Objectives:
 Hydrosols, also known as herbal water, floral water, and hydrolate, are aqueous products co-produced during the steam distillation of various plant materials. Hydrosol obtained from the flowers of Rosa damascena (rose water) has pleasant scent and is one of the most popular of these products. It has been traditionally used as skin or mucous conditioners with beneficial activity against troubles such as erythema, itchiness and swelling. One of the causes of these skin or mucous troubles is microbial infection. Among them, superficial candidiasis is a widespread fungal infection, mainly caused by Candida albicans. The treatment for infectious conditions usually focuses on antimicrobial effects. However, inflammatory symptoms accompanying infection are serious under clinical conditions and therefore suppression of inflammation is also very important. Although there are anecdotal evidences regarding the efficacy of rose water, there have been few experimental studies to examine its activities. Here, we investigated its effects on the growth of Candida albicans and the function of neutrophils which play a major role in the regulation of inflammatory reactions.

Methods:
Candida cells (C. albicans, TIMM1768) were incubated with diluted rose water for 16 h at 37°C in a 5% CO2 incubator. The mycelial growth of C. albicans was evaluated by measuring the OD620 of adherent mycelial cells to plastic plates. To assess modulatory activity of rose water on neutrophils, its effects against neutrophil adhesion response were examined. Human peripheral blood neutrophils obtained from healthy volunteers were incubated with stimulants and rose water for 1hr at 37°C in a 5% CO2 incubator. Neutrophil adhesion to the plates was evaluated by measuring the OD620. The study was performed in accordance with the Declaration of Helsinki and was approved by the ethics committee of Teikyo University Review Board. All volunteers gave informed consent to participating in the study.

Results:
Rose water inhibited mycelial growth of C. albicans at a concentration of ca. 2.2%, and inhibited yeast growth at 50%. Rose water suppressed neutrophil activation induced by bacterial lipopolysaccharide (LPS), tumor necrosis factor alpha (TNF-α), N-formyl-Met-Leu-Phe (fMLP) at 5% – 15%. It also reduced the LPS- and TNF-α-induced cell surface expression of the adhesion-related molecule, cluster of differentiation (CD) 11b, but did not affect the migratory capacity of neutrophils with or without chemoattractant.

Conclusion:
These results suggest that rose water may reduce the pathogenicity of candida by inhibiting mycelial growth, and attenuate neutrophil stimulation, which is involved in inflammatory responses. These findings suggest that rose water has a potential effect to inhibit skin and mucous inflammation caused by candida infection. We are also evaluating anti-microbial effect against other microbes.

Hydrosol prepared from Rosa damascena is a candidate for therapeutic agents against superficial candidiasis