Supercritical Carbon Dioxide Antisolvent Fractionation for the Sustainable Concentration of Lavandula luisieri (Rozeira) Riv.- Mart Antimicrobial and Antioxidant Compounds and Comparison with Its Conventional Extracts

Abstract

Lavandula stoechas subsp. luisieri is a Spanish subspecies from the Lamiaceae family. Its essential oil has been traditionally used for several medical applications though little is known about other extracts. Similar to many other studies aiming to obtain traditional plant extracts to be used in different applications, this work evaluated the antioxidant and antimicrobial activities of Lavandula luisieri extracts and the correlation with their composition. Traditional hydrodistillation and ethanolic maceration were used to obtain the essential oil and the maceration extract, respectively. A green and sustainable methodology was applied to the maceration extract that was under a Supercritical Antisolvent Fractionation process to obtain a fine solid enriched in rosmarinic acid and the terpenes oleanolic and ursolic acids. Antimicrobial activities of all extracts and pure identified compounds (rosmarinic and ursolic acids) were evaluated against five bacterial strains; Listeria monocytogenes, Enterococcus faecium, Staphylococcus aureus, Salmonella Typhimurium and Escherichia coli and were compared with the pure compounds identified, rosmarinic and ursolic acids. All strains were sensitive against L. luisieri essential oil. The solid product obtained from the supercritical process was concentrated in the identified actives compared to the maceration extract, which resulted in higher antimicrobial and DPPH scavenging activities. The supercritical sustainable process provided L. luisieri compounds, with retention of their antimicrobial and antioxidant activities, in a powder exemptof organic solvents with potential application in the clinical, food or cosmetic fields.

Keywords: SAF; antimicrobial activity; antioxidant activity; oleanolic acid; rosmarinic acid; ursolic acid.

Figure 1

Scheme of the SAF plant. Feed solution reservoir (FS); liquid pump (P-LIQ); CO₂ reservoir (R), cooling bath (CB); CO₂ pump (P-SCF); heat exchanger (HE); precipitation vessel (PV); Thermopar (T); automated back pressure regulator (ABPR); back pressure regulator (BPR); downstream vessel (DV).

Figure 2

Overlayed chromatograms at 330 nm (0–6 min) and 210 nm (6–10 min) of pure rosmarinic acid (red, retention time 1.622 min), pure oleanolic and ursolic acids (black, retention times 7.781 min and 8.133 min) and the ethanolic extract of L. luisieri (blue).

Figure 3

Logarithmic curve representation of the antioxidant activity of Lavandula luisieri ethanolic maceration extract (ME) and its SAF fractions: precipitation vessel fraction (PV) and downstream vessel fraction (DV). Positive controls 6-hdroxy-2,5,7,8-tetramethylchromane- 2-carboxylic acid (Trolox) and rosmarinic acid (RA).