GSE is a natural rich source of the polyphenols. The polyphenols in the GSE were often measured as gallic acid equivalent 
. Gallic acid was identified as the major activity component of GSE in many articles 
. GSE exerted potent antifungal activity against the yeast-like fungi strains and lower activity against dermatophytes and molds 
. In another experiment Ignacio and Thai demonstrated that GSE is as effective as miconazole nitrate salt 
. In this study we found 0.13 mg/mL GSE could inhibit the yeast effectively, which is coincident with 
. As no one had reported why GSE could kill the fungi. Then it is helpful to study the inhibitory mechanism for better understanding of this fungicide.
Severin and colleagues elegantly extended their findings towards a timeline of events, proposing a scheme of the mitochondrial death cascade in yeast. In summary, treatment of yeast cells with α-factor or amiodarone leads to hyperpolarisation of the mitochondrial membrane potential ΔΨmt. Elevation of ΔΨmt promotes ROS production, which then initiates the mitochondrial thread-grain transition (mitochondrial fragmentation) and de-energisation. The mitochondrial de-energisation finally results in loss of ΔΨmt 
. ΔΨmt and ROS changes in our study were consistent with Pozniakovsky et al. and Severin et al. 
Proline is a water-soluble amino acid that prevents cell death from dehydration under osmotic stress 
and increased the performance of yeast against GSE. The pantothenic acid content increased because its conversion to CoA was blocked. Without CoA, pyruvic acid could not enter into the citric acid cycle, which was consistent with reduction of CIT1 and PDB1. Although the synthesis of CoA was not effective, dissipative γ-Aminobutyrate turned into succinate which could enter into the TCA cycle to support the energy generation during the apoptosis 
. The increase of creatine illustrated that the yeast cells mainly relied on aerobic respiration under the GSE suppressed condition 
. The increase in glucitol was a sign of the decomposition of the cell wall 
GSE reduced the expression of RPL14A. We previously measured the total amount of the protein expression decreased in line and found that the expression of TEF1 was reduced. CPR2 expression increased due to protein structure distortion under the GSE stress.
Changes in glutamate and glutamate dehydrogenase expression were consistent. The expression of glutamate declined, while the expression of glutamate dehydrogenase increased. Glutamate could still produce energy despite the decline in citrate synthase because the glutamate-generated α-Ketoglutarate could continue to enter into the citric acid cycle to produce energy, which was consistent with the rise in malate dehydrogenase. Six glycolytic pathway proteins (TDH1, GPM1, FBP1, TPI1, ADH1 and PDC1) were increased, which explained the energy production during apoptosis that both occurs by glycolysis and glutamate metabolism in the TCA cycle. The increase of ATP2 showed that the production of energy was accelerated in yeast cells. Apoptosis was an energy-dependent process since apoptotic cells were metabolically active, and thus need high-energy compounds to maintain metabolic activity 
. The results in this study are consistent with the above theory. GSE induced apoptosis changes of metabolites and proteins strengthen the energy production, although some part of the functions were damaged.
Cu/Zn superoxide dismutase (SOD1), a protein previously identified to have antioxidant properties, was upregulated with metals stress, indicating the protein may be actively involved in metal detoxification of yeast 
. The results in this study is in good agreement with their work, because the stress proteins, TSA1 and SOD1, increased intracellularly to combat the explosive increase in oxidative substances. The increase of three kinds of cell wall proteins indicated that cell membrane damage had occurred and that the yeast cells were capable of remediation. Consistent with the report by Eisenberg et al. 
, the expression level of the membrane protein POR1 also increased. The increase in DNA repair enzymes demonstrated that yeast cells attempted to improve the DNA repair. The expression of COF1 increased, indicating the structural damage and repair of the cells.
Proteomics and metabonomics research is relative and based on the total content of the proteins and the metabolites in samples. GSE inhibition influenced protein expression and reduced the gross expression of metabolites in yeast. In this study, the relative increase of proteins and metabolites showed the tenacious resistance of the yeast cells to cell death, however, GSE induced yeast cell apoptosis by destruction of the mitochondrial 60 S ribosomal protein L14-A and prevention of the conversion of pantothenic acid to CoA.
The apoptotic phenotypes associated with CIT1 deletion were rescued by the addition of exogenous glutathione or glutamate, indicating that supply of glutamate for glutathione biosynthesis was likely to be a factor affecting ROS accumulation and cell death 
. Glutamate can be converted to α-ketoglutarate, an integral component of the citric acid cycle. It is a component of the antioxidant glutathione. The cyclization of glutamate produces proline, an amino acid important for resisting apoptosis 
. Although the role of glutamate was diminished in this study, it contributed substantially to fighting against apoptosis.
In summary, GSE-induced apoptosis was mediated by mitochondria-dependent pathway. Although initiated by the mitochondria, other organelles were also involved in this apoptosis. The changes in the yeast cells during apoptosis were indicative of their struggle with cell death. However, the destruction of the mitochondrial 60 S ribosomal protein L14-A and the cessation of the conversion of pantothenic acid to CoA resulted in apoptosis. The method can be used as a preliminary study of apoptosis, to identify interest proteins or metabolites and then further detailed study is needed to find out the exact mechanism of apoptosis.