Table 3 VOCs found to correlate with glucose levels

2-pentyl nitrate [22]

Generated through pathways involving organic peroxy radical (RO2▪) with NO or NO2. Could be modulated by acute changes in systematic oxidative status [22].

Acetone [20–22, 32]

Derived from acetoacetate and is produced by synthesis and degradation of ketone bodies and is therefore related to blood glucose levels [32].

Glycolysis/Pyruvate metabolism

Cabon monoxide [27]

Possibly due to activation of HO by glucose, and the positive modulation of CO non insulin secretion [27].

Ethanol [20, 22, 32]

Not produced by mammalian cells. Likely due to alcoholic fermentation of glucose by gut bacteria and yeast [32].

Glycolysis/Gluconeogenesis

Ethyl benzene [20, 22]

Inhaled and partly metabolized by liver, then exhaled at lower concentration. Rapid-onset hyperglycemia likely suppressed hepatic metabolism causing peaks in exhaled air [20].

M/P-xylene [20]

Inhaled and partly metabolized by liver, then exhaled at lower concentration. Rapid-onset hyperglycemia likely suppressed hepatic metabolism causing peaks in exhaled air [20].

Methanol [22]

Reflects gut flora activity and therefore responsive to glycemic fluctuations [22].

Methyl nitrate [22, 39]

A small fraction of superoxide ion (O2▪−), a byproduct of oxidative reactions, reacts with nitric oxide which in turn can react with methanol to eventually form an isomer of Methyl nitrate [39].

O-xylene [20]

Inhaled and partly metabolized by liver, then exhaled at lower concentration. Rapid-onset hyperglycemia likely suppressed hepatic metabolism causing peaks in exhaled air [20].

Propane [22]

Reflects gut flora activity and therefore responsive to glycemic fluctuations [22].

N-4 fatty acid Peroxidation Protein oxidation