Differential Expression of Thymoquinone and Its Localization in Different Parts of Nigella sativa L.

Abstract

The present study was aimed to identify the localization of thymoquinone in vegetative parts, viz. leaf, stem, root, flower forming bud, flower, and seed forming bud of Nigella sativa plant. Isocratic RP-HPLC method was used with mobile phase methanol/water 70:30, C-18 column, detection wavelength 254 nm (confirmed by spectrum scanning), flow rate of 1.0 ml/min, retention time 8.8 min. A linear standard calibration curve of thymoquinone was prepared with R2 as 0.9569 and % RSD as 20.7518. The results showed maximum yield in seed forming bud (6.433 ± 0.450%) using benzene as solvent, whereas the methanol extract has minimum yield in stem (2.200 ± 0.300). Maximum thymoquinone content was found in seed forming bud with (0.0648 ± 0.0038%) and (0.7830 ± 0.0360%) in methanolic and benzene extracts (washed with ethanol; EtOH), respectively. It was further observed that benzene extract (EtOH) was about 12-fold more than methanolic extract (EtOH). When total antioxidant activity was explored using DPPH free radical assay, it was found maximum in flowering bud (77.076 ± 5.889%), while minimum was observed in roots (47.933 ± 4.003%). When correlation was established between methanolic (EtOH) and benzene extracts (EtOH) with antioxidant activity, a strong positive correlation of 0.9535 and 0.7406, respectively, was observed. Thus, it is evident that the level of thymoquinone content in different plant parts is analogous to its antioxidant activity. Therefore, it can be concluded that benzene (EtOH) is the better solvent for extraction of thymoquinone from Nigella sativa; further, seed forming bud is a better source of thymoquinone which can be useful in nutraceutical and pharmaceutical industry for better herbal drug formulations.