Activity-guided supercritical CO2 isolation of antioxidative constituents from Eucommia ulmoides
Increasing evidence exhibited that antioxidants played very important role in protecting against various diseases like cancer, atherosclerosis, diabetes, cataracts, neurodegenerative disorders . Eucommia ulmoides Oliv., the sole species in Eucommia genus and Eucommiaceae family, is a large medicinal hardwood native to China and widely cultured in Eastern Asia and has widely been used as a tonic to strengthen the kidney and liver, against diabetics, strong bones, ache knees, treat lower back pain, prevent fatigue and miscarriage [2, 3]. In present study, crude extracts of E. ulmoides wood were initially obtained by supercritical CO2 isolation. And DPPH free radical scavenging assay, a standard in vitro model, was employed for the activity-guided purification to identify the antioxidative constituents of E. ulmoides. The crude extracts were suspended in water, and then successively partitioned to a serious of polar solvents to yield fractions soluble in n-hexane, dichloromethane, ethyl acetate, n-buthanol and water. Ethyl acetate fraction exhibited most significant capacity to scavenge DPPH radical, and thus was further subjected to repeated sephadex LH-20 open column to separate the individual antioxidative compounds. Guided by DPPH assay, the fraction having superior activity was identified as containing five major yellow amorphous compounds, including gallic acid, ellagic acid, caffeic acid, (+)-catechin and kaempferol and were obtained. The structures of the isolated antioxidants were mainly elucidated and established by spectroscopic analysis, such as NMR and MS, as well as cellulose TLC. To the best of our knowledge, this was the first time of phytochemical investigation of E. ulmoides wood.
Acknowledgement: This work was financially supported by Program for New Century Excellent Talents in University (NCET 2010), Foundation for the Development of Science and Technology in Tianjin Universities (No. 20080616), National Natural Science Foundation of China (NSFC, No. 31000279) and Natural Science Foundation of Tianjin City (No. 09JCYBJC15800).
References: 1. Si CL et al. (2009) Planta Med 75: 1165–1167.
2. Chang H., Yan SZ (1979) Flora Republicae Popularis Sinicae. Science Press. Beijing.
3. Takamura C et al. (2007)J Nat Pro. 70: 1312–1316.