Abstract:

Change of antioxidant capacity of the organic-free-radical scavengers to 1.1-diphenyl-2-picrylhydrazyl (DPPH·) reagent in the leaf extracts of the seedlings and young trees of four woody species (Schima superba Gardn. et Champ., Castanopsis fissa (Champ. ex Benth.) Rehd. et Wils., Psychotria rubra (Lour.) Poir., Ardisia quinquegona Bl.) in exposureto different light intensities was investigated. The organic free radical scavenging capacity (ORSC) expressed as the percentage of decreasing DPPH· was 16%-59% (pot seedlings) or 48%-88% (young trees in the forest). The highest ORSC was observed in plants grown under natural light, and the ORSC reduced with the decreasing light intensity. Similar trend was observed through the assay of inhibition to linoleic acid oxidation. The ORSC of P. rufra, an understory shrub, was more sensitive to the change of light intensity. A linear relationship was found between ORSC and AsA (ascorbic acid) content (r=0.92) or the absorption around the wavelength of 204-227 nm. It is proposed that ORSC of leaf was regulated by incident light intensity, and the contents of AsA and, flavonoid phenolics might be the important components contributed to ORSC and total antioxidant activity of leaves. The increasing ORSC is likely to be a protective strategy of plant in response to strong light.

光对4 种木本植物叶片清除有机自由基能力的影响
彭长连 林植芳 林桂珠
（中国科学院华南植物研究所，广州510650）

摘要：生长在不同光强下的 4种木本植物荷树 (Schimasuperba Gardn .etChamp .)、黧蒴 (Castanopsisfissa (Champ .exBenth .)Rehd .etWils.) (乔木 )和九节 (Psychotriarubra (Lour.)Poir.)、罗伞 (ArdisiaquinquegonaBl.) (林下灌木 )幼苗(盆栽 )或幼树 (自然林下 )叶片的 5 0 %乙醇提取液具有明显的清除有机自由基二苯基苦基苯肼 (1,1-diphenyl-2-picrylhydrazyl,DPPH·)的能力。清除率在 16 %～ 5 9% (盆栽苗 )和 48%～ 88% (林下幼树 )之间 ,自然光下生长的植物对DPPH·有机自由基的清除能力 (organicfreeradicalscavengingcapacity ,ORSC)最强 ,降低光强减弱叶片的ORSC。林下灌木九节的ORSC对光强变化有较高的敏感性。几种植物的ORSC及其随光强的变化与叶片的抗坏血酸 (AsA)含量和叶提取液在 2 0 4～ 2 2 7nm紫外区的吸光值皆呈线性相关。结果认为 ,光调节叶片的ORSC ,AsA和黄酮类、酚类化合物是贡献于ORSC总抗氧化活性的重要组分 ,提高ORSC是植物响应于强光的保护策略。

关键词： 有机自由基清除能力；光；有机自由基二苯基苦基苯肼；木本植物

Key words: organic free radical scavenging capacity, light, DPPH·(1.1-diphenyl-2-picrylhydrazy), woody plants