Rosemary: Benefits, Dosage, Contraindications

Hepatoprotective

The hepatoprotective effect of rosemary is linked to the presence of carnosic acid, carnosol, and rosmarinic acid. The hepatoprotective action of carnosic acid and carnosol may in part be due to their ability to maintain and increase enzymatic activity of glutathione peroxidase and superoxide dismutase, whose activity is reduced in the presence of toxic elements. In vivo, rosemary demonstrated a protective effect against hepatic steatosis by reducing hepatic triglyceride levels in rats fed a high-fat diet.

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Antioxidant

The antioxidant activity of rosemary is due to a variety of compounds, particularly phenolic diterpenes and phenolic acids such as rosmarinic acid. These antioxidant effects can contribute to membrane stabilization and the reduction of free radical production, aiding in the electron donor capacity of rosemary diterpenes to protect membranes from oxidative damage. It has been demonstrated that rosemary leaf extract increases superoxide dismutase activity and has a stronger effect than vitamin E in oxygen radical trapping. In cell culture studies, rosemary extract at concentrations of 1/2000 and 1/1000 significantly inhibited nitric oxide (NO) production. It is suggested that carnosol and carnosic acid represent over 90% of its antioxidant properties. Carnosic acid has been shown to have a photoprotective action on human dermal fibroblasts exposed to ultraviolet rays in vitro, and rosemary extract inhibits oxidative alterations of skin surface lipids, both in vitro and in vivo, and enhances cell-mediated immunity in rats subjected to oxidative stress. Rosmarinic acid has also been studied for its antioxidant activities and plays an important role in the antioxidant capacity of extracts containing very similar diterpene concentrations. In a study, extracts with a lower concentration of rosmarinic acid (50:50) exhibited poorer antioxidant capacity, and antioxidant activity was further enhanced by the presence of carnosol as a major diterpene content. Antioxidant activity has also been studied in a macular degeneration model. Sprague-Dawley rats received a rosemary test solution intraperitoneally 1 hour before light exposure tests. Both rosemary powder extract (34 mg/kg) alone and when combined with zinc (1.3 mg/kg) effectively decreased the extent of retinal light lesions. Rosemary treatment (17 mg/kg) and zinc (1.3 mg/kg) reduced oxidative stress protein markers and improved visual cell survival, demonstrated by improved photoreceptor cell morphology and reduced retinal DNA degradation.

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Anti-inflammatory

In vitro research shows that rosemary extract can inhibit human leukocyte elastase activity, which plays a role in inflammation. Research suggests that rosemary may induce a beneficial mechanism in cellular protection and the resolution of inflammation. Rosemary, particularly carnosol and carnosic acid, act by inhibiting 5-lipoxygenase activation and thus reducing pro-inflammatory responses in stimulated leukocytes. Rosemary's ursolic acid may inhibit the activation of the nuclear transcription factor kappaB. Some animal research suggests that rosemary extract can prevent allergic airway inflammation by inhibiting interleukin (IL)-13 expression.

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Cholagogue

A lyophilized ethanolic tincture of rosemary dissolved in perfusate was injected in doses corresponding to 0.5 g, 1 g, or 2 g/kg body weight into the jugular vein of rats under constant perfusion of a sodium taurocholate solution. A significant rapid increase in bile flow was observed; it reached a maximum in 30 minutes then returned to baseline within 2 hours after 1 g or 2 g/kg, and within an hour after 0.5 g/kg. Intravenous administration of a 15% alcohol lyophilized extract of rosemary flowering tops to bile duct-cannulated guinea pigs, at 100 mg/kg body weight, caused a 138% increase in bile flow within 30 minutes, followed by a period of slower activity, but reaching a second peak of 218% after 105-120 minutes. The results indicate both cholagogue and cholerectic activity of the extract.

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Cholerectic

Lyophilized ethanolic tincture of Rosemary dissolved in perfusion fluid, at 0.5 g, 1 g, and 2 g/kg drug, in the rat jugular vein under sodium taurocholate, causes rapid bile flow increase, reaching a maximum in 30 minutes, then returning to basic flow.

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Antiallergic

In humans, rosmarinic acid would significantly improve seasonal allergy symptoms compared to a placebo. These effects would occur through the inhibition of the induction of certain adhesion molecules and cyclooxygenase-2 (COX-2)1.

Anticancer

Animal research suggests that rosemary extract can decrease the incidence of carcinogen-induced tumors, tumor load, and tumor yield. Rosemary extract and certain components, such as carnosic acid, appear to inhibit proliferation and potentially induce apoptosis in leukemia cells. Other in vitro research suggests that rosmarinic acid, a rosemary constituent, reduces the expression of the pro-inflammatory cyclooxygenase-2 (COX-2) gene. This gene is considered a risk factor for cancer development. Rosemary extract and rosemary essential oil may also reduce cancer development by protecting DNA against oxidative damage; this is attributed to rosemary's phenolic constituents. Additionally, rosemary polyphenols may reduce procarcinogen activation and increase detoxification pathways. Other cell culture research suggests that carnosol, a rosemary constituent, inhibits cancer cell metastasis by reducing matrix metalloproteinase-9 (MMP-9) activity.

Antimicrobial

Various cell culture studies show that rosemary essential oil and rosemary extract have antibacterial activity against Gram-negative and Gram-positive bacteria, including some drug-resistant strains and foodborne pathogens, as well as activity against certain yeast and fungi species, notably Candida albicans. Rosemary essential oils containing the highest amounts of camphor, borneol, and verbenone seem to exert the greatest antimicrobial activity. Rosemary extract containing carnosic acid, carnosol, and rosmarinic acid appears to have the highest antimicrobial activity. However, other research suggests that rosemary does not exhibit antifungal activity against Candida species.

Neurological

Rosemary shows promising potential for brain protection and the prevention of neurodegenerative diseases. It can inhibit certain brain enzymes, protect dopamine-producing neurons, and possesses antidepressant and pain-relieving properties. Studies on cell cultures indicate that rosemary might promote nerve growth and protect against oxidative stress thanks to carnosic acid, which has neuroprotective effects by activating the brain's antioxidant defenses. The effectiveness of carnosic acid depends on its ability to reach the brain. Research has shown that after oral administration in mice, carnosic acid successfully crosses the blood-brain barrier, suggesting potential application in the treatment of neurodegenerative diseases. Carnosic acid also increases antioxidant levels in the brain, which could contribute to its neuroprotective capacity. However, further studies are needed to better understand these mechanisms and their applicability to humans.

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Dermatological Effect

It is believed that rosemary polyphenols, rosmarinic acid, carnosic acid, and carnosol induce these photoprotective effects. Additionally, rosemary essential oil has been shown to increase blood circulation in hair follicles and combat hair loss.

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Gastroprotective

Rosemary has potential anti-ulcer activity. A rosemary extract has demonstrated antibacterial activity in vitro against Helicobacter pylori (Mahady et al 2005). Dias and colleagues (2000) studied the anti-ulcerogenic activity of crude hydroalcoholic rosemary extract in an experimental rat model. The extract was made from the dried aerial parts of rosemary that were processed. In the ethanol-induced ulcer model, doses of 100 and 200 mg/kg of this extract showed no anti-ulcerogenic activity, whereas doses of 500 and 1000 mg/kg inhibited the ulcer lesion index by 70% and 74.6%, respectively. In the indomethacin-induced ulcer model, the extract (1000 mg/kg) inhibited the ulcer lesion index by 44%. Anti-ulcerogenic activity was also maintained in the ethanol-induced ulcer model, with prior administration of indomethacin, inhibiting the ulcer lesion index by 70%. The results of this study suggest that the hydroalcoholic rosemary extract possesses active substances that increase the non-protein sulfhydryl group content of the mucosa.