Evaluation of antioxidant and prooxidant activities of bamboo Phyllostachys nigra var. henonis leaf extract in vitro

Solvent-extracted bamboo leaf extract (BLE) containing chlorogenic acid, ca ffeic acid, and luteolin 7-glucoside was evaluated in vitro for free radica l scavenging and antioxidant activities using a battery of test methods. BL E exhibited a concentration-dependent scavenging activity of DPPH radical. BLE prolonged the lag phase and suppressed the rate of propagation of lipos ome peroxidation initiated by peroxyl radical induced by 2,2'-azobis(2-amid inopropane dihydrochloride (AAPH) at 37 degrees C. BLE also prevented human low-density lipoprotein oxidation, mediated by Cu2+, which was monitored b y the lower formation of conjugated diene and fluorescence and a reduced ne gative charge of apo-B protein. Finally, BLE protected supercoiled DNA stra nd against scission induced by AAPH-mediated peroxyl radical. Prooxidant ac tivity of BLE was seen in a Cu2+-induced peroxidation of structured phospha tidylcholine liposome, indicating catalytic peroxidation due to a relativel y high reducing power of BLE. It was concluded that the BLE has both antiox idant activity and prooxidant activity; the antioxidant activity was attrib uted to free radical scavenging activity, and the prooxidant activity, albe it minor, resulted from the reducing power of plant phenolics in the presen ce of transitional metal ions.