Characteristic Components Of Five Special Monofloral Honeys From Northwest China And The Gastroprotective Effect Against Ethanol-induced Gastric Injury

Monofloral honey,the sweet substance formed from the complete conversion of nectar that collected predominantly from one single botanical origin,usually own the unique flavor and bioactive characteristics due to chemical compositions of botanical origin,leading to more preference and profit.The characteristic flavor and bioactive properties of special monofloral honey are the points of honey research.Unfortunately,monofloral honey has been a target of adulteration through substituting or mixing with other cheap honey.The botanical origin adulteration has developed as a serious handicap to honey industry,mainly attributed to its widespread influence and difficulty to identify.The present study aimed at identifying the botanical markers of five novel monofloral honeys from Northwest China,including Apocynum venetum L.honey（AVH）,Elaeagnus angustifolia L.honey（EAH）,Lavandula angustifolia Mill.honey（LAH）,Ziziphus jujuba Mill.honey（ZJH）and Amorpha fruticose L.honey（AFH）,according to the physicochemical parameters,volatile components and phenolic composition.Furthermore,the gastroprotective effects of AFH and EAH on ethanol-induced gastric injury were also estimated.This research will increase the current scarce knowledge about the identification and bioactivities of the five monofloral honeys mentioned above leading to further investigations with regard to authentication and health-benefit values of monofloral honeys in Northwest China.There are six parts of this research and the main contribution are as follow.1.Physicochemical parameters and nutritional composition were analyzed to characterize AVH,EAH,LAH,ZJH and AFH.The results showed that all physicochemical parameters of five monofloral honeys are in the line with the criterion order prescribed in Chinese National Food Safety Standards and Codex Alimentarius Commission.Nevertheless,all the monofloral honey samples were correctly classified according to their botanical origin based on chemometrics,mainly principal component analysis and orthogonal projections.The results of chemometrics analyses also discriminated some characteristic parameters that showed the strong influence on the discrimination of botanical origin,including the total acidity（25.85-37.94 meq/kg）and Mg content（20.108-79.018 mg/kg）of AVH,the K content（706.391-848.680 mg/kg）of EAH,the Na content（19.305-42.672 mg/kg）of LAH,the values of p H（6.24-7.25）and free acidity（5.21-11.98 meq/kg）of ZJH,as well as the values of F/G（1.35-1.70）,lactonic acidity（3.17-4.50meq/kg）and fructose content（39.94-49.79 g/100g）of AFH.2.The aim of this part was to investigate the volatile fraction and discriminate AVH,EAH,LAH,ZJH and AFH according to botanical origin,using HS-SPME-GC-TQ-MS in combination with chemometric.One hundred and thirteen volatile compounds belonging to different classes,such as ketones,alcohols,aldehydes,esters,hydrocarbons,etc,were identified and semi-quantified,and some of them could regarded as the specific volatile compounds corresponding to honey botanical origin,for example,the menthol,dihydrooxophorone and1,1,6-trimethyl-1,2-dihydronaphthalene of AVH,the 2-nonanone,styrene and 3-methyl-pentanoic acid of EAH,the hexanal,hexanol,heptanal and heptanol of LAH,the 2-octenal,2-ethylhexanol,anisaldehyde and methyl salicylate of ZJH,as well as the theaspirane,caryophyllene,pinene and 1-octen-3-ol of AFH.Furthermore,on the basis of the odour active values and odour contribute rate analyses,twenty-seven volatile compounds were revealed as odour-active compounds among whichβ-damascenone,nonanal,linalool,decanal and phenylacetaldehyde should be considered as the common major odour-active compositions for the sweet,floral and honey-like odour in five special monofloral honey.1,1,6-trimethyl-1,2-dihydronaphthalene,3-methyl-pentanoic acid,anisaldehyde and 1-octen-3-ol should be accountable for the wood-like flavor of AVH,herbal-like flavor of EAH,spicy flavor of ZJH and mushroom flavor of AFH,respectively.The green and grass odour in LAH could be attributed to the presence of the hexanol and heptanal.3.HPLC-DAD/Q-TOF-MS was applied for identification of a total of forty-six phenolic compounds in AVH,EAH,LAH,ZJH and AFH.Hyperoside could be considered as potential specific phenolic marker compounds in AVH.Formononetin and chrysoeriol were identified as the promising markers for AFH.Gallocatechin,catechin and isorhamnetin in EAH were related to the botanical origin and could be regarded as the specific phenolic compounds.Ferulic acid could be a potential characteristic phenolic compound of ZJH.In terms of LAH,protocatechuic acid and rosmarinic acid were the major phenolic compounds,and accountable for more than30%of the total phenolic content.4.Chemical experiment and cell model were applied for the estimation on antioxidant activities of monofloral honeys in vitro.AFH demonstrated high levels of DPPH radical scavenging activity(IC₅₀ 80.94-132.81 mg/m L),ferric reducing antioxidant power（1.38-2.52μmol Fe SO₄·7H₂O/g）and ferrous ion-chelating activity（65.51-111.47 mg Na₂EDTA/kg）,as well as the dose-dependent preventive effects on p BR322 plasmid DNA and mouse lymphocyte DNA damage in response to oxidative stress.Furthermore,to estimate the gastroprotective effect of the monofloral honey against ethanol-induced acute gastric ulcer,the rats pretreated with high antioxidant active AFH via oral gavage were administered by ethanol once to form the gastric ulcer injury.The results revealed that AFH protected the integrity of gastric mucosa,and alleviated the degradation of SOD and GSH as well as the accumulation of MDA,caused by the ethanol,significantly.Compared with gastric ulcer control group,the rats in AFH treated groups showed significant higher contents of PGE2 and NO,as well as significant effect on the downregulation of inflammatory response mediated by NF-κB pathway.5.The gastroprotective effect of EAH was evaluated against chronic gastric injury induced by ethanol abuse in mice.The gastroprotective effect and potential mechanism was estimated based on the observation of gastric lesions,measures of biochemical indexes of oxidant stress,expression of inflammatory cytokine and microbial community of the intestinal contents of mice.The result revealed that EAH could significantly alleviate gastric injury,as was indicated by the depressed levels of MDA,upregulations of SOD,GSH,NO and PGE2,and the decreased gene expression of inflammatory cytokines TNF-α,i NOS,IL-6,IL-1βand COX-2accompanied by downregulation on the expression of COX-2 protein,relative to the ethanol model group.Furthermore,treatment with EAH altered the gut microbial community structure of mice with gastritis,showing that,at the phylum level,the abundances of Bacteroidetes and Verrucomicrobia were significantly reduced and the abundance of Firmicutes was markedly increased.EAH could inhibit the over-colonization of Christensenellaceae at the family level,induced by ethanol abuse.Given above,EAH could exert the gastroprotective effect against the chronic ethanol-induced gastric injury,via protecting the gastric mucosa,improving gastric inflammation and oxidative stress resistance,as well as modulating gut microbiota.