A pair of enantiomeric 5-oxabicyclic[4.3.0]lactam derivatives and one new polyketide from the marine-derived fungus Penicillium griseofulvum

Penicipyrrolizidinones A-C, three pyrrolizidinone alkaloids with unprecedented skeletons from the mangrove-derived fungus Penicillium sp. DM27

Three previously undescribed pyrrolizidinone alkaloids, penicipyrrolizidinones A and B (1 and 2), possessing an unprecedented 2-methyl-2-(oct-6-enoyl)pyrrolizidin-3-one skeleton, and penicipyrrolizidinone C (3), featuring a rare 1-alkenyl-2-methyl-pyrrolizidin-3,7-dione skeleton, together with four known pyrrolidine derivatives (4-7) were isolated from the mangrove-derived fungus Penicillium sp. DM27. Their structures were elucidated through comprehensive spectroscopic analysis, theoretical calculations of ECD spectra, and the modified Mosher's method. A plausible biosynthetic pathway for penicipyrrolizidinones A-C (1-3) was proposed. Compounds 4 and 5 exhibited moderate cytotoxicity against B16-F10 melanoma cells with IC50 values of 10.5 μM and 15.5 μM, respectively.

Two new lactam derivatives from a Sphagneticola trilobata derived fungus Penicillium rubens PQJ-2

A new bicyclic lactam derivatives penicilactam B (1) and a new monocyclic amide penicillamide D (2), along with four known compounds (3-6), were isolated from the fermentation broth of the derived fungus Penicillium rubens PQJ-2. Their structures and stereochemistry were elucidated by comprehensive spectroscopic analyses and quantum ECD calculations. All the compounds were evaluated for their antibacterial activities against Staphylococcus aureus subsp, Candida albicans, Escherichia coli and insecticidal activity against Helicoverpa armigera Hubner. Compounds 1-3 exhibited modest insecticidal activity against H. armigera Hubner.

Peniciriols A and B, two new citrinin derivatives from an endophytic fungus Penicillum citrinum TJNZ-27

Two undescribed citrinin derivatives, named peniciriols A-B (1-2), together with six known compounds were isolated from endophytic fungus Penicillum citrinum TJNZ-27. The structures of two new compounds were well established by the detail interpretation of NMR and HRESIMS data as well as ECD measurement powered by molecular calculation. Among them, compound 1 shared an unprecedented dimerized citrinin skeleton with the formation of an intriguing 9H-xanthene ring system, whereas compound 2 possess a highly substituted phenylacetic acid skeleton, which was rarely-occurring in natural secondary metabolites. Moreover, these novel compounds were tested for cytotoxic and antibacterial activities, whereas these novel compounds did not exhibit any noticeable cytotoxic or antibacterial activities.

Pegriseofamines A-E: Five cyclopiazonic acid related indole alkaloids from the fungus Penicillium griseofulvum

Five new cyclopiazonic acid related indole alkaloids, pegriseofamines A-E (1-5), were isolated from the fungus Penicillium griseofulvum. Their structures and absolute configurations were determined by NMR, HRESIMS, quantum-chemical calculation, and X-ray diffraction experiments. Among them, pegriseofamine A (1) possesses an undescribed 6/5/6/7 tetracyclic ring system generated by the fusion of an azepine and an indole unit via a cyclohexane, and the postulated biosynthetic origin of 1 was discussed. Compound 4 could relieve liver injury and prevent hepatocyte apoptosis in ConA-induced autoimmune liver disease.

Natural Enantiomers: Occurrence, Biogenesis and Biological Properties

The knowledge that natural products (NPs) are potent and selective modulators of important biomacromolecules (e.g., DNA and proteins) has inspired some of the world's most successful pharmaceuticals and agrochemicals. Notwithstanding these successes and despite a growing number of reports on naturally occurring pairs of enantiomers, this area of NP science still remains largely unexplored, consistent with the adage "If you don't seek, you don't find". Statistically, a rapidly growing number of enantiomeric NPs have been reported in the last several years. The current review provides a comprehensive overview of recent records on natural enantiomers, with the aim of advancing awareness and providing a better understanding of the chemical diversity and biogenetic context, as well as the biological properties and therapeutic (drug discovery) potential, of enantiomeric NPs.

Piperazine-2,5-dione derivatives and an α-pyrone polyketide from Penicillium griseofulvum and their immunosuppression activity

Four undescribed piperazine-2,5-dione derivatives designated janthinolides C-F, and an α-pyrone-containing polyketide namely trichopyrone C, were isolated from the extract of the fungus Penicillium griseofulvum along with four known products. Among them, janthinolide C represents the first naturally occured piperazine-2,5-dione analogue featuring a cleavaged piperazinedione ring with an oxime group, while the structure of janthinolide D possesses a rare N-methoxy group in natural products. Their structures and absolute stereochemistry were elucidated based on spectroscopic data, theoretical NMR and ECD calculations, Snatzke's method, and modified Mosher's method. All compounds were evaluated for in vitro immunosuppression activity in murine splenocytes stimulated by anti-CD3/anti-CD28 mAbs, of which janthinolides B and C showed potential inhibitory activity with IC₅₀ values at 9.3 and 1.3 μM, respectively.

Asperpenes D and E from the fungus Aspergillus sp. SCS-KFD66 isolated from a bivalve mollusk, Sanguinolaria chinensis

Two new compounds named asperpenes D (1) and E (2) were isolated from the marine-derived fungus Aspergillus sp. SCS-KFD66. Their structures were determined on the basis of spectroscopic methods. Compound 2 represents the first natural product bearing a 2-substituted-5-oxo-4-phenyl-2,5-dihydrofuran-3-carboxylic acid skeleton. All the compounds were tested for enzyme inhibitory activity against AChE and α-glucosidase and DPPH radical scavenging activity, respectively. [Formula: see text].

Recent progress of antibacterial natural products: Future antibiotics candidates

The discovery of novel antibacterial molecules plays a key role in solving the current antibiotic crisis issue. Natural products have long been an important source of drug discovery. Herein, we reviewed 256 natural products from 11 structural classes in the period of 2016-01/2020, which were selected by SciFinder with new compounds or new structures and MICs lower than 10 μg/mL or 10 μM as criterions. This review will provide some effective antibacterial lead compounds for medicinal chemists, which will promote the antibiotics research based on natural products to the next level.

Newly reported alkaloids produced by marine-derived Penicillium species (covering 2014-2018)

Alkaloids, especially heterocyclic alkaloids, have received remarkable attention due to their intriguing structures and potential pharmacological activities. The marine fungi residing in extreme environmental conditions are among the richest sources of these basic nitrogen-containing compounds. Fungal species belonging to the genus Penicillium have been studied worldwide for their biosynthetic potential for generating bioactive alkaloids. This paper offers a systematic review of the newly reported alkaloids produced by marine-derived Penicillium species over the past five years (covering the literature from the beginning of 2014 through the end of 2018) and describes the structural diversity, biological activities, and plausible biosynthetic pathway of the reported compounds. A total of 106 alkaloids and 81 references are included in this review, which is expected to be beneficial for drug development and biosynthesis in the near future.

Discovery of Bioactive Indole-Diketopiperazines from the Marine-Derived Fungus Penicillium brasilianum Aided by Genomic Information

Identification and analysis of the whole genome of the marine-derived fungus Penicillium brasilianum HBU-136 revealed the presence of an interesting biosynthetic gene cluster (BGC) for non-ribosomal peptide synthetases (NRPS), highly homologous to the BGCs of indole-diketopiperazine derivatives. With the aid of genomic analysis, eight indole-diketopiperazines (1−8), including three new compounds, spirotryprostatin G (1), and cyclotryprostatins F and G (2 and 3), were obtained by large-scale cultivation of the fungal strain HBU-136 using rice medium with 1.0% MgCl₂. The absolute configurations of 1−3 were determined by comparison of their experimental electronic circular dichroism (ECD) with calculated ECD spectra. Selective cytotoxicities were observed for compounds 1 and 4 against HL-60 cell line with the IC₅₀ values of 6.0 and 7.9 μM, respectively, whereas 2, 3, and 5 against MCF-7 cell line with the IC₅₀ values of 7.6, 10.8, and 5.1 μM, respectively.

Anti-Vibrio Indole-Diterpenoids and C-25 Epimeric Steroids From the Marine-Derived Fungus Penicillium janthinellum

A systematic chemical exploration of the marine-derived fungus Penicillium janthinellum led to the isolation of four indole-diterpenoid derivatives (1–4), including new penijanthines C and D (1 and 2), and a pair of new steroidal epimers, penijanthoids A and B (5 and 6). The calculated ECD spectra and Snatzke's method for the new compound 1 were carried out to determine its absolute configuration. The absolute configuration of 3 was established by X-ray diffraction and calculated ECD methods for the first time. DP4plus approach was used to elucidate the absolute configurations of the C-25 epimeric steroids 5 and 6. 25-Epimeric 5 and 6 represent the first examples of steroids forming a five-membered lactone between C-23 and C-27 from marine fungi. Compounds 1, 2, 5, and 6 displayed significant anti-Vibrio activity (Minimum inhibitory concentration, MIC values ranging from 3.1 to 50.0 μM) against three pathogenic Vibrio spp.

New Verrucosidin Derivatives from the Marine-Derived Fungus Penicillium sp. XL-01

Two new verrucosidin derivatives, named nordeoxyverrucosidin (1) and norverrucosidinol acetate (2), along with three known analogues (3–5) were isolated from the marine-derived fungus Penicillium sp. XL-01 collected from the Bohai Sea. Their structures and relative configurations were elucidated by comparing with literature data and a combination of spectroscopic techniques. The absolute configuration of 1 was assigned by quantum chemical calculation of the electronic circular dichroism (ECD) spectrum. Compounds 1 and 3 displayed promising cytotoxic activity against the MGC-803 cell line, with IC50 values of 0.96 and 1.14 μM, respectively, more effective than the positive control (cisplatin).

New Oxygenated Steroid from the Marine-Derived Fungus Aspergillus flavus

One new oxygenated steroid, named aspersteroid A (1), and three known analogues (2–4) were isolated from the marine-derived fungus Aspergillus flavus collected from the Bohai Sea. Their structures were elucidated by spectroscopic analyses and by comparison with previously reported data. The absolute configuration of tetracyclic nucleus in 1 was assigned by quantum chemical calculation of the electronic circular dichroism (ECD) spectrum. All the compounds were evaluated for their cytotoxic and antibacterial activities.