Trachystemon orientalis (L.) G. Don as a Valuable Source of Rosmarinic Acid: Biological Activities and HPLC Profiles

Trachystemon orientalis (L.) G. Don, colloquially known in Türkiye as "kaldırık", is an edible plant belonging to the Boraginaceae. This plant has been practiced in traditional medicine for many years for its various therapeutic benefits. The effectiveness and chemical composition of plants can vary depending on their parts, age, and extraction solvent. Therefore, the current study aimed to define the biological activities of various parts and extracts of T. orientalis, which were collected in distinct seasons as young and mature, and investigate the main component responsible for these biological effects.

Plant material was collected in different seasons from the northwest of Türkiye. 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activities were investigated to assess antiradical and antioxidant potential of the extracts. Anti-inflammatory activity of the extracts was also tested using human red blood cell membrane stabilizing method. Folin-Ciocalteu test was conducted to determine the total phenolic content. Reverse phase-high performance liquid chromatography-photodiode array detector (RP-HPLC-PDA) analysis was performed.

Both methanol and aqueous extracts exhibited significant radical scavenging and anti-inflammatory activities compared with control (p<0.05). The highest percentage of inhibition on ABTS and DPPH free radicals was obtained in aqueous extracts of the mature herbs and roots, respectively. Methanol extracts of the mature roots and herbs exhibited the strongest anti-inflammatory capacity. Rosmarinic acid possessed a much higher antioxidant and anti-inflammatory effect than the reference compounds used in each assay in our study. High rosmarinic acid content of the extracts suggests that the compound responsible for the great biological activity potential is rosmarinic acid.

To the best of our knowledge, the presence of rosmarinic acid in herbs and roots of T. orientalis was shown for the first time in our present study. Phytochemical composition and effective biological activities of T. orientalis explain its traditional use and indicate its significant potential in pharmaceutical industry applications.