| Elm is widely distributed in various provinces and regions in the north and southwest of China,and are also planted in the downstream region of Changjiang River.Elm has a larger diameter and is mostly used in the manufacture of wood products such as indoor furniture,floors,doors and windows,and root carvings.The wood,bark,and roots of elm contain unique odorous extracts and pyrolysis products,but their main components,efficacy and release mechanisms are still unclear.In this study,the elm tree was used as the research object,and Fourier transform infrared spectroscopy(FT-IR),Gas chromatography-mass spectrometry(GC-MS),Thermogravimetric pyrolysis with gas chromatography-mass spectrometry(PY-GC-MS),Combined gas chromatography-ion Mobility spectrometry(GC-IMS)were used to analyze the molecular species and composition of volatile compounds and pyrolysis products in the elm wood,bark and root extraction to clarify its antibacterial and antioxidant properties,and to analyze the release characteristics of volatile compounds from elm at high temperature and room temperature,and establish volatilization model of the room temperature.The main research contents are as follows:(1)Composition analysis and properties of elm extractsThe elm wood,bark and root were extracted with ethanol,acetone and benzene,the extracts from different parts of the same solvent had not much differs,indicting the components and types almost similar.the extraction efficiency of ethanol was the highest.According to the functional groups of the extracts,there are mainly alcohols,phenols,alkenes,olefin and ketones.The composition and content of the extracts obtained by different extraction solvents were significantly different.The ethanol,acetone and benzene extracts of elm wood contained 60,80 and 130 kind compounds respectively.As well,there were 71,122 and 142 kind species in bark,and the roots contained 41,98 and 120 species,respectively.The contents of homocoumarins,alkaloids,flavonoids and terpenoids in the extract were higher;the relative contents of terpenes and carbohydrates in the ethanol extract were higher than those in the acetone and benzene extracts.Meanwhile,the content of coumarins in benzene and acetone extracts was higher than that of non-volatile ethanol extracts,while the content of alkaloids in acetone and ethanol extracts was higher than benzene extracts.In addition,through comparison,it was found that the main components in the extract can be used as raw and auxiliary materials of chemical,pharmaceutical,food and cosmetics.Such as the Vendolin(11.70%)with the highest relative content in the ethanol extract of tree roots has the functions of lowering blood sugar,diuretic antibacterial,anti-inflammatory and anti-cancer.Meanwhile,the second content of Cucurbitacin E(10.13%)has various pharmacological effects such as anti-inflammatory,anti-tumor and antioxidant.(2)Analysis and volatilization characteristics of elm pyrolysis products at high temperatureThe release of volatile substances of elm wood during heat treatment was analyzed by TG,and found that elm wood had a large weight loss around 43℃(25℃-75℃).Py-GC-MS analysis identified there were 75,68 and 117 kinds volatile organic compounds in the elm wood,bark and root,respectively.By comparison,it was found that the addition of nano-catalysts Mo and Fe3O4 to the root had little effects on the volatilization characteristics of pyrolysis products,while the addition of nano-catalysts Ag and Fe2O3 to the bark could reduce the chemical composition of oxygen-rich components and increases the hydrocarbon ratio.The volatile organic compounds(VOCS)produced by high temperature treatment in different parts were different,and the main components of the elmwood mainly included alcohols,aldehydes,ketones,acids,esters and carbohydrates,etc.as well bark included aromatic,olefins,aldehydes,furans and pyrrole.The root pyrolysis products mainly contained alcohols,acids,benzenes,alkanes,alkenes,furans,furfurals,amines and pyrroles.Through comparative analysis,it was found that piperol,glycine and other volatile components have antioxidant,bactericidal and anti-inflammatory effects,which will have a positive effect on the indoor air environment.(3)Antibacterial and antioxidant properties of the extracts and pyrolysis productsThe antibacterial activities of different extracts were measured by filter paper AGAR plate diffusion method.It was found that the sensitivity of the extracts to staphylococcus aureus,bacillus cerus,bacillus subtilis,bacillus escherichia coli and salmonella was from high to low.All extracts had significant antibacterial activity against Staphylococcus aureus,but the bacteriostatic effects of extracts from different parts and solvents were different.Among of them,the acetone extract from tree root had the best antibacterial effect,the benzene extract from bark shown the best antibacterial effect,and the benzene extract from elm wood presented the best antibacterial effect on Bacillus cereus.At the same times,most of the extracts also had certain inhibitory effect on Bacillus subtilis.The minimum bactericidal concentration(MBC)of the extracts was determined by double broth dilution method and 96-well plate.It was found that the minimum bactericidal concentration of the extracts from roots to Escherichia coli was 12.5 mg/mL.Simultaneously,the minimum bactericidal concentration of the absolute ethanol extract of elm wood to Staphylococcus aureus was 3.125 mg/mL,well the minimum bactericidal concentration of tree root extract against Salmonella is 25 mg/mL.Meanwhile,the pyrolysis products had good bacteriostatic effect on mixed bacterial communities and E.coli,and the minimum inhibitory concentrations were similar,which were 4.705 mg/mL and 4.805 mg/mL,respectively.In antioxidant analysis,it was found that the extracts had strong scavenging ability on DPPH· and ABTS free radicals.With the increase of the extract concentration,it became stronger and gradually stabilized,which was similar to the Vc of the control group.The scavenging ability of ethanol,acetone and benzene extracts to ABTS radicals increased from high to low,and the reducing ability also had the same trends.Meanwhile,in the comparative analysis of the same solvents,it was found that the antioxidant effects of benzene-root extract,acetone-root extract and ethanol-bark extract were better,among which ethanol-bark extract had the strongest reducing ability.(4)Analysis and volatilization of volatile components from ELM extracts at room temperatureAt room temperature,the total volatile organic compounds(TVOC)content of elm tree increased with the increase of temperature,and decreased with the time prolonging.At room temperature,the volatiles mainly include alkanes,olefins,alcohols,aldehydes,ketones,esters,acids and amines,and are dominated by alkanes,amines and esters,Among them,steroidal 3,5-diene and ethyl acetate have antioxidant,bactericidal and anti-inflammatory effects.With the increase of temperature,the species of volatile organic compounds increased,among which the species of elm wood increased from 25(25℃)to 56(35℃),the species of root increased from 24(25℃)to 54(35℃),but TVOC counts of bark presented the trend of first increased and then decreased.At the same time,with the increase of temperature,the ester compounds in different parts showed a decreasing trend.When the temperature increased from 25℃ to 30℃,the relative contents of alkenes and esters increased significantly,while the acid compounds decreased significantly.For elm wood,the relative contents of olefin and ester gradually increased with the increase of temperature,especially with the temperature increase from 30 ℃ to 35 ℃,while ketones gradually decreased with the increase of temperature.Meanwhile,based on finite difference mathematical method and Fortran language,the volatilization model of elm wet and dry materials in indoor environment was constructed,and its release law at room temperature was explained.By studying the types and effects of volatiles extracted and pyrolyzed from elm,and discovering the release mechanism,it has important scientific value for optimizing indoor air environment and expanding the application of elm trees. |
