General Description

The natural compound rosmarinic acid (RA; (R)-(+)-rosmarinic acid) is a common ester derived from caffeic acid and (R)-(+)-3-(3,4-dihydroxyphenyl)lactic acid that can accumulate in high amounts in many plant species.

Plant sources

Rosmarinic acid (RA) is a compound found in various plants. Originally isolated and named after rosemary (Rosmarinus officinalis, Lamiaceae), RA is also found in numerous other plants classified in the subfamily Nepetoideae, family Lamiaceae, such as sage, mint, thyme, lemon balm, basil, oregano, and others [1]. The presence of RA is not reserved solely for Lamiaceae, as it can be found in other plants, primarily in the representatives of the Boraginaceae family but also in many others (e.g., Apiaceae, Araliaceae, Cucurbitaceae, Rubiaceae, Plantaginaceae, Polygonaceae, as well as in some hornworts, ferns and sea grasses). The compound represents a phenolic secondary biomolecule, an ester of caffeic acid and (R)-(+)-3-(3,4-dihydroxyphenyl)lactic acid originating from amino acids L-phenylalanine and L-tyrosine, respectively.

Clinical studies with isolated rosmarinic acid

RA was clinically investigated in atopical dermatitis due to its in vitro and in vivo anti-inflammatory effects, such as its ability to block complement fixation, inhibit lipoxygenase and cyclooxygenase activity, and suppress IKK-β downstream signalling in the TNF-α-induced upregulation of CCL11[2].

Oil-in-water cream with or without rosmarinic acid (0.3%) was applied to the elbow flexures of 21 subjects (14 women and seven men; 15.1 ± 3.1 years) twice daily for 4 and 8 weeks. The subjects were clinically graded as having moderate atopic dermatitis, according to the guidelines of the SCORAD index. The authors reported that RA cream caused no reactions in the patch test on the patient, suggesting that RA can safely be applied to human skin. After treatment with RA, the authors observed a statistically significant reduction in the SCORAD score, a decrease in itching, and a decrease in TEWL, suggesting that RA is a possible atopical dermatitis-mitigating agent. Likewise, considering that RA is a strong anti-inflammatory agent in several animal models, a 21-day randomized controlled trial was undertaken to determine whether oral RA supplementation [200 mg (n = 10) or 50 mg (n = 9)] is an effective intervention for patients with seasonal allergic rhinoconjuctivitis. The patients recorded their symptoms daily in a diary card, and profiles of infiltrating cells, concentrations of eotaxin, IL-1β, IL-8, and histamine in nasal lavage fluid and serum IgE concentrations were measured. The authors found that RA supplementation resulted in a significant increase in responder rates for itchy nose, watery eyes, itchy eyes, and overall symptoms (p < 0.05). Additionally, the treatment significantly decreased the numbers of neutrophils and eosinophils in nasal lavage fluid, compared to placebo supplementation. Patients reported no adverse events, and no significant abnormalities were detected in routine blood tests.

Reference

[1] Maja Hitl. “Rosmarinic Acid-Human Pharmacokinetics and Health Benefits.” Planta medica 87 4 (2021): 273–282.

[2] Solomon K S Amoah. “Rosmarinic Acid–Pharmaceutical and Clinical Aspects.” Planta medica 82 1 (2016): 388–406.