| Menthae Herba is the dry aerial part of M.haplocalyx Briq.whose taste is pungent and cool.It has the efficacy of evacuating wind heat,clearing head,promoting pharynx,penetrating rash,dispersing liver and Qi.It is not only a traditional dual-purpose plant for medicine and food,but also a significant spice raw material.M.haplocalyx Briq.contains essential oil,flavonoids,phenolic acids and polysaccharides and so on,among which essential oil is the main functional component.Modern research shows that the essential oil of M.haplocalyx Briq.has expectorant,cholagogic,antibacterial,anti-inflammatory,analgesic,antioxidant and permeability promoting activities.M.haplocalyx Briq.is widely distributed in the world,mainly distributed in temperate areas of the northern hemisphere.In China,it is distributed mainly in the north and south,such as Anhui,Jiangsu,Zhejiang,Hubei and other places,among which Jiangsu is a traditional real estate area.Due to its wide distribution,the broad range of ecological adaptation,and the common phenomenon of human and natural hybridization,as well as the coexistence of sexual reproduction and natural reproduction,there are many morphological and chemical variations in this population.Reports about the intraspecific chemical variation of M.haplocalyx Briq.is relivered,but studies on the correlation between the chemotype and the efficacy of M.haplocalyx Briq.is few.In the early stage of our research group,57 batches of M.haplocalyx Briq.samples from different places were analyzed,and according to the relative percentage of the main components of the essential oil,they were divided into four chemotypes: L-menthol chemotype,pulegone chemotype,carvone chemotype and L-menthone chemotype.In this paper,the dynamic changes of the main components of three different chemotypes of M.haplocalyx Briq.essential oil during different growth stages were studied,the botanical characteristics of different chemotypes were analyzed and the differences of antibacterial and antioxidant activities of four different chemotypes of M.haplocalyx Briq.essential oil was investigated,in order to provide a scientific reference for the variety selection of M.haplocalyx Briq.and further guiding the development and application of M.haplocalyx Briq..The main research contents are as follows:1.Study on the dynamic changes of the essential oil components of different chemotypes of Mentha haplocalyx Briq.during different growth stages Contents of cineole,limonene,Lmenthone,L-menthol,pulegone and menthyl acetate in the essential oils of L-menthol and pulegone chemotype at different growth stages and the contents of limonene and carvone in the essential oils of carvone chemotype were determined by gas chromatography.The results showed that the chemotype of L-menthol mint was stable from May to November,and L-menthol accounted for 35.94%～66.29% of the total essential oil.The content of the other five terpenoids was relatively low,and the relative percentage range was 3.35%～14.01% 、 1.21%～4.59% 、0.03%～0.39%、0.23%～1.31%、1.61%～9.48%,respectively.The chemotype of pulegone mint was also stable from June to November.The chemotype of pulegone mint was stable from June to November,and pulegone accounted for 40.37%～57.28% of the total essential oil.The content of other five terpenoids is relatively low,accounting for 1.68%～12.13% 、 9.54%～22.62% 、0.04%～0.25%、1.25%～4.20%、0.10%～2.31%,respectively.The chemotype of carvone mint remained stable and fragrant from May to November,and carvone accounted for 58.98%～74.74%of the total essential oil,and the relative percentage of limonene was 10.03%～25.38%.The above results showed that the chemotypes of L-menthol,pulegone and carvone chemotype mint remained stable in the harvest period(from July to October).2.Analysis of botanical characters of different chemotypes of Mentha haplocalyx Briq.The botanical traits of a total of twenty batches of M.haplocalyx Briq.samples from four chemotypes were studied,and they were labeled and clustered using "binary traits" and "ordered polymorphic traits",and combined with the results of chemotype classification to explore the correlation between M.haplocalyx Briq.chemotype and botanical traits.The results of cluster analysis showed that twenty batches M.haplocalyx Briq.samples were grouped into five categories,type I consisted of 9 batches of samples(S1,S2,S6,S10,S16,S17,S18 and S19),type II consisted of 5 batches of samples(S3,S5,S8,S9 and S15),type III consisted of 4 batches of samples(S4,S7,S12 and S14),type IV consisted of sample S13 and type V consisted of sample S20.L-menthol chemotype of M.haplocalyx Briq.samples include S1,S2,S6,S7,S10,S11,S16-S18,including types I and III.The common morphological characteristics of this chemotype mint are as follows: the stems and leaves are densely hairy,the stem color is mostly purple,but also blue,the shape of the leaves is mostly lanceolate,the edges of the leaves are mostly uniform serrated,with cool fragrance;carvone chemotype of mint samples include S8,S9,S20,including types II and V,the common features of this chemotype mint are: purple stem colour,dark green leaves,sweet taste,weak cool air;L-menthone mint samples include S12,S13,S15,including types II,III and IV,pulegone mint samples include S3-S5,S14,S19,including types I,II and III,this two chemotype samples are diverse in morphology and similar in appearance and properties.3.The antibacterial activity of different chemotypes of Mentha haplocalyx Briq.essential oils The antimicrobial effects of four chemotypes of M.haplocalyx Briq.on Staphylococcus aureus,Escherichia coli,Salmonella typhimurium,Pseudomonas aeruginosa and Bacillus subtilis were studied by means of paper agar diffusion and double microdilution.The results showed that the four chemotypes of mint essential oil had strong inhibition on S.aureus and E.coli,but weak inhibition on P.aeruginosa.The DIZ of pulegone and L-menthol chemotype were 18.70-22.08 mm and 18.93-22.75 mm,respectively,and the DIZ of carvone and L-menthone chemotype were 13.25-16.75 mm and 13.18-16.27 mm,respectively.The results of MIC and MBC showed that the MIC ranges of pulegone chemotype and L-menthol chemotype essential oils were0.16-1.25 mg/m L and 0.31-1.25 mg/m L,respectively,and MBC ranges were 0.31-1.25 mg/m L and 0.62-1.25 mg/m L,respectively.The MIC range of carvone chemotype and L-menthone chemotype essential oil to five kinds of bacteria was 0.62-2.50 mg/m L and 1.25-2.50 mg/m L,MBC range was 0.62-5.00 mg/m L and 2.50-5.00 mg/m L,respectively,whose effect was relatively weak;the results of MIC and MBC were basically consistent with that of DIZ.The above results showed that the antibacterial activities of the essential oil of L-menthol chemotype and pulegone chemotype were better than those of carvone chemotype and L-menthone chemotype.4.The antioxidant activity of different chemotypes of Mentha haplocalyx Briq.essential oils The DPPH free radical scavenging rate,·OH free radical scavenging rate,total reducing capacity and total antioxidant capacity were used to comprehensively evaluate the in vitro antioxidant effects of four chemotypes mint essential oils.The results show that the DPPH free radical scavenging ability is carvone chemotype > L-menthol chemotype > L-menthone chemotype > pulegone chemotype;·OH radical scavenging ability,total antioxidant and total reducing ability are carvone chemotype > L-menthol chemotype > pulegone chemotype > Lmenthone chemotype.The above research results indicate that the carvone chemotype essential oil possesses the strongest in vitro antioxidant activity. |
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