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

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 alpha-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}