Chaetoglobosin A

Chaetoglobosin A is a complex macrocyclic alkaloid with potent antimycotic, antiparasitic and antitumor properties. However, the low output and high cost of chaetoglobosin A biosynthesis have hampered the application and commercialization of chaetoglobosin A in agriculture and biomedicine. Here, the CgMfs1 gene, which encodes the major facilitator superfamily secondary transporter, was identified based on bioinformatics analysis, and an intensive study of its effects on chaetoglobosin A biosynthesis and secretion was performed using CgMfs1-silencing and CgMfs1-overexpression strategies. Inactivation of CgMfs1 caused a notable decrease in chaetoglobosin A yield from 58.66 mg/L to 19.95 mg/L (MFS1-3) and 17.13 mg/L (MFS1-4). The use of an efficient expression plasmid in Chaetomium globosum W7 to generate the overexpression mutant OEX13 resulted in the highest chaetoglobosin A increase to 298.77 mg/L. Interestingly, the transcription level of the polyketide synthase gene significantly fluctuated with the change in CgMfs1, confirming that the predicted efflux gene CgMfs1 could play a crucial role in chaetoglobosin A transportation. Effective efflux of chaetoglobosin A could possibly alleviate feedback inhibition, resulting in notable increase in the expression of the polyketide synthase gene. Furthermore, we utilized cornstalk as the fermentation substrate to produce chaetoglobosin A, and scanning electron microscopy and Fourier transform-infrared spectroscopy revealed that the strain OEX13 could well degrade cornstalk, presenting significant increases in the chaetoglobosin A yield, when compared with that produced by the wild-type strain (from 40.32 to 191.90 mg/L). Thus, this research provides a novel analogous engineering strategy for the construction of high-yielding strain and offers new insight into large-scale chaetoglobosin A production.

A new chaetoglobosin, penochalasin K (1) bearing an unusual six-cyclic 6/5/6/5/6/13 fused ring system, along with the known analogues, chaetoglobosin C (2), penochalasin I (3), and chaetoglobosin A (4) were isolated from the solid culture of the mangrove endophytic fungus Penicillium chrysogenum V11. Their structures were elucidated by 1D, 2D NMR spectroscopic analysis and high resolution mass spectroscopic data. The absolute configuration of compound 1 was determined by comparing the theoretical and experimental electronic circular dichroism curves. Compound 1 displayed significant inhibitory activities against Colletotrichum gloeosporioides and Rhizoctonia solani (MICs=6.13, 12.26μM, respectively), which was better than those of carbendazim, and exhibited potent cytotoxicity against MDA-MB-435, SGC-7901 and A549 cells (IC50<10μM). An effective biomimetic transformation of chaetoglobosin C (2)/chaetoglobosin A (4) into penochalasin K (1)/penochalasin I (3) was developed, which provided a simple method for the semi-synthesis of chaetoglobosins with a six-cyclic 6/5/6/5/6/13 fused system formed by the connectivity of C-5 and C-2' from their corresponding epoxide analogues.

Chaetoglobosin A is an antibacterial compound produced by Chaetomium globosum, with potential application as a biopesticide and cancer treatment drug. The aim of this study was to evaluate the feasibility of utilizing cornstalks to produce chaetoglobosin A by C. globosum W7 in solid-batch fermentation and to determine an optimal method for purification of the products. The output of chaetoglobosin A from the cornstalks was 0.34mg/g, and its content in the crude extract was 4.80%. Purification conditions were optimized to increase the content of chaetoglobosin A in the crude extract, including the extract solvent, temperature, and pH value. The optimum process conditions were found to be acetone as the extractant, under room temperature, and at a pH value of 13. Under these conditions, a production process of the antifungal chaetoglobosin A was established, and the content reached 19.17%. Through further verification, cornstalks could replace crops for the production of chaetoglobosin A using this new production process. Moreover, the purified products showed great inhibition against Rhizoctonia solani, with chaetoglobosin A confirmed as the main effective constituent (IC50=3.88μg/mL). Collectively, these results demonstrate the feasibility of using cornstalks to synthesize chaetoglobosin A and that the production process established in this study was effective.