Rosemary, Part 1

A member of the Lamiaceae family, Salvia rosmarinus (rosemary),* an aromatic plant native to the Mediterranean region and now cultivated globally, has been used for centuries in cuisine and medicine, with several well-established biological activities.^1-3 Thought to contribute to preventing hair loss, rosemary oil was also used for hundreds of years in hair rinses in the Mediterranean area.⁴ In traditional Iranian medicine, rosemary essential oil has been topically applied as an analgesic, anti-inflammatory, and anti-acne remedy.⁵ Rosemary is known to absorb UV light well and to impart antibacterial and antifungal activity, as well as help maintain skin homeostasis.³ It is also used and under further study for its anti-inflammatory, antioxidant, anti-infective, and anticancer activity.^2,6-9 The health benefits of rosemary are typically ascribed to its constituent carnosol/carnosic and ursolic acids.⁷ In part 1 of this update on rosemary, the focus will be on chemical constituents, wound healing, anticancer activity, and hair care potential.

Chemical Constituents

The key chemical components of S. rosmarinus include bitter principle, resin, tannic acid, flavonoids, and volatile oils (made up of borneol, bornyl acetate, camphene, cineol, pinene, and camphor).¹⁰ Other important constituents of rosemary oil, in particular, include p-Cymene, linalool, gamma-terpinene, thymol, beta-pinene, alpha-pinene, eucalyptol, and carnosic acid.⁹ Volatile oils of rosemary have been used in various oils and lotions to treat wounds and with the intention of stimulating hair growth.¹⁰

Wound Healing

In a 2022 study in 60 adult male rats, Bulhões and colleagues found that the use of rosemary leaf essential oil-based ointments on skin lesions spurred wound healing, decreased inflammation, and enhanced angiogenesis as well as collagen fiber density.¹¹

Three years earlier, Labib and colleagues studied the wound healing capacity of three chitosan-based topical formulations containing either tea tree essential oil, rosemary essential oil, or a mixture of both oils in an excision wound model in rats.

^{HUIZENG HU/Moment/Getty Images}

The combination preparation was found to be the most effective in fostering various stages of wound healing, with significant increases in wound contraction percentage observed in the combination group compared with either group treated using individual essential oils or the untreated animals.¹²

A 2010 in vivo study by Abu-Al-Basal using BALB/c mice with diabetes revealed that the topical application of rosemary essential oil for three days reduced inflammation, enhanced wound contraction and re-epithelialization, and promoted angiogenesis, granulation tissue regeneration, and collagen deposition.¹³

Anticancer Activity

Using a 7,12-dimethlybenz(a)anthracene (DMBA)-initiated and croton oil-promoted model in 2006, Sancheti and Goyal determined that rosemary extract administered orally at a dose rate of 500 mg/kg body weight/mouse significantly inhibited two-stage skin tumorigenesis in mice.¹⁴ Nearly a decade later, Cattaneo and colleagues determined that a rosemary hydroalcoholic extract displayed antiproliferative effects on the human melanoma A375 cell line.⁸

The polyphenols carnosic acid and rosmarinic acid are most often cited as the sources of the reputed anticancer effects of rosemary.¹⁵

Hair Health

Early in 2023, Begum and colleagues developed a 1% hair lotion including a methanolic extract of the aerial part of S. rosmarinus that they assessed for potential hair growth activity in C57BL/6 mice. Using water as a control and 2% minoxidil hair lotion as standard, the investigators determined that their rosemary hair lotion demonstrated significant hair growth promotion, exceeding that seen in the mice treated with the drug standard.¹

^{Baumann Cosmetic & Research Institute}

Dr. Leslie S. Baumann

In a randomized controlled study in C57BL/6NCrSlc mice a decade earlier, Murata and colleagues evaluated the anti-androgenic activity and hair growth potential imparted by topical rosemary oil compared with finasteride and minoxidil. Rosemary oil leaf extract, with 12-O-methylcarnosic acid as its most active component, robustly suppressed 5alpha-reductase and stimulated hair growth in vivo in both the androgenetic alopecia/testosterone-treated mouse model, as well as the hair growth activating mouse model as compared with minoxidil. Further, the inhibitory activity of rosemary was 82.4% and 94.6% at 200 mcg/mL and 500 mcg/mL, respectively, whereas finasteride demonstrated 81.9% at 250 nM.¹⁶

A human study two years later was even more encouraging. Panahi and colleagues conducted a randomized comparative trial with 100 patients to investigate the effects of rosemary oil as opposed to minoxidil 2% for the treatment of androgenetic alopecia over 6 months. By 6 months, significantly greater hair counts were observed in both groups compared with baseline and 3-month readings, but no significant variations between groups. No differences were found in the frequency of dryness, greasiness, or dandruff at any time point or between groups. Scalp itching was significantly greater at the 3- and 6-month points in both groups, particularly in the minoxidil group at both of those time points. The investigators concluded that rosemary oil compared well with minoxidil as androgenetic alopecia therapy.¹⁷