Fig. 1 in Identification and functional characterization of a γ-terpinene synthase in Nigella sativa L (black cumin)

Fig. 1. Predicted biosynthetic pathway for the production of thymoquinone in N. sativa seed. The precursor geranyl diphosphate (GDP) is converted to γ-terpinene by the γ-terpinene synthase NsTPS1. This product may be oxidized by cytochrome P450 monooxygenases (P450s) of the CYP71D subfamily to produce an unstable cyclohexadienol intermediates which is then dehydrogenated by a short-chain dehydrogenase/reductase (SDR) to the corresponding ketone. The resulting carvacrol and thymol may then be hydroxylated to thymo-hydroquinone and further oxidized to thymoquinone (based on Krause et al., 2021).