Novel Flavonol Alkaloids in Green Tea: Synthesis, Detection, and Anti-Alzheimer's Disease Effect in a Transgenic CL4176 Model.

Novel -ethy-2-pyrrolidinone-substituted flavonols, myricetin alkaloids A-C (-), quercetin alkaloids A-C (, , and ), and kaempferol alkaloids A and B ( and ), were prepared from thermal reaction products of myricetin, quercetin, kaempferol─l-theanine, respectively. We used HPLC-ESI-HRMS/MS to detect - in 14 cultivars of green tea and found that they were all present in "Shuchazao," "Longjing 43", "Fudingdabai", and "Zhongcha 108" green teas. The structures of - and were determined by extensive 1D and 2D NMR spectroscopies. These flavonol alkaloids along with their skeletal flavonols were assessed for anti-Alzheimer's disease effect based on molecular docking, acetylcholinesterase inhibition, and the transgenic CL4176 model. Compound strongly binds to the protein amyloid β (Aβ) through hydrogen bonds (BE: -9.5 kcal/mol, : 114.3 nM). Compound (100 μM) is the strongest one in significantly extending the mean lifespan (13.4 ± 0.5 d, 43.0% promotion), delaying the Aβ-induced paralysis (PT: 40.7 ± 1.9 h, 17.1% promotion), enhancing the locomotion (140.0% promotion at 48 h), and alleviating glutamic acid (Glu)-induced neurotoxicity (153.5% promotion at 48 h) of CL4176 worms ( < 0.0001).