Chemical profiling and biological activity assessment of volatile and non-volatile compounds in Rosmarinus officinalis residues

Abstract

Rosmarinus officinalis L. is a Mediterranean medicinal and aromatic plant, widely used in several industries. The present study aimed to characterize the chemical composition of volatile compounds, encompassing essential oils (EO): hydrosol extract (HE): and water residue extract (WRE₁). Additionally, the investigation focused on non-volatile components, including powder phenolic extract (PPE): water residue extract (WRE₂): and solid residue extract (SRE): while also assessing their antioxidant and antibacterial activities. The chemical compositions of volatile components were determined by using a Gas Chromatograph equipped with a Mass Spectrometer (GC/MS): while polyphenol extracts were analyzed using Ultra-High-Performance Liquid Chromatograph equipped with a photodiode array detection Mass Spectrometer (UHPLC-DAD-ESI/MS). The antioxidant activity was determined by 1,1-diphenyl-2-picrylhydrazyl free radical scavenging (DPPH) and ferric reducing antioxidant power (FRAP): while the antibacterial effect was evaluated against four pathogenic bacterial strains using disc diffusion and broth microdilution methods. The GC/MS analysis showed that R. officinalis EO was dominated by 1,8-cineole (47.70%) and α-pinene (15.50%). 1,8-cineole (56.67%) and camphor (26.27%) were found as the predominant constituents of HE, while volatile components of WRE₁ were mainly dominated by camphor (10.11%). The UHPLC-DAD-ESI/MS analysis revealed the existence of a plethora of polyphenolic components. In PPE and SRE, the predominating compounds were carnosic acid and carnosol, respectively. Rosmarinic acid was the main constituent in WRE₂. The results of DPPH free radical scavenging and FRAP activities showed that PPE exhibited strong antioxidant activity, followed by SRE and WRE₂. EO and HE showed moderate antioxidant activity, while volatile components of WRE₁ exhibited the lowest antioxidant effect. Regarding the antibacterial activity, PPE and SRE indicated the highest effect against the pathogenic bacteria, while WRE₁ volatile components had the weakest antibacterial activity. The conducted study showed that material plant left after hydrodistillation of R. officinalis may be used as a new source of bioactive volatile and polyphenolic components with valuable pharmacological activities.

GRAPHICAL ABSTRACT

Keywords:

• Rosmarinus officinalis L
• phenols
• essential oil
• residue by-products
• chemical composition
• antioxidant activity
• antibacterial activity