STR3 and CYS3 Contribute to 2‑Furfurylthiol Biosynthesis in Chinese Sesame-Flavored Baijiu Yeast

2-Furfurylthiol is an important aroma compound with characteristic sesame flavor. It was recently identified as the representative aroma compound of Chinese sesame-flavored Baijiu. But its formation mechanism is unclear. In this study, the dominant yeast species <i>Saccharomyces cerevisiae</i>, <i>Pichia kudriavzevii</i>, and <i>Wickerhamomyces anomalus</i> were isolated from samples of Chinese sesame-flavored fermentation and were screened for the capacity of 2-furfurylthiol biosynthesis. Some isolates were found to be capable of generating 2-furfurylthiol using furfural and l-cysteine as precursors, among which <i>S. cerevisiae</i> G20 exhibited the strongest capacity with a yield of 3.03 mg/L. Furthermore, the genes <i>STR3</i> and <i>CYS3</i> from <i>S. cerevisiae</i> were cloned and overexpressed in the reference strain <i>S. cerevisiae</i> S288c and the isolate strain G20, respectively, which resulted in a significant increase in 2-furfurylthiol release in the two strains. Moreover, inactivation of <i>STR3</i> gene in S288c and G20 led to obvious reduction in 2-furfurylthiol production, demonstrating that <i>STR3</i> got involved in 2-furfurylthiol biosynthesis in <i>S. cerevisiae.</i> It is the first time that the yeast isolates with high capacity of 2-furfurylthiol biosynthesis were found during Chinese sesame-flavored Baijiu fermentation and confirmed that the genes <i>STR3</i> and <i>CYS3</i> were closely relevant to 2-furfurylthiol biosynthesis

A new lindenane-type sesquiterpenoid lactone from <i>Chloranthus japonicus</i>

<p>Chromatographic fractionation of the EtOH extracts of the Traditional Chinese Medicine (TCM) <i>Chloranthus japonicus</i>, has led to the isolation of a new lindenane-type sesquiterpenoid lactone derivative (<b>1</b>). Rosmarylchloranthalactone E (<b>1</b>), which consists of lindenane sesquiterpenoid lactone and rosmarinic acid moieties linked via an ester bridge, was structurally elucidated by 1D and 2D NMR and HRMS data. Compound <b>1</b> was a potent phosphodiesterase-4 (PDE4) inhibitor with an IC₅₀ value of 0.96 ± 0.04 μM.</p

Generation of 2‑Furfurylthiol by Carbon–Sulfur Lyase from the <i>Baijiu</i> Yeast <i>Saccharomyces cerevisiae</i> G20

2-Furfurylthiol is the representative aroma compound of Chinese sesame-flavored <i>baijiu</i>. Previous studies demonstrated that <i>baijiu</i> yeasts could generate 2-furfurylthiol using furfural and l-cysteine as precursors and that the <i>Saccharomyces cerevisiae</i> genes <i>STR3</i> and <i>CYS3</i> are closely related to 2-furfurylthiol biosynthesis. To confirm the mechanism of the <i>STR3</i>- and <i>CYS3</i>-gene products on 2-furfurylthiol biosynthesis, their encoded proteins were purified, and we confirmed their activities as carbon–sulfur lyases. Str3p and Cys3p were able to cleave the cysteine–furfural conjugate to release 2-furfurylthiol. Moreover, the characterization of the enzymatic properties of the purified proteins shows good thermal stabilities and wide pH tolerances, which enable their strong potential for various applications. These data provide direct evidence that yeast Str3p and Cys3p release 2-furfurylthiol in vitro, which can be applied to improve <i>baijiu</i> flavor

New bioactive labdane diterpenoids from <i>Marrubium aschersonii</i>

<p>A phytochemical investigation of the ethanol extract of <i>Marrubium aschersonii</i> Magnus (Lamiaceae) collected from Tunisia led to the isolation and identification of two new labdane diterpenoids, marrubaschs A (<b>1</b>) and B (<b>2</b>), along with two known compounds (<b>3</b> and <b>4</b>). Their structures were elucidated by spectroscopic methods including HRESIMS and NMR techniques. All compounds were evaluated for their inhibitory effects on the nitric oxide (NO) production induced by lipopolysaccharide in RAW 264.7 macrophage cells. Compound <b>2</b> exhibited weak inhibition of NO production with an IC₅₀ value of 35 ± 1.0 μM.</p

Electrochemical Reduction of Perfluorooctanoic Acid (PFOA): An Experimental and Theoretical Approach

Perfluorooctanoic acid (PFOA) is an artificial chemical of global concern due to its high environmental persistence and potential human health risk. Electrochemical methods are promising technologies for water treatment because they are efficient, cheap, and scalable. The electrochemical reduction of PFOA is one of the current methodologies. This process leads to defluorination of the carbon chain to hydrogenated products. Here, we describe a mechanistic study of the electrochemical reduction of PFOA in gold electrodes. By using linear sweep voltammetry (LSV), an E0′ of −1.80 V vs Ag/AgCl was estimated. Using a scan rate diagnosis, we determined an electron-transfer coefficient (αexp) of 0.37, corresponding to a concerted mechanism. The strong adsorption of PFOA into the gold surface is confirmed by the Langmuir-like isotherm in the absence (KA = 1.89 × 1012 cm3 mol–1) and presence of a negative potential (KA = 3.94 × 107 cm3 mol–1, at −1.40 V vs Ag/AgCl). Based on Marcus–Hush’s theory, calculations show a solvent reorganization energy (λ0) of 0.9 eV, suggesting a large electrostatic repulsion between the perfluorinated chain and water. The estimated free energy of the transition state of the electron transfer (ΔG‡ = 2.42 eV) suggests that it is thermodynamically the reaction-limiting step. 19F – 1H NMR, UV–vis, and mass spectrometry studies confirm the displacement of fluorine atoms by hydrogen. Density functional theory (DFT) calculations also support the concerted mechanism for the reductive defluorination of PFOA, in agreement with the experimental values

A new bisabolane sesquiterpenoid and a new abietane diterpenoid from <i>Cephalotaxus sinensis</i>

<p>Phytochemical investigation of <i>Cephalotaxus sinensis</i> has led to the isolation of a new bisabolane sesquiterpenoid (<b>1</b>), a new abietane diterpenoid (<b>2</b>), and <b>13</b> known compounds (<b>3–15</b>). Their structures were elucidated by extensive spectroscopic analysis (MS, UV, IR, and NMR).</p

Jatrophane Diterpenoids as Modulators of P‑Glycoprotein-Dependent Multidrug Resistance (MDR): Advances of Structure–Activity Relationships and Discovery of Promising MDR Reversal Agents

The phytochemical study of <i>Pedilanthus tithymaloides</i> led to the isolation of 13 jatrophane diterpenoids (<b>1</b>–<b>13</b>), of which eight (<b>1</b>–<b>8</b>) are new. Subsequent structural modification of the major components by esterification, hydrolysis, hydrogenation, or epoxidation yielded 22 new derivatives (<b>14</b>–<b>35</b>). Thus, a jatrophane library containing two series of compounds was established to screen for P-glycoprotein (Pgp)-dependent MDR modulators. The activity was evaluated through a combination of Rho123 efflux and chemoreversal assays on adriamycin resistant human hepatocellular carcinoma cell line HepG2 (HepG2/ADR) and adriamycin resistant human breast adenocarcinoma cell line MCF-7 (MCF-7/ADR). Compounds <b>19</b>, <b>25</b>, and <b>26</b> were identified as potent MDR modulators with greater chemoreversal ability and less cytotoxicity than the third-generation drug tariquidar. The structure–activity relationship (SAR) was discussed, which showed that modifications beyond just increasing the lipophilicity of this class of Pgp inhibitors are beneficial to the activity. Compound <b>26</b>, which exhibited a remarkable metabolic stability in vitro and a favorable antitumor effect in vivo, would serve as a promising lead for the development of new MDR reversal agents

Jatrophane Diterpenoids as Modulators of P‑Glycoprotein-Dependent Multidrug Resistance (MDR): Advances of Structure–Activity Relationships and Discovery of Promising MDR Reversal Agents

The phytochemical study of <i>Pedilanthus tithymaloides</i> led to the isolation of 13 jatrophane diterpenoids (<b>1</b>–<b>13</b>), of which eight (<b>1</b>–<b>8</b>) are new. Subsequent structural modification of the major components by esterification, hydrolysis, hydrogenation, or epoxidation yielded 22 new derivatives (<b>14</b>–<b>35</b>). Thus, a jatrophane library containing two series of compounds was established to screen for P-glycoprotein (Pgp)-dependent MDR modulators. The activity was evaluated through a combination of Rho123 efflux and chemoreversal assays on adriamycin resistant human hepatocellular carcinoma cell line HepG2 (HepG2/ADR) and adriamycin resistant human breast adenocarcinoma cell line MCF-7 (MCF-7/ADR). Compounds <b>19</b>, <b>25</b>, and <b>26</b> were identified as potent MDR modulators with greater chemoreversal ability and less cytotoxicity than the third-generation drug tariquidar. The structure–activity relationship (SAR) was discussed, which showed that modifications beyond just increasing the lipophilicity of this class of Pgp inhibitors are beneficial to the activity. Compound <b>26</b>, which exhibited a remarkable metabolic stability in vitro and a favorable antitumor effect in vivo, would serve as a promising lead for the development of new MDR reversal agents

Chemical constituents of <i>Penicillium ferraniaense</i> GE-7 and their cytotoxicities

Phytochemical investigation on the plant endophytic fungus Penicillium ferraniaense GE-7 led to the isolation of 18 compounds including one new α-pyrone derivative, peniferranige A (1). The structure including the absolute configuration of compound 1 was elucidated by NMR, HRMS, and ECD data. Demethoxyfumitremorgin C (16) and meleagrin (17) possessed moderate activities against the human lung cancer cell line H1975 with IC50 values of 28.52 ± 1.07 and 13.94 ± 1.92 μM, respectively.</p

Novel Method for l‑Methionine Production Catalyzed by the Aminotransferase ARO8 from <i>Saccharomyces cerevisiae</i>

The aminotransferase ARO8 was proved to play an efficient role in conversion of l-methionine into methionol via the Ehrlich pathway in <i>Saccharomyces cerevisiae</i> in our previous work. In this work, the reversible transamination activity of ARO8 for conversion of α-keto-γ-(methylthio) butyric acid (KMBA) into l-methionine was confirmed in vitro. ARO8 was cloned from <i>S. cerevisiae</i> S288c and overexpressed in <i>Escherichia coli</i> BL21. A 2-fold higher aminotransferase activity was detected in the recombinant strain ARO8-BL21, and ARO8 was detected in the supernatant of ARO8-BL21 lysate with IPTG induction by SDS-PAGE analysis. The recombinant ARO8 was then purified and used for transforming KMBA into l-methionine. An approximately 100% conversion rate of KMBA into l-methionine was achieved by optimized enzymatic reaction catalyzed by ARO8. This work fulfilled l-methionine biosynthesis catalyzed by the aminotransferase ARO8 using glutamate and KMBA, which provided a novel method for l-methionine production by enzymatic catalysis with the potential application prospect in industry