Cutaneous and foliar volatile organic compounds

Supplementary data for investigating 1) Foliar VOCs_peak area and 2) Cutaneous VOCs_peak area. This dual study investigates the applicability of comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS), in combination with machine learning, in identifying chemical markers — in the form of biogenic volatile organic compounds (VOCs) — as a tool of classification and prediction of discrete biological states.Samples of biogenic VOCs are varied and complex, presenting a significant challenge to analytical scrutiny. The first study of identifying predictive volatile markers of genus for southern African Plectranthus and Coleus using GC×GC-TOFMS and machine learning investigates foliar VOCs as markers of genus for southern African Plectranthus and Coleus species. The second study of identifying predictive volatile markers of malaria infection from human skin using GC×GC-TOFMS and machine learning investigates cutaneous VOCs from the human epidermis as markers of malaria-infection. GC×GC-TOFMS was used to analyse the relevant VOC analytes, and three machine learning algorithms (an elastic-net regression, a random forest and a support-vector machine) were used to construct models of the acquired data from a training set, and to make predictions — of genus, in the case of the first study, and on malaria-infection status, in the case of the second study — on samples from a testing set.