Tracing metabolic route of thymoquinone biosynthesis in diverse Nigella sativa L. cultivars using RP-HPLC technique

Although the therapeutic role of Nigella sativa has been known for a long time, for optimal utilization of plant parts, the developmental profiling of bioactive constituents and their dependence on germplasm diversity need to be assessed.Different cultivars of Nigella sativa (covering 3 samples from northern states of India and 3 reference samples) were taken to explore the relative accumulation of thymol (Thy) and thymoquinone (TQ) in different plant parts, i.e., stem, leaf, bud, flower, fruit, and seeds. Amongst all N. sativa cultivars, the maximum TQ content was found in the seed (45.3885 +/- 0.3616 mg/g fresh weight) of the RS cultivar. Seeds of the AN1 cultivar showed the maximum Thy content (2.7853 +/- 0.3535 mg/g fresh weight). The minimum Thy content was found in leaves of Haryana (0.0009 +/- 0 mg/g fresh weight) and leaves from RS showed the minimum TQ content (0.0029 +/- 0.0001 mg/g fresh weight). There are indications that mature seeds are the best source for both Thy and TQ, followed by fresh seeds collected from the intact fruit of N . sativa . In addition, Thy (precursor) and TQ (product)contentin many plant parts are inversely related to each other, especially in the buds. This indicatedthe interdependence of these two bioactive constituents, but not necessarily in all plant parts. It appears that there might be another functional precursor (in addition to Thy)leading to TQ biosynthesis (speculated to be Carvacrol) in Nigella. Such relative dominance of bioactive compounds and their precursors may be used for designing formulations and setting biotransformation experiments for further value addition.