Furaneol CAS 3658-77-3

3. Daily chemical and tobacco
Daily chemical products: As the raw material of essence, furanone can provide lasting fruit fragrance for shampoo and shower gel, and mask the pungent smell of chemical ingredients.
Tobacco flavoring: In cigarette filter additives, furanone reduces tar irritation, enhances smoking comfort, and gives a unique caramel aftertaste.
Natural and synthetic comparison: Although trace amounts of furanone are present in natural ingredients such as pineapple and strawberry, their content is not sufficient to meet industrial needs. The food industry generally uses chemical synthesis methods (such as hydroxyketone lactone reaction) to prepare high-purity furanone, which is only 1/10 of the cost of natural extraction.

In the field of medicine: a versatile approach from anti infection to anti-tumor

The antibacterial, anti-inflammatory, and anti biofilm activities of furanone have made it a hot topic in drug development, and its mechanism of action covers the following directions:

1. Broad-spectrum antibacterial agent
Gram positive/negative bacteria: By disrupting cell membrane permeability, they inhibit the formation of biofilms by pathogenic bacteria such as Escherichia coli and Staphylococcus aureus. For example, 2 (5H) - furanone can reduce the attachment of juvenile thick shelled mussels and inhibit the formation of marine bacterial biofilm.

1. Hypothesis of Furanone Synthesis in Strawberries

Figure 1 Hypothesis on the biosynthetic pathway of furanone in strawberry fruit. 4-Hydroxy-5-methyl-2-methylene-3 (2H) -furanone HMMF; 4-hydroxy-2, 5 - dimethyl-3 (2 h) -furanone HDMF; Strawberry quinone oxidoreductase (FaQR); F. Ananassa ketone oxidoreductase FaEO; F. Ananassa O-methyltransferase FaOMT.

Then, partially purify an enzyme involved in HDMF biosynthesis. The observed distribution of enzyme activity is related to the presence of a single peptide. Sequence analysis showed that the enzyme is completely identical to the protein sequence of a mature inducible auxin dependent quinone oxidoreductase (FaQR). FaQR protein is functionally expressed in Escherichia coli and catalyzes the formation of HDMF. 4-hydroxy-5-methyl-2-methyl-3 (2H) - furanone (HMMF) was identified as a natural substrate of FaQR and a precursor of HDMF (Figure 1).

FaQR catalyzes the reduction of alpha and beta unsaturated bonds in highly reactive ketene HMMF, later renamed as F Ananassa ketone oxidoreductase (FaEO). FaEO does not reduce the double bonds of straight chain 2-enal and 2-enal, but rather hydrogenates some HMMF derivatives substituted with methylene functional groups. HMMF was also detected in tomato and pineapple fruits, indicating that HDMF is synthesized through similar pathways in different fruits. Cloning of Solanum lycopersicon EO (SlEO) from cDNA and identification of the recombinant protein. Biochemical studies have confirmed that SlEO is involved in the formation of HDMF in tomato fruits. Compared with the other two NAD (P) H-dependent non flavone reductases, FaEO and SlEO exhibit narrower substrate spectra. Until recently, in order to elucidate the molecular mechanism of the special reaction catalyzed by FaEO, its crystal structure was determined in six different states or complexes, including complexes with HDMF and three substrate analogues. The results indicate that the 4R hydride of NAD (P) H is transferred to the unsaturated outer ring C-6 carbon of HMMF, forming an optically inactive enol intermediate, which then undergoes protonation to form HDMF.

It is worth noting that some reports suggest that the production of furanone may not be a direct activity of plant metabolic pathways, but rather a joint effort of strawberry plants and a related bacterium - Methanobacterium. However, the proposed route is not convincing as there are conflicting reports on the final steps of HDMF and DMMF, and tracer experiments do not support the proposed conversion of intermediate products lactose and 6-deoxy-D-fructose-1-phosphate to furanone.

2. Yeast synthesis of Furaneol

As the main flavor component of fermented soy sauce, HEMF has been isolated from fermented soy sauce for the first time. The formation of HEMF was promoted by culturing salt tolerant yeast, Zygosaccharomyces rouxii, in a medium containing the reaction products of ribose and glycine aminocarbonyl (Maillard). The mechanism of the compound was studied using its stable isotopes. The pentagonal skeleton and side chain methyl of HEMF are derived from ribose, while the ethyl group is derived from D-glucose or acetaldehyde. The role of yeast in the formation of HEMF is not only to provide D-glucose metabolites (acetaldehyde), but also to bind Maillard reaction products with D-glucose metabolites.

After incubation with some phosphate carbohydrates, the formation of HMF was found in the cytoplasmic extract of Saccharomyces cerevisiae. Since HMF is spontaneously formed from ribulose-5-phosphate via the Maillard intermediate 4,5-dihydroxy-2,3-pentanedione, it can be assumed that ribulose-5-phosphate is enzymatically generated in cytoplasmic extracts and then converted to HMF through chemical reactions. This hypothesis was confirmed by the production of hydroxymethylfurfural in a mixture containing commercially available enzymes and isotope labeled D-glucose-6-phosphate. Interestingly, HMF has been identified as an extracellular signaling molecule Al-2 catalyzed by LuxS enzyme and plays a role in bacterial intercellular communication. The chemical formation of Al-2 from 5-phosphate ribulose may also occur in vivo, which may be the reason for the Al-2-like activity in organisms lacking luxS genes.

The process of HDMF formation in Z. rouxii yeast under different culture conditions was studied using D-1,6-diphosphate fructose as raw material. When D-1,6-diphosphate fructose is used as the sole carbon source, the growth of Z. rouxii yeast and the formation of HDMF are not significant. Although Z. rouxii yeast cells grow in a medium with D-glucose as the sole carbon source, HDMF is only produced when D-fructose-1,6-diphosphate is added. The HDMF level is consistently correlated with yeast cell count and D-fructose-1,6-diphosphate concentration. After adding 1-13C-D-fructose-1,6-diphosphate, only single labeled HDMF was formed, while after adding 13C6-D-glucose, unlabeled furanone was formed. Therefore, the carbon of HDMF is entirely derived from exogenous D-fructose-1,6-diphosphate. A higher pH value of the culture medium has a positive effect on the formation of HDMF, but it can delay cell growth, so the optimal pH value is 5.1. Salt stress stimulated the production of HDMF. Adding o-phenylenediamine (a capture reagent for α - dicarbonyl (Maillard) intermediate) to the culture medium can yield three quinolone derivatives derived from D-fructose-1,6-diphosphate. The identification of this structure confirmed for the first time the chemical formation of 1-deoxy-2,3-hexadisase-6-phosphate, an intermediate in the HDMF formation pathway that was widely expected but never discovered. Due to the fact that HDMF is only available in Z It was detected in the presence of Rouxii cells, therefore it is assumed that there are more enzyme steps involved. At ambient temperature, HDMF can also be chemically generated in a solution containing D-fructose-1,6-diphosphate and NAD (P) H. NAD (P) H is necessary, and the application of labeled precursors indicates that the hydride of D-fructose-1,6-diphosphate backbone is transferred to C-5 or C-6. The biological and chemical processes of generating HDMF from D-fructose-1,6-diphosphate seem to follow a similar pathway.

Natural products with optical activity exhibit unique enantiomeric excess during biosynthesis due to stereoselectivity and enzyme catalyzed reactions. Although it is expected that HDMF will be generated through the combination of Z. rouxii yeast and fruit enzymes, the naturally occurring compound is racemic. The rapid racemization of HDMF explains this phenomenon due to the tautomerism of ketoenols. The 1H-NMR and chiral capillary electrophoresis analysis of proton deuterium exchange on the furanone ring of C-2 showed that the racemization rate of HDMF was the lowest at pH 4-5. Therefore, in order to verify the enzymatic formation of HDMF, we conducted incubation experiments with Z. rouxii yeast and strawberry protein extract at pH 5. The formation of enantiomerically enriched HDMF was confirmed in both experiments, while racemic furanone was detected under neutral pH conditions.

3. Bacterial synthesis of furanone

HDMF was detected after 4 days of growth of Pichia capsulata on casein peptone medium containing L-rhamnose. Stable isotope ratio mass spectrometry analysis confirmed that L-rhamnose is the carbon source of HDMF. The time course experiment led to the hypothesis that HDMF is formed by an intermediate produced by Pichia pastoris during the thermal sterilization process of the culture medium, as proposed by the Lutheran conjugative yeast. Similarly, in the results of the Maillard reaction, HDMF was detected in the medium prepared by heating sugar and amino acids. In the same fermentation medium, HDMF levels were also increased by fermentation of Lactococcus lactis subsp. cremoris.

4. Summary of the synthesis of furanone

3 (2H) - furanone compounds have low odor thresholds and enticing aroma characteristics, making them important aromatic chemicals. They are chemically formed from different carbohydrates during the Maillard reaction, and therefore exist in many processed foods, contributing to the production of aroma. But furanone can also be produced by yeast, bacteria, and plants, and its physiological function may be related to redox activity. Although deoxysugars such as L-rhamnose are effective precursors for HDMF in the Maillard reaction, D-1,6-diphosphate fructose has been identified as a natural precursor in fruits. In strawberry fruit, phosphorylated carbohydrates are converted into HMMF by phosphate and water elimination, and HMMF is ultimately reduced to HDMF by FaEO (FaQR). The methylation of HDMF leads to the accumulation of DMMF and is catalyzed by FaOMT. Overall, significant progress has been made in elucidating the biosynthetic pathways of natural furanone in microorganisms and plants due to the application of isotope labeled precursors. In the near future, understanding the genome sequence of forest strawberries will help detect genes with missing HDMF pathways, and improved imaging systems will help locate intracellular furanone. Understanding the relevant genes and enzymes will provide a foundation for the production of natural furanone through biotechnology.