Glucosides from the roots of Capparis tenera

Two new lignan glucosides, compounds 2 and 3, two new 1H-indole-alkaloid glucosides, 5 and 6, as well as two new phenolic glucosides, 7 and 10, were isolated from the roots of Capparis tenera, together with five known compounds. Their structures were characterized by chemical and spectroscopic methods. Most of these isolates were obtained for the first time from Capparidaceae. The antioxidant and anti-inflammatory activities of the new compounds were investigated.     

Tetralones and flavonoids from Pyrola calliantha

Two new tetralones, pyrolones A (1) and B (2), and a new flavonol glycoside, 2'-O-(4-hydroxybenzoyl)hyperin (3), were isolated from Pyrola calliantha (whole plant), together with six structurally related compounds, including 2'-O-galloylhyperin (4), hyperin (5), formononetin (6), quercetin 3-O-alpha-L-arabinopyranoside (7), quercetin 3-O-alpha-L-arabinofuranoside (8), and kaempferol 3-O-beta-D-galactopyranoside (9). The structures and absolute configurations of the new compounds were elucidated on the basis of spectroscopic (UV, ORD, CD, NMR) and mass-spectrometric (HR-ESI-MS) analyses.     

Identification of triterpene biosynthetic genes from Momordica charantia using RNA-seq analysis

Cucurbitaceae plants contain characteristic triterpenoids. Momordica charantia, known as a bitter melon, contains cucurbitacins and multiflorane type triterpenes, which confer bitter tasting and exhibit pharmacological activities. Their carbon skeletons are biosynthesized from 2,3-oxidosqualene by responsible oxidosqualene cyclase (OSC). In order to identify OSCs in M. charantia, RNA-seq analysis was carried out from ten different tissues. The functional analysis of the resulting four OSC genes revealed that they were cucurbitadienol synthase (McCBS), isomultiflorenol synthase (McIMS), β-amyrin synthase (McBAS) and cycloartenol synthase (McCAS), respectively. Their distinct expression patterns based on RPKM values and quantitative RT-PCR suggested how the characteristic triterpenoids were biosynthesized in each tissue. Although cucurbitacins were finally accumulated in fruits, McCBS showed highest expression in leaves indicating that the early step of cucurbitacins biosynthesis takes place in leaves, but not in fruits.

Abbreviations: OSC: oxidosqualene cyclase; RPKM: reads perkilobase of exon per million mapped reads     

毛蕊花糖苷的生物合成研究进展

毛蕊花糖苷是由咖啡酸、羟基酪醇、葡萄糖和鼠李糖组成的苯乙醇苷类衍生物,广泛存在于多种天然药用植物中,具有抗炎、抗菌、抗病毒、抗肿瘤、抗氧化、镇痛、神经保护、改善性功能、免疫调节和改善细胞记忆等多方面的生物活性.然而,植物提取来源的毛蕊花糖苷存在含量低、环境污染问题,无法实现绿色可持续的规模化生产.利用合成生物学成功构建...     

Steroidal saponins from the aerial parts of Tribulus pentandrus Forssk

Seven new steroidal glycosides named pentandrosides A(1)-G(7) were isolated from the EtOH extract of the aerial parts of Tribulus pentandrus. Pentandrosides A(1)-E(5) possess cholestane aglycones, pentandroside F(6) a furostan-type aglycone and pentandroside G(7) an unusual acyloxypregnane aglycone probably derived from the degradation of a furostan skeleton. Structure elucidation of 1-7 was accomplished through the extensive use of 1D- and 2D NMR experiments including 1H-1H (DQF-COSY, 1D-TOCSY) and 1H-13C (HSQC, HMBC) spectroscopy along with ESIMS and HRESIMS.     

The structure of bovine lysosomal alpha-mannosidase suggests a novel mechanism for low-pH activation

Lysosomal alpha-mannosidase (LAM: EC 3.2.1.24) belongs to the sequence-based glycoside hydrolase family 38 (GH38). Two other mammalian GH38 members, Golgi alpha-mannosidase II (GIIAM) and cytosolic alpha-mannosidase, are expressed in all tissues. In humans, cattle, cat and guinea pig, lack of lysosomal alpha-mannosidase activity causes the autosomal recessive disease alpha-mannosidosis. Here, we describe the three-dimensional structure of bovine lysosomal alpha-mannosidase (bLAM) at 2.7A resolution and confirm the solution state dimer by electron microscopy. We present the first structure of a mammalian GH38 enzyme that offers indications for the signal areas for mannose phosphorylation, suggests a previously undetected mechanism of low-pH activation and provides a template for further biochemical studies of the family 38 glycoside hydrolases as well as lysosomal transport. Furthermore, it provides a basis for understanding the human form of alpha-mannosidosis at the atomic level. The atomic coordinates and structure factors have been deposited in the Protein Data Bank (accession codes 1o7d and r1o7dsf).     

Rebaudioside F, a diterpene glycoside from Stevia rebaudiana

The sweet diterpenoid glycoside, rebaudioside F, was isolated from leaves of a high rebaudioside C producing line of Stevia rebaudiana, and its structure was established by chemical and spectral studies.     

Scaphopetalone and scaphopetalumate,a lignan and a triterpene ester from Scaphopetalum thonneri

From the methanol extract of the stem bark of Scaphopetalum thonneri, two new compounds, including one lignan, named scaphopetalone, one new ester of ferulic acid, named scaphopetalumate were isolated together with three known compounds including: two coumarins (scopoletin and scopolin), and one pentacyclic triterpene (oleanolic acid). The structure of the new compounds were elucidated by means of spectroscopic analyses.     

Cyanogenic Eucalyptus nobilis is polymorphic for both prunasin and specific beta-glucosidases

Cyanogenesis (i.e. the evolution of HCN from damaged plant tissue) requires the presence of two biochemical pathways, one controlling synthesis of the cyanogenic glycoside and the other controlling the production of a specific degradative beta-glucosidase. The sole cyanogenic glycoside in Eucalyptus nobilis was identified as prunasin (D-mandelonitrile beta-D-glucoside) using HPLC and GC-MS. Seedlings from three populations of E. nobilis were grown under controlled conditions and 38% were found to be acyanogenic, a proportion far greater than reported for any other cyanogenic eucalypt. A detailed study of the acyanogenic progeny from a single open-pollinated parent found that 23% lacked a cyanogenic beta-glucosidase, 32% lacked prunasin and 9% lacked both. Of the remaining seedlings initially identified as acyanogenics, 27% contained either trace amounts of beta-glucosidase or prunasin, while 9% contained trace amounts of both. Results support the hypothesis that the two components necessary for cyanogenesis are inherited independently. Trace amounts are likely to result from the presence of non-specific beta-glucosidases or the glycosylation of the cyanohydrin intermediate by non-specific UDP glycosyl transferases.     

Sesquiterpene lactone glucosides and alkyl glycosides from the fruit of cumin

From the polar portion of the methanolic extract of cumin (fruit of Cuminum cyminum L.), two sesquiterpenoid glucosides, cuminoside A and B, and two alkyl glycosides were isolated together with five known compounds. Their structures were established as (1S,5S,6S,10S)-10-hydroxyguaia-3,7(11)-dien-12,6-olide beta-D-glucopyranoside, (1R,5R,6S,7S,9S,10R,11R)-1,9-dihydroxyeudesm-3-en-12,6-olide 9-O-beta-D-glucopyranoside, methyl beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside and ethane-1,2-diol 1-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside, respectively.