Quantification of rosmarinic acid and caffeic acid in some plants of family Lamiaceae using high performance liquid chromatography with electrochemical detection

Rosmarinic acid (RA) and caffeic acid (CA) are simple phenolic coumpounds widely distributed in the plants. Various phenolic acids and phenolic glycosides of many different types are widerspread in nature and are to be found in most classes of natural compounds having aromatic units. In this study, using HPLC-ED system, quantitative analysis of RA and CA was carried out in water extracts of some herbs and leaves of sage, mint, coleus, rosemary, thyme (Thymus vulgaris L., Thymus serpyllum L., and Thymus sibthorii Benth.), marjoram, oregano, and lemon balm. All examined plants belonging Lamiaceae family. The drug (1g) was powdered and extracted with pure water (9ml). Afterward 1ml of that extract was decanted and centrifuged. Supernatant was used for analysis. The standard solutions were RA, and CA dissolved in mobile phase. HPLC conditions were following: Mobile phase methanol-acetonitrile-water-acetic acid (20+10+70+1); ED detector with range 50nA, potential +0.840 V, filter 0.02Hz; flow rate 1ml/min; temperature 25°C. The content in (mg/g) of RA was in the sage 5.45 and CA 0.73, mint 5.1 and CA 0.01, coleus, 0.46 and CA 0.10, rosemary 14,64 and CA 0.96, thyme: (Thymus vulgaris L. 4.27 and CA 0.66, Thymus serpyllum L., 17.7 and CA 1.36, Thymus sibthorii Benth. 5.5 and CA 0.95), marjoram 11.36 and CA 0.31, oregano 5.82 and CA 0.7, and lemon balm 5.1 and CA 0.14. The highest content of RA and CA was found in the leaves of Thymus serpyllum L., and rosemary.