| Neem oil, extracted from the seeds of Azadirachta indica A. juss, has been well known in the Indian, as a traditional medicine product possessing a wide pharmaco-activity, including anti-parasite activity, antimicrobial activity, antipyretic activity, anti-inflammatory activity, immunostimulant activity, antiulcer activity and promotion of wound healing, etc. A single compound possessing the acaricidal and antibacterial activities, extracted and isolated from neem oil, was identified as octadecanoic acid-tetrahydrofuran-3,4-diyl ester on previous research. To further the study on the pharmacological mechanism of octadecanoic acid-tetrahydrofuran-3,4-diyl ester, based on the investigation of synthesizing technology and ingredients, this study focused on the chemical synthesis and antibacterial activity in vitro of octadecanoic acid-tetrahydrofuran-2,3-diyl ester, isomer of octadecanoic acid-tetrahydrofuran-3,4-diyl ester. The main results as follows:1. Select of synthesis of octadecanoic acid-tetrahydrofuran-2,3-diyl esterThe method of synthesizing 2,3-tetrahydrofuran glycol was investigated by comparision of bromine water oxidation and acid oxidation of organic peroxide and then the method of synthesizing octadecanoic acid-tetrahydrofuran-2,3-diyl ester was investigated by by comparision of chloride acolholysis and DCC/DMAP dehydration esterfication. The products were analysed through Infrared spectroscopy(IR) and then the ultimate synthetic route was determined.The product oxidized by bromine water, whose IR spectrum was as follows: 3407.1,1636.2,1457.9,1440.1,1395.0, could not be identified as 2,3-tetrahydrofuran glycol in that the charaterestic peaks of five-ring oxygen and acolhol was not shown. The product oxidized by superroxide fomic acid, whose IR spectrum was as follows: 3399.0,2949.9,2881.2 (vOH),1028.6 (C-O-C),1144.4,1187.0 (vC-OH),1243.5, 1284.4,1317.2,1364.2 (dOH), could be identified as 2,3-tetrahydrofuran glycol in that the charaterestic peaks of five-ring oxygen and acolhol could be observed. The product oxidized by superroxide acetic acid, whose IR spectrum was as follows: 3435.5,2956.4,2884.4 (vOH),1067.3 (C-O-C),1144.1,1185.6 (vC-OH),1242.9, 1341.7,1367.5 (dOH), could be identified as 2,3-tetrahydrofuran glycol in that the charaterestic peaks of five-ring oxygen and acolhol could be observed. Finally, the synthetic route of 2,3-tetrahydrofuran glycol was determined as acid oxidation of organic peroxide.The product synthesized by thionyl chloride, whose IR spectrum was as follows: 2924.3,2853.8,1466.1,1376.9,721.6 (alkyls),1801.2 (-CO-),953.2 (vC-Cl), 680.3 (dC-Cl), could be identified as stearoyl chloride in that the characterstic peaks of methyl, methylene, carbonyl and carbon-halogen could be observed.The products synthesized through stearic acid chloride alcoholysis, whose IR spectrum was as follows:3431.4,2955.6,2917.5,2849.2,729.1,719.7 (alkyls), 1820.3,1812.8 (vs-CO-),1740.2,1716.4 (vas-CO-),1141.7,1134.0 (C-O-C), could be identified as stearic acid anhydride rather than octadecanoic acid-tetrahydrofuran-2,3-diyl ester in that the characteristic peaks of stearic acid anhydride could be observed. The products with ESI-MS ([M]+, at m/z 636), synthesized through DCC/DMAP dehydration esterfication, whose IR spectrum was as follows:3488.7,2955.5,2914.4,2849.3,1471.9,717.1 (alkyls),1734.7,1183.9, 1199.8,1218.1 (-CO-O-),1139.1 (-O-), could be identified as octadecanoic acid-tetrahydrofuran-2,3-diyl ester in that the characteristic peaks of ester could be observed and the molecular weight of the product accorded with that of octadecanoic acid-tetrahydrofuran-2,3-diyl ester.By comparision, the ultimate synthetic route was determined as follows: octadecanoic acid-tetrahydrofuran-2,3-diyl ester was prepared by treating stearic acid with 2,3-tetrahydrofuran glycol, synthesized by acid oxidation of organic peroxide, in the mix of DCC/DMAP.2. Optimization of synthesis of octadecanoic acid-tetrahydrofuran-2,3-diyl ester The single factor method was designed by selecting ratio of formic acid to hydrogen peroxide, synthesizing temperrature and time-duration of superroxide formic aid, oxidizing temperature of 2,3-Dihydrofuran, drapping 2,3-Dihydrofuran rate, Ph and temperature of hydrolysis as factors to discuss the optimal reactive conditions. when the ratio of formic acid to hydrogen peroxide was 17.5:1, and superroxide formic aid was run for 90 min at 25℃, while maitaining drapping 2,3-Dihydrofuran in 45min, the pH in range of 9 and temperature of hydrolysis at 43℃, the yield of 2,3-tetrahydrofuran glycol was about 57%.The single factor method was designed by selecting mol ratio of acetic acid and acetic anbydride to discuss its effect on the yield of 2,3-tetrahydrofuran glycol, and then Four factors three levels orthogonal design is used by selecting the volume of acetic acid (A), volume of hydrogen peroxide (B),volume of sulfuric acid (C) and the remaining time (D) as four main factors to further discuss those effect on the yiled of 2,3-tetrahydrofuran glycol. when the ratio of acetic acid to hydrogen peroxide was 4:1, and superroxide acetic aid was run for 90 min at 25℃and then was remained for 12h, while maitaining drapping 2,3-Dihydrofuran in 45min, the pH in range of 9 and temperature of hydrolysis at 43℃, the yield of 2,3-tetrahydrofuran glycol was about 63.56%.The single factor method was designed by selecting the time-duration and temperature of esterification to discuss those effect on the yield of octadecanoic acid-tetrahydrofuran-2,3-diyl ester. When the reaction was run for 10h at 60℃, the yield of octadecanoic acid-tetrahydrofuran-2,3-diyl ester was 85%.3. Antibacterial activity of 2,3-dihydrofuran,2,3-tetrahydrofuran glycol and octadecanoic acid-tetrahydrofuran-2,3-diyl ester in vitroThe Minimum Inhibitory Concentration(MIC) of 2,3-dihydrofuran, 2,3-tetrahydrofuran glycol and octadecanoic acid-tetrahydrofuran-2,3-diyl ester were measured by double dilution method. The results showed that the MIC of 2,3-dihydrofuran against S.aureus ATCC25923, E. coli 44102 and Salmonella50041 was 12.5mg/ml; the MIC of 2,3-tetrahydrofuran glycol against S.aureusATCC25923, E. coli 44102 and Salmonella50041 were 3.125mg/ml,1.5625mg/ml和1.5625mg/ml respectively; the MIC of octadecanoic acid-tetrahydrofuran-2,3-diyl ester against S.aureusATCC25923, E. coli 44102 and Salmonella50041 were 12.5mg/ml, 12.5mg/ml和6.25mg/ml respectively.2,3-tetrahydrofuran showed better antibacterial activity compared with 2,3-dihydrofuran, and possessed better antibacterial activity against Gram-negative bacteria compared with that against Gram-positive bacteria. The MIC of octadecanoic acid-tetrahydrofuran-2,3-diyl ester against S.aureus ATCC25923,E. coli 44102 was lower than that against Salmonella50041.
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