Hydroxycinnamic acid amides from Lycium barbarum and their anti-inflammatory mechanisms
Creators: name: Wang, Siyu
Publisher: name: No Publisher Supplied
Year: 2018

description: Over the past few decades, much research has identified chronic inflammation as a critical component in many human diseases. Due to the intimate relationship between chronic inflammation and human diseases and conditions, an accumulating number of studies aimed to identify and discover anti-inflammatory molecules from natural resources because these molecules are able to interact with inflammatory mediators as well as modulate inflammatory pathways. Hydroxycinnamic acid amides (HCAA) are the secondary metabolites ubiquitously exist in flowering plants, formed by condensation between hydroxycinnamates and mono or polyamines. HCAA species not only serve multiple functions in plant growth and development, but also exert significant positive effects on human health. HCAA family has been recognized as the most characteristic and abundant chemical species of Lycium barbarum. The plant has been recognized as traditional remedies for hyperglycemia and other health conditions. Wolfberry or Goji berry, the fruits of Lycium barbarum, are widely consumed in Asian cuisine due to their health-promoting properties. In the first part of my work, we synthesized a set of HCAA compounds, including trans-caffeic acid, trans-ferulic acid, and 3,4-dihydroxyhydrocinnamic acid, with extended phenolic amine components as standards to identify and quantify the corresponding compounds from different parts of Lycium barbarum. With optimized LC–MS/MS and NMR analysis, nine amide compounds were identified from the fruits, and 10 new HCAA species were further identified in root barks in addition to the ones reported in the literature. HCAA species were reported in leaves for the first time. The quantification showed the amide compounds with a tyramine moiety were the most abundant.Moreover, the method was fully validated with respect to specificity, linearity, intra- and inter-day precision and accuracy, limit of detection (LOD), limit of quantification (LOQ), recovery, and reproducibility. The anti-inflammatory properties of identified HCAAs were also examined by nitric oxide (NO) inhibition assay. Seven HCAA compounds had a potent NO inhibitory effect with IC50 as low as 2.381 μM (trans-N-caffeoyl phenethylamine). Two HCAA compounds (trans-N-caffeoyl tryptamine and trans-N-caffeoyl tyramine) were chosen to investigate their anti-inflammatory molecular mechanisms by both in vitro and in vivo assays. These two HCAAs inhibited NF-κB signaling pathway in murine macrophage RAW264.7, accompanied by inhibition of PI3K/Akt/IKK pathway. In vivo mouse ear edema model indicated that with treatment of the two HCAAs, TPA-induced ear edema was significant reduced by showing as reduction of ear weight and thickness, pro-inflammatory enzyme expression as well as immune cells infiltration.The developed analytical method largely improved analytical sensitivity of HCAAs species that potentially contributes to plant metabolomics and drug discovery studies. HCAAs demonstrated promising anti-inflammatory properties that could be used as preventive agent for inflammation and inflammation-related diseases.