The majority of published research on Cistus species focuses on the aromatic resin labdanum, which demonstrates high antimicrobial activity. However, the aerial parts of rockrose plants have been used in Greek traditional medicine as anti-inflammatory agents for rheumatism and skin diseases [1]. This study emphasizes on the exploration of the phenolic content and anti-oxidant potential of five species (C. monspeliensis, C. salvifolius, C. parviflorus, C. creticus spp creticus, C. creticus spp eriocephalus) belonging to the Greek flora. After successive extraction with c-hexane, ethylacetate, methanol and water by Accelerated Solvent Extraction, all extracts were tested for their phenolic content and antioxidant capacity by TPC, ABTS and DPPH assays and their chemical profile was compared with HPTLC.
The methanolic extract of C. monspeliensis as well as methanolic and ethylacetate extracts of C. parviflorus were further analysed. However, the challenge faced for the isolation of the bioactive compounds was the presence of high amount of tannins. For this purpose, two methodologies were implemented, FCPC chromatography using a three-phase solvent system (C. monspeliensis) and adsorption resin XAD-4 (C. parviflorus), resulting to removing of tannins and fractionation of the extracts. Further purification of compounds was accomplished with MPLC, Sephadex CC and prep-TLC. Their purity and identity was confirmed by NMR and LC-MS. The abovementioned process afforded to the isolation of over 40 compounds, among them 5 novel metabolites and over 15 known compounds isolated for the first time from the genus Cistus.
To the best of our knowledge, this is the first thorough phytochemical investigation of the methanolic extracts of the aerial parts of Greek C. monspeliensis and C. parviflorus, demonstrating simultaneously that the enrichment of crude extracts in polyphenols increase their antioxidant properties, while wise-chosen methodologies simplify the separation of natural compounds from complex matrices.
[1] Demetzos CN, et al. Fitoterapia 1990; 61(5): 439-442;