Phytochemical and biological activity profiles of Thymbra linearifolia: An exclusively native species of Libyan Green mountains

Abstract

Thymbra linearifolia, a Green Mountain endemic Libyan plant species belonging to the family Lamiaceae, was investigated as the plant's first documented phytochemical and biological evaluation report.The plant is used for bronchitis, cough, asthma, and gastrointestinal ailments, including dyspepsia, colic pain, and diarrhea.The phenolic and flavonoid contents of T. linearifolia were analyzed qualitatively and quantitatively by LC-MS analysis and spectrophotometric assays. These analyses revealed the presence of 60.67 mg/g of GAE (Gallic Acid Equivalents) and 26.79 mg/g of RE (Rutin Equivalents) of the phenolics and flavonoids, respectively, in the aerial parts of the plants’ ethanolic extract. Cyanidin-3-O-rutinoside (2.26 %), pelargonidin-3-O-rutinoside (2.36 %), gallocatechin (2.94 %), taxifolin (1.22 %), kaempferol-3-O-rutinoside (0.81 %), quercetin-3-O-retinosie (1.20 %), luteolin (0.99 %), apigenin (2.0 %), dimethoxy luteolin (2.97 %), and pinobanksin-3-O-acetate (2.56 %) were detected to be the major flavonoids, whereas the syringic acid hexoside (1.38 %), and rosmarinic acid (2.54 %) were among the most abundant phenolic acids in the plant’s extract. The DPPH scavenging activity was measured at an IC50 value of 34.48 μg/mL. In addition,potential reducing, metal chelating, and free radical scavenging potentials were exhibited in the in vitro assays, i.e., ABST, ORAC, FRAP, and MC. The remarkable antioxidant activity of the plant was attributed to its phenolic and flavonoid contents. The plant extract had strong cytotoxic effects on three types of cancer cell lines, i.e., MCF-7, HepG2, and Panc-1, with IC50 values of 24.023, 22.94, and 33.30 μg/mL, respectively. Furthermore, the plant extract also exhibited cytotoxic effects greater than the standard anticancer drug, doxorubicin, against all the tested cell lines. The in-silicobinding studies also demonstrated that the phytochemical constituents of T. linearifolia have a high binding affinity against the epidermal growth factor receptor (EGFR) protein, which supported the anticancer potentials of the plant.The antimicrobial assay conducted with the well-diffusion method revealed the moderate effects of the plant’s extract against Bacillus subtilis, Staphylococcus aureus, Saccharomyces cerevisiae, and Candida albicans. However, weak antimicrobial effects were recorded against the Gram-negative bacteria, Escherichia coli, and Salmonella typhimurium. These findings corroborated the immense health benefits of the plant, and substantiatedthe medicinal value claims of the plant, which is currently under use in different forms as part of the locals’ folk-medicinal chest.