Wu Jun, Shui Hua, Zhang Mengke, Zeng Yida, Zheng Mingxin, Zhu Kong-Kai, Wang Shou-Bao, Bi Hongkai, Hong Kui, Cai You-Sheng
Department of Nephrology, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan, China.
Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Ministry of Education and School of Pharmaceutical Sciences, Wuhan University, Wuhan, China.
Front Microbiol. 2023 Feb 27;14:1138830. doi: 10.3389/fmicb.2023.1138830. eCollection 2023.
Dimeric natural products are widespread in plants and microorganisms, which usually have complex structures and exhibit greater bioactivities than their corresponding monomers. In this study, we report five new dimeric tetrahydroxanthones, aculeaxanthones A-E (), along with the homodimeric tetrahydroxanthone secalonic acid D (), chrysoxanthones B and C ( and ), and 4-4'-secalonic acid D (), from different fermentation batches of the title fungus.
A part of the culture was added to a total of 60 flasks containing 300 ml each of number II fungus liquid medium and culture 4 weeks in a static state at 28˚C. The liquid phase (18 L) and mycelia was separated from the fungal culture by filtering. A crude extract was obtained from the mycelia by ultrasound using acetone. To obtain a dry extract (18 g), the liquid phase combined with the crude extract were further extracted by EtOAc and concentrated in vacuo. The MIC of anaerobic bacteria was examined by a broth microdilution assay. To obtain MICs for aerobic bacteria, the agar dilution streak method recommended in Clinical and Laboratory Standards Institute document (CLSI) M07-A10 was used. Compounds 1-9 was tested against the Bel-7402, A-549 and HCT-116 cell lines according to MTT assay.
The structures of these compounds were elucidated on the base of 1D and 2D NMR and HR-ESIMS data, and the absolute configurations of the new xanthones were determined by conformational analysis and time-dependent density functional theory-electronic circular dichroism (TDDFT-ECD) calculations. Compounds 1-9 were tested for cytotoxicity against the Bel-7402, A549, and HCT-116 cancer cell lines. Of the dimeric tetrahydroxanthone derivatives, only compound 6 provided cytotoxicity effect against Bel-7402 cell line (IC50, 1.96 µM). Additionally, antimicrobial activity was evaluated for all dimeric tetrahydroxanthones, including four Gram-positive bacteria including Enterococcus faecium ATCC 19434, 168, ATCC 25923 and MRSA USA300; four Gram-negative bacteria, including 129, G27, as well as 26,695, and multi drug-resistant strain 159, and one ATCC 607. However, only compound 1 performed activities against G27, 26695, 129, 159, USA300, and 168 with MIC values of 4.0, 4.0, 2.0, 2.0, 2.0 and 1.0 μg/mL, respectively.
二聚体天然产物广泛存在于植物和微生物中，其结构通常较为复杂，且比相应的单体表现出更强的生物活性。在本研究中，我们从标题真菌的不同发酵批次中报道了5种新的二聚体四氢呫吨酮，即刺芒柄花呫吨酮A - E（），以及同二聚体四氢呫吨酮secalonic酸D（）、金黄呫吨酮B和C（和），还有4 - 4'-secalonic酸D（）。
将一部分培养物加入总共60个烧瓶中，每个烧瓶含有300 ml的II号真菌液体培养基，并在28˚C下静态培养4周。通过过滤将液相（18 L）和菌丝体从真菌培养物中分离出来。使用丙酮通过超声从菌丝体中获得粗提物。为了获得干燥提取物（18 g），将液相与粗提物合并，用乙酸乙酯进一步萃取并真空浓缩。通过肉汤微量稀释法检测厌氧菌的最低抑菌浓度（MIC）。为了获得需氧菌的MIC，使用了临床和实验室标准协会文件（CLSI）M07 - A10中推荐的琼脂稀释划线法。根据MTT法对化合物1 - 9针对Bel - 7402、A - 549和HCT - 116细胞系进行测试。
这些化合物的结构基于一维和二维核磁共振以及高分辨电喷雾电离质谱（HR - ESIMS）数据得以阐明，新呫吨酮的绝对构型通过构象分析和含时密度泛函理论 - 电子圆二色光谱（TDDFT - ECD）计算确定。对化合物1 - 9针对Bel - 7402、A549和HCT - 116癌细胞系进行细胞毒性测试。在二聚体四氢呫吨酮衍生物中，只有化合物6对Bel - 7402细胞系表现出细胞毒性作用（IC50，1.96 μM）。此外，对所有二聚体四氢呫吨酮进行了抗菌活性评估，包括四种革兰氏阳性菌，即粪肠球菌ATCC 19434、168、ATCC 25923和耐甲氧西林金黄色葡萄球菌USA300；四种革兰氏阴性菌，包括129、G27，以及26,695，还有多重耐药菌株159，以及一种ATCC 607。然而，只有化合物1对G27、26695、129、159、USA300和168表现出活性，其MIC值分别为4.0、4.0、2.0、2.0、2.0和1.0 μg/mL。
