Chemical composition and antioxidant, antibacterial and cytotoxic properties of essential oil from Teucrium polium L. from Riyadh province

Abstract

This study was carried out to extract essential oil from the aerial parts of Teucrium polium L. (TPO) using hydro-distillation, and to determine the chemical composition of the extract with GC-MS analysis. The plant was obtained from Huraymila City in the North-Western Riyadh. Total contents of phenolics (TPC) and flavonoids (TFC) were estimated as gallic acid (GA) equivalent and catechin (CH) equivalent, respectively, whereas the antioxidant activity was measured with DPPH assay. Agar disc diffusion and micro-broth dilution methods were utilized for antibacterial evaluation, while MTT assay was used for cytotoxicity evaluation. The average yield of TPO was 0.26±0.01%(v: w), and the predominant constituents were τ-cadinol (25.58%), α-fenchene (20.09%), β-eudesmol (11.76%), β-myrcene (8.02%), γ-cadinene (5.22%), α-phellandrene (3.11%), epi-bicyclosesquiphellandrene (3.07%), and caryophyllene oxide (2.48%), all of which accounted for 79.33% of the identified compounds. The TPC and TFC of TPO were 138.33±3.1 µg GA equivalents mL−1 and 19±2.15 µg CH equivalents mL−1, respectively. The oil had good radical-scavenging activity, with IC50 of 61.38± 4.33 µg mL−1. It exhibited antibacterial activity against Gram-positive S. aureus and MRSA at 16.67 % (v/v), with inhibition zones of 13± 0.09 and 11± 0.13 mm, respectively, and MIC: MBC values of 0.26/0.52 and 0.5/21.04, respectively. However, it had no effect on the growth of negative strains (S. sonnei, P. aeruginosa, K. pneumoniae and E. coli). Results of anti-proliferative effects of TPO on two human colon cancer cell lines (HT-29 and HCT116) and hepatic cancer HepG2 cells, showed that it had a more cytotoxic effect on HT-29 and HCT116 cells, with IC50 values of 0.07± 0.03 and 0.14±0.06, respectively than on HepG2 which was markedly inhibited only at higher concentrations (p< 0.001). In conclusion, TPO exerted antimicrobial and antiproliferative properties. Overall, these findings are considered useful addition to biodiversity data and may be useful in food biotechnology and pharmaceutical industries. Keywords: Herbal Medicine; Gas Chromatography-Mass Spectrometry; Teurium Polium L.; Antibacterial Activity; Anticancer Activity; Essential Oil.