A phytochemical study of the leaves of Italian populations of Rosmarinus officinalis L

Rosmarinus officinalis L. has been well known since antiquity for its carminative properties against stomach diseases and for its tonic-stimulant and antimicrobic effects; the phenolic fraction and volatile components (terpenes) contribute to these activities. Antioxidative properties mainly due to rosmarinic acid and phenolic diterpenes have also highlighted. The objective of this study was to analyse fresh leaf samples from natural Italian populations and clones in order to estimate their phenolic and volatile constituents. Ultrasounds, using ethanol as solvent, were applied to extract the diterpenes and phenolic fraction from the leaves. This procedure has recently been suggested as able to improve the extraction efficiency of carnosic acid and to shorten extraction times. The optimized HPLC/DAD/MS method was able to detect up to 30 different components, among them rosmarinic acid, carnosol, rosmadialdehide and several flavonoids. The proposed method allowed monitoring of different constituents, all relevant for the selection of Rosmarinus officinalis L. accessions and for optimization of antioxidant yield. The wide variability noted in the rosmarinic acid content (from 0.1-6 mg/g fresh tissue) has been principally related to the epigenetic differences among young and adult plants, storage of the fresh leaves before the extraction, and time of harvest. The results from the Head-space-GC analysis of samples from adult plants indicated that all the monoterpenes were significantly different among the provenances. The analysis of enantiomeric monoterpenes correctly classified all plants belonging to each provenance. Based on these data, further studies on geographic variability of the terpene and phenol constituents of R. officinalis L. are warranted in order to select superior chemotypes that can be used for specific commercial applications in pharmacy, and food and flavouring industries.