Phytochemical Biological and Cytotoxic Activities of Calothamnus quadrifidus Leaves Cultivated in Egypt

The hydro distilled essential oil obtained from Calothamnus quadrifidus leaves was analyzed by gas liquid chromatography-mass spectroscopy. Quantification of the oil constituents was carried out using the gas liquid chromatography-flame ionization detection device where 1,8-cineole was quantified as 525.62 μg/ml. The oil showed potential antioxidant activity when tested by 1,1-diphenyl-2-picrylhydrazine radical scavenging assay where the concentration required to scavenge 1,1-diphenyl-2-picrylhydrazine by 50 %=37.3 μg. The cytotoxic activity of the essential oil was evaluated using 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide assay compared with 1,8-cineole and doxorubicin. Calothamnus quadrifidus leaves essential oil cytotoxic activity was significant against human lung cell line A-549 (2.37 μg), human colon cell line HCT-116 (2.39 μg), human hepato-cellular cell line HepG-2 (2.55 μg) and intestinal epithelium carcinoma Caco-2 (5.80 μg) cell lines, respectively. The oil cytotoxicity exceeded 1,8-cineole except for intestinal epithelium carcinoma Caco-2. Additionally, the antimicrobial activity was evaluated using agar disc diffusion and minimum inhibitory concentration where the oil exhibited the best activity against Penicillium italicum and Geotrichum candidum with minimum inhibitory concentration=0.49 and 0.98 μg, respectively. Structure elucidation of the pure compounds isolated from Calothamnus quadrifidus leaves was done according to their chromatographic behavior, chemical and spectroscopic data. These compounds were isolated for the first time from Calothamnus quadrifidus leaves and identified as gallic acid, gallic acid methyl ester, 7,4`-dimethoxy-apigenin, 6,7-dimethoxy-apigenin, (Bis[3(2-methyl propan-1- one)-2, 6 dihydroxy-4- methoxy phenyl] methane, quercetin 3-O-beta-D-arbinopyranoside and quercetin 3-O-beta-D-4C1-xylopyranoside. In addition to the molecular docking of novel compound 3 was done in peroxiredoxins and the binding mode was found. Conformation 2 was found to be the most stable and may be responsible for the antioxidant effect as it showed the best free binding energy and affinity when compared to conformations.