Natural dibenzo-α-pyrones are an important group of metabolites derived from fungi, mycobionts, plants and animal feces. They exhibit a variety of biological activities such as toxicity on human and animals, phytotoxicity as well as cytotoxic, antioxidant, antiallergic, antimicrobial, antinematodal, and acetylcholinesterase inhibitory properties. Dibenzo-α-pyrones are biosynthesized via the polyketide pathway in microorganisms or metabolized from plant-derived ellagitannins and ellagic acid by intestinal bacteria. At least 53 dibenzo-α-pyrones have been reported in the past few decades. This mini-review aims to briefly summarize the occurrence, biosynthesis, biotransformation, as well as their biological activities and functions. Some considerations related to synthesis, production and applications of dibenzo-α-pyrones are also discussed.

The genus Ultragryllacris is mainly distributed in China and Thailand, and the type species Ultragryllacris pulchra Gorochov & Dawwrueng, 2015 includes four subspecies. Up to now, these subspecies were identified mainly based on their morphological characteristics, and no study on the molecular identification of subspecies and phylogenetic analyses has been reported. Here we obtained three mitogenomes of U. pulchra rubricapitis and one mitogenome of Homogryllacris yunnana and reconstructed the relationship of Ultragryllacris among genera. Species identification was performed with ABGD, jMOTU, and NJ tree based on cox1 (658 bp) and cob (550 bp) genes. The mitogenomes of U. pulchra rubricapitis and H. yunnana were 15558–16625 bp and 16209 bp in length, respectively. Most of the PCGs started with the typical ATN codons and terminated with complete TAA/TAG. Four mitogenomes showed positive AT skews and negative GC skews. Besides, the phylogenetic tree of BI and ML revealed that Ultragryllacris was a monophyletic group. One geographical population of Ultragryllacris pulchra rubricapitis was described and illustrated.

Hyalodendriella sp. Ponipodef12, an endophytic fungus from the hybrid “Neva” of Populus deltoides × P. nigra, is a high producer of the bioactive dibenzo-α-pyrones botrallin and TMC-264. However, both the botrallin and TMC-264 produced by Hyalodendriella sp. Ponipodef12 were retained as both intracellular and extracellular products. The aim of this study was to evaluate an in situ macroporous resin adsorption for enhancement of botrallin and TMC-264 production in mycelial liquid culture of Hyalodendriella sp. Ponipodef12. Production of botrallin and TMC-264 was most effectively enhanced by macroporous resin DM-301 among the thirteen nonionic macroporous resins tested. The highest botrallin yield (51.47 mg/L, which was 2.29-fold higher than the control at 22.49 mg/L) was obtained by adding resin DM-301 at 4.38% (g/mL) to the culture broth on day 24 and allowing a period of 4 days for adsorption. The highest TMC-264 yield reached 47.74 mg/L, which was 11.76-fold higher than that of the control (4.06 mg/L), and was achieved by adding DM-301 resin at 4.38% (w/v) in the culture broth on day 24 and allowing a period of 6 days for adsorption. The results show that in situ resin adsorption is an effective strategy for enhancing production of botrallin and TMC-264, and also for facilitating their recovery from mycelial liquid culture of Hyalodendriella sp. Ponipodef12.

The influences of eight metal ions (i.e., Na⁺, Ca²⁺, Ag⁺, Co²⁺, Cu²⁺, Al³⁺, Zn²⁺, and Mn⁴⁺) on mycelia growth and palmarumycins C₁₂ and C₁₃ production in liquid culture of the endophytic fungus Berkleasmium sp. Dzf12 were investigated. Three metal ions, Ca²⁺, Cu²⁺ and Al³⁺ were exhibited as the most effective to enhance mycelia growth and palmarumycin production. When calcium ion (Ca²⁺) was applied to the medium at 10.0 mmol/L on day 3, copper ion (Cu²⁺) to the medium at 1.0 mmol/L on day 3, aluminum ion (Al³⁺) to the medium at 2.0 mmol/L on day 6, the maximal yields of palmarumycins C₁₂ plus C₁₃ were obtained as 137.57 mg/L, 146.28 mg/L and 156.77 mg/L, which were 3.94-fold, 4.19-fold and 4.49-fold in comparison with that (34.91 mg/L) of the control, respectively. Al³⁺ favored palmarumycin C₁₂ production when its concentration was higher than 4 mmol/L. Ca²⁺ had an improving effect on mycelia growth of Berkleasmium sp. Dzf12. The combination effects of Ca²⁺, Cu²⁺ and Al³⁺ on palmarumycin C₁₃ production were further studied by employing a statistical method based on the central composite design (CCD) and response surface methodology (RSM). By solving the quadratic regression equation between palmarumycin C₁₃ and three metal ions, the optimal concentrations of Ca²⁺, Cu²⁺ and Al³⁺ in medium for palmarumycin C₁₃ production were determined as 7.58, 1.36 and 2.05 mmol/L, respectively. Under the optimum conditions, the predicted maximum palmarumycin C₁₃ yield reached 208.49 mg/L. By optimizing the combination of Ca²⁺, Cu²⁺ and Al³⁺ in medium, palmarumycin C₁₃ yield was increased to 203.85 mg/L, which was 6.00-fold in comparison with that (33.98 mg/L) in the original basal medium. The results indicate that appropriate metal ions (i.e., Ca²⁺, Cu²⁺ and Al³⁺) could enhance palmarumycin production. Application of the metal ions should be an effective strategy for palmarumycin production in liquid culture of the endophytic fungus Berkleasmium sp. Dzf12.

This paper reports one newly recorded species and one new species from China, namely Anelytra (Lichnofugia) symfioma (Ingrisch, 1998) and Liara (Liara) shii Liu & Bian sp. nov. All the species of Agraeciini Redtenbacher, 1891 from China are listed. The examined specimens are deposited in Guangxi Normal University. The complete mitochondrial genome of Palaeoagraecia brunnea Ingrisch, 1998 was 15984 bp and consisted of 37 genes and a control region. The A + T content of the mitogenome was as high as 70.2%. Most protein-coding genes started with the codon ATN and ended with typical stop codons TAA. Phylogenetic analyses based on mitogenomes suggested that Palaeoagraecia brunnea and the genus Pseudorhynchus had the closest genetic relationship.

The bacterium Xanthomonas citri subsp. citri (Xcc), which causes citrus canker disease, has caused great harm to citrus production worldwide. In this study, we aimed to clarify the antibacterial activities of extracts prepared with solvents of different polarities from the fungus Nemania sp. LJZ-Y-11 against Xcc, isolate and identify the active secondary metabolites, as well as evaluate the effects of the active compound on the Xcc. The results showed that extracts displayed significant antibacterial activities with the minimum inhibitory concentrations (MICs) and the minimal bactericidal concentrations (MBCs) at 0.3125 − 5 mg.mL ⁻¹ and 0.625 − 5 mg.mL ⁻¹ , respectively. Especially the ethyl acetate (EtOAc) extract displayed the highest activity (MIC = 0.3125 mg.mL ⁻¹ , MBC = 0.625 mg.mL ⁻¹ ). Five known compounds ( 1 − 5 ) were obtained from the EtOAc extract of Nemania sp. LJZ-Y-11, and identified as chrysogeside D ( 1 ), 2-pyruvoylaminobenzamide ( 2 ), 4-hydroxybenzaldehyde ( 3 ), stigmasta-7,22-diene-3β,5ɑ,6α-triol ( 4 ), and (2 S ,5 R )-2-ethyl-5-methylhexanedioic acid ( 5 ) based on spectroscopic analysis. Among them, compounds 3 and 5 showed significant inhibitory effects against Xcc, with MICs at 0.25 and 0.125 mg.mL ⁻¹ , respectively, and compound 5 showed more anti-Xcc potential with the MBC of 0.25 mg.mL ⁻¹ . The effects of compound 5 on the growth and cell morphology were dose-dependent and could reduce the formation of lesions or no lesions in leaves. Overall, the results indicated that citrus endophytic fungi could produce active products against the citrus canker pathogen, both crude extracts and compounds of the endophytic fungus Nemania sp. LJZ-Y-11 showed good anti-Xcc potential and encouraged further investigation of active compounds produced by citrus endophytic fungi.