Sources and structure
Sources
Rosmarinic acid is found the following food products and spices:
Perilla frutescens,[1] the seeds from which Perilla Oil is derived from at 1.716.9μg/g in the seeds (49% of total phenolics[2]) with a glucoside of rosmarinic acid (rosmarinic acid-3-O-glucoside) at 1752.7μg/g (48% total phenolics[2]); reaching 0.34% perilla seed oil by weight[2]
Rosemary[3] from where it derives its name
Basil[8] and the Ayurvetic medicine Holy Basil[9]
The following dietary supplements:
Melissa officinalis (Labiatae) at 2.2-5.5%, although it can be higher if specific extracts are taken
And a variety of uncommon plants including:
Clerodendranthus spicatus (Thunberg)[11]
Verbascum xanthophoeniceum (Scrophulariaceae)[12]
Heliotropium foertherianum (Boraginaceae)[13]
Rosmarinic acid is a fairly widespread component of plants that is not limited to one particular plant family, but is found in higher than normal levels in some dietary supplements where it mediates many benefits associated with the supplement
Structure
It is structurally a dimer of caffeic acid and 3,4-dihydroxyphenyllactic acid, bound by an ester linkage[14] and known as a phenylpropanoid.[12]
Pharmacology
Serum
Ingested rosmarinic acid is found systemically in its intact form, and also as various metabolites such as m-coumaric acid, m-phenylhydroxypropionic acid, and sulfated forms of caffeic, coumaric and ferulic acids.[15][16] These same metabolites are found in human blood/urine after ingestion.[17][18]
Rosmarinic acid is methylated into methyl-rosmarininc acid via the catechol-o-methyltransferase (COMT) enzyme.[18]
Ingestion of Perilla Extract (a common source of rosmarinic acid) containing 200mg Rosmarininc Acid while fasted results in approximately a peak concentration of 1.15+/-0.28umol/L in the plasma after 30 minutes, and the methylated metabolite (methyl-rosmarinic acid) may rise to a peak of 0.65+/-0.07umol/L at the 2 hour mark.[18] Up to 75% of Rosmarinic acid and its metabolites are excreted in the first 6 hours after ingestion. There are differences between rats and humans in this regard, with rats excreting more as a glucuronide conjugate and humans as a sulfate conjugation.[18]
In rats, it has been reported that Rosmarinic acid can be absorbed through the skin, and the build-up of rosmarinic acid favors skin, muscle, and bone deposition rather than organ deposition percutaneously.[19] The absolute bioavailability in this study was 60%, enhanced by ethanol solvent, and a dose of 3mg over 20cm2 was used.
Enzymatic Interactions
Rosmarinic Acid appears to inhibit human organic anion transporter 1 (SLC22A6) and 3 (SLC22A8) with inhibitory constants (Ki values) of 0.35+/-0.06uM and 0.55+/-0.25uM respectively via competitive inhibition.[20]
Cardiovascular Health
Endothelium
Rosmarinic acid contributes to endothelial (blood vessel) and blood cell health. The former is typically indirect via systemic anti-oxidation and anti-inflammation (as discussed previously). In regards to the latter, rosmarinic acid can ease hemolysis, the breaking of red blood cells, via C3-convertase inhibition.[21]
Inflammation and Immunology
Rosmarinic acid is being investigated for its interactions with inflammation and immunology due to it being an ingredient of Perilla Oil, and the plant the oil is derived from (Perilla frutescens Britton) being a component of the Kampo (Traditional Japanese) medicine known as Saiboku-To which is demonstrated effective against allergies.[22][23][24]
Mechanisms
Rosmarinic Acid seems to be able to suppress 5-lipoxygenase and 5-HETE synthesis (a pro-inflammatory compound in the omega-6 metabolic chain). Unlike caffeic acid (a related compound), rosmarinic acid does not affect prostaglandin synthesis per se.[25]
Interventions on Inflammation
When tested in rats via an edema test, Rosmarinic acid is able to suppress the inflammatory response from administered TPA (pro-inflammatory agent), and a reduction in the oxidative increases by TPA were also observed.[26]
Interventions on Allergies
Oral supplementation of Perilla oil (in mice) has been demonstrated to suppress the allergic response by 43% at an oral dose of 500mg/kg, as assessed by an ear-passive cutaneous anaphylaxis test.[27] Later, a human study consisting of 30 persons aged 21-53 with mild cedar allergies (who get stuffy noses during allergy season) were given either 50mg Rosmarinic acid, 200mg, or placebo to be taken with breakfast for 21 days.[28] Rosmarinic acid appeared to be effective in suppressing allergies in a dose-dependent manner, with 30% of the placebo group reporting symptom relief compared to 55.6% of the 50mg group and 70% of the 200mg group.[28]
In the human study, there was a significant reduction in immune cells in the nasal mucus by the third day with 200mg (PMNLs down to 84% of baseline, Eosinophils down to 86% of baseline, Neutrophils down to 72% of baseline) but it appeared to normalize, with no significant difference at day 21.[28]
Preliminary evidence suggests that a once-daily dose of Rosmarinic acid may help allergy sufferers
Interactions with Oxidation
Rosmarinic Acid has been shown to exert anti-oxidant effects in vitro against superoxide radicals and hydroxyl radicals.[29]
It can also prevent the oxidation of LDL molecules, and works synergistically in this regard with lycopene.[30]
Interactions with Organ Systems
Liver
10, 25, or 50mg/kg Rosmarinic acid was given orally once daily for two days, each time 6 hours after injection of the hepatoxin CCl4. Rosmarinic acid itself did not alter liver weight (absolute or relative to the body) nor ALT levels, but 50mg/kg after CCl4 normalized 56% of the increase in absolute liver weight (only 26% relative weight changes) while reducing the spike in ALT by 23%.[31] There was a reported reduction in liver necrosis and fibrosis associated with Rosmarinic acid.[31]
Interactions with Cancer Metabolism
Skin
Rosmarininc acid (typically via Perilla Oil) is used topically to combat skin carcinogenesis. This has been shown in rat models[32][33] alongside general topical anti-inflammatory benefits, and appears to also be absorbed via the skin in humans in the form of 'perillyl alcohol'.[34][35]
