engleski

Supercritical CO2 and deep eutectic solvents for sequential extraction of Lavandula stoechas L. and attainment of antioxidant and antibacterial agents

The aim of this work was to investigate the possibility of sequential extraction and a more efficient use of Lavandula stoechas L. material, by extracting non-polar and polar fractions using green solvents, supercritical CO2 and natural deep eutectic solvents (NADES). In the first step, supercritical CO2 extraction (pressure 200 bar, temperature 40°C, CO2 flow 20 g/min, and extraction time 3 h) was performed for the extraction of lipophilic components. Moreover, the exhausted material was used in the next step for the extraction of polar compounds using NADES (betaine:ethylene glycol (Bet:EG) (1:3), betaine:glycerol (Bet:Gly) (1:2), and glycerol:glucose (Gly:Glu) (4:1)) and ultrasound- assisted extraction (temperatures 30 and 60°C, extraction time 30 min). The control extracts were obtained from material that was not used in the CO2 extraction (non-residue). All extracts were examined in terms of polyphenol composition using high-performance liquid and gas chromatography and their antibacterial and antioxidant potentials were also investigated. In the volatile profile of the supercritical extract, 59 components were identified. Oxygenated terpenes were predominantly present with 72.50%, among which monoterpenes made up 55.69% with fenchone and verbenone being the most dominant. The presence of different classes of components - flavonoids, hydrolysable tannins, derivatives of hydroxycinnamic and hydroxybenzoic acids, and coumarins was identified in NADES extracts. Observing the total sum of identified components, the highest phenolic content was recorded in the extract obtained with Bet:EG (664.19 µg/mL ; 60°C), while the second highest phenolic content was in the extract obtained from non-residue material at 30°C (555.43 µg/mL). A strong correlation was observed between the content of total identified polyphenols and the antioxidant activity determined by the DPPH assay, therefore, the most potent extracts were Bet:EG. All NADES extracts exhibited a higher antibacterial activity against Gram-positive bacteria (minimal inhibitory concentrations (MIC) 0.781 mgmL-1) compared to the Gram-negative (1.563 mgmL-1). NADES extracts obtained at 60°C exhibited stronger antibacterial activity than those obtained at 30°C. Supercritical extract showed weaker activity than NADES extracts, with MIC 3.39 mgmL-1 against E. coli, B. subtilis, and S. aureus, and the most resistant being P. aeruginosa with MIC 6.775 mgmL-1. It was established that sequential extraction represents a good approach for a more efficient use of materials and obtaining L. stoechas extracts that can serve as antioxidant and antibacterial agents.

supercritical CO2 extraction ; natural deep eutectic solvents ; polyphenol composition ; antibacterial properties ; antioxidant potentials

nije evidentirano