Studies of the structure-antioxidant activity relationships and antioxidant activity mechanism of iridoid valepotriates and their degradation products

• Published in: PloS one 2017-12, Vol.12 (12), p.e0189198
• Main Authors: Wang, Feifei, Zhang, Yumei, Wu, Shouhai, He, Yi, Dai, Zhong, Ma, Shuangcheng, Liu, Bin
• Format: Article
• Language: English
• Subjects: Antioxidants; Antioxidants (Nutrients); Antioxidants - chemistry; Antioxidants - pharmacology; Apoptosis; Apoptosis - drug effects; Biology and Life Sciences; Cancer; Cell Line, Tumor; Cell Proliferation - drug effects; Chromatography; Chromatography, Liquid; Cytotoxicity; Degradation; Degradation products; Ethylene oxide; Food; Free radicals; Human Umbilical Vein Endothelial Cells; Humans; Hydroxyl groups; Illnesses; Mass Spectrometry; Medicine; Metabolites; Neoplasms - pathology; Nervous system; Neurodegeneration; Nuclei (cytology); Nutrition research; Oxidation; Oxidation resistance; Oxidative stress; Physical Sciences; Physiological aspects; Properties; Reactive oxygen species; Reactive Oxygen Species - metabolism; Research and Analysis Methods; Scientific imaging; Signal transduction; Signaling; Structure-Activity Relationship; Structure-activity relationships (Biochemistry); Studies; Valerian; Valerian - chemistry; Valeriana; γ-Aminobutyric acid
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0189198

Oxidative stress has been associated with diverse diseases, including obesity, cancer and neurodegeneration. In fact, Valeriana jatamansi Jones (valerian) and its extracts possess strong antioxidant activities that extend their application in clinical practice to the treatment of these illnesses, even though the underlying mechanisms are not well understood. Iridoid valepotriate, a characteristic iridoid ester in valerian with poor chemical stability, possesses considerable antioxidant components. The original compounds and their degradation products have been found to exhibit strong antioxidant activities. However, the relationship between their structure and antioxidant effects and the mechanism underlying their oxidation resistance remain unclear. A forced degradation study using three iridoid valepotriates (valtrate, acevaltrate and 1-β acevaltrate) was performed in this work, and the structures of their degradation products were estimated by TLC-MS and LC-MS. Comparison of the antioxidant activities of the iridoid valepotriates before and after forced degradation revealed that degradation reduced the activities of the iridoid valepotriates in free radical scavenging and cytotoxic and cell apoptosis tests. The results suggested that the oxirane nucleus is important for defining the antioxidant profile of iridoid valepotriate. We uncovered possible mechanisms that could explain the antioxidant activities, including the generation of two hydroxyl groups through intramolecular transfer of an H• from an oxirane ring and a reduction in ROS levels through interactions with GABAergic signalling pathways.