Antioxidants: flavonoids from Eucommia ulmoides leaves
Extraction, purification and evaluation in vitro and in vivo
The flavonoids from Eucommia ulmoides leaves were extracted with an ultrasonic cell disrupter with an extraction yield of 2.04%. The XDA-8 macroporous adsorption resin was used to purify the crude extract, resulting in a 47.9% increase in the flavonoids content in the purified extract. The antioxidant activities of the flavonoids were evaluated by measuring 2,2-diphenyl-1-picrylhdrazyl (DPPH), hydroxyl, and superoxide radical scavenger activities in vitro and by measuring superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) activities and serum MDA levels of malondialdehyde (MDA) in mice. The results showed that DPPH radical scavenging increased from 15.6% to 97.6% at different concentrations (0.030–0.300 mg/mL) of the purified flavonoids, while the DPPH activity of the crude extract flavonoids sample increased from 18.5% to 95.2% at different concentrations (0.10–1.00 mg/mL). The activities of GSH-PX and SOD were reduced from 498.4 U/L and 186.4 U/mL to 448.5 U/L and 168.2 U/mL, respectively, when the crude extract sample was purified, whereas the level of MDA in the serum increased from 13.6 nmol/mL to 15.2 nmol/mL. The oxidant capacity appeared to be dependent on the flavonoid content because the in vivo antioxidant activities decreased when the flavonoids of the crude extract were purified, and this effect is probably due to the loss of active components. The results indicated that the flavonoids of crude extraction and the flavonoids purified by resin from Eucommia ulmoides leaves have significant antioxidant activities in vitro and in vivo and can potentially be used as sources of antioxidants.
Eucommia ulmoides, also known as Du-zhong, is a deciduous tree and a special plant in China (1). Eucommia ulmoides has been studied as a treatment or preventive agent for a number of diseases, including diabetes (2-4), hypertension (5, 6), osteoporosis (7), and hepatopathy (8). Research has shown that the bark and leaves of Eucommia ulmoides have similar components and pharmacological functions (9, 10). Thus, Eucommia ulmoides leaves have been used instead of bark as the raw material for functional food.
Oxidative stress is involved in many human disease conditions such as cancer, ageing, and neurodegenerative disease. Moreover, the innate defence in the human body may not be sufficient to combat severe oxidative stress (11). BHA and BHT are widely used synthetic antioxidants that exhibit marked antioxidant activity, but there are toxicity concerns surrounding these compounds, and their use has been restricted recently (12, 13). Therefore, there is a need for research and development of safer, natural antioxidants that can maintain an adequate level of antioxidants and b ...