Characterization, Production And Bioactivity Of Active Substances From Usneas

Usnea, belonging to the usnea genera of Ascus lichens Lecanoromycetes families, contains usnic acid and usnic polysaccharide that have bioactivitiy substances.4 usnea, i.e., Usnea longissima (Tibet Autonomous Region and Hei Long-jiang province), U.diffracta (Hei Long-jiang province), U.montis-fuji (Shan Xi province) and U.subfloridanu (Xin Jiang Uygur Autonomous Region) were selected for their characterizations and productions of bioactive compounds. The extraction, purification and partial physiolygical functions of the main components including polysaccharides and usnic acid from these usneas were investigated. The obectives of this study are to characterize the roles of usnic acids and usnic polysaccharides in health food production. The following are main results.1. Usnic acid content and activities1) TLC-UV was proved to be a good method for the determination of usnic acid from usneas due to good recovery as well as standard addition ranging above 94.85% and the relative standard deviation (RSD) less than3.86%. Moreover, the levels of usnic acid in usneas, depending on different producing areas, ranked firstly by Usnea longissima (Hei Long-jiang Province), followed by Usnea longissima (Tibet), U. suhfloridana, U. diffracta and U. monlis-fuji.2) Factors influencing the extraction of usnic acids from usnea included extract temperature, extract time, ethanol concentrations, and ratio of raw material to water (m/m). The optimum operating parameters for yielding usnic acids were 75℃of extract temperature,4.5h of extract time,85%of ethanol concentration, and ratio of raw material to water(m/m) 29.00:2.00. The yield of usnic acids crude extract was 8.05mg/g, with an experimental error less than 5%. Moreover, usnic-acid crude extracts from five usneas had a good ability to scavenge DPPH free radical. The highest DPPH free radical scavenging was produced by U.montis-fuji, followed by Usnea longissima (Tibet), Usnea longissima (Hei Long-jiang province), U.subfloridana, and U.diffracta. The crude extract of usnic acid (ULXCUA) from U.longissima (Tibet) showed antibacterial activity against Escherichia coli, Staphylococcus aureus, Aspergillus niger, Aspergillus flavus and Candida sp.. Usnic acids were suggested to be the major antibacterial compounds. The viability of spoiled bacteria was lower in fresh meat, bean curd and milk treated with ULXCUA, compared to the control. It means that ULXCUA should be a good preservator for extending the shelf-life of food products, especially food with high fat content.3) Five compounds were purified from crude extract of usnic acids in U.snea longissima (Tibet). The structures of these compounds were as follows:Compound-1 C11H14O4, M=210.25; Compound-2 C19H20O7, M=360.36; Compound-3 C18116O7, M=344.32; Compound-4 C8H10O2, M=138.16, Compound-5 C18H32O2, M=280.45.2. Usnic polysaccharides and their bio-activities1) The levels of usnic polysaccharide in usneas, depending on different producing areas, ranked firstly by U.montis-fuji, followed by Usnea longissima (Tibet), U. subfloridana, Usnea longissima (Ilei Long-jiang province), U. diffracfa. Further study showed that factors influencing the extraction of usnic polysaccharides from usnea included extract temperature, extract time, and ratio of raw material to water (m/m). The optimum operating parameters were 80℃of extracting temperature,3h of extracting time, and ratio of raw material to water (m/m) 40.00:1.00. The yield of usnic polysaccharides extracted reached 80.16 mg/g, with an experimental error less than 5%.2) Usnic polysaccharides extracted from usneas had a DPPH free radical scavenging ability. The highest DPPH free radical scavenging was produced by U.montis-fuji. followed by Usnea longissima (Hei Longjiang Province), U.subfloridana. U.diffracted and U. longissima (Tibet). The numbers average of molecular weight for each usnic polysaccharide purified from usneas extract ranged from 5.22×105Da to 8.81×106Da. The weight average of molecular weight for each purified polysaccharide varied between 8.49×105 Da and 1.62×107Da. The molecular weight of usnic polysaccharides purified from U.subfloridna was higher than that from other four usneas. Additionally, the more molecular weight was, the more total antioxidant capacity was. In conclusions, usnic acids and usnic polysaccharides were the major bioactive components in existing in usnea, and their yields, together with their antioxidant and antibacterial activities largely depended on producing areas. The present data favor the long-term utilizations of usneas resources.