In vitro anti-oxidative effects of extracts from various parts of Panax notoginseng. A: Vitamin C at various concentrations (0, 17.6, 35.2, 52.8 and 88 μg/ml) was pre-incubated with xanthine oxidase before the addition of the xanthine substrate. The xanthine oxidase activity was measured at 550 nm absorbance. B: Extracts (0.1 mg/ml) from the biennial flower, stem-leaf, rhizome and fiber root of Panax notoginseng were assayed for their anti-xanthine oxidase activity as in [A]. Vitamin C (35.2 μg/ml) served as positive control. Data were expressed as% of inhibition where all the values were normalized by the control (no drug treatment), Mean ± SD, n = 6. Statistical significance is indicated as ** P = 0.00876 for biennial flower vs stem-leaf; and *** P = 0.000586 for biennial flower vs root-rhizome.