Rosmarinic acid (RA), an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid, is a potent radical scavenger, a chelator of prooxidant ions, and an inhibitor of lipid peroxidation. RA-containing extracts are widely used natural antioxidants in food products, and many herbal preparations and food supplements, containing RA, are marketed with claims of beneficial health effects. The current study investigated the effectiveness of subcritical water extraction (SWE) for the recovery of RA from lemon balm (Melissa officinalis), as a “green” alternative to conventional hydro-alcoholic extraction. Different durations (10 min and 20 min) and extraction temperatures (100 °C and 150 °C) were applied. Subcritical water applied at a temperature of 100 °C was equally efficient as 50% ethanol in extracting RA. However, the further elevation of temperature to 150 °C decreased RA content by up to 20% due to thermal degradation. The content of RA in dried extracts was between 2.36% and 5.55% and the higher temperature of SWE increased extract yield by up to 41%. The higher extraction yield resulted from the degradation of plant material by subcritical water as evidenced by the increased extraction and degradation of proteins, pectin, and cellulose. These results reveal that SWE is an efficient technology for the extraction of RA and other antioxidants from lemon balm at reduced extraction time and without the use of toxic organic solvents. Furthermore, by modification of SWE conditions, dry extracts with different purity and content of RA are obtained. These extracts could be used in the food industry as food antioxidants, or in the development of food supplements and functional foods.

A comprehensive chemical profiling of 1,1,1,2-tetrafluoroethane (freon R134a) subcritical extracts from the main genotypes of oil-bearing roses, was performed by gas chromatography–mass spectrometry (GC/MS) and gas chromatography with flame ionization detection (GC-FID) in order to reveal the differences in their chemical composition. One hundred and three individual compounds were identified using GC/MS and their quantitative content was determined using GC-FID, representing 89.8, 92.5, 89.7 and 93.7% of the total content of Rosa gallica L., Rosa damascena Mill., Rosa alba L. and Rosa centifolia L. extracts, respectively. The compounds found in the extracts are representatives of the following main chemical classes: mono-, sesqui- and triterpenoids, phenylethanoids and phenylpropanoids and aliphatic hydrocarbons. Fatty acids, esters and waxes were found, as well. The study revealed that 2-phenylethanol is the most abundant component, ranging 9.0–60.9% followed by nonadecane and nonadecene with 5.1–18.0% geraniol (2.9–14.4%), heneicosane (3.1–11.8%), tricosane (0.1–8.6%), nerol (1.3–6.1%) and citronellol (1.7–5.3%). The extracts demonstrate a specific chemical profile, depending on the botanical species—phenylethanoids and phenyl propanoids are the main group for R. damascena, aliphatic hydrocarbons for R. alba and R. centifolia, while both are found in almost equal amounts in R. gallica. The terpenoid compounds show relatively broad variations: monoterpenes—11.9–25.5% with maximum in R. centifolia; sesquiterpenes—0.6–7.0% with maximum in R. gallica and triterpenes—0.4–3.7% with maximum in R. gallica extract.

The white oil-bearing Rosa alba L. was subjected to green subcritical water extraction. The two factor modeling process revealed that 150 °C and 30 min treatment resulted in the maximum yield of phytochemicals, including essential oils, phenolic compounds, total carbohydrates, proteins, and simple sugars. A quantitative and qualitative analysis of the products was performed. The essential oil contained mainly phenylethyl alcohol, citronellol, geraniol, and hydrocarbons (paraffins). The phenolic substances were represented by phenolic acids (gallic acid: 30.92–113.37 µg/mL; ferulic acid: 44.50–99.96 µg/mL; rosmarinic acid: 25.27–80.47 µg/mL; protocatechuic acid: 13.05–25.48 µg/mL), as well as flavonoids (both quercetin and kaempferol: 8.35–8.56 µg/mL) and their glycosides (15.91–58.08 µg/mL). The monosaccharides were determined to include glucose (3.09–15.29 mg/mL), galacturonic acid (1.02–2.34 mg/mL), galactose (0.18–0.78 mg/mL), rhamnose (0.17–0.48 mg/mL), and xylose (0.07–0.17 mg/mL). The content of total phenols, flavonoids, and antioxidant activity were reported by the DPPH, ABTS, FRAP, and CUPRAC methods. The complex composition and activity of the extracts suggests their application directly as a food supplement or in cosmetic preparations.

Green subcritical water extraction has been applied with the white oil-bearing rose Rosa alba L. The two factor modeling process revealed that 150 °C and 30 minute treatment resulted maximum yield of phytochemicals: essential oil, phenolic compounds, total sugars, proteins and simple sugars. A quantitative and qualitative analysis of the products was performed. The essential oil contains mainly phenylethyl alcohol, citronellol, geraniol and hydrocarbons (paraffins). The phenolic substances were represented by phenolic acids (gallic acid: 30.92-113.37 µg/mL; ferulic acid: 44.50-99.96 µg/mL; rosmarinic acid: 25.27-80.47 µg/mL and protocatechuic acid: 13.05-25.48 µg/mL), flavonoids (both quercetin and kaempferol: 8.35-8.56 µg/mL and their glycosides: 15.91-58.08 µg/mL). The monosaccharides determined were glucose (3.09-15.29 mg/mL), galacturonic acid (1.02-2.34 mg/mL), galactose (0.18-0.78 mg/mL), rhamnose (0.17-0.48 mg/mL) and xylose (0.07-0.17 mg/mL). The content of total phenols, flavonoids and antioxidant activity were reported by DPPH, ABTS, FRAP and CUPRAC methods. The complex composition and activity of the extracts suggests their application directly as a food supplement or in cosmetic preparations.

The chemical composition of Rosa alba L. aromatic products extracted with liquified 1,1,1,2-tetrafluoroethane (freon R134a) has been evaluated in static and dynamic modes of extraction. The yield varies in the range 0.039–0.048% for the different variants. In order to reveal the chemical composition and aroma profile of the extracts, they were analyzed by means of gas chromatography-mass spectrometry (GC-MS) and gas chromatography with flame ionization detection (GC-FID). As a result of the analysis, more than 80 compounds with concentrations higher than 0.01% were identified and quantified in the extracts, representing 92.7, 88.4, and 88.0% of the total content. The study indicated that 2-phenyl ethanol (12.57–14.97%), geraniol (12.09–14.82%), nerol (5.90–6.39%), benzyl alcohol (3.63–5.34%), and citronellol (3.21–4.04%) were the main components of the aroma-bearing fraction. The solid phase consists mainly of nonadecane+nonadecene (15.21–16.85%), heneicosane (11.81–13.78%), and tricosane (2.46–2.96%). In addition, olfactory evaluation of the extracts was performed. The comprehensive assessment of the quantitative and qualitative characteristics of the extracts indicates that the static, one-stage mode is the most appropriate for the subcritical extraction of R. alba blossoms with freon R134a.