Study On Antibacterial Components And Properties Of Apocynum Venetum Fibers

Apocynum venetum (AV) is a type of wild perennial shrub and named for Luobu Plain in Xinjiang Province, China, of which roots, bark, leaves and flowers have been used as a traditional Chinese medicine for a long time. AV fibers are the bast fibers obtained from AV bast. The AV fibers obtained by degumming methods have excellent mechanical properties. At the same time, the studies also showed that the AV fibers had antibacterial properties. The AV bast is the raw materials for AV fibers. Reports have showed that there are flavonoid compounds in AV flowers. Hence, some reports speculated that there were flavonoids in AV bast and the antibacterial properties of AV fibers may be ascribed to residual flavonoid compounds in AV fibers. The purpose of this research is to disclose the mechanism of antibacterial properties of AV fibers and explore the relationship between the chemical components and antibacterial functions of AV fibers. This research started with the chemical components in AV bark and the antibacterial components in AV bark were isolated by modern isolation techniques and the structures of these compounds were analyzed by various methods. Then, High performance liquid chromatogram (HPLC), Electronic Ionic Mass sepctra (EI-MS) and Gas chromatogram-Mass spectra (GC-MS) were used to isolate and identify the chemical components in AV fibers. The mechanisms of antibacterial properties of the AV fibers were revealed by molecular level.Firstly, the bioactive components were fully extracted by organic solvents. The ethyl acetate fraction and n-BuOH fraction were isolated.11 compounds were isolated and identified as quercetin, kaempferol, isoquercitrin, luteolin, hyperoside,7-hydroxy-6-methoxy -2H-1-benzopyran-2-one, stigmasterol,3,4-dihydroxy-benzoic acid methyl ester,3, 5-dihydroxybenzaldehyde and 3,4-dihydroxy-benzoic acid were firstly isolated from AV bark. The results showed that the flavonoid compounds in AV bast with high content. The antibacterial properties of these compounds were tested. The results demonstrated that quercetin had inhibition effect against all the strains tested. Kaempferol could inhibit the growth of Staphylococcus aureus, Bacillus lentus and Escherichia coli. Isoquercitrin inhibited the growth of Staphylococcus aureus and Bacillus lentus. Hyperoside only have inhibition effect on Bacillus lentus.Then, the flavonoids compound isolated with high content were used as standards to compare with the AV fiber extract. The HPLC results showed that there were no flavonoid compounds in AV fibers. We can preliminarily conclude that the antibacterial properties of AV fibers can not be ascribed to flavonoid compounds. Further, the chemical components were prepared from AV extract ethyl acetate fraction by HPLC and the chemicals were qualitatively dentified by EI-Mass. The results showed that unsaturated fatty acids had highly content in AV fibers, including cis-9-octadecenoic acid, cis-9-hexadecenoic acid, cis-3-octyl-oxiraneoctanoic acid and cis-3-octyl-oxiranedodecanoic acid. It is reported that cis-9-octadecenoic acid and cis-9-hexadecenoic acid had antibacterial properties. The derivatives of AV fiber extract and volatile components in AV fibers were further analyzed by GC-MS. the results preliminary showed that the fatty acids were the main components for the fibers’ antibacterial properties.At last, the antibacterial properties of AV fiber extract and volatile components in AV fibers were tested. The results showed the extracts of the AV fibers has inhibited effect against Gram-positive and Gram-negative bacteria, as well as fungus. The most effective part was ethyl acetate. The ultra structure and morphology of Candida albicans cells which were incubated with the AV extraction were observed by Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM). The findings showed that the organisms of cells and morphologies were all obviously changed. All these further substantiated the antibacterial properties of AV fibers.Based on this research, the guideline can be set to evaluate the antibacterial properties of AV textiles. This research can make a foundation to optimize the degumming process and protect the bioactive chemicals in AV fibers. It is also provide the theory to develop the AV textiles in different areas.