Abstract: Seasonal variations of total flavonoids(TF)and total lactones(TL)in bamboo leaves of Phyllostachys nigra(Lodd.ex.Lindl.)Munro(as example of Phyllostachys genus),and their anti-free radical activity were investigated using spectrophotometric and chemiluminescent analyses,respectively.Results showed that TF,on dry basis of leaves,varied in a range of 0.67%- 1.71% throughout a year,kept at a much higher level from November through next April.During the same period,TL varied between 0.44%- 1.02%.The IC 50 of dry leaves on O₂^·- and ^·OH were 2.94-33.05 μg/mL and 3.47-8.78 mg/mL, respectively.The scavenging activity on O₂^·- was the strongest in February and the weakest in June,and generally much stronger from November through early May.However,the scavenging activity on ^·OH was rather stable throughout the year.Optimum time for leaf picking is the period from November through next March.

Key words: bamboo leaf, Phyllostachys nigra, total flavonoids, total lactones