LC-MS phenolic profile and quantification of rosmarinic acid in methanolic extracts from Bulgarian Thymus species

Abstract

Thymus species are well-known medicinal and aromatic plants widely used to heal various respiratory and gastrointestinal diseases due to their biological activities such as antibacterial, antifungal, spasmolytic and antioxidant properties. Bulgarian flora is represented by 21 species belonging to two sections – Hyphodromi and Serpyllum, as all they are poorly studied [1]. The phenolic profile of 15 Thymus species was analyzed by HPLC–DAD–MS, and a total of 22 individual compounds were identified – mainly phenolic acids, flavonoids and flavonoid glycosides, typical for the genus. In addition, the phenolic profile of the methanolic extracts displayed relatively constant qualitative composition in comparison to the data of their essential oils [2]. However, rosmarinic acid was found as the major compound, and common phenolic constituent, in all analyzed samples. Having in mind that rosmarinic acid is a valuable compound, widely used in food and cosmetic industries due to its proven antioxidant, anti-inflammatory, hepatoprotective and neuroprotective properties, its quantitation was further performed by HPLC–DAD. The results showed that the content of rosmarinic acid varies significantly (19.7 mg/g and 90.6 mg/g), with minimum and maximum content in T. perinicus and T. pulegioides, respectively. Although Rosmarinus species have been used as the main source of rosmarinic acid [3], our results show that Bulgarian Thymus species are valuable as a source of this substance and other biologically active phenols.