Do Abiotic Stresses Affect the Aroma of Damask Roses?

Pharmaceutical Potential Evaluation of Damask Rose By-Products from Volatile Oil Extraction

Despite its well-known fragrance in cosmetics and medicine, a complete understanding of the phytochemical properties within by-products generated during commercial extraction of Damask rose remains elusive. Cultivated in Thailand for their essential oil, Damask rose varieties, including Mon Dang Prasert, Mon Klai Kangwon, and Bishop's Castle, share phenylethyl alcohol (57.62-61.11%) as the dominant component, which is responsible for their characteristic floral, sweet, rosy, and bready aroma. Through a circular hydro-distillation process, three different by-product fractions, including distilled water (D), hydrosol (H), and rose dreg (R), were recovered. Subsequently, we assessed their pharmaceutical potential, including the antioxidant, antimicrobial, anti-inflammatory, and anti-melanogenesis properties of these residual substances. The H fraction displayed the highest total phenolics (10.56 mgGAE/g) and flavonoids (6.93 mgCE/g) and significant antioxidant activity (IC50, 0.67-0.97 µg/mL). While the H fraction inhibited melanin formation at 50 μg/mL, the R fraction of MK (100 μg/mL) surprisingly promoted melanin production in B16-F10 cells. Nevertheless, the antimicrobial assay against Staphylococcus aureus, Cutibacterium acnes, Staphylococcus epidermidis, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans revealed no antimicrobial activity in any fraction. Murine macrophage stimulation (J774A.1) with lipopolysaccharide revealed no anti-inflammatory effects from the by-products, as measured by IL-1β production. In summary, the H fraction exhibited the highest level of phenolic and flavonoid contents, as well as antioxidant and anti-melanogenesis activities. Therefore, this by-product is a desirable choice for the development of value-added products such as functional food, cosmetics, and pharmaceutical products.

Physiological and Biochemical Analysis Revealing the Key Factors Influencing 2-Phenylethanol and Benzyl Alcohol Production in Crabapple Flowers

Floral scent (FS) plays a crucial role in the ecological functions and industrial applications of plants. However, the physiological and metabolic mechanisms underlying FS formation remain inadequately explored. Our investigation focused on elucidating the differential formation mechanisms of 2-phenylethanol (2-PE) and benzyl alcohol (BA) by examining seven related enzyme concentrations and the content of soluble sugar, soluble proteins, carbon (C) and nitrogen (N), as well as the C/N ratio. The findings revealed that the peak content of 2-PE in M. 'Praire Rose' and BA in M. 'Lollipop' occurred during the end flowering stage (S4) and flowering stage (S3) periods, respectively. The enzyme concentration change trends of phenylpyruvate decarboxylase (PDL), phenylacetaldehyde reductase (PAR), soluble protein, C, N, and C/N ratio changes during the S3-S4 period in M. 'Praire Rose' and M. 'Lollipop' were entirely opposite. Correlation and PCA analysis demonstrated that the content of CYP79D73 (a P450) and N, and the C/N ratio were key factors in 2-PE production in M. 'Praire Rose'. The production of BA in M. 'Lollipop' was more influenced by the content of phenylacetaldehyde synthase (PAAS), CYP79D73, and soluble sugar. As CYP79D73 exits oppositely in correlation to 2-PE (M. 'Praire Rose') and BA (M. 'Lollipop'), it is hypothesized that CYP79D73 was postulated as the primary factor contributing to the observed differences of 2-PE (M. 'Praire Rose') and BA (M. 'Lollipop') formation. These results carry significant implications for crabapple aromatic flower breeding and the essential oil industry etc.