Isolation, structure elucidation and anti-inflammatory testing of some sesquiterpene lactones and methoxylated flavonoids from Achillea millefolium L.

Achillea millefolium L. is a medicinal plant with a long traditional use in a wide variety of cultures from Europe to Asia. Yarrow contains a broad range of secondary metabolites such as essential oil, sesquiterpene lactones, among them several proazulenes, as well as flavonoids and various other phenols. The herb is mostly used for gastrointestinal problems, inflammations, hepatobiliary disorders, or wound healing. As the anti-inflammatory effects of yarrow are not completely understood, it was aimed to work on the isolation, structural elucidation and subsequent anti-inflammatory in vitro testing of A. millefolium. Fourteen isolates including one sesquiterpene, nine sesquiterpene lactones – all of them guaianolide type – and four methylated flavonoids were obtained using various chromatographic techniques such as CPC and preparative HPLC. Four guaianolides 1-4 were isolated for the first time ([Fig. 1]). The isolated molecules were elucidated by NMR spectroscopy and mass spectrometry. Further characterisation was done by using polarimetry, UV- and CD-spectroscopy. Furthermore, ten selected compounds were tested in the Griess assay. Thereby, the LPS-induced nitric oxide release in a mouse macrophage cell line (RAW 264.7 cells) was significantly reduced in a concentration range from 0.5 – 75 µM by six isolates, namely 9-episintenin, 8α- angloxyartabsin, 8-desacetyl-8-angeloyl-4-epi-matricin, artemetin, pectolarigenin, and centaureidin. Methylated flavonoids (0.5 – 75 µM) showed higher activity than sesquiterpene lactones (12.5 – 50 µM). In future, the anti-inflammatory activity of the molecules will be further investigated in the ICAM-1-assay using a human endothelial cell line (HMEC-1).

Fig. 1 Structures 1-4 of isolated sesquiterpene lactones described for the first time.

Publication History

Article published online:
16 November 2023