Molecular characteristics and function of elliptical Kiwifruit

2.1 Experimental material

The material used for this study was the entire elliptical Kiwifruit. This elliptical Kiwifruit was produced in Xixia County, Nanyang City, Henan Province. Xixia County is located between longitude 111°48′ E, latitude 33°28′ N. It is rich in fruit resources, it is known as the hometown of kiwi. Kiwi varieties used in this experiment are shown in the following Fig. 1.

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Fig. 1

Experimental Materials.

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2.2 Experimental methods

The elliptical Kiwifruit of this study used sample should clean by deionized water. Then crushed entire fruit flesh together with pericarp. Divided pulp into two parts, respectively added methanol and ethanol as solvents to perform extraction experiments (Ge et al., 2017b). In order to acquire more accurate experimental data, we put the leaching liquor into rotator evaporator to evaporate the water and redundant solvents. Finally, send the sample to do FT-IR and GC–MS detections.

2.2.1

2.2.1 FT-IR analysis

The study uses infrared spectroscopy to analyze the structure and chemical bonds of molecules, and can identify the type of compound by the characteristic wave number of the chemical bond (Ge et al., 2017c). In this study, we used the polished KBr slice as the salt slice of infrared spectrometer. The recorded range of FT-IR spectra was all in 4000 cm⁻¹-400 cm⁻¹ (Sherazi, 2009; Li, 2015) (see Fig. 2).

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Fig. 2

The diagram of experimental process.

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3.1 Analysis of FT-IR

Based on the data obtained from FT-IR analysis, we can make a chart as Fig. 3, and referenced to existing books and other scholars’ research results, we made Table 1. According Fig. 4 we can find that as a whole, the absorption peaks of leaching liquor extracted by methanol (M) was stronger than the absorption peaks of leaching liquor extracted by ethanol (E). The phenomenon was because it extracted more chemical components by methanol solvent. According Table 1 and Fig. 3, we can know that in the range of 3650 cm⁻¹ to 3200 cm⁻¹ wave number, shown a wide and strong absorption peak of O-H stretching vibration. The types of compound that may be in this band was carboxylic acid, alcohol, phenol. In the range of 2975 cm⁻¹ to 2840 cm⁻¹ wave number, shown several absorption peak of C-H stretching vibration. At 1648 cm⁻¹, the absorption peak was C⚌C Stretching vibration. At 1450 cm⁻¹, the absorption peak was benzene ring stretching vibration. At 1420 cm⁻¹, 1412 cm⁻¹ and 1329 cm⁻¹, the absorption peak was C-N stretching vibration. At 1383 cm⁻¹, the absorption peak was C-H flexural vibration. In the range of 1110–1018 cm⁻¹ wave number, shown several absorption peak of C-O stretching vibration. At 881 cm⁻¹, the absorption peak was benzene ring stretching vibration. Some scholars reported that the characteristic absorption peak of cellulose was 2900 cm⁻¹, 1425 cm⁻¹, 1370 cm⁻¹ and 895 cm⁻¹. In our study, we can find absorption peak at 2930 cm⁻¹, 1420 cm⁻¹, 1383 cm⁻¹ and 881 cm⁻¹ in E. We can consider that these were characteristic absorption peak of cellulose and this kind of elliptical Kiwifruit has abundant cellulose (Schwanninger et al., 2004; Szymańska-Chargot et al., 2011) (see Table 2).

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Fig. 3

FT-IR curves of methanol extractives and ethanol extractives.

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Fig. 4

The total ion chromatogram of methanol and ethanol extractives by GC–MS.

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3.2 Analysis of GC–MS

The result was shown that in GC–MS analysis, the leaching liquor of methanol solvent was detected 25 peaks and indentified 18 types chemical components. The main chemical compositions were 5-hydroxymethylfurfural (37.58%; PubChem CID: 237332), 1,2,3,5-cyclohexanetetrol (12.60%; PubChem CID: 548226), quinic acid (12.29%; PubChem CID: 6508), d-alanine, N-propargyloxycarbonyl-, isohexyl ester (6.59%), 4H-Pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl- (6.52%), cyclotetrasiloxane, octamethyl- (6.40%; PubChem CID:121111), furfural (4.07%; PubChem CID: 7362), cis-aconitic anhydride (1.81%; PubChem CID: 65163), cyclobutanecarboxylic acid, nonyl ester (1.76%; PubChem CID: 568107) and ethyl propionylacetate (1.42%; PubChem CID: 78656) and so on (see Table 3).

The result was shown that the leaching liquor of ethanol solvent was detected 29 peaks and indentified 21 types chemical components. The main chemical compositions were 5-hydroxymethylfurfural (42.26%; PubChem CID: 237332), quinic acid (26.17%; PubChem CID: 6508), cyclotetrasiloxane, octamethyl- (7.50%; PubChem CID:121111), 4H-pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl- (6.21%), pyrazole-4-carboxaldehyde, 1-methyl- (4.73%), 3-methoxycarbonylpyrazole (2.99%; PubChem CID: 565662), 2,5-furandione, 3-methyl- (1.75%; PubChem CID: 12012), 1,3-dioxepane, 2-pentadecyl- (1.36%) and 3,5-dimethylpyrazole (1.10%; PubChem CID: 6210).

These organic components can be used at food processing, medical treatment and light industry fields. For example: 5-hydroxymethylfurfural has rich chemical property, and it can potential be acquired from carbohydrates, like inulin, cellulose, sucrose, fructose and glucose. It’s a kind of important chemical intermediate (Rosatella et al., 2011). For a long time, quinic acid has been used as antioxidant, and might have anticarcinogenic properties (Wang et al., 2009b). Cyclotetrasiloxane, octamethyl- (octamethylcyclotetrasiloxane) has been used in industrial applications, personal care consumer products and other industries for more than 40 years. It has thermal stability, chemical stability, UV radiation resistance and low surface tension (Zareba et al., 2002). Furfural is a raw material for preparing many medicine and industrial products. The chemical properties of furfural are active, numerous derivatives can be prepared by condensation reaction and oxidation reaction. And it is widely used in the synthesis of organic products such as resins, pharmaceuticals, varnishes, rubbers, coatings and pesticides. Its derivatives also are potential bio-fuel components worthy attention (Lange et al., 2012). Ethyl propionylacetate can be used in the essences and spices industry with a mild fruity fragrance. It is also used as a solvent for paints, varnishes, nitro spray paints and various resins.

According this study, we learned from books, literature, and experiments that Kiwifruit has rich nutritional, medicinal, and industrial value. In the report of FT-IR, we known that there were O-H stretching vibration, C-H stretching vibration, C⚌C stretching vibration, benzene ring stretching vibration, C-N stretching vibration, C-H flexural vibration, C-O stretching vibration and anomeric carbon vibrational frequency in our sample. The types of compound that may be in this band is cellulose, carboxylic acid, alcohol, phenol, amine and ester. In the report of GC–MS, we known that 25 peaks and indentified 18 types chemical components were detected in M and 29 peaks and indentified 21 types chemical components were detected in E. The main chemical compounds were 5-hydroxymethylfurfural (PubChem CID: 237332), 1,2,3,5-cyclohexanetetrol (PubChem CID: 548226), quinic acid (PubChem CID: 6508), d-alanine, N-propargyloxycarbonyl-, isohexyl ester, 4H-Pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl-, cyclotetrasiloxane, octamethyl- (PubChem CID:121111) and furfural (PubChem CID: 7362). And these organic components can be used at food processing, medical treatment and light industry fields.