New cryptotanshinone derivatives with anti-influenza A virus activities obtained via biotransformation by Mucor rouxii

Recent advances in anti-inflammation via AMPK activation

Inflammation is a complex physiological phenomenon, which is the body's defensive response, but abnormal inflammation can have adverse effects, and many diseases are related to the inflammatory response. AMPK, as a key sensor of cellular energy status, plays a crucial role in regulating cellular energy homeostasis and glycolipid metabolism. In recent years, the anti-inflammation effect of AMPK and related signalling cascade has begun to enter everyone's field of vision - not least the impact on metabolic diseases. A great number of studies have shown that anti-inflammatory drugs work through AMPK and related pathways. Herein, this article summarises recent advances in compounds that show anti-inflammatory effects by activating AMPK and attempts to comment on them.

Anti-inflammatory Activity of Tanshinone-Related Diterpenes from Perovskia artemisioides Roots

Perovskia artemisioides is a perennial and aromatic plant widely distributed in the Baluchestan region of Iran. Phytochemical analysis of a n-hexane extract of P. artemisioides roots, guided by an analytical approach based on LC-ESI/LTQOrbitrap/MS/MS, yielded six previously undescribed diterpenoid compounds (2, 9-11, 16, and 20), and 19 known diterpenoids, for which the structures were elucidated by 1D and 2D NMR experiments. Some of the isolated compounds showed significant anti-inflammatory activity using J774A.1 macrophage cells stimulated with Escherichia coli lipopolysaccharide. In particular, compounds 6, 8, 17, 18, 20, and 22 significantly inhibited the release of nitric oxide and the expression of related pro-inflammatory enzymes, such as inducible nitric oxide synthase and cycloxygenase-2. Moreover, two compounds that showed the highest activity in reducing nitric oxide release (6 and 18) were tested to evaluate their effects on nitrotyrosine formation and reactive oxygen species release. Both compounds inhibited ROS release and, in particular, compound 6 also inhibited nitrotyrosine formation at all tested concentrations, thus indicating a significant antioxidant potential.

A review of the biological activity and pharmacology of cryptotanshinone, an important active constituent in Danshen

Cryptotanshinone (IUPAC name: (R)-1,2,6,7,8,9-hexahydro-1,6,6-trimethyl-phenanthro(1,2-b)furan-10,11-dione), a biologically active constituent extracted from the roots and rhizomes of the plant Salvia miltiorrhiza, has been studied in depth as a medicinally active compound and shown to have efficacy in the treatment of numerous diseases and disorders. In this review, we describe in detail the current status of cryptotanshinone research, including findings relating to the structure, pharmacokinetics, pharmacological activity, and derivatives of this compound. Cryptotanshinoneh as a diverse range of pharmacological effects, including anti-cancer, anti-inflammatory, immune regulatory, neuroprotective, and anti-fibrosis activities. Studies on the molecular mechanisms underlying the activities of cryptotanshinone have established that the JAK2/STAT3, PI3K/AKT, NF-κB, AMPK, and cell cycle pathways are involved in the inhibitory and pro-apoptotic effects of cryptotanshinone on different tumor cell lines, these molecular pathways interact in a coordinated manner to inhibit cell proliferation, migration and invasion,and induce transformation, autophagy, necrosis, and cellular immunity. The anti-inflammatory mechanisms of cryptotanshinone have been found to be associated with the TLR4-MyD88/PI3K/Nrf2 and TLR4-MyD88/NF-κB/MAPK pathways, whereasthe Hedgehog, NF-κB, and Nrf-2/HO-1 pathways are regulated by cryptotanshinone to reduce organ fibrosis, and its inhibitory effects on the PI3K/AKT-eNOS pathway have been linked to neuroprotective effects. Given the potential medicinal utility of cryptotanshinone, further research is needed to verify the efficacy and safety of this compound in clinical use, evaluate its pharmacological activity, and identify molecular targets.

Bioactive Terpenes and Their Derivatives as Potential SARS-CoV-2 Proteases Inhibitors from Molecular Modeling Studies

The coronavirus disease 2019 (COVID-19) pandemic is caused by a novel coronavirus; the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). Millions of cases and deaths to date have resulted in a global challenge for healthcare systems. COVID-19 has a high mortality rate, especially in elderly individuals with pre-existing chronic comorbidities. There are currently no effective therapeutic approaches for the prevention and treatment of COVID-19. Therefore, the identification of effective therapeutics is a necessity. Terpenes are the largest class of natural products that could serve as a source of new drugs or as prototypes for the development of effective pharmacotherapeutic agents. In the present study, we discuss the antiviral activity of these natural products and we perform simulations against the M^pro and PL^pro enzymes of SARS-CoV-2. Our results strongly suggest the potential of these compounds against human coronaviruses, including SARS-CoV-2.

The oxygenated products of cryptotanshinone by biotransformation with Cunninghamella elegans exerting anti-neuroinflammatory effects by inhibiting TLR 4-mediated MAPK signaling pathway

Cryptotanshinone (1), a major bioactive constituent in the traditional Chinese medicinal herb Dan-Shen Salvia miltiorrhiza Bunge, has been reported to possess remarkable pharmacological activities. To improve its bioactivities and physicochemical properties, in the present study, cryptotanshinone (1) was biotransformed with the fungus Cunninghamella elegans AS3.2028. Three oxygenated products (2-4) at C-3 of cryptotanshinone (1) were obtained, among them 2 was a new compound. Their structures were elucidated by comprehensive spectroscopic analysis including HRESIMS, NMR and ECD data. All of the biotransformation products (2-4) were found to inhibit significantly lipopolysaccharide-induced nitric oxide production in BV2 microglia cells with the IC₅₀ values of 0.16-1.16 μM, approximately 2-20 folds stronger than the substrate (1). These biotransformation products also displayed remarkably improved inhibitory effects on the production of inflammatory cytokines (IL-1β, IL-6, TNF-α, COX-2 and iNOS) in BV-2 cells via targeting TLR4 compared to substrate (1). The underlying mechanism of 2 was elucidated by comparative transcriptome analysis, which suggested that it reduced neuroinflammatory mainly through mitogen-activated protein kinase (MAPK) signaling pathway. Western blotting results revealed that 2 downregulated LPS-induced phosphorylation of JNK, ERK, and p38 in MAPK signaling pathway. These findings provide a basal material for the discovery of candidates in treating Alzheimer's disease.

Annular oxygenation and rearrangement products of cryptotanshinone by biotransformation with marine-derived fungi Cochliobolus lunatus and Aspergillus terreus

Structural modification of natural products by biotransformation with fungi is an attractive tool to obtain novel bioactive derivatives. In the present study, cryptotanshinone (1), a quinoid abietane diterpene from traditional Chinese medicine Salvia miltiorrhiza (Danshen), was transformed by two marine-derived fungi. By using Cochliobolus lunatus TA26-46, one new oxygenated and rearranged product (2), containing a 5,6-dihydropyrano[4,3-b]chromene moiety, together with one known metabolite (10), were obtained from the converted broth of cryptotanshinone (1) with the isolated yields of 1.0% and 2.1%, respectively. While, under the action of Aspergillus terreus RA2905, seven new transformation products (3-9) as well as 10 with the fragments of 2-methylpropan-1-ol and oxygenated p-benzoquinone were produced and obtained with the isolated yields of 0.1%-1.3%. The structures of the new compounds were elucidated by comprehensive spectroscopic analysis including High Resolution Electrospray Ionization Mass Spectroscopy (HRESIMS), Nuclear Magnetic Resonance (NMR) and Electronic Circular Dichroism (ECD). The metabolic pathways of cryptotanshinone by these two fungi were presumed to be the opening and rearrangement of furan ring, and/or oxygenation of cyclohexane ring. Cryptotanshinone (1) and its metabolites displayed anti-inflammatory activities against NO production in LPS-stimulated BV-2 cells and antibacterial activities towards methicillin-resistant Staphylococcus aureus. These findings revealed the potential of marine fungi to transform the structures of natural products by biotransformation.

Genome-based mining of new antimicrobial meroterpenoids from the phytopathogenic fungus Bipolaris sorokiniana strain 11134

Polyketide-terpenoid hybrid compounds are one of the largest families of meroterpenoids, with great potential for drug development for resistant pathogens. Genome sequence analysis of secondary metabolite gene clusters of a phytopathogenic fungus, Bipolaris sorokiniana 11134, revealed a type I polyketide gene cluster, consisting of highly reducing polyketide synthase, non-reducing polyketide synthase, and adjacent prenyltransferase. MS- and UV-guided isolations led to the isolation of ten meroterpenoids, including two new compounds: 19-dehydroxyl-3-epi-arthripenoid A (1) and 12-keto-cochlioquinone A (2). The structures of 1-10 were elucidated by the analysis of NMR and high-resolution electrospray ionization mass spectroscopy data. Compounds 5-8 and 10 showed moderate activity against common Staphylococcus aureus and methicillin-resistant S. aureus, with minimum inhibitory concentration (MIC) values of 12.5-100 μg/mL. Compound 5 also exhibited activity against four clinical resistant S. aureus strains and synergistic antifungal activity against Candida albicans with MIC values of 12.5-25 μg/mL. The biosynthetic gene cluster of the isolated compounds and their putative biosynthetic pathway are also proposed. KEY POINTS: • Ten meroterpenoids were identified from B. sorokiniana, including two new compounds. • Cochlioquinone B (5) showed activity against MRSA and synergistic activity against C. albicans. • The biosynthetic gene cluster and biosynthetic pathway of meroterpenoids are proposed. • Genome mining provided a new direction to uncover the diversity of meroterpenoids.

New diterpenoid quinones derived from Salvia miltiorrhiza and their cytotoxic and neuroprotective activities

One new tanshinone derivative, which possesses an unusual 6/6/5/6 fused-ring skeleton system (1), together with four new five-membered lactone benzohexa-membered ring compounds (2, 3, 4A and 4B), and three new carboxyl substituted 5,5-spiroketal compounds (5–7), were isolated from the dried rhizomes of Salvia miltiorrhiza. The structures of these compounds were determined by multiple spectral analyses (UV, IR, NMR, and HR-ESI-MS). In addition, the absolute configurations were established by X-ray diffraction experiments, calculated and experimental circular dichroism spectra. Evaluation of antitumor activity showed that 1 had strong cytotoxicity to tumor-repopulating cells (TRCs) with an IC₅₀ value of 2.83 μM. In the evaluation of neuroprotective activity, 4A and 6 showed a strong improvement in the survival rates of SK-N-SH cell injury induced by oxygen glucose deprivation (OGD).

A new tanshinone derivative, which possesses an unusual 6/6/5/6 fused-ring skeleton together with 4 new five-membered lactone benzohexa-membered ring compounds and 3 new carboxyl substituted 5,5-spiroketal compounds, were isolated from dried rhizomes of Salvia miltiorrhiza.

Genome- and MS-based mining of antibacterial chlorinated chromones and xanthones from the phytopathogenic fungus Bipolaris sorokiniana strain 11134

Halogen substituents are important for biological activity in many compounds. Genome-based mining of halogenase along with its biosynthetic gene cluster provided an efficient approach for the discovery of naturally occurring organohalogen compounds. Analysis of the genome sequence of a phytopathogenic fungus Bipolaris sorokiniana 11134 revealed a polyketide gene cluster adjacent to a flavin-dependent halogenase capable of encoding halogenated polyketides, which are rarely reported in phytopathogenic fungi. Furthermore, MS- and UV-guided isolation and purification led to the identification of five chlorine-containing natural products together with seven other chromones and xanthones. Two of the chlorinated compounds and four chromones are new compounds. Their structures were elucidated by NMR spectroscopic analysis and HRESIMS data. The biosynthetic gene clusters of isolated compounds and their putative biosynthetic pathway are also proposed. One new chlorinated compound showed activity against Staphylococcus aureus, methicillin-resistant S. aureus, and three clinical-resistant S. aureus strains with a shared minimum inhibitory concentration (MIC) of 12.5 μg/mL. Genome-based mining of halogenases combined with high-resolution MS- and UV-guided identification provides an efficient approach to discover new halogenated natural products from microorganisms.

Benzannulated spiroketal natural products: isolation, biological activity, biosynthesis, and total synthesis

A review discussing the isolation, biological activity, biosynthesis, and total synthesis of naturally occurring benzannulated spiroketals.

An Overview of Biotransformation and Toxicity of Diterpenes

Diterpenes have been identified as active compounds in several medicinal plants showing remarkable biological activities, and some isolated diterpenes are produced at commercial scale to be used as medicines, food additives, in the synthesis of fragrances, or in agriculture. There is great interest in developing methods to obtain derivatives of these compounds, and biotransformation processes are interesting tools for the structural modification of natural products with complex chemical structures. Biotransformation processes also have a crucial role in drug development and/or optimization. The understanding of the metabolic pathways for both phase I and II biotransformation of new drug candidates is mandatory for toxicity and efficacy evaluation and part of preclinical studies. This review presents an overview of biotransformation processes of diterpenes carried out by microorganisms, plant cell cultures, animal and human liver microsomes, and rats, chickens, and swine in vivo and highlights the main enzymatic reactions involved in these processes and the role of diterpenes that may be effectively exploited by other fields.