebo group. Results suggest potential for decreasing risk factors for diabetes and cardiovascular diseases, and benefits for T2DM. (16)
• Quality Control Study / Bay Leaf Substitutes: Bay leaf is a name applied to several species of aromatic plants. True "bay leaf," also known as "bay laurel," is from Laurus nobilis. In herbal commerce, bay leaf may refer to other species viz., Cinnamomum tamala, Litsea glaucescens, Pimenta racemosa, Syzygium polyanthum, and Umbellularia californica, often substituted or mistaken for true bay leaf because of similarity in leaf morphology, aroma, and flavor. Some of these substitutes can cause potential health problems. Correct identification is important. The study provides a detailed comparative study. (List of plants substituted or confused with bay leaves) (17)
• Wound Healing: Study evaluated aqueous extracts of Allamanda cathartica and Laurus nobilis for wound healing activity using excision and incision wound models in Sprague Dawley rats. Wile A. cathartica showed better wound healing, in Laurus nobilis treated animals, the rate of wound contraction, weight of granulation tissue and hydroxyproline content were moderately high (p<0.05). Histological study of granulation tissue showed larger number of inflammatory cells and lesser collagen than Allamanda but better than the control group of animals. (18)
• Sesquiterpene Lactones / Leaves and Fruits: The plant fruit and leaves contain more than 30 sesquiterpene lactones (SL), including eudesmanolides, germacranolides, guaianolides. Sesquiterpene lactones possess antimicrobial, anti-diabetic, anti-inflammatory, hepatoprotective, neuroprotective and cytotoxic activities. SL inhibit the absorption of alcohol, increases activity of hepatic glutathione-S-transferase. These SL are an important source of raw materials for creation of new medicines. (20)
• Antiviral / Anti-SARS-CoV / Essential Oils: Study evaluated the chemical composition of essential oils of seven plants viz., Laurus nobilis, J. oxycedrus, T. orientalis, C. sempervirens, P. palaestina, S. officinalis, and S. thymbra. The oils were evaluated for their inhibitory activity against SARS-CoV and HSV-1 replication in vitro by visual scoring of the virus-induced cytopathogenic effect post-infection. Laurus nobilis exhibited interesting activity against SARS-CoV with IC50 of 120 µg/ml and a selectivity index (SI) of 4.16. The oil was characterized by the presence of ß-ocimene, 1,8-cineole, α-pinene, and ß-pinene as main constituents. (21)
• Insecticidal / Essential Oil: Study evaluated the insecticidal activity of bay leaf oil fractions, and isolated compounds against stored grain pest of wheat i.e., Tribolium castaneum. Extensive column chromatography of polar fraction yielded eugenol and 7,7 dimethyl-3--methylene bicyclo[2.2.1]heptan-4-ol. Results showed the EO may have potential to control grain pest, T. castaneum. Adults were more susceptible to eugenol. (22)
• Fumigant Potential / Essential Oil: Study evaluated the fumigant toxicity of essential oil from Laurus nobilis and Myrtus communis against larvae and adults of red flour beetle, Tribolium castaneum. Results showed the essential oils have potential as botanic control against larvae and adults of T. castaneum, an alternative to chemical pesticides, (24)
• Essential Oil from Different Seasons: Study evaluated the essential oil of leaves collected during different seasons. Oil yield was lowest (0.13%) in March, and highest in September (0.36%). GLC showed 70 peaks, 27 of wh8ich were identified. In the March, July, and September samples, cineole and eugenol were the major components. (25)
• Antimicrobial Sesquiterpenoids / Leaves: Study of activity guided fractions of leaf extracts from Laurus nobilis isolated a known sesquiterpene lactone, deacetyl laurenobiolide (1), which showed antimicrobial activity against periopathic pathogens (Actinomyces viscosus. Porphyromonas gingivalis, Prevotella intermedia and Actinobacillus actinomycetemcomitans), opportunistic Gram-positive bacteria (Staphylococcus aureus and Streptococcus pyogenes) and fungi (Candida albicans, Cryptococcus neoformans and Aspergillus fiumigatus). Acetylation and cyclisation of compound 1 yielded laurenobiolide (2) and a new compound, (55,6R,7S,8S,10R)-6,8-dihydrooxyeudesma-4(15),11(13)-dien-12-oic acid 12,8-lactone (3). Compounds 2 and 3 also showed antimicrobial activity. (26)
• Acetylcholinesterase Enzyme Inhibition / Antioxidant: Om a study of 10 Portuguese plants, Laurus nobilus was one of four plants that showed inhibitory activity of the enzyme acetylcholinesterase and antioxidant activity. A decoration of L. nobility showed to be an effective scavenger of radicals. (27)
• Effect pf Daily Tea Consumption on Lipid Profile: Study evaluated the effect of daily L. nobilis tea consumption on plasma levels of lipid biomarkers on 30 healthy volunteers. aged 20-57. Infusion was prepared with 5 g of dried leaves in 100 cc of boiled water. taken once daily for ten days. Results showed significant increase in HDL cholesterol )p=0.01). There was a slight decrease in LDL and triglycerides that was not statistically significant (p<0.05). Results suggest potential beneficial effect on lipid and cardiovascular profile. (28)
• GC-MS Comparative Study of Leaf Essential Oil in Commercial Samples: Comparative GC-MS study evaluated leaf essential oil in commercial samples. Sixty=four compounds were identified, accounting for 91-99% of total oil. Oxygenated compounds were the principle fraction in all analyzed oils and consisted in oxygenated monoterpenes (73.13%) in medicinal EO, and oxygenated monoterpenes (37.60 and29.82%), oxygenated sesquiterpenes (15.98 and 22.99%) and phenylpropanoids (24.78 and 26.33%), respectively, in commercial food items. Commercial food items yielded high content of methyl eugenol (19, 21%) and α-terpinyl acetate (18, 17%), while commercial pharmaceutical items yielded main compounds of of 1,8-cineole (51%) and α-terpinyl acetate (10%). (29)
• Cytotoxic Sesquiterpenes / Fruits: Study of methanol extract of fruits isolated a new sesquiterpene, lauroxepine and six known sesquiterpene lactones The hexane soluble part of the extract yielded lauroxepine, costunolide, and gazaniolide, while the dichlormethane-soluble part yielded costunolide and four other sesquiterpene lactones (santamarine, reynosine, 11,13-dehydrosantonin, and spirafolide. The extracts were were evaluated for both ovarian cytotoxic activity and DNA damaging properties. Extracts prepared from fruits showed most cytotoxic activity against ovarian cancer cell line with 95% inhibition. Only the fruit extract showed marginal inhibition (63.2%) against DNA repair-deficient yeast strain. The six known sesquiterpene lactones were found to be hghly cytotoxic against the A2780 ovarian cancer cell line. Lauroxepine was not found effective against A2780. (30)
• Artecanin / SARS-Cov-2 Main Protease Inhibitor: Main protease (Mpro) is a critical enzyme in the life cycle of severe acute respiratory syndrome Coronavirus-2 (SARS-Cov-2). Inhibition of Mpro is one of the essential ways of preventing the outbreak of COVID-19. A total of 3392 compounds from 66 medicinal plants were retrieved from PubChem database and docked against Mpro. Thirty compounds with highest docking scores with Mpro were virtually screened for druglikeness and toxicity potential/ Out of the screened compounds, artecaniin was predicted to exhibit the most favorable druglieness potential, with no predicted hepatotoxicity, carcinogenicity, mutagenicity. and cytotoxicity. The Mpro-artecanin complex exhibited comparable stability. Results showed artecanin from Laurus nobilis provided a novel static and dynamic inhibition for Mpro with excellent safety, oral bioavailability, and pharmacokinetic profile. Artecanin has potential as a natural inhibitor to bloc or counteract the SARS-Cov-2 invasion. (31)
• Anticonvulsant / Leaf Essential Oil: Study evaluated leaf essential oil of Laurus nobilis for anticonvulsant activity against experimental seizures. Results showed protection of mice against tonic convulsions induced by maximal electroshock and especially pentylenetetrazole. Effect may be due to components such as methyleugenol, eugenol and pinene present in the essential oil. At anticonvulsant doses, the EO produced sedation and motor impairment, which may be due to eugenol, cineol, and methyleugenol. (32)
• Effect on Vital Organs of STZ-Induced Diabetic Rats / Leaves: Study evaluated the effects of leaf extract on vital organs in streptozotocin-induced diabetic rats. Laurus nobilis has a valuable effect on blood glucose level and an ameliorative effect on pancreatic islets.. It has also displayed insuliin-enhancing effects in vitro. It restored altered kuver enzymes, urea, creating sealskin, total protein levels, calcium, and ferrite to near normal. (33)
• Anti fungal / Antioxidant / Flower Essential Oil: Study evaluated the chemical composition, antioxidant and antifungal activities of essential oil from Laurus nobilis flowers The flower essential oil showed significant antifungal activity against seven fungal strains tested: Aspergillus clavatus, A. niger, Chaetomium globosum, Cladosporium cladosporioides, Myrothecium verrucaria. Penicillium citrinum and Trichoderma viride. The flower EO also exhibited strong total antioxidant capacity (TAC) as indicated by its ability to scavenge free radical DPPH. The antifungal and antioxidant activities were attributed to 1,8-cineole. (see constituents above) (34)
• Cosmetic Usage of Leaf Volatile Oil: GC-MS study of leaf volatile oil yielded 1,8-cineole, alpha terpinyl acetate, alpha-pinene, terpinen-4-ol and sabinene as major compounds. The volatile oil was used to make skin lotion. The highest amounts of total flavonoid content were found in ethyl acetate and ethanol extracts. Highest amounts of total phenolic compounds were also in the EA and ethanol extracts According to ABTS, DPPH, and ß-carotene linoleic acid assays, the ethyl acetate extract was the most active extract. (35)
• Antibiofilm Formation / Antibacterial: Study evaluated the antibacterial activity of leaf extracts of Laurus nobilis against Gram positive S aureus, Enterococcus faecalis, and Staphylococcus epidermis and Gram-negative E. coli and P. aeruginosa. Results showed the alginate, fucoidan, fatty oils and essential oil have good antibacterial activities against the tested strains, Biofilm activity of fucoidan, laminaran, fatty oil and essential oil were negligible. Alginate showed promising biofilm eradication. even at low concentration. (36)
• Antibacterial / Essential Oil of Leaves: Study evaluated the in vitro antibacterial effect of essential oil of Laurus nobilis using paper disc diffusion. GC=MS analysis showed oxygenated monoterpenes as the highest component, representing 59% of the EO. A total of 27 compounds were identified wish major components of 1,8-cineole (30.1%), α-terpinyl acetate (26.1%), methyl eugenol (16.9%), Highest antibacterial activity was reported in Streptococus faecalis and Staphylococcus aureus with iinhibition zones of 13.6 and 11.2 mm, respectively. (37)
• Antiproliferative ./ Human Breast Adenocarcinoma Cells: Study evaluated four plants commonly used as spices for antiproliferative activity to adenocarcinoma of breast cell line (MCF7). The ethanol crude extract of EO of Laurus nobilis showed antiproliferative activity to MCF7 with IV50 24.49 µg/ml. The hydrodistilled EP did not show cytotoxic activity. (38)
• Effect of Drying Methods on the Essential Oil of Leaves: Study evaluated the qualitative and quantitative changes in essential oil of Laurus nobilis leaves affected by different drying methods. Results showed that air crying at ambient temperature and infrared drying at 45°C significantly increased the essential oil content. Forty-seven compounds were identified, mostly oxygenated monoterpenes, which was not significantly affected by the method of drying except for air-drying at ambient temperature. The main components: 1,8-cineole, methyl eugenol, terpinen-4-ol, linalool, and eugenol showed significant variations with drying methods, the concentrations of which increased significantly with air-drying at ambient temperature Results suggest that drying influenced both the quality and quantity of bay laurel oil. (39)
• Urease Inhibitory Activity / Potential Use in H. pylori Infection: H. pylori is a common cause of stomach and duodenal ulcers. It uses urease enzyme product 'ammonia' to neutralize and protect itself from the stomach acidic condition and urease enzyme activity is essential to the colonization of H. pylori. Study evaluated 20 traditional medicinal plants against Jack bean urease activity by Berthelot reaction to obtain natural sources of urease inhibitors. Eight of the 3-0 were found effective. The most potent urease inhibitory activity was observed for Zingiber officinale, Laurus nobilis and Nigella sativa with IC50s of 48.54, 48.69, and 59.10 µg/ml, respectively. (40)
- Herbal products, leaf extracts essential oils in the cybermarket.