Within-Plant Variation in Rosmarinus officinalis L. Terpenes and Phenols and Their Antimicrobial Activity against the Rosemary Phytopathogens Alternaria alternata and Pseudomonas viridiflava.

This study investigated within-plant variability of the main bioactive compounds in rosemary (Rosmarinus officinalis L.). Volatile terpenes, including the enantiomeric distribution of monoterpenes, and phenols were analyzed in young and mature foliar, cortical and xylem tissues. In addition, antimicrobial activity of rosmarinic acid and selected terpenes was evaluated against two rosemary pathogens, Alternaria alternata and Pseudomonas viridiflava. Data showed that total concentration and relative contents of terpenes changed in relation to tissue source and age. Their highest total concentration was observed in the young leaves, followed by mature leaves, cortical and xylem tissues. Rosmarinic acid and carnosic acid contents did not show significant differences between leaf tissues of different ages, while young and mature samples showed variations in the content of four flavonoids. These results are useful for a more targeted harvesting of rosemary plants, in order to produce high-quality essential oils and phenolic extracts. Microbial tests showed that several terpenes and rosmarinic acid significantly inhibited the growth of typical rosemary pathogens. Overall, results on antimicrobial activity suggest the potential application of these natural compounds as biochemical markers in breeding programs aimed to select new chemotypes less susceptible to pathogen attacks, and as eco-friendly chemical alternatives to synthetic pesticides.

An innovative approach to the recovery of phenolic compounds and volatile terpenes from the same fresh foliar sample of Rosmarinus officinalis L.

Rosmarinus officinalis L. is a plant of relevant commercial interest because of its volatile fraction and also its phenolic constituents which are both well known for their numerous properties. Nevertheless, an extractive method suitable to recovering both the aromatic and phenolic fractions from the same fresh foliar tissue has not yet been reported. In this work we have optimized a two-step procedure able to recover first the phenolic compounds and successively the volatile terpenes from the same foliar sample. The recovery of the whole phenolic fraction, partially degraded using a traditional extractive method, was guaranteed and we observed a significant increment in the amount of volatile terpenes compared to a traditional extraction procedure. We also highlight crucial information on the enzymatic activity of the endogenous oxidases that rapidly transform the phenolic substrates, mainly the rosmarinic acid. Our results suggest that this extractive procedure could also be used for other aromatic plants, thus providing a useful tool for more complete analyses of the main phytochemicals available in fresh foliar samples and creating the possibility of incrementing yields of volatile compounds.