Glycosylated Natural Products From Marine Microbes

Targeted Discovery of Glycosylated Natural Products by Tailoring Enzyme-Guided Genome Mining and MS-Based Metabolome Analysis

Glycosides make up a biomedically important class of secondary metabolites. Most naturally occurring glycosides were isolated from plants and bacteria; however, the chemical diversity of glycosylated natural products in fungi remains largely unexplored. Herein, we present a paradigm to specifically discover diverse and bioactive glycosylated natural products from fungi by combining tailoring enzyme-guided genome mining with mass spectrometry (MS)-based metabolome analysis. Through in vivo genes deletion and heterologous expression, the first fungal C-glycosyltransferase AuCGT involved in the biosynthesis of stromemycin was identified from Aspergillus ustus. Subsequent homology-based genome mining for fungal glycosyltransferases by using AuCGT as a probe revealed a variety of biosynthetic gene clusters (BGCs) containing its homologues in diverse fungi, of which the glycoside-producing capability was corroborated by high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis. Consequently, 28 fungal aromatic polyketide C/O-glycosides, including 20 new compounds, were efficiently discovered and isolated from the three selected fungi. Moreover, several novel fungal C/O-glycosyltransferases, especially three novel α-pyrone C-glycosyltransferases, were functionally characterized and verified in the biosynthesis of these glycosides. In addition, a proof of principle for combinatorial biosynthesis was applied to design the production of unnatural glycosides in Aspergillus nidulans. Notably, the newly discovered glycosides exhibited significant antiviral, antibacterial, and antidiabetic activities. Our work demonstrates the promise of tailoring enzyme-guided genome-mining approach for the targeted discovery of fungal glycosides and promotes the exploration of a broader chemical space for natural products with a target structural motif in microbial genomes.

A review on marine source as anticancer agents

This review investigates the potential of natural compounds obtained from marine sources for the treatment of cancer. The oceans are believed to contain physiologically active compounds, such as alkaloids, nucleosides, macrolides, and polyketides, which have shown promising effects in slowing human tumor cells both in vivo and in vitro. Various marine species, including algae, mollusks, actinomycetes, fungi, sponges, and soft corals, have been studied for their bioactive metabolites with diverse chemical structures. The review explores the therapeutic potential of various marine-derived substances and discusses their possible applications in cancer treatment.

Natural and engineered xylosyl products from microbial source

Glycosylation is a prevalent post-modification found in natural products and has a significant impact on the structural diversity and activity variation of natural products. Glucosylation is the most common type of glycosylation, whereas xylosylation is relatively rare. Despite their unique chemical structures and beneficial activities, xylosylated natural products from microorganisms have received little attention. This review provides, for the first time, a comprehensive summary of 126 microbial-derived xylosylated natural products, including xylosyl-cyathane diterpenes, xylosylated triterpenes, xylosyl aromatic compounds, and others. Among these compounds, xylosyl-cyathane diterpenes represent the highest number of derivatives, followed by xylosylated triterpenes. Xylosyl compounds from bacterial sources have less defined structural profiles compared to those from fungi. The characterization of xylosyltransferase EriJ from Basidiomycota extended the structural diversity of xylosyl cyathane diterpenes. This work provides a valuable reference for the research and use of xylosyltransferase for drug discovery and synthetic chemistry. Further work is needed to explore the potential applications of microbial derived xylosyl compounds and to develop novel xylosyl transferases. With the deepening of genomic sequencing of medicinal fungi, more biosynthesis of bioactive xylosyl compounds is expected to be elucidated in the future.

Neurotrophic neolignans of Pinus koraiensis twigs

Four undescribed neolignan analogs, together with eight known compounds, were isolated from the twigs of Pinus koraiensis (Korean pine). The chemical structure of the isolated compounds was determined through extensive spectroscopic analysis and chemical method. Their relative and absolute configurations were assigned through a well-established empirical rule and electronic circular dichroism (ECD) analysis, respectively. Four compounds (3 and 9-11) at 20 μM concentration showed significant neurotrophic effect by inducing nerve growth factor (NGF) secretion in C6 cells with the stimulation levels a range of 140.82 ± 4.62% to 160.04 ± 11.04%. Additionally, the result indicated that the glycosylation of neolignan led to an improvement in neurotrophic activity compared to their aglycone form. A compound (7) inhibited nitric oxide production with an IC50 value of 31.74 μM in LPS-activated BV2 cells.

Glycosylated and Succinylated Macrocyclic Lactones with Amyloid-β-Aggregation-Regulating Activity from a Marine Bacillus sp

Two new glycosylated and succinylated macrocyclic lactones, succinyl glyco-oxydifficidin (1) and succinyl macrolactin O (2), were isolated from a Bacillus strain collected from an intertidal mudflat on Anmyeon Island in Korea. The planar structures of 1 and 2 were proposed using mass spectrometric analysis and NMR spectroscopic data. The absolute configurations of 1 and 2 were determined by optical rotation, J-based configuration analysis, chemical derivatizations, including the modified Mosher's method, and quantum-mechanics-based calculation. Biological evaluation of 1 and 2 revealed that succinyl glyco-oxydifficidin (1) inhibited/dissociated amyloid β (Aβ) aggregation, whereas succinyl macrolactin O (2) inhibited Aβ aggregation, indicating their therapeutic potential for disassembling and removing Aβ aggregation.

Bioactive Alpha-Pyrone and Phenolic Glucosides from the Marine-Derived Metarhizium sp. P2100

Glycoside compounds have attracted great interest due to their remarkable and multifarious bioactivities. In this study, four hitherto unknown 4-methoxy-β-D-glucosyl derivatives were obtained and identified from the marine-derived fungus Metarhizium sp. P2100, including three alpha-pyrone glycosides (1-3) and one phenolic glycoside (4). Their planar structures were elucidated by comprehensive spectroscopic analysis, including 1D/2D NMR and HRESIMS. The absolute configurations of 1-3 were determined by a single-crystal X-ray crystallographic experiment, a comparison of the experimental, and a calculated electronic circular dichroism (ECD) spectra, respectively. Compounds 2 and 3 are a pair of rare epimeric pyranoside glycosides at C-7 with a core of aglycone as 2H-pyrone. Compounds 1-4 exhibited weak anti-inflammatory activities. In particular, compounds 1-3 displayed inhibitory activities against α-amylase, showing a potential for the development of a new α-amylase inhibitor for controlling diabetes.

Characterization of seahorse (Hippocampus comes L.) extracts originating from culture and nature in Pesawaran, Lampung, Indonesia

Objective

Indonesia is an archipelagic country with a mega biodiversity, among others, in the marine area. Seahorses (Hippocampus spp.) are a marine fish known to have biocompounds used in traditional medicine "Jamu," such as Hippocampus comes L. (HCL). The present study aims to analyze and compare the chemical contents of cultured seahorse (CS) and natural seahorse (NS) extracts.

Materials and Methods

The CS and NS were identified morphometrically. After freeze-drying, the seahorses were ground into powder with a grinder. The seahorse powder was extracted with ethanol and a water solvent. The extract contained biocompounds, proximate, amino acids, and steroids with high-performance liquid chromatography.

Results

The study found unique characteristics of HCL. The highest yield was obtained in NS using a water solvent (18.6%). The biocompounds in seahorses consist of alkaloids and triterpenoids. The highest proximate of water content (11.03%) and ash content (42.50%) was found in NS. In addition, other compounds were also detected in CS, such as fat (7.48%) and protein (47.67%). Both of HCL's different sources had all essential and nonessential amino acids in which the highest concentration were in NS, i.e., L-arginine (56,537.22 mg/kg), L-lysine (17,794.17), glycine (113,649.80 mg/kg), L-proline (47,056.15), and L-alanine (43,451.81). The analysis of the steroid compound of the extract suggested the presence of steroid glycosides.

Conclusion

The highest yield of the seahorse extract with a water solvent is about 18.6% and protein content of 47.67% in CS. The crude extract has alkaloids, triterpenoids, and glycine (113,649.80 mg/kg) in NS with water, suggesting the presence of steroid glycosides.

New Glycosylated Secondary Metabolites from Marine-Derived Bacteria

Three new glycosylated secondary metabolites, including a new indole alkaloid, pityriacitrin D (1), and two new trehalose lipids (2 and 3), together with three known compounds (4–6) were isolated from two marine-derived bacterial strains, Bacillus siamensis 168CLC-66.1 and Tsukamurella pseudospumae IV19-045. The structures of 1–3 were determined by extensive analysis and comparison of their spectroscopic data with literature values. The absolute configurations of sugar moieties were determined by chemical derivatization followed by LC-MS analysis. Cytotoxicity of 1–3 against six cancer cell lines was evaluated by SRB assay, and 1 showed moderate activity against all the tested cell lines with GI₅₀ values ranging from 8.0 to 10.9 µM.

Marine natural products

Covering: 2020This review covers the literature published in 2020 for marine natural products (MNPs), with 757 citations (747 for the period January to December 2020) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1407 in 420 papers for 2020), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. A meta analysis of bioactivity data relating to new MNPs reported over the last five years is also presented.

Synthesis of the α-Linked Digitoxose Trisaccharide Fragment of Kijanimicin: An Unexpected Application of Glycosyl Sulfonates

Previously, we demonstrated that glycosyl tosylates are effective for the synthesis of β-glycosides of gluco-configured 2-deoxy sugars. Here, we show the same sulfonate system can be used for the selective synthesis of α-glycosides containing the allo-configured 2-deoxy sugar digitoxose. As with previous work, optimal selectivity is obtained through matching the donor with the appropriate arylsulfonyl chloride promoter. The utility of this method is demonstrated through the synthesis of the α-linked digitoxose trisaccharide fragment of kijanimicin.

Flavonoids from Marine-Derived Actinobacteria as Anticancer Drugs

Flavonoids represent a large diverse group of natural products that are used as a traditional medicine against various infectious diseases. They possess many biological activities including antimicrobial, antioxidant, anti-inflammatory, anti-cancer and anti-diabetic activities. Commercially, flavonoids are mainly obtained from plants, however, several challenges are faced during their extraction. Microorganisms have been known as natural sources of a wide range of bioactive compounds including flavonoids. Actinobacteria are the most prolific group of microorganisms for the production of bioactive secondary metabolites, thus facilitating the production of flavonoids. The screening programs for bioactive compounds revealed the potential application of actinobacteria to produce flavonoids with interesting biological activities, especially anticancer activities. Since marine actinobacteria are recognized as a potential source of novel anticancer agents, they are highly expected to be potential producers of anticancer flavonoids with unusual structures and properties. In this review, we highlight the production of flavonoids by actinobacteria through classical fermentation, engineering of plant biosynthetic genes in a recombinant actinobacterium and the de novo biosynthesis approach. Through these approaches, we can control and improve the production of interesting flavonoids or their derivatives for the treatment of cancer.