Oxygen radical based on non-thermal atmospheric pressure plasma alleviates lignin-derived phenolic toxicity in yeast

Table 1 Detected vanillin-specific compounds derived from oxygen-radical treatment

No.	Identified compounds	Concentration (mM)
1	Methoxy oxalic acid	–^a
2	Oxalic acid	3.031 ± 0.618
3	Methyl-2,5-dihydroxy-6-oxohexa-2,4-dienoate	–
4	Vanillin	0.957 ± 0.133
5	Methoxyhydroquinone	0.032 ± 0.008
6	Protocatechuic aldehyde	0.143 ± 0.043
7	4-Hydroxy-6-methoxy-6-oxohexa-2,4-dienoic acid	–
8	4-Formyl-6-methoxy-6-oxohexa-2,4-dienoic acid	–
9	Trihydroxy-5-methoxybenzene	–
10	3,4-Dihydroxy-5-methoxybenzaldehyde	0.139 ± 0.037
11	4-(2-Methoxy-2-oxoethylidene)pent-2-enedioic acid	–
12	Vanillic acid	0.198 ± 0.050
13	Unidentified compound that is contaminant in original reagent	–
14	Protocatechuic acid	0.011 ± 0.003
15	Unidentified compound that is putative aromatic dimer	–

Initial concentration of vanillin was 5.0 mM. The concentrations of vanillin and the reactants irradiated with oxygen-radical treatment for 20 min were quantified by GC–MS. Reaction products were trimethylsilylated and analysed by GC–MS. Numbers indicate the GC peaks shown in Fig. 1a. Mass spectra obtained from each GC peak are shown in Additional file 1: Figure S2
^aThese compounds were not quantified because these reagents were not commercially available

ISSN: 2731-3654