Microbial transformations of aryltetralone and aryltetralin lignans by Cunninghamella echinulata and Beauveria bassiana

Lignans from the leaves of Styrax japonicus and their anti-inflammatory activity

Five novel lignans, namely styraxjaponica A-E (1-5), together with eight known compounds (6-13) were isolated from the leaves of Styrax japonicus Siebold & Zucc. Their chemical structures were characterized by extensive analysis of 1D and 2D NMR, UV, IR, HRESIMS spectroscopic analysis as well as by comparison to the literature. The absolute configurations of the new compounds were further determined by quantum chemical electronic circular dichroism (ECD) calculations powered by time-dependent density functional theory (TDDFT). Moreover, the anti-inflammatory effects of compounds 1-5 in lipopolysaccharide (LPS)-induced RAW 264.7 cells were also evaluated by measuring nitric oxide (NO) concentrations. All compounds displayed significant anti-inflammatory activity without affecting cell viability in vitro.

Chemistry and Biological Activities of Naturally Occurring and Structurally Modified Podophyllotoxins

Plants containing podophyllotoxin and its analogues have been used as folk medicines for centuries. The characteristic chemical structures and strong biological activities of this class of compounds attracted attention worldwide. Currently, more than ninety natural podophyllotoxins were isolated, and structure modifications of these molecules were performed to afford a variety of derivatives, which offered optimized anti-tumor activity. This review summarized up to date reports on natural occurring podophyllotoxins and their sources, structural modification and biological activities. Special attention was paid to both structural modification and optimized antitumor activity. It was noteworthy that etoposide, a derivative of podophyllotoxin, could prevent cytokine storm caused by the recent SARS-CoV-2 viral infection.

Recent advances in research on lignans and neolignans

Covering: 2009 to 2015Lignans and neolignans are a large group of natural products derived from the oxidative coupling of two C6-C3 units. Owing to their biological activities ranging from antioxidant, antitumor, anti-inflammatory to antiviral properties, they have been used for a long time both in ethnic as well as in conventional medicine. This review describes 564 of the latest examples of naturally occurring lignans and neolignans, and their glycosides in some cases, which have been isolated between 2009 and 2015. It comprises the data reported in more than 200 peer-reviewed articles and covers their source, isolation, structure elucidation and bioactivities (where available), and highlights the biosynthesis and total synthesis of some important ones.

Asymmetric synthesis of ent-fragransin C1

The first asymmetric synthesis of ent-fragransin C₁ bearing 2,3-anti-3,4-syn-4,5-anti stereochemistries is reported.

Triflimide-catalyzed allylsilane annulations of benzylic alcohols for the divergent synthesis of indanes and tetralins

The development of a triflimide-catalyzed annulation of benzylic alcohols with allylsilanes for the synthesis of indane or tetralin structures is reported. In this fragment coupling reaction, complexity is built rapidly from readily available starting materials to yield diverse sets of products with up to three contiguous stereocenters. Indanes or tetralins can be generated from common precursors depending on the structure of the allylsilane reagent used. The concise synthesis of several lignan natural products highlights the utility of this newly devised methodology.

Lignans from the fruit of Schisandra glaucescens with antioxidant and neuroprotective properties

Two rare 7,8-seco-lignans (1, 2), three new lignan glycosides (3, 4a, 4b), and 10 known lignans (5-14) were isolated from the fruit of Schisandra glaucescens Diels. The absolute configurations of 1 and 2 were determined by comparing their experimental and calculated electronic circular dichroism spectra. The molecular structures of the new compounds (3, 4a, and 4b), including their absolute configurations, were determined using various spectroscopic methods and hydrolysis reactions. The antioxidant activities of the isolated compounds were tested using 2,2-diphenyl-1-picrylhydrazyl and ferric reducing antioxidant power assays. Compounds 4, 7, 8, 10, 11, and 12 exhibited antioxidant activities of varying potential in both assays. Of these compounds, 7 showed the strongest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, with IC50 values of 15.7 (150 μM DPPH) and 34.6 μM (300 μM DPPH), respectively, and 4, 12, and 7 displayed higher total antioxidant activities than Trolox in the ferric reducing antioxidant power assay. The neuroprotective effects of these compounds against Aβ25-35-induced cell death in SH-SY5Y cells were also investigated. Compounds 1, 2, 6, 7, 8, 11, and 12 exhibited statistically significant neuroprotective effects against Aβ25-35-induced SH-SY5Y cell death compared with the group treated only with Aβ25-35.

Stereo and Regioselective Microbial Reduction of the Clerodane Diterpene 3,12-Dioxo-15,16-epoxy-4-hydroxycleroda-13(16),14-diene

The biotransformation of the clerodane diterpene, 3,12-dioxo-15,16-epoxy-4-hydroxy-cleroda-13(16),14-diene (1), obtained from Croton micans var. argyroglossum (Baill.) Müll., was investigated for the first time. Whole cells of Cunninghamella echinulata and Rhizopus stolonifer were used as enzymatic systems, and with both fungi the only biotransformation product obtained was the new ent-neo-clerodane diterpene (3 R,4 S,5 S,8 S,9 R,10 S)-3,4-dihydroxy-15,16-epoxy-12-oxo-cleroda-13(16),14-diene (2a). The absolute stereochemistry of 2a was inferred by comparison of its optical rotation with those of the chemical reduction product of 1 and its quasienantiomer 2c.

Discovering the secondary metabolite potential encoded within entomopathogenic fungi

This highlight discusses the secondary metabolite potential of the insect pathogensMetarhiziumandBeauveria, including a bioinformatics analysis of secondary metabolite genes for which no products are yet identified. (Top picture is a mole cricket infected withBeauveria bassianaand the bottom picture is a wasp infected withBeauveria bassiana.)

Microbial Biotransformation of 16α,17-Epoxy-Ent-kaurane-19-oic acid by Beauveria Sulfurescens ATCC 7159-F

Biotransformation of 16α,17-epoxy- ent-kaurane-19-oic acid (1) by Beauveria sulfurescens ATCC 7159-F led to the production of a new ent-kaurane diterpenoid, 7β,17-dihydroxy- ent-kaur-15-en-19-oic acid (7), and four other ent-kauranes (8 - 11), all of which were identified as their methyl esters. Compounds 9 and 10 were found to be new stereoisomers. Structures of these were established by the extensive usage of their spectroscopic characteristics.

4,5-seco-guaiane and a nine-membered sesquiterpene lactone from Holostylis reniformis

Root extracts of Holostylis reniformis (Aristolochiaceae) yielded three new natural sesquiterpenes, a sesquiterpene with an unusual carbon skeleton, 4,5-seco-guaiane (7-epi-11-hydroxychabrolidione A, 1), a nine-membered lactone with new carbon skeleton (holostylactone, 2), and a new megastigmane [(6S,7E)-6,9-dihydroxy-10-(2'-hydroxy-ethoxy)-4,7-megastigmadien-3-one, 3], together with bulnesol and sitosterol-3-O-β-D-glucopyranoside. The structures of these compounds were determined by spectroscopic analyses and B3LYP/STO-3G** theoretical studies.