Perangustols A and B,a pair of new azaphilone epimers from a marine sediment-derived fungus Cladosporium perangustm FS62

A pair of new azaphilone epimers, perangustols A-B (1–2), and two new natural products (3–4), together with two known metabolites (5–6) were isolated from the culture of the marine sediment-derived fungus Cladosporium perangustum FS62. The structures of these compounds were established on the basis of extensive spectroscopic analysis. The isolated compounds (1–6) were evaluated for their cytotoxic activities against the SF-268, MCF-7, NCI-H460, and HepG-2 tumor cell lines. Nonetheless, no significant activity was observed.     

Genetic, molecular, and biochemical basis of fungal tropolone biosynthesis

A gene cluster encoding the biosynthesis of the fungal tropolone stipitatic acid was discovered in Talaromyces stipitatus (Penicillium stipitatum) and investigated by targeted gene knockout. A minimum of three genes are required to form the tropolone nucleus: tropA encodes a nonreducing polyketide synthase which releases 3-methylorcinaldehyde; tropB encodes a FAD-dependent monooxygenase which dearomatizes 3-methylorcinaldehyde via hydroxylation at C-3; and tropC encodes a non-heme Fe(II)-dependent dioxygenase which catalyzes the oxidative ring expansion to the tropolone nucleus via hydroxylation of the 3-methyl group. The tropA gene was characterized by heterologous expression in Aspergillus oryzae, whereas tropB and tropC were successfully expressed in Escherichia coli and the purified TropB and TropC proteins converted 3-methylorcinaldehyde to a tropolone in vitro. Finally, knockout of the tropD gene, encoding a cytochrome P450 monooxygenase, indicated its place as the next gene in the pathway, probably responsible for hydroxylation of the 6-methyl group. Comparison of the T. stipitatus tropolone biosynthetic cluster with other known gene clusters allows clarification of important steps during the biosynthesis of other fungal compounds including the xenovulenes, citrinin, sepedonin, sclerotiorin, and asperfuranone.     

嗜氮酮类化合物Penicilone B的体外抗氧化活性研究

目的研究嗜氮酮类化合物Penicilone B的体外抗氧化活性,并采用密度泛函理论(DFT)分析其抗氧化机制。方法先采用2,2′-联氮-双-3-乙基苯并噻唑啉-6-磺酸(ABTS)自由基清除能力、1,1-二苯基-2-三硝基苯肼(DPPH)自由基清除能力和氧自由基吸收能力(ORAC)3种体外抗氧化方法测定Penicilone B的抗氧化活性;再采用DFT进行Penicilone B的分子结构优化,并在M06-2x/6-31+G**水平从分子结构参数、酚羟基解离焓(BDE)、电离势(IP)、前线分子轨道(FMO)等方面分析Penicilone B的抗氧化机理。结果体外抗氧化实验结果显示,Penicilone B具有一定的体外抗氧化活性,在100μg/mL时,其对ABTS自由基和DPPH自由基的清除率分别为(11.62±1.19)%、(22.68±2.81)%,阳性对照维生素C(Vc)的清除率分别为(43.17±3.88)%、(58.73±4.70)%。此外,Penicilone B和Vc的ORAC值分别为(1.06±0.06)、(2.87±0.15)μmol trolox/mg。DFT计算结果表明,Penicilone B的C15位酚羟基易发生抽氢反应;Penicilone B还可能通过直接和活泼自由基结合而终止氧化的链锁反应,A环和B环是主要活性位点。结论本研究首次采用DFT研究嗜氮酮类化合物的抗氧化机理,理论计算和实验结果基本一致,可为进一步研究嗜氮酮类化合物提供理论依据。     

1株软珊瑚共附生真菌Penicillium sclerotiorum中azaphilones类化合物及其生物活性研究

目的对1株西沙群岛永兴岛海域来源短指软珊瑚sinularia sp.共附生真菌Penicillium sclerotiorum中的azaphilones类化合物及其生物活性进行研究。方法利用硅胶柱层析、薄层色谱、Sephadex LH-20凝胶柱层析、MPLC、HPLC等分离手段对菌株发酵提取物进行分离和纯化;运用NMR、MS等现代波谱学方法,并结合相关文献数据比对,鉴定化合物的结构;通过细胞毒活性模型评价化合物抗肿瘤活性。结果从真菌Penicillium sclerotiorum的代谢产物中获得了9个azaphilones类合物,分别(+)-Sclerotiorin(1), Isochromophilone Ia(2), Isochromophilone Ib(3), Isochromophilone III(4), epi-isochromophilone III (5), Isochromophilone IV(6), dechloroisochromophilone IV(7), Isochromophilone VIII(8), TL-1-monoAc(9),其中化合物8在30μmol.L_^-1浓度下对HL-60细胞的抑制率达到97.87%,IC₅₀值为11.81μmol.L_^-1。     

Design,Synthesis and Fungicidal Activity of Novel Sclerotiorin Derivatives

Sclerotiorin, a chlorine‐containing azaphilone‐type natural product, was first isolated from Penicillium sclerotiorum and has been reported to exhibit weak fungicidal activity. Optimization of the substituents at the 3‐ and 5‐positions of the sclerotiorin framework was investigated with the aim of discovering novel fungicides with improved activity. The design of sclerotiorin analogues involved replacing the diene side chain with a phenyl group or an aromatic‐ or heteroaromatic‐containing aliphatic side chain. The designed compounds were synthesized by cycloisomerization and subsequent oxidation of suitable 2‐alkynylbenzaldehydes, in which a variety of substituents were introduced using a Sonogashira coupling reaction. The structures of these newly prepared compounds were confirmed by ¹H and ¹³C NMR spectroscopy, HRMS and single‐crystal X‐ray analysis. The antifungal activity of the synthesized compounds was evaluated against seven phytopathogenic species. Compounds 3 , 9g and 9h were found to have a broad spectrum of fungicidal activity, and these structurally simpler products can be recognized as lead compounds for further optimization.     

一株渤海来源真菌Pleosporales sp.中嗜氮酮类化合物及其生物活性△

目的 对一株渤海来源真菌Pleosporales sp.中嗜氮酮类化合物进行分离鉴定,并探讨其生物活性。方法 利用硅胶柱层析和高效液相色谱等分离手段对化合物进行分离和纯化;运用NMR和MS等现代波谱方法,并结合相关文献,对化合物的结构进行鉴定;运用抗真菌活性模型对化合物的生物活性进行评价。结果 从该真菌中分离获得了6个嗜氮酮类化合物isochromophilone I, VI, IX (1–3), (+)-sclerotiorin (4), 5-chloroisorotiorin (5), hypocrellone A (6)。化合物1–6对三株农业致病真菌Thielaviopsis paradoxa, Pestalotia calabae, 和Glorosprium musarum均显示出中等强度的抑制活性。结论 化合物1–6均为首次从Pleosporales属真菌中分离得到,具有作为抗农业致病真菌药的研究价值。