Yang Li,Kai Li,Bin Hu,Zhen-xi Zhang,Guan Zhang,Shi-yu Feng,Ti-peng Wang,Qiang Lu
As a value-added chiral chemical, 1-hydroxy-3,6-dioxobicyclo[3.2.1]oct-2-one (LAC) can be obtained via cellulose pyrolysis, but its yield is extremely low in the conventional pyrolysis process. Herein, novel nickel-tin layered double oxide (NiSn-LDO) catalysts were developed for the selective production of LAC from the in-situ catalytic fast pyrolysis (CFP) of cellulose. Several layered double oxides (LDOs) were prepared and evaluated via pyrolysis-chromatography/mass spectrometry (Py-GC/MS) tests for the in-situ CFP of cellulose. NiSn-LDO was determined as the most capable catalyst for selective LAC preparation, and further experiments were conducted to confirm the optimal condition to produce LAC over several essential factors of reaction temperature, Ni/Sn molar ratio in the NiSn-LDO catalyst, and catalyst-to-cellulose (CA-to-CL) ratio. The results demonstrated that LAC was sensitive to the reaction conditions, and its yield always exhibited the tide of first increasing followed with decreasing along with the increase of pyrolysis temperature, Ni/Sn molar ratio, and CA-to-CL ratio. The maximal LAC yield reached 9.11 wt% over the pyrolysis temperature of 320 °C using NiSn-LDO with a Ni/Sn molar ratio of 2/1 at the CA-to-CL ratio of 1/1, which was more than 5 times of that from the non-catalytic process (1.72 wt%). In addition, the NiSn-LDOs possessed much better catalytic capability to yield LAC with high selectivity than previously reported catalysts.
Two new metabolites, an α-pyridone derivative, 3-hydroxy-2-methoxy-5-methylpyridin-2(1H)-one (1), and a ceramide derivative, 3-hydroxy-N-(1-hydroxy-3-methylpentan-2-yl)-5-oxohexanamide (2), and a new natural product, 3-hydroxy-N-(1-hydroxy-4-methylpentan-2-yl)-5-oxohexanamide (3), along with 15 known compounds including chaetoglobosin C (7) and chaetoglobosin F (8) were isolated from the solid culture of the endophytic fungus Botryosphaeria dothidea KJ-1, collected from the stems of white cedar (Melia azedarach L). The structures were elucidated on the basis of spectroscopic analysis (1D and 2D NMR experiments and by mass spectrometric measurements), and the structure of 1 was confirmed by X-ray single-crystal diffraction. These metabolites were evaluated in vitro for antimicrobial, antioxidant, and cytotoxicity activities. Pycnophorin (4) significantly inhibited the growth of Bacillus subtilis and Staphyloccocus aureus with equal minimum inhibitory concentration (MIC) values of 25 μM. Stemphyperylenol (5) displayed a potent antifungal activity against the plant pathogen Alternaria solani with MIC of 1.57 μM comparable to the commonly used fungicide carbendazim. Both altenusin (9) and djalonensone (10) showed markedly DPPH radical scavenging activities. In addition, stemphyperylenol (5) and altenuene (6) exhibited strong cytotoxicity against HCT116 cancer cell line with a median inhibitory concentration (IC50) value of 3.13 μM in comparison with the positive control etoposide (IC50 = 2.13 μM). This is the first report of the isolation of these compounds from the endophytic B. dothidea.
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