Studies On The Phytochemicals Of Camellia Nitidissima Chi Flowers And Their Quorum Sensing Inhibiting Based Bioactivities

Camellia nitidissima Chi is a valuable medicinal and edible plant in China,which is called "panda of the plant kingdom".So far,the phytochemicals of C.nitidissima Chi are still unknown,and most of the bioactivity studies about C.nitidissima Chi focused on the extractive.So,the phytochemicals of C.nitidissima Chi flowers and the bioactivities were studied in this thesis,and three chapters are included as follows.Chapter One reviewed the phytochemicals and their bioactivities of C.nitidissima Chi.Next,as one main components in C.nitidissima Chi,the anti-quorum sensing,the inhibition effects on advance glycation end products(AGEs),the anti-inflammatory activity,and the antioxidant activity of natrual polyphenols were also reviewed.Chapter Two studied the phytochemicals of C.nitidissima Chi flowers.Forty-five compounds were isolated and elucidated totally,of which 6 compounds were new and 37 known compounds were isolated for the first time from C.nitidissima Chi flowers.The types of these compounds covered catechins,kaempferol derivatives,quercetin derivatives,lignins,steroid,terpenoid,phenolic acid,and fatty acids.Chapter Three studied the bioactivities of C.nitidissima Chi flowers,which included four parts.Part One investigated the inhibitory effects of the extracts from C.nitidissima Chi flowers on the pyocyanin production,swarming motility,and swimming motility of Pseudomonas aeruginosa PAO1 at sub-minimum inhibitory concentrations.The results showed that the dichloromethane fraction(DF)had a remarkable inhibitory effect on pyocyanin production,and concentration-dependent inhibitory effects on swarming and swimming motility.The half maximal inhibitory concentrations(IC50)were 0.158 ± 0.009,0.139 ± 0.004,and 0.334 ± 0.049 mg/mL for pyocyanin production,swarming motility,and swimming motility,respectively.RT-PCR showed that the DF significantly down-regulated the expressions of lasR and rhlR.In addition,6 polyphenols,identified in the DF,showed inhibitory effects on pyocyanin production,swarming motility,and swimming motility,especially,ellagic acid showed the strongest effects.Part Two investigated the inhibitory effects of C.nitidissima Chi flowers on the AGE formation.The results showed that the ethyl acetate fraction had the highest inhibitory effects on AGE formation.Bovine serum albumin(BSA)-glucose and BSA-methylglyoxal assay showed that the ethyl acetate fraction inhibited AGE formation by 74.49%and 34.33%at 1 mg/mL,respectively.As the main components,four flavonoids compounds showed remarkable inhibitory effects on AGE formation by scavenging methylglyoxal,next two catechin-carbonyl adducts were identified using HPLC-ESI-MS/MS.And the potential structure-activity relationship showed the glycosides could reduce the inhibitory effects.Part Three investigated the anti-inflammatory activity of kaempferol 3-0-(3",6"-(O-trans-p-coumaroyl)-β-D-glucopyranoside,which was isolated from C.nitidissima Chi flowers.The results showed that this compound had inhibitory effects on NO production and pro-inflammatory cytokines(TNF-α,IL-β,IL-6)in LPS-stimulated macrophage RAW 264.7 cells,and inhibited the mRNA expression of iNOS,TNF-α,IL-1β,and IL-6.Then,the results of nuclear magnetic resonance(NMR)-based metabolomics analysis showed that 35 metabolites were identified in LPS-stimulated macrophage RAW 264.7 cells and the compound could regulate cholinergic anti-inflammatory pathway,oxidative stress,energy metabolism,and amino acid metabolism of LPS-stimulated macrophage RAW 264,7 cells.Part Four investigated the antioxidant activity of C.nitidissima Chi flowers.The results showed that the ethyl acetate fraction of C.nitidissima Chi flowers exhibited the strongest antioxidant capacity and highest total phenolic content(TPC)compared with the other fractions.Furthermore,in the ethyl acetate fraction,the 50%effective concentrations(EC50)of ABTS+and DPPH radical scavenging activities were 64.24±1.80 and 78.80± 0.34 μg/mL,respectively,and the ferric reducing antioxidant power(FRAP)was 801.49 ± 2.30 μM FeSO4 at 1000 μg/mL.To exploit the antioxidants in C.nitidissima Chi flowers,21 phenolic compounds in the ethanolic extract fraction were identified by HPLC Triple TOF MS/MS.Next,the antioxidant efftets of 12 isolated and elucidated flavonoids were tested furtherly,and the potential structure-activity relationship among these 12 flavonoids showed that(1)the o-catechol group in the B-ring was primarily responsible for the antioxidant capacity of flavonoids and(2)steric hindrance,produced by glycosides and other groups,could reduce the antioxidant capacity of the flavonoids.