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51.
The leaves of Buxus sempervirens L. contain sitosterol, stigmasterol, cycloartenol, lupeol, germanicol and β-amyrin in the free state. All of these compounds, except stigmasterol, were also found in the esters fraction, as were obtusifoliol, 24-methylenelophenol, and 24-ethylidenelophenol, The triterpene diois betulin and moradiol were isolated, the latter for the first time from a plant source. In nineteen Buxus samples from England, Wales and Scotland, the sterol compositions were quite similar while those of the triterpene monols varied considerably. 相似文献
52.
β-Glucosyl esters of A-ring oxygenated 19α-hydroxyursolic acids were isolated from the leaves of Rubus microphyllus, R. koehneanus, R. trifidus and R. medius. Comparisons of the glycoside fractions of the leaves of 39 Rubus species were conducted, indicating the chemotaxonomic significance of this type of glucosyl ester in this genus. 相似文献
53.
《Bioscience, biotechnology, and biochemistry》2013,77(10):2233-2242
Site-directed mutagenesis experiments on all the conserved residues of Phe and Tyr in all the known squalene-hopene cyclases (SHCs) were carried out to identify the active site residues of thermophilic Alicyclobacillus acidocaldarius SHC. The following functions are proposed on the basis of kinetic data and trapping of the prematurely cyclized products: (1) The Y495 residue probably amplifies the D376 acidity, which is assumed to work as a proton donor for initiating the polycyclization cascade, but its role is moderate. (2) Y609 possibly assists the function of F365, which has previously been assigned to exclusively stabilize the C-8 carbocation intermediate through cation-π interaction. The Y609A mutant produced a partially cyclized bicyclic triterpene. (3) Y612 works to stabilize both the C10 and C8 carbocations, this being verified by the finding that mono- and bicyclic products were formed with the Y612A mutant. (4) F129 was first identified to play a crucial role in catalysis. (5) The three redsidues, Y372, Y474 and Y540, are responsible for reinforcing the protein structure against thermal denaturation, Y474 being located inside QW motif 3. 相似文献
54.
55.
A new lanostane-type triterpene, 6α-hydroxy-dehydrotumulosic acid (1), together with 12 known compounds (2–13), was isolated and characterized from the sclerotium of Poria cocos. Their structures were confirmed by 1D and 2D NMR spectroscopic methods and by comparison with values previously reported in the literature. Compounds 11–13 were reported for the first time from Poria cocos. The chemotaxonomic significance of the isolated compounds was discussed. 相似文献
56.
Wei Wang Guo-Dong Yao Xin-Yue Shang Ying-Ying Zhang Xiao-Yu Song Toshihiko Hayashi 《Free radical research》2019,53(6):655-668
Oxidative stress accompanying excessive accumulation of reactive oxygen species (ROS) and mitochondrial dysfunction leads to the occurrence of neurodegenerative diseases. Our previous study showed that Eclalbasaponin I (EcI), a triterpene saponin isolated from Aralia elata (Miq.) Seem. (A. elata), repressed oxidative stress in human neuroblastoma SH-SY5Y cells. However, the detailed mechanism remains unclear. In this study, pretreatment with EcI in SH-SY5Y cells significantly activated the p38-mitogenactivated protein kinase (p38), the extracellular regulated protein kinase (ERK), whereas it did not affect the c-jun NH2 terminal kinases (JNK). In accordance with the initial findings, EcI-induced neuroprotective effect was attenuated by SB203580 (SB, a p38 inhibitor) or FR180204 (FR, an ERK inhibitor), being further confirmed by specific small interfering RNA (siRNA). Inhibition of either p38 or ERK up-regulated the apoptosis induction in EcI- and H2O2-cotreated cells. Furthermore, p38 or ERK suppression enhanced intracellular and mitochondrial ROS generation, decreased the activities of endogenous antioxidant defences as well as the mitochondrial membrane potential (MMP), resulting in dysfunction of mitochondria. In addition, EcI-induced autophagy and mitophagy were obviously down-regulated when p38 or ERK activation was blocked. Cumulatively, these findings supported that EcI-caused mitophagy contributed to the neuroprotective effect through p38 or ERK activation. Mitophagy induction might be an effective therapeutic intervention in neurodegenerative diseases. 相似文献
57.
Toshio Morikawa Yuanyuan Xie Yasunobu Asao Masaki Okamoto Chihiro Yamashita Osamu Muraoka Hisashi Matsuda Yutana Pongpiriyadacha Dan Yuan Masayuki Yoshikawa 《Phytochemistry》2009,70(9):1166-1172
The methanolic extract from the pericarps of Sapindus rarak DC. was found to show pancreatic lipase inhibitory activity (IC50 = ca. 614 μg/mL). From the extract, oleanane-type triterpene oligoglycosides, rarasaponins I–III (1–3), and raraoside A (4), were isolated together with 13 known saponins and four known sesquiterpene glycosides. Among them, several saponin constituents including rarasaponins I (1, IC50 = 131 μM) and II (2, 172 μM), and raraoside A (4, 151 μM) inhibited pancreatic lipase activity, which were stronger than that of theasaponin E1 (270 μM). 相似文献
58.
59.
Massimo Confalonieri † Maria Cammareri † Elisa Biazzi † Paola Pecchia Manuel Pedro Salema Fevereiro Alma Balestrazzi Aldo Tava Clara Conicella 《Plant biotechnology journal》2009,7(2):172-182
Triterpene saponins are a group of bioactive compounds abundant in the genus Medicago , and have been studied extensively for their biological and pharmacological properties. In this article, we evaluated the effects of the ectopic expression of AsOXA1 cDNA from Aster sedifolius on the production of triterpene saponins in barrel medic ( Medicago truncatula Gaertn.). AsOXA1 cDNA encodes β-amyrin synthase, a key enzyme involved in triterpene saponin biosynthesis. One of the four transgenic lines expressing AsOXA1 accumulated significantly larger amounts of some triterpenic compounds in leaf and root than did control plants. In particular, the leaf exhibited significantly higher levels of bayogenin, medicagenic acid and zanhic acid. The amounts of medicagenic acid and zanhic acid, which represent the core of the M. truncatula leaf saponins, were 1.7 and 2.1 times higher, respectively, than the amounts extracted from the control line. In root, the production of bayogenin, hederagenin, soyasapogenol E and 2β-hydroxyoleanolic acid was increased significantly. The increase in the total amounts of triterpenic compounds observed in the leaves of transgenic lines correlated with the AsOXA1 expression level. Interestingly, the plants expressing AsOXA1 showed, under different growth conditions, improved nodulation when compared with the control line. Nodulation enhancement was also accompanied by a significant change in the soyasapogenol B content. Our results indicate that the ectopic expression of AsOXA1 in barrel medic leads to a greater accumulation of triterpene saponins and enhanced root nodulation. 相似文献
60.
Chenopodium quinoa Willd. is a valuable food source which has gained importance in many countries of the world. The plant contains various bitter-tasting
saponins which present an important antinutritional factor. Various triterpene saponins have been reported in C. quinoa including both monodesmosidic and bidesmosidic triterpene saponins of oleanolic acid, hederagenin, phytolaccagenic acid,
and serjanic acid as the major aglycones and other aglycones as 3β-hydroxy-23-oxo-olean-12-en-28-oic acid, 3β-hydroxy-27-oxo-olean-12-en-28-oic
acid, and 3β, 23α, 30β-trihydroxy-olean-12-en-28-oic acid. A tridesmosidic saponin of hederagenin has also been reported.
Here we review the occurrence, analysis, chemical structures, and biological activity of triterpene saponins of C. quinoa. In particular, the mode of action of the mono- and bidesmosidic triterpene saponins and aglycones are discussed. 相似文献