Chemical composition, in vitro antibacterial and antioxidant potential of Omani Thyme essential oil along with in silico studies of its major constituent

Abstract

Thyme is an evergreen shrub that has been utilized in traditional medicine and culinary packages for centuries because of its aroma and medicinal properties. The medicinal properties of thyme leaves are attributed to its volatile constituents. The study aimed to identify the volatile constituents in the oil extracted from the Thyme sp grown in Oman and to evaluate its in vitro antibacterial and antioxidant activity. Fresh Thyme leaves were collected from Muscat, Sultanate of Oman in the month of September 2018. Thyme oil was isolated from leaves by hydro-distillation. The volatile chemical constituents present in the thyme oil were analyzed by Gas Chromatograph coupled with Mass Spectrometer. The ability of isolated oil to scavenge free radicals was evaluated by an in vitro DPPH assay method while antimicrobial activity was tested against S. aureus and E. coli bacterial strains by disc diffusion method. The bioactivity of the major constituent of the oil was predicted with the help of PASS and CLC-pred software. Molecular docking studies were performed by docking server. GC–MS analysis of thyme oil revealed the presence of 11 components. Carvacrol and γ-terpinene were identified as the major volatile constituents in thyme oil. Thyme oil inhibited 71.57% of DPPH radicals at 40 µg/mL concentration. Thyme oil displayed the better antimicrobial activity than the standard drug ampicillin against both the bacteria. Antiseptic, antiinfective, reductant and antimutagenic bioactivities of carvacrol as predicted by PASS support the in vitro experimental results. CLC-pred showed carvacrol to be active against Metastatic melanoma, Oligodendroglioma and Non small cell lung cancer cell lines. The antioxidant and antimicrobial activity of Omani thyme oil could be due to its high content of carvacrol. Omani thyme oil seems to be a viable alternative source of natural antimicrobial agent(s) and warrants further studies to ascertain its therapeutic spectrum of biological studies.