Dammarane-type triterpenoid saponins isolated from Gynostemma pentaphyllum ameliorate liver fibrosis via agonizing PP2Cαand inhibiting deposition of extracellular matrix

Gypenosides,structurally analogous to ginsenosides and derived from a sustainable source,are recognized as the principal active compounds found in Gynostemma pentaphyllum,a Chinese medicinal plant used in the treatment of the metabolic syndrome.By bioactive tracking isolation of the plants collected from different regions across China,we obtained four new gypenosides(1−4),together with nine known gypenosides(5−13),from the methanol extract of the plant.The structures of new gypenosides were elucidated by one-dimensional(1D)and two-dimensional(2D)nuclear magnetic resonance(NMR)spectra,complemented by chemical degradation experiments.Through comprehensive evaluation involving COL1A1 promoter assays and PP2Cαactivity assays,we established a definitive structure-activity relationship for these dammarane-type triterpenoids,affirming the indispensability of the C-3 saccharide chain and C-17 lactone ring in effectively impeding extracellular matrix(ECM)deposition within hepatic stellate cells.Further in vivo study on the CCl4-induced liver damage mouse model corroborated that compound 5 significantly ameliorated the process of hepatic fibrosis by oral administration.These results underscore the potential of dammarane-type triterpenoids as prospective antifibrotic leads and highlight their prevalence as key molecular frameworks in the therapeutic intervention of chronic hepatic disorders.

Recombineering enables genome mining of novel siderophores in a non-model Burkholderiales strain

Iron is essential for bacterial survival,and most bacteria capture iron by producing siderophores.Burkholde-riales bacteria produce various types of bioactive secondary metabolites,such as ornibactin and malleobactin siderophores.In this study,the genome analysis of Burkholderiales genomes showed a putative novel siderophore gene cluster crb,which is highly similar to the ornibactin and malleobactin gene clusters but does not have pvdF,a gene encoding a formyltransferase for N-δ-hydroxy-ornithine formylation.Establishing the bacteriophage recom-binase Redγ-Redδβ7029 mediated genome editing system in a non-model Burkholderiales strain Paraburkholderia caribensis CICC 10960 allowed the rapid identification of the products of crb gene cluster,caribactins A-F(1-6).Caribactins contain a special amino acid residue N-δ-hydroxy-N-δ-acetylornithine(haOrn),which differs from the counterpart N-δ-hydroxy-N-δ-formylornithine(hOrn)in ornibactin and malleobactin,owing to the absence of pvdF.Gene inactivation showed that the acetylation of hOrn is catalyzed by CrbK,whose homologs proba-bly not be involved in the biosynthesis of ornibactin and malleobactin,showing possible evolutionary clues of these siderophore biosynthetic pathways from different genera.Caribactins promote biofilm production and en-hance swarming and swimming abilities,suggesting that they may play crucial roles in biofilm formation.This study also revealed that recombineering has the capability to mine novel secondary metabolites from non-model Burkholderiales species.

Nobachelins,new siderophores from Nocardiopsis baichengensis protecting Caenorhabditis elegans from Pseudomonas aeruginosa infection

The biosynthetic potential of actinobacteria to produce novel natural products is still regarded as immense.In this paper,we correlated a cryptic biosynthetic gene cluster to chemical molecules by genome mining and chemical analyses,leading to the discovery of a new group of catecholate-hydroxamate siderophores,nobachelins,from Nocardiopsis baichengensis DSM 44845.Nobachelin biosynthesis genes are conserved in several bacteria from the family Nocardiopsidaceae.Structurally,nobachelins feature fatty-acylated hydroxy-ornithine and a rare chlorinated catecholate group.Intriguingly,nobachelins rescued Caenorhabditis elegans from Pseudomonas aeruginosa-mediated killing.

A novel PGAM5 inhibitor LFHP-1c protects bloodebrain barrier integrity in ischemic stroke

Bloodebrain barrier(BBB)damage after ischemia significantly influences stroke outcome.Compound LFHP-1 c was previously discovered with neuroprotective role in stroke model,but its mechanism of action on protection of BBB disruption after stroke remains unknown.Here,we show that LFHP-1 c,as a direct PGAM5 inhibitor,prevented BBB disruption after transient middle cerebral artery occlusion(tMCAO)in rats.Mechanistically,LFHP-1 c binding with endothelial PGAM5 not only inhibited the PGAM5 phosphatase activity,but also reduced the interaction of PGAM5 with NRF2,which facilitated nuclear translocation of NRF2 to prevent BBB disruption from ischemia.Furthermore,LFHP-1 c administration by targeting PGAM5 shows a trend toward reduced infarct volume,brain edema and neurological deficits in nonhuman primate Macaca fascicularis model with t MCAO.Thus,our study identifies compound LFHP-1 c as a firstly direct PGAM5 inhibitor showing amelioration of ischemia-induced BBB disruption in vitro and in vivo,and provides a potentially therapeutics for brain ischemic stroke.

In vitro characterization of a nitro-forming oxygenase involved in 3-(trans-2’-aminocyclopropyl)alanine biosynthesis

In vitro characterization experiments revealed the formations of 3-(trans-2’-aminocyclopropyl)alanine((3-Acp)Ala)and 3-(trans-2’-nitrocyclopropyl)alanine((3-Ncp)Ala)are originated via two homologous proteins,BelK and HrmI,which regioselectively catalyze the N𝜀-oxygenation of l-lysine.The two enzymes belong to the emerg-ing heme-oxygenase-like diiron oxidase and oxygenase(HDO)superfamily and the catalytic center of BelK is validated by homology modeling and site-directed mutations.Based on the in vitro characterization,the biosyn-thetic pathways of(3-Acp)Ala and(3-Ncp)Ala are proposed.

Recent developments in the identification and biosynthesis of antitumor drugs derived from microorganisms

Secondary metabolites in microorganisms represent a resource for drug discovery and development.In particular,microbial-derived antitumor agents are in clinical use worldwide.Herein,we provide an overview of the devel-opment of classical antitumor drugs derived from microorganisms.Currently used drugs and drug candidates are comprehensively described in terms of pharmacological activities,mechanisms of action,microbial sources,and biosynthesis.We further discuss recent studies that have demonstrated the utility of gene-editing technologies and synthetic biology tools for the identification of new gene clusters,expansion of natural products,and eluci-dation of biosynthetic pathways.This review summarizes recent progress in the discovery and development of microbial-derived anticancer compounds with emphasis on biosynthesis.