Molecular characteristics of volatile components from willow bark

2.1 Materials and reagents

Willow bark is manufactured by Jiangsu Nantong forging equipment Co., Ltd. After drying under natural conditions, the willow peel was crushed into powder with a fz102 grinder for use in the factory (Tanjingtai Ins). Unless otherwise stated, the AS200 screening instrument (USA) is used for treatment, and all reagents used are purchased from Sigma Chemical (USA).

2.2 Methods

3.1 Analysis of VOC components in extracts of willow bark

The TDS-GC/MS chromatogram of the extract of “Willow bark” VOC in the range of 50 °C–250 °C is shown in Fig. 1. It can be seen that a total of 12 compounds were detected, and the extract had two distinct peaks between 19.585 min and 25.344 min. In 19.585 min in essence is 1,2-Benzenedicarboxylic acid, bis (2-methylpropyl) ester (content 59.04%), referred to as DIBP, chemical formula for c16h22o4, it can be used as a plasticizer for cellulose resin, vinyl resin, nitrile rubber and chlorinated rubber. (Wang, 2008) Plasticity and DBP similar, but the volatile and water pumping than DBP, DBP can be used as a substitute, the goods have toxic effects on crops, not suitable for agricultural PVC film. The goods low toxicity, rat oral LD 50 20–25 g/kg (Sedha et al., 2015). Britain, the Netherlands, the United States to allow the goods used in food packaging materials, the United Kingdom provides in the PVC and vinyl chloride copolymer food packaging products, the maximum amount of the goods should not exceed 40%, DIBP for the main plasticizer one. it can be used as a plasticizer for cellulose resin, vinyl resin, nitrile rubber and chlorinated rubber. The plasticizer is similar to DBP, and has excellent solubility, dispersibility and adhesion. This product and the pigment can be good compatibility, can be used for coloring film, leather and plastic products, this product can also be used as natural rubber and synthetic rubber softener, can improve the resilience of the products can be used to replace the DBP, but did not measure the material at 25.344 min (Sun et al., 2013; Wang, 2008).

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Fig. 1

Shows the extraction of VOC ion chromatograms from willow bark by TDS-GC/MS.

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Among them, including Ethanol, 2- (2-butoxyethoxy) - (content of 0.72%), can be used as diluent, stabilizer, and base inhibitor (Bing et al., 2015); 2,2,4-Trimethyl-1,3-pentanediol diisobutyrate (content of 1.24%), he can also be used as plasticizer (Schwarzbauer et al., 2010); Ethanol, 2- (2-butoxyethoxy) -, acetate (content of 6.28%), for high boiling solvent and latex paint (Harutyunyan et al., 2005); Propanoic acid, 2-methyl-, 3-hydroxy-2,2,4-trimethylpentyl ester (content of 1.98%), mainly used as a coating agent, but also for gold, coal and other flotation agent, but also available For plasticizer (Xian et al., 2006); Benzene, 1,2,3-trimethoxy-5- (2-propenyl) - (content of 4.17%) was measured at 13.636 min and 15.211 min and it was mainly used for anesthesia (Naher et al., 2013); Dimethyl phthalate (content 1.35%), used as a cellulose acetate plasticizer, insect repellent and polyvinyl fluoride paint solvent, it is an intermediate of the rodenticide and is also an important solvent. It also has good film formation and water resistance. Cellulose acetate film, varnish, transparent paper and molding powder can be used in conjunction with diethyl phthalate. The product can also be used as plasticizer nitrile rubber and a small amount in the production of nitrocellulose. Mixed with other plasticizers, it can overcome the shortcomings of volatility and low temperature crystallization. can also be used as a mosquito oil (crude oil) and DDT solvent and gas chromatography fixative, toughening agent, high boiling solvent, plasticizer, gas chromatographic fixation (the maximum temperature of 122 °C, solvent ether), separation and analysis Hydrocarbons and esters (Gooch, 2011); Phthalic acid, hex-3-yl isobutyl ester (content of 1.01%) and 1,2-Benzenedicarboxylic acid, butyl 2-methylpropyl ester (content of 1.13%), but only the chemical formula and chemical structure are now measured, and its functional characteristics are worth We will carry out in-depth study.

3.2 Changes of chemical tissue and residual characteristics of willow bark

Fourier transform infrared spectroscopy (FTIR) is a fast detection technique. It has high sensitivity and is suitable for the identification of chemical bonds and functional groups of various compounds (Li et al., 2017). In this experiment, the changes of the COSC and extracted residues’ chemical groups were shown in Fig. 2, and the overall trend of the absorption peak of COSC and the extracted residues in the range from 4000 cm⁻¹ to 400 cm⁻¹ did not change significantly except the minority, and the absorption peak mainly occurred from 1742 cm⁻¹ to 1058 cm⁻¹. As shown in Fig. 2 in this experiment, the extraction of other residual chemical organic matter, the change of total absorption peak and extracted residue from 4000 cm⁻¹ to 500 cm⁻¹ was not obvious, except for a few range, and the absorption peak mainly appeared between 1740 cm⁻¹ to 1056 cm⁻¹ (Lui et al., 2013).

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Fig. 2

Infrared spectra of VOC extractives from Wllow Bark.

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As can be seen from Fig. 2, it shows a total of 21 absorption peaks. First of all, there is a strong absorption peak at 636 cm⁻¹, for the C—H bond, which is consistent with the results of TDS-GC/MS. However, the structure of aromatic compounds is complex, and a large number of absorption peaks overlap in the range of 900 cm⁻¹, which will affect the determination of chemical structure reliability. In the 1740 cm⁻¹ peak corresponding to the C⚌O bond ester compounds, at the same time there is C-O stretching vibration between 1056 cm⁻¹ and 1250 cm⁻¹ peaks to verify the production of ester compounds at one time; the 1647 cm⁻¹ peak corresponds to the bending vibration of the N—H bond, thereby obtaining an amide compound. 3672 cm⁻¹ and 3344 cm⁻¹ two peaks with O—H-based stretching vibration, alcohol and phenolic compounds produced; 2926 cm⁻¹ and 2860 cm⁻¹ have two peaks with saturated C—H stretching vibration; 1516 cm⁻¹ and 1541 cm⁻¹ peaks proved that the C⚌C stretching vibration of mononuclear aromatic hydrocarbons, so there are aromatic compounds; the peaks at 1454 cm-to 1377 cm⁻¹ demonstrate the bending vibration of —CH₂ and —CH₃; in the 1056 cm⁻¹ peak corresponds to the C—O—C bond asymmetric stretching vibration, the generation of ether compounds; 889 cm⁻¹ peak corresponds to the R₂C⚌CH₂ bond and the 825 cm⁻¹ peak corresponds to the R₂C⚌CHR bond. The C⚌O stretching vibration of the aldehyde compound corresponds to a peak at 2860 cm⁻¹ and the latter two are overlapping peaks. The peak corresponding to the nitrogen-containing heterocyclic compound is 779 cm⁻¹ (Mathi et al., 2016).

In addition, the general strong exponential vibration C≡C is substituted between 2150 cm⁻¹-2100 cm⁻¹, however, it is observed from the known infrared absorption peaks in this range. Thus, it can be said that the instability of certain chemical bonds of VOC and condensation that occur under the high temperature conditions of the C≡C bond should not be included. In addition, the chemical structure of VOCs in gas chromatography/mass spectrometry is consistent with that of IR spectra, further demonstrating that the extracts are ethers, amides, esters, alcohols and the like (Min et al., 2018; Shen et al., 2017)

3.3 Analysis of fluctuation characteristics of willow bark by thermal stability

Willow bark quality changes from 30 °C to 600 °C as show in Fig. 3. The total heat loss is divided into two distinct phases: the first stage of the loss from 50 °C to 100 °C, the temperature at which the mass remains at 3.95 mg is 100 °C, which is due to the loss of a small amount of water and volatile matter released by evaporation. The second phase begins at 150 °C until the quality of 250 °C is reduced to 3.56 mg (10.31%). There is a slight loss of quality that should be further contraction caused by intermolecular. According to the DTG curve, the mass loss rate was observed directly, the order is: the second stage, the first stage, and there is a critical temperature of the turning point in the whole process of the total mass of these temperatures have undergone significant changes. This may lead to significant chemical changes in the compounds. For example, macromolecules break down to form volatile small molecules. Therefore, these data temperature points provide a theoretical basis for total thermogravimetric measurement (Lourençon et al., 2015).

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Fig. 3

heat curve of Wllow Bark.

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3.4 The characterization of the pyrolyzed matter of the residue

As shown in Fig. 4, a total of 50 compounds were detected by the PY-GC/MS method for the total pyrolysis of the total extract at 250 °C. For example, the peak at 4.09 min corresponds to Carbamic acid, monoammonium salt, used as an intermediate for phosphide, and also for pharmaceuticals and aminating agents (Wang et al., 2016); the corresponding peaks at 19.72 min is Phenol, 2-methoxy-(Lee et al., 2014), used in pharmaceuticals, dyes and perfume intermediates, and can also be used for dye synthesis and analysis reagents, As well as in medicine for the manufacture of calcium guaiacosulfonate and perfume industry used to make vanillin and artificial musk, test copper, hydrocyanic acid and nitrite. 8.73 min corresponding to the peak Furfural, mainly used as industrial solvents and the preparation of furfuryl alcohol, furoic acid, tetrahydrofuran, γ-valerolactone, pyrrole, tetrahydropyrrole and so on, can also be used as analytical reagents, organic synthesis of raw materials for tanning leather and so on; another 17.12 min corresponds to the peak 2-Cyclopenten-1-one, 2-hydroxy-3-methyl-9 (Ren et al, 2016), used as a fragrance and sweetness enhancer; 19.17 min corresponding p-Cresol, the central nervous system has a toxic effect, severe death, LD501800 mg/kg (rat, oral). But as a spice can be safely used in food (FDA, § 172.515, 2000), GB 2760--1996 provides for the use of edible spices and fungicides, fungicides, organic synthesis; 25.97 min corresponds to the peak of the compound is Catechol, it is an important chemical intermediate, which can be used in the manufacture of rubber curing agent, electroplating additive, skin preservative and analytical reagent, etc. It is also an intermediate of fungicides, methicillin, insecticides and carbofuran, not only that can also be used as an important pharmaceutical intermediate, used to make berberine and isoproterenol and so on. But there is a kind of extract Glycolaldehyde dimer, accounting for a higher proportion but has not yet found any effect, to be we continue to study.

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Fig. 4

Total ion chromatograms of Wllow Bark by Py-GC–MS.

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Through the PY-GC/MS method, the extract contains organic acids, alcohols, ketones, phenols and esters, etc., through the thermal gradient of the temperature gradient, the application of the extract will be expanded, it should be Its high quality and high efficiency to provide scientific basis.