No abstract

We describe the regioselective complexation of a non-symmetric 5-bromovaleronitrile axle by a non-symmetric pillar[5]arene bearing different alkyl (methyl and pentyl) rims, forming an oriented interpenetrated complex with the directionality of CN@methyl rim and Br@pentyl rim.

The exploration of molecular recognition of synthetic macrocycles in aqueous media is significantly important since most biological functions, activities and processes take place in water. Pillar[n]arenes (n = 5-10) have been recognized as a new generation of macrocyclic arenes; much attention has been devoted to their host-guest chemistry. This review summarizes the host-guest properties of water-soluble pillararenes towards biologically significant molecules and drugs. These water-soluble pillararenes are classified into three major classes according to the electric charges of hydrophilic groups at their portals: anionic pillar [n]arenes (AP[n]s), cationic pillar[n]arenes (CP[n]s), and neutral pillar[n]arenes (NP[n]s). The host-guest affinities, binding modes, binding selectivity, stimuli-responsiveness, as well as biomedical applications are comprehensively discussed.

Bupleurum falcatum L. is frequently used in traditional herbal medicine in Asia. Saikosaponins (SSs) are the main bioactive ingredients of B. falcatum, but the biosynthetic pathway of SSs is unclear, and the biosynthesis of species-specific phytometabolites is little known. Here we resolved the transcriptome profiles of B. falcatum to identify candidate genes that might be involved in the biosynthesis of SSs. By isoform sequencing (Iso-Seq) analyses of the whole plant, a total of 26.98 Gb of nucleotides were obtained and 124,188 unigenes were identified, and 81,594 unigenes were successfully annotated. A total of 1033 unigenes of 20 families related to the mevalonate (MVA) pathway and methylerythritol phosphate (MEP) pathway of the SS biosynthetic pathway were identified. The WGCNA (weighted gene co-expression network analysis) of these unigenes revealed that only the co-expression module of MEmagenta, which contained 343 unigenes, was highly correlated with the biosynthesis of SSs. Comparing differentially expressed gene analysis and the WGCNA indicated that 130 out of 343 genes of the MEmagenta module exhibited differential expression levels, and genes with the most “hubness” within this module were predicted. Manipulation of these genes might improve the biosynthesis of SSs.

Bupleurum chinense DC. is a commonly used plant in traditional Chinese medicine, and saikosaponins(SSs) are the main active oleanane-typetriterpene saponins in B. chinense . β-Amyrin synthase (β-AS) is an important enzyme in oleanane-type triterpenoid saponin synthesis, but its role in saikosaponin synthesis has rarely been studied. Here, the putative β-AS gene BcBAS1(Accession No.ON890382) selected according to metabolomic and transcriptomic analyses was cloned and functionally characterized by heterologous expression in Escherichia coli and Pichia pastoris , and its subcellular localization and expression patterns were examined. The molecular weight of the BcBAS1 recombinant protein was approximately 87 kDa, and this protein could catalyse the production of β-amyrin, the precursor of SSs. Furthermore, BcBAS1 was located in the cytosol, and relative expression in four tissues of the four genotypes was positively correlated with SSa and SSd contents. Our results indicate that BcBAS1 is a β-AS gene and may play an important role in saikosaponin biosynthesis and regulation. This study sheds light on the role of β-AS genes in the synthesis of SSs and provides insights for the metabolic engineering of SSs.