Functional characterization of a cycloartenol synthase and four glycosyltransferases in the biosynthesis of cycloastragenol-type astragalosides from Astragalus membranaceus

Astragalosides are the main active constituents of traditional Chinese medicine Huang-Qi, of which cycloastragenol-type glycosides are the most typical and major bioactive compounds. This kind of compounds exhibit various biological functions including cardiovascular protective, neuroprotective, etc. Owing to the limitations of natural sources and the difficulties encountered in chemical synthesis, re-engineering of biosynthetic machinery will offer an alternative and promising approach to producing astragalosides. However, the biosynthetic pathway for astragalosides remains elusive due to their complex structures and numerous reaction types and steps. Herein, guided by transcriptome and phylogenetic analyses, a cycloartenol synthase and four glycosyltransferases catalyzing the committed steps in the biosynthesis of such bioactive astragalosides were functionally characterized from Astragalus membranaceus. AmCAS1, the first reported cycloartenol synthase from Astragalus genus, is capable of catalyzing the formation of cycloartenol; AmUGT15, AmUGT14, AmUGT13, and AmUGT7 are four glycosyltransferases biochemically characterized to catalyze 3-O-xylosylation, 3-O-glucosylation, 25-O-glucosylation/O-xylosylation and 2'-O-glucosylation of cycloastragenol glycosides, respectively. These findings not only clarified the crucial enzymes for the biosynthesis and the molecular basis for the structural diversity of astragalosides in Astragalus plants, also paved the way for further completely deciphering the biosynthetic pathway and constructing an artificial pathway for their efficient production.

Effects of cycloastragenol on carbon tetrachloride-induced hepatic fibrosis and glycolysis in mice / 中国药房

OBJECTIVE To study the effects of cy cloastragenol （CAG） on carbon tetrachloride （CCl4）-induced hepatic fibrosis（HF）and glycolysis in mice. METHODS Male ICR mice were randomly divided into blank group ，model group ，CAG low-dose，medium-dose and high-dose groups （60，120，240 mg/kg），with 6 mice in each group. Except that blank group was given olive oil intraperitoneally ，the mice in other groups were intraperitoneally injected with 10％CCl4-olive oil solution （5 mL/kg） three times a week for 8 weeks to induce HF model. From the 4th week after modeling ，mice in each drug group were given corresponding drug solution intragastrically （10 mL/kg），and mice in blank group and model group were given 0.5％ sodium carboxymethyl cellulose solution intragastrically （10 mL/kg），once a day for 4 weeks. During the experiment ，the body weight of mice were weighted ；after last gastrogavage ，the liver weight was weighted and liver indexes of mice were calculated. The changes of hepatic injury indexes [aspartate aminotransferase （AST）， alanine aminotransferase （ALT）]， related indexes of HF [hematoxylin-eosin （HE）staining score ，Masson and Picrosirius red staining collagen volume fraction ，collagen Ⅰ，α-smooth muscle actin （α-SMA）] and related indexes of glycolysis [lactic acid （LD），hexokinase（HK），phosphofructokinase（PFK）， pyruvate kinase （PK）] were all detected. RESULTS Compared with model group ，the collagen deposition and fibrosis of mice in each drug group were reduced ，and the body weights of mice （except for CAG low-dose group ）were increased to some extent （P＜0.05）. Liver indexes ，serum levels of ALT and AST ，HE staining score of liver histopathology ，Masson and Picrosirius red staining collagen volume fraction ，protein expression of collagen Ⅰ and α-SMA，serum content of LD ，the levels of HK ，PFK and PK in serum and hepatic tissues （except for hepatic tissue of CAG low-dose group ）were all decreased significantly （P＜0.05）. CONCLUSIONS CAG can improve HF in mice induced by CCl 4，and reduce the levels of key enzymes and products of glycolysis.

A New Triterpenoid Saponin from Aidi Injection / 中草药·英文版

ObjectiveTo investigate the chemical constituents from Aidi Injection.Methods The chemical constituents were isolated by chromatography on Sephadex LH-20 gel columns and reverse phase semi-preparative HPLC repeatedly.Their structures were identified by spectroscopic analysis (NMR and MS).ResultsTwenty-two compounds were isolated and identified to be 3-O-3',4'-diacetyl-β-D-xylopyranosyl-6-O-β-D-glucopyranosylcycloastragenol (1),astragaloside IV (2),astragaloside Ⅱ (3),astragaloside I (4),isoastragaloside I (5),acetylastragaloside I (6),ginsenosid Re (7),ginsenoside Rf (8),ginsenoside Rg1 (9),ginsenoside Rb3 (10),notoginsenoside R4 (11),ginsenoside Rb1 (12),ginsenoside Rc (13),ginsenoside Rb2 (14),ginsenoside Rd (15),lucyoside H (16),3-O-ββ-D-glucopyranosyl(l→4)-β-D-glucopyranosyl(l→3)-α-L-rhamnopyranosyl (1→2)-α-Larabinopyranosyl oleanolic acid 28-O-α-L-rhamnopyranosyl(l→4)-β-D-glucopyranosyl(1→6)-β-D-glucopyranoside (17),3-O-β-D-glucopyranosyl(1→3)-α-L-rhamnopyranosyl [β-D-glucopyranosyl-(l→4)]-(l→2)-αt-L-arabinopyranosyl oleanolic acid 28-O-α-L-arabinopyranosyl(1→4)-β-D-glucopyranosyl(1→6)-β-D-glucopyranoside (18),syringin (19),elentheroside E (20),4-(1,2,3-trihydroxypropyl)-2,6-dimethoxyphenyl-I-O-β-D-glucopyranoside (21),and coniferin (22).ConclusionCompounds 1-6 are originated from Astragalus membranceus,compounds 7-18 are originated from Panax ginseng,and compounds 19-22 are originated from Acanthopanax senticosus by LC-MS analysis.Compound 1 is a new compound.