Project description:A total of 12 new cycloartane- and lanostane-type triterpenoids including 16-deoxyargentatin A (1), 16-deoxyisoargentatin A (2), 7-oxoisoargentatin A (3), 24-epi-argentatin H (4), 24-O-p-anisoylargentatin C (5), 24-O-trans-cinnamoylargentatin C (6), 16-dehydroargentatin C (7), 16,17(20)-didehydroargentatin C (8), isoargentatin C (9), isoargentatin H (10), 3-epi-quisquagenin (11), and isoquisquagenin (12) together with 10 known triterpenoids (13-22) were isolated from the resin of Parthenium argentatum AZ-2 obtained as a byproduct of Bridgestone guayule rubber production. The structures of new triterpenoids 1-12 and argentatin H (13), which has previously been characterized as its diacetate (23), were elucidated by extensive analysis of their spectroscopic data and chemical conversions, and the known compounds 14-22 were identified by comparison of their spectroscopic data with those reported. Of these, 13, 14, and 18 exhibited weak cytotoxic activity for several cancer cell lines.
Project description:BACKGROUND:Natural rubber is currently produced nearly exclusively from latex of the Para rubber tree, Hevea brasiliensis. The desire to reduce the environmental cost of rubber production, fears of pathogen susceptibility in clonal Hevea plantations, volatility in the price of natural rubber, and increasing labor costs have motivated efforts to diversify the supply of natural rubber by developing alternative rubber crops such as guayule (Parthenium argentatum Gray). In Hevea, latex is produced as an exudate following wounding while in guayule, rubber is deposited within the cortical parenchyma and its production is strongly influenced by environmental conditions. RESULTS:To better understand the enzymology and regulation of guayule rubber biosynthesis and to identify genes with potential uses in the improvement of rubber yields, we conducted de novo transcriptome assembly and differential gene expression analyses of this process in guayule. This analysis supports a role for rubber in the defense against pathogens, identified new enzymes potentially involved in the biosynthesis of rubber as well as transcription factors specifically expressed in rubber-producing tissues. CONCLUSIONS:Data presented here will be useful in the improvement of guayule as an alternative source of natural rubber and in better understanding the biosynthesis of this critical polymer. In particular, some of the candidate transcription factors are likely to control the rubber biosynthesis pathway and are good targets for molecular breeding or engineering of guayule plants with higher and more consistent production of rubber.
