Weiyun Chai

New Metabolites and Bioactive Actinomycins from Marine-Derived Streptomyces sp. ZZ338

An extract prepared from the culture of a marine-derived actinomycete Streptomyces sp. ZZ338 was found to have significant antimicrobial and antiproliferative activities. A chemical investigation of this active extract resulted in the isolation of three known bioactive actinomycins (1–3) and two new metabolites (4 and 5). The structures of the isolated compounds were identified as actinomycins D (1), V (2), X0β (3), 2-acetylamino-3-hydroxyl-4-methyl-benzoic acid methyl ester (4), and N-1S-(4-methylaminophenylmethyl)-2-oxo-propyl acetamide (5) based on their nuclear magnetic resonance (NMR) and high resolution electrospray ionization mass spectroscopy (HRESIMS) data as well as their optical rotation. This class of new compound 5 had never before been found from a natural resource. Three known actinomycins showed activities in inhibiting the proliferation of glioma cells and the growth of methicillin-resistant Staphylococcus aureus, Escherichia coli, and Candida albicans and are responsible for the activity of the crude extract. Actinomycin D (1) was also found to downregulate several glioma metabolic enzymes of glycolysis, glutaminolysis, and lipogenesis, suggesting that targeting multiple tumor metabolic regulators might be a new anti-glioma mechanism of actinomycin D. This is the first report of such a possible mechanism for the class of actinomycins.

Cytotoxic Bagremycins from Mangrove-Derived Streptomyces sp. Q22

New bagremycins C-E (3-5) and bagrelactone A (6), together with known bagremycins A (1) and B (2), 4-hydroxystyrene (7), and 4-hydroxystyrene 4-O-α-d-galactopyranoside (8), were isolated from a mangrove-derived actinomycete, Streptomyces sp. Q22. Structures of these new compounds were elucidated based on their NMR and HRESIMS spectroscopic data as well as chemical degradation. Bagremycin C (3) is a unique analogue with an N-acetyl-(S)-cysteine moiety, while bagrelactone A (6) represents the first example of this type of bagremycin-derived macrolide. Bagremycin C (3) was active against four glioma cell lines, with IC50 values in the range from 2.2 to 6.4 μM, induced apoptosis in human glioma U87MG cells in a dose- and time-dependent manner, and arrested the U87MG cell cycle at the G0/G1 phase.

Rare Polyene-polyol Macrolides from Mangrove-derived Streptomyces sp. ZQ4BG

Bioactive natural products from mangrove-derived actinomycetes are important sources for discovery of drug lead compounds. In this study, an extract prepared from culture of an actinomycete Streptomyces sp. ZQ4BG isolated from mangrove soils was found to have activity in inhibiting proliferation of glioma cells. Large culture of this mangrove actinomycete in Gause’s liquid medium resulted in isolation of seven novel polyene-polyol macrolides, named as flavofungins III–IX (3–9), together with known flavofungins I (1) and II (2) and spectinabilin (10). Structures of these isolated compounds were elucidated by extensive NMR analyses and HRESIMS data. The stereochemical assignments were achieved by a combination of NOE information, universal NMR database, and chemical reactions including preparation of acetonide derivatives and Mosher esters. Flavofungins IV–VIII (4–8) are rare 32-membered polyene-polyol macrolides with a tetrahydrofuran ring, while flavofungin IX (9) represents the first example of this type of macrolide with a unique oxepane ring. Flavofungins I (1) and II (2) and spectinabilin (10) showed anti-glioma and antifungal activities.

A unique indolizinium alkaloid streptopertusacin A and bioactive bafilomycins from marine-derived Streptomyces sp. HZP-2216E

Streptopertusacin A, a unique indolizinium alkaloid existing as a zwitterion, and six bafilomycins including two previously undescribed ones of 21,22-en-bafilomycin D and 21,22-en-9-hydroxybafilomycin D were isolated from a culture of the seaweed-derived Streptomyces sp. HZP-2216E. Structures of these isolated compounds were determined based on extensive NMR spectroscopic analyses, HRESIMS and MS-MS data. The stereochemical assignments were achieved by NOE information, chemical degradation, Marfeys method, and electronic circular dichroism (ECD) calculation. Streptopertusacin A is the first example of this type of indolizinium alkaloid from microorganisms and showed moderate activity against the growth of methicillin-resistant Staphylococcus aureus (MRSA). 21,22-en-bafilomycin D and 21,22-en-9-hydroxybafilomycin D had potent activities in inhibiting the proliferation of glioma cells and the growth of MRSA.

Novel propanamide analogue and antiproliferative diketopiperazines from mangrove Streptomyces sp. Q24

Abstract A new propanamide analogue (1), along with one known alkaloid (2) and four known diketopiperazines (3–6), was isolated from a cultured broth of the actinomycete Streptomyces sp. Q24 that was obtained from a sample of mangrove soil. The structures of these isolates were characterised as 3-acetylamino-N-2-thienyl-propanamide (1), N-acetyltryptamine (2), cyclo-(l-phenylalanine-l-4-hydroxyproline) (3), cyclo-(l-leucine-l-4-hydroxyproline) (4), cyclo-(l-phenylalanine-d-4-hydroxyproline) (5) and cyclo-(l-leucine-l-proline) (6) based on their NMR and HRESIMS data as well as optical rotation. Three diketopiperazines (3, 4, 6) showed activity in inhibiting the proliferation of human glioma U87-MG and U251 cells. This type of the new propanamide analogue (1) is first found from a nature source and the antiproliferative property of these three diketopiperazines against glioma cells is also reported herein for the first time.

Anti-glioma Natural Products Downregulating Tumor Glycolytic Enzymes from Marine Actinomycete Streptomyces sp. ZZ406

Marine natural products are important resources for discovering novel anticancer drugs. In this study, an extract prepared from the culture of a sea anemone-derived actinomycete Streptomyces sp. ZZ406 in soluble starch and casein-related liquid medium was found to have activity in inhibiting the proliferation of glioma cells and reducing the production of lactate in glioma cells. Chemical investigation of this active crude extract resulted in the isolation of four new compounds and seven known ones. Structures of the new compounds were determined by a combination of extensive NMR analyses, HRESIMS and MS-MS data, electronic circular dichroism calculation, chemical degradation, and Marfey’s method. New compound 1 showed potent activity against the proliferation of different glioma cells with IC50 values of 4.7 to 8.1 μM, high selectivity index (>12.3 to 21.3), and good stability in human liver microsomes. Western blot analysis revealed that compound 1 remarkably downregulated the expressions of several important glioma glycolytic enzymes. The data from this study suggested that compound 1 might have potential as a novel anti-glioma agent to be further investigated.

Peniciphenalenins A−F from the culture of a marine-associated fungus Penicillium sp. ZZ901

Marine-derived fungi of the genus Penicillium represent a huge potential for synthesizing the secondary metabolites with structural and bioactive uniqueness and diversity. In this study, six previously undescribed compounds peniciphenalenins A-F and four known compounds (+)-sclerodin, (+)-scleroderolide, (+)-sclerodione, and physcion were isolated from the culture of a marine-derived fungus Penicillium sp. ZZ901. Structures of the isolated compounds were elucidated by a combination of extensive NMR spectroscopic analysis, HRESIMS data, optical rotation value, ECD calculation, and single crystal X-ray diffraction. Peniciphenalenins A-C are the second examples of the type of neoherqueinones. The possible biosynthetic route of nine phenalenone derivatives has been suggested. The known (+)-scleroderolide showed both antiproliferative activity against glioma cells with IC50 values of 23.24-37.26 μM and antibacterial activity in suppressing the growth of methicillin-resistant Staphylococcus aureus and Escherichia coli with MIC values of 7.0 and 9.0 μg/mL, respectively.

Antiglioma pseurotin A from marine Bacillus sp. FS8D regulating tumour metabolic enzymes

Abstract Pseurotin A was isolated from a culture of marine Bacillus sp. FS8D and showed to be active against the proliferation of four different glioma cells with IC50 values of 0.51–29.3 μM. It has been found that pseurotin A downregulated the expression of tumour glycolytic enzymes pyruvate kinase M2 (PKM2) and lactate dehydrogenase 5 (LDH5) and upregulated the expression of pyruvate dehydrogenase beta (PDHB), adenosine triphosphate synthase beta (ATPB) and cytochrome C (Cyto-C), the important regulators for tricarboxylic acid cycle and oxidative phosphorylation. The data suggested that targeting multiple metabolic enzymes might be one of the antiglioma mechanisms of pseurotin A.

Anti-glioma Efficacy and Mechanism of Action of Tripolinolate A from Tripolium pannonicum

Tripolinolate A as a new bioactive phenolic ester was previously isolated from a halophyte of Tripolium pannonicum. However, the in vitro and in vivo anti-glioma effects and mechanism of tripolinolate A have not been investigated. This study has demonstrated that (1) tripolinolate A inhibited the proliferation of different glioma cells with IC50 values of 7.97 to 14.02 µM and had a significant inhibitory effect on the glioma growth in U87MG xenograft nude mice, (2) tripolinolate A induced apoptosis in glioma cells by downregulating the expressions of antiapoptotic proteins and arrested glioma cell cycle at the G2/M phase by reducing the expression levels of cell cycle regulators, and (3) tripolinolate A also remarkably reduced the expression levels of several glioma metabolic enzymes and transcription factors. All data together suggested that tripolinolate A had significant in vitro and in vivo anti-glioma effects and the regulation of multiple tumor-related regulators and transcription factors might be responsible for the activities of tripolinolate A against glioma.

Bioactive Penicipyrrodiether A, an Adduct of GKK1032 Analogue and Phenol A Derivative, from a Marine-Sourced Fungus Penicillium sp. ZZ380

Penicipyrrodiether A, an adduct of GKK1032 analogue and phenol A derivative, was isolated from a culture of marine-associated fungus Penicillium sp. ZZ380 and represents the first example of this type of fungal metabolite. Its structure was elucidated by extensive spectroscopic analyses, including 1D- and 2D-NMR, HRESIMS, MS/MS, and electronic circular dichroism calculation as well as single-crystal X-ray diffraction. Penicipyrrodiether A showed antibacterial activity in inhibiting the growth of methicillin-resistant Staphylococcus aureus with a MIC value of 5.0 μg/mL. Its plausible pathway for biosynthesis has been proposed.