Phytotoxicity of umbelliferone and its analogs: Structure-activity relationships and action mechanisms.
Two coumarins, umbelliferone and daphnoretin, were isolated from roots of Stellera chamaejasme L; the former had been identified as one of the main allelochemicals in our previous studies. Both of them have the skeleton of 7-hydroxycoumarin, but showed different phytotoxic effects. Umbelliferone and its analogs were then prepared to investigate the structure-activity relationship of hydroxycoumarins and screened for phytotoxicity. The inhibitory effects varied observably in response to the coumarin derivatives, especially umbelliferone (1), 7-hydroxy-4-methylcoumarin (3) and coumarin (10) displayed strong inhibition of lettuce and two field weeds, Setaria viridis and Amaranthus retroflexus, and compounds 11 and 12 also exhibited phytotoxic activity with species specificity. The number and location of hydroxyl groups were importantly responsible for the phytotoxicity. A C7 hydroxyl group was considered to be a potentially active site and methyl substitution at the C4 position contributed significantly to the activity. The phytotoxic mechanism was briefly studied with umbelliferone by evaluating the reactive oxygen species (ROS) and chlorophylls level in lettuce seedlings. The results showed that umbelliferone induced the accumulation of ROS in the root tip and significantly decreased the chlorophyll content in the leaves. Thus, a ROS-mediated regulation pathway and the inhibition of photosynthesis were definitely involved in the phytotoxicity of umbelliferone.
Key Laboratory of Chemistry of Northwestern Plant Resources of CAS and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Le
L
Pan
Key Laboratory of Chemistry of Northwestern Plant Resources of CAS and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China.
Xiu-Zhuang
XZ
Li
Key Laboratory of Chemistry of Northwestern Plant Resources of CAS and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China.
Zhi-Qiang
ZQ
Yan
Key Laboratory of Chemistry of Northwestern Plant Resources of CAS and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Hong-Ru
HR
Guo
Key Laboratory of Chemistry of Northwestern Plant Resources of CAS and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China. Electronic address: bqin@licp.cas.cn.
Bo
B
Qin
D002734:Chlorophyll / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development; D010944:Plants / Q000187:drug effects* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development; D013329:Structure-Activity Relationship; D014468:Umbelliferones / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity*
D017382:Reactive Oxygen Species; D014468:Umbelliferones; D002734:Chlorophyll
Analogs; Mechanisms; Phytotoxicity; Structure–activity relationships; Umbelliferone