| Conyza bonariensis is one of the species belongs to genus Conyza, family Asteraceae. C. bonariensis(L.) is widely used as a folk medicine for treatments of rheumatism, gout, cystitis, nephritis, dysmenorrhea, tooth pain, headache and has anticoagulant activity. In addition, it includes alkaloids, volatile oils, terpenoids, phenolic acids, flavonoids and hydrolysable tannins.The objectives of this research are :(1) Evaluating the antioxidant activity, antimicrobiological activity, total phenols(TP), total flavonoids(TF), total tannins(TT) and total anthocyanin(TA) of some of the aromatic plants grown in Yemen and choose the best plant has antioxidant activity and best the inhibition of bacterial.(2) Identify active compounds using gas chromatography–mass spectrometry(GC – MS) of the essential oils extracted from C. bonariensis.(3) Determination of the optimum conditions for extraction rate, antioxidant activity and TP, of C. bonariensis by the response surface methodology(RSM).(4) Isolation, purification and identification of the flavonoid compounds by different type of macroporous resin, different concentrations of the solvent, column chromatography(silica gel), column chromatography(sephadex LH-20), liquid chromatography–mass spectrometry(LC – MS), 1H NMR and 13 C NMR.(5) Investigation and evaluation of the cytoprotective activity of the pure flavonoid compounds against hydrogen peroxide-induced toxicity in Hep G2 cells.Extracts of C. bonariensis contained TP 144.1 mg/g extract, TF 143 mg/g extract, TT 0.99 mg/g extract, and TA 0.97 mg/100 g extract, with 94.57% inhibition of 2,2-diphenyl-1-picrylhydrazyl(DPPH) and 92.47% inhibition of β-carotene bleaching(BCB), and strong inhibitory effects against Shigella dysenteriae, Escherichia coli, Salmonella typhimurium, Streptococcus pyogenes and Staphylococcus aureus, where the extracts of C. bonariensis was the most effective with the zone of inhibition ranging from14.6 to 19.8 mm at 20 mg/ml.The major component in the essential oil was sesquiterpene accounting for 51.14% of the total oil composition. The principal components were Aromadendrene oxide-(2)(17.38%), Cedren- 13- ol, 8(17.30%), Caryophyllone oxide(7.23%), alpha – Bisabolol(2.32%), Isoaromadendrene epoxide(1.69 %), Globulol(1.49%), Thymol(2.86%), Tetracyclo(6.3.2.0(2.5).0(1.8) tridecan-9-ol,4,4-dimethyl(8.41%),1-Naphthalenol, decahydro-1,4a-dimethyl-7-) 1- methylethylidene-(1R-(1.alpha.,4abeta,8a.Alpha) 7.20%), Butanoic acid, 3,7- dimethyl-2,6- octadianyl ester(5.87%), n- hexadecanoic acid(4.27%), 4-Penten-2- 0l(3.76%), phenol, 4- methoxy- 2,3,6 – trimethyl(3.02 %). The essential oil of C. bonariensis exhibited a strong antioxidant potential displaying at(0.01 mg/ml) 92.12 % DPPH and 1.74(μg/ml) of IC50 compared with extracts of C. bonariensis(74.06 % DPPH and 4.68 μg/ml of IC50). The essential oil of C. bonariensis possessed strong inhibitory effects against tested bacteria.The optimal conditions for extraction of phenolics, including: 1-butyl-3-methylimidazolium bromide [BMIM] Br best the solvent with 45.47 min and 300.60 w power, lead to the best extraction rate(25.94%), maximum DPPH radical scavenging(95.90%) and maximum TP(174.18 mg GAE/g). Under these conditions, the experimental extraction rate was 25.13±0.8 %, DPPH radical scavenging was 93.8±1.67% and TP was 171.5±1.06 mg GAE/g of the C. bonariensis extract, which matched the predicted values.Highest adsorption of phenolic compounds was obtained from C. bonariensis at used macroporous resin D 4020. The results demonstrated different quality of phenolic compounds that have separated because of the different concentrations of the solvent used. Antioxidant activity was the best at a concentration of 30 % or 50% ethanol.The compound 5,7,2’, 5’-tetrahydroxy-3,4’- dimethoxyflavone(TDF) was identified by isolation, purification, analysis and identification of the D4020 macroporous resin column, column chromatography(silica gel), column chromatography(sephadex LH-20), LC- MS, 1H NMR and 13 C NMR. The DPPH radical scavenging assay showed that the compound had a generally high antioxidant activity.The TDF had good antioxidant ability for superoxide radical scavenging activity, reducing power, and protection against oxidative damage induced by hydroxyl radicals. These results demonstrated that TDF has significant protective effects against H2O2-induced cytotoxicity in Hep G2 cells. Therefore, our findings suggest that TDF and has a significant ability to prevent oxidative stress. It may protect cells from oxidative stress by H2O2- mediated disruption of cellular antioxidant systems and inhibited apoptosis in Hep G2 cells through diminishing the malondialdehyde(MDA) generation and ROS level, restoring catalase(CAT), glutathione peroxidase(GPx), glutathione(GSH), total antioxidant capacity(T-AOC) and superoxide dismutase(SOD) activity. |
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