Figure 1. Thin layer chromatography (TLC) analysis of the radiolabelled products formed following administration of different putative ¹⁴C-labelled precursors to tissue slices of fresh vanilla pods.

The ¹⁴C-labelled products formed following 48 h incubation were extracted into 70% MeOH, separated by TLC and monitored by autoradiography. The position of the radiolabelled precursors following chromatographic separation is shown on the right part of the thin layer. (*) indicates formation of ¹⁴C-labelled vanillin glucoside from the administered precursor. The presence of ultraviolet-absorbing components in the vanilla extracts as well as the position of the putative substrates after chromatographic separation was also monitored following exposure to ultraviolet light (254 nm) (Supplementary Fig. 1).