Taxonomic distribution of thymoquinone and related compounds in selected plant species

Abstract

Because of their significant biological activities, such as anti-inflammatory [1], anti-microbial [2], or anti-tumor [3] effects, in recent years a growing attention has been devoted to plant-derived quinones dithymoquinone (DTQ), thymohydroquinone (THQ), and thymoquinone (TQ). At present, a well-known natural source of TQ is the oil from the seeds of Nigella sativa [4]. In our study, twenty-one plant species were analyzed for the content of DTQ, THQ, and TQ with the aim to compare their quantities and taxonomic distribution in plants. The dried plant material was extracted with n-hexane; the analytes were reextracted to methanol and quantified by capillary GC with a flame-ionization detector (identity confirmation by GC/MS). The results of analysis were as following (mg.kg-1 of dried matter): Monarda didyma 98 (DTQ), 1811 (THQ), 1905 (TQ), Nigella sativa (seeds) 38 (DTQ), 76 (THQ), 1597 (TQ), Satureja hortensis 16 (THQ), 54 (TQ), Satureja montana 88 (THQ), 152 (TQ), Thymus serpyllum 15 (THQ), 44 (TQ), and Thymus vulgaris 21 (THQ), 143 (TQ). Trace amounts of TQ (<10mg.kg-1) were found in Eupatorium cannabinum and Juniperus communis. Thus, we confirmed previously reported presence of TQ in following four families: Asteraceae, Cupressaceae, Lamiaceae, and Ranunculaceae. According to the above presented results, Monarda didyma can be recommended as an alternative source of TQ and related compounds, especially in the climatic conditions of moderate zone.