Chemical Composition and Biological Activity of Aerial Parts of Thymus collinus Bieb. Growing in Georgia

Abstract

Background: Thymus L is one of the most important genera of the Lamiaceae family. In traditional medicine, leaves and flowers of Thymus species are used as a tonic, antiseptic, analgesic, anti-inflammatory, and antitussive. Complex medicines are prepared from Thymus species, such as Neopertussin and Pertussin. Objectives: The research aimed to study essential oil's chemical composition and biological from aerial part of Thymus collinus Bieb. endemic species growing in Georgia. Methods: Thymus collinus aerial parts essential oil were hydro-distilled with a Clevenger-type apparatus. The quantitative content of the dominant compound thymol was determined. In order to develop a rational use of raw material and a resource-saving technology, the study on biologically active, nonvolatile substances in the residual plant material was continued. The aqueous extract was lyophilized, and the dried residual plant material was successfully extracted with chloroform and methanol. The obtained extracts were dried using a rotary evaporator. Essential oil DPPH radical scavenging capacity was evaluated. Also, the antibacterial activity of essential oil was evaluated using five different strains. Essential oil cytotoxic screening was conducted against lung carcinoma A-549, colon carcinoma DLD-1, and human normal fibroblasts WS-1 cell lines. Total phenolic content in aqueous, methanolic, and chloroformic extracts was determined using the Folin-Ciocalteu (FC) reagent. Essential oil, aqueous, methanolic, and chloroformic extracts antioxidant activity was evaluated using ORAC test and tests on human skin fibroblast (WS1). Also, anti-inflammatory activity was evaluated (inhibition of nitric oxide production). Results: In the essential oil from aerial parts of Thymus collinus, endemic to the Caucasus, the major constituents are thymol (42.62 %) and carvacrol (16.51 %). Among the terpene compounds, oxygenated monoterpenes are dominants - 63.23 %. A high content of phenols (53.2 ± 0.9 %) was detected in aqueous extract. Essential oil's scavenging rate of DPPH free radicals was 94.2 % at a concentration of 2.87 mg/ml. The essential oil showed high antioxidant activity in the ORAC and in vitro tests using a cellular model (WS-1). At the same time, essential oil showed high antibacterial activity against 5 (Escherichia coli, Salmonella enterica, Enterococcus faecium, Staphylococcus epidermidis, and Pseudomonas aeruginosa) strains. Thymus collinus essential oil at 80 μg/ml has inhibited NO production by 63 %; no toxicity was revealed even at 160 μg/ml concentration. Thymus collins aqueous extract showed high antioxidant activity in the ORAC test (3.38 ± 0.05 μmol TE/mg); in the case of methanolic extract, slight anti-inflammatory activity was revealed. Essential oil demonstrated moderate general cytotoxicity (85 ± 16 µg/ml) against lung carcinoma (A-549). Conclusions: Thymol is the main component in Thymus collinus essential oil; oxygenated monoterpenes are abundant in essential oil. EO exhibited high antioxidant, anti-inflammatory, and antibacterial activities. Based on the results, Thymus collinus Bieb., an endemic species to Caucasus, may be used as a substitute raw material for officinal species.