Phytochemical study, antioxidant and antimicrobial activity of the essential oil and phenolic extracts from thymus algeriensis

Abstract

Algeria, due to its diversified environment, boasts a vast diversity of plant life, including numerous aromatic and medicinal species. This study focused on Thymus algeriensis, a plant widely used in traditional medicine in the M'sila region of north-eastern Algeria. The primary objective was to investigate the phytochemical composition (total phenolic and flavonoid contents by spectrophotometric assays, and essential oil profile analyzed by GC-MS), antioxidant activity (DPPH assay), and anti-bacterial properties of both phenolic extracts and the essential oil of T. algeriensis. The extraction yields of methanolic and aqueous extracts were very close (8.2 and 8.5%, respectively), while the yield of essential oil was 1.88%. The highest phenolic content was found in the methanolic extract (236.18 ?g gallic acid equivalents/mg of extract), whereas the aqueous extract was the richest in flavonoids (17.15 ?g quercetin equivalents/mg of extract). The methanolic extract showed the best scavenging activity against the DPPH radical (IC50= 0.79 mg? mL^{-1} ). The antibacterial activity results showed that only the methanolic extract exhibited inhibition against S. aureus, with an inhibition zone of 11.33 mm at a concentration of 250 mg? mL^{-1} . Among the tested strains, E. coli and S. aureus were highly sensitive to the essential oil, with inhibition zones of 29 and 25.5 mm, respectively. Eighty-four compounds were identified in the essential oil by GC-MS, with ?-pinene (17.29%), camphor (11.65%), endo-borneol (9.45%), eucalyptol (7.61%), ?-pinene (7.14%), camphene (6.35%), and ?-myrcene (4.14%) as the major components. These findings demonstrate that Thymus algeriensis exhibits notable antibacterial and antioxidant activities, likely due to its richness in phenolic compounds and terpenes.