Chemical Profiling, Antioxidant Activity of Inula viscosa Essential Oil and Extracts: Impact of Syrian Environmental Conditions

Inula viscosa (L.) Aiton is a perennial aromatic shrub with strong odor belonging to the Asteraceae family. It has long been recognized for its broad range of therapeutic effects. Essential oils extracted from this plant have attracted significant scientific interest due to their rich content of volatile compounds, particularly sesquiterpenes and monoterpenes. There remains a significant gap in understanding the essential oil profiles of I. viscosa across different regions. This study investigates the essential oil composition and antioxidant activity of Inula viscosa (L.) Aiton collected from four distinct Syrian regions: Rif’Dimashq, Daraa, Lattakia, and Homs. Essential oils were obtained from the aerial parts via hydrodistillation and analyzed using Gas Chromatography-Mass Spectrometry (GC-MS), while ethanolic extracts were prepared and evaluated for their total phenolic content (TPC), total flavonoid content (TFC), and DPPH free radical scavenging activity using Spectrophotometric methods. Across all samples, a total of 38 volatile compounds were identified, with major constituents including dl-Limonene, Caryophyllene oxide, Phytol, n-Eicosane, Geranyl isohexanoate, and Bisabolol oxide A, with oxygenated sesquiterpenes being the most frequently represented chemical class. Compounds such as Geranyl isohexanoate and Hexahydrofarnesyl acetate appear to be region-specific and previously unreported in I. viscosa literature. Each sample's unique chemical composition suggests distinct therapeutic applications, such as antiinflammatory and anticancer in Rif’Dimashq sample, dermatological and antimicrobial applications from Homs sample, antioxidant and neuroprotective uses from Lattakia sample, and Antimicrobial and analgesic applications from Daraa sample. The Daraa extract exhibited the highest antioxidant activity (RSA% = 71.69%), TPC (94.15±0.38mg GAE/g DE), and TFC (10.21±0.05mg QE/g DE), while the Homs extract had the lowest values. A strong correlation was found between TPC, TFC, and RSA%, highlighting the role of polyphenols and flavonoids in antioxidant efficacy. The results revealed significant regional variation in the composition and abundance of bioactive compounds, underlining the influence of geographical factors on the phytochemical profile and biological potential of I. viscosa. And confirmed that I. viscosa in Syria exhibits rich chemical diversity with promising pharmaceutical and nutraceutical potential.