Abstract

This study aimed to determine the chemical composition of methanolic extracts of thirteen Eucalyptus species leaves cultivated in north east of Tunisia and their antioxidant activity was also investigated. Some of them were investigated for the first time. The total phenol and total condensed tannin contents varied significantly among species, E. lehmannii had the highest values. Significant difference was also found in total flavonoid contents and the highest one was observed in E. astringens. The HPLC analysis indicated that the main phenolic compounds were the flavonoid rutin in some species such as E. maidenii and acid gallic acid in other species as E. lehmanii. Different assays were used to evaluate the antioxidant activities; Total antioxidant activity test, DPPH radical scavenging, ABTS scavenging activity, reducing power, and β-carotene-linoleic acid bleaching. All these tests showed a high influence of the interspecific variation. However, all species exhibited interesting antioxidant activities, and DPPH radical scavenging was the most remarkable one whose all extracts were more active than the positive control. E. erythrocorys has the strongest activity with IC₅₀ = 5.07 ± 0.54 µg/mL. All results confirmed that the secondary metabolites of these studied species could be used as a source of natural antioxidants.

摘要

本研究旨在确定突尼斯东北部种植的13种桉树叶片的甲醇提取物的化学成分，并研究其抗氧化活性。其中一些是第一次被调查。各物种中总酚和总缩合单宁含量差异显着，雷曼氏大肠杆菌的值最高。总黄酮含量也有显着差异，涩肠杆菌中黄酮含量最高。HPLC分析表明，主要酚类化合物是某些物种（如mai.ii. maidenii）中的类黄酮芦丁，而其他物种（如lehmanii）中的酸没食子酸。使用不同的分析方法评估抗氧化剂的活性。总抗氧化剂活性测试，DPPH自由基清除，ABTS清除活性，还原能力和β-胡萝卜素-亚油酸漂白。所有这些测试显示出种间变异的高度影响。但是，所有物种均表现出令人感兴趣的抗氧化活性，最明显的是清除DPPH自由基，其所有提取物均比阳性对照更具活性。E. erythrocorys具有最强的活性，IC ₅₀ = 5.07±0.54 µg / mL。所有结果证实，这些研究物种的次生代谢产物可以用作天然抗氧化剂的来源。