[Research progress on application of multi-enzyme-catalyzed cascade reactions in enzymatic synthesis of natural products].

As a biocatalyst, enzyme has the advantages of high catalytic efficiency, strong reaction selectivity, specific target products, mild reaction conditions, and environmental friendliness, and serves as an important tool for the synthesis of complex organic molecules. With the continuous development of gene sequencing technology, molecular biology, genetic manipulation, and other technologies, the diversity of enzymes increases steadily and the reactions that can be catalyzed are also gradually diversified. In the process of enzyme-catalyzed synthesis, the majority of common enzymatic reactions can be achieved by single enzyme catalysis, while many complex reactions often require the participation of two or more enzymes. Therefore, the combination of multiple enzymes together to construct the multi-enzyme cascade reactions has become a research hotspot in the field of biochemistry. Nowadays, the biosynthetic pathways of more natural products with complex structures have been clarified, and secondary metabolic enzymes with novel catalytic activities have been identified, discovered, and combined in enzymatic synthesis of natural/unnatural molecules with diverse structures. This study summarized a series of examples of multi-enzyme-catalyzed cascades and highlighted the application of cascade catalysis methods in the synthesis of carbohydrates, nucleosides, flavonoids, terpenes, alkaloids, and chiral molecules. Furthermore, the existing problems and solutions of multi-enzyme-catalyzed cascade method were discussed, and the future development direction was prospected.

Two new anthraquinone glycosides from the roots of Rheum palmatum.

Two new anthraquinone glycosides, named 1-methyl-8-hydroxyl-9,10-anthraquinone-3-O-ß-D-(6'-O-cinnamoyl)glucopyranoside (1) and rhein-8-O-ß-D-[6'-O-(3''-methoxyl malonyl)]glucopyranoside (2), have been isolated from the roots of Rheum palmatum, together with seven known compounds, rhein-8-O-ß-D-glucopyranoside (3), physcion-8-O-ß-D-glucopyranoside (4), chrysophanol-8-O-ß-D-glucopyranoside (5), aleo-emodin-8-O-ß-D-glucopyranoside (6), emodin-8-O-ß-D-glucopyranoside (7), aleo-emodin-ω-O-ß-D-glucopyranoside (8), and emodin-1-O-ß-D-glucopyranoside (9). Their structures were elucidated on the basis of chemical and spectral analysis.