GC-QTOF-MS as valuable tool to evaluate the influence of cultivar and sample time on olive leaves triterpenic components

Pentacyclic triterpenes play an important role in plant defense and have demonstrated beneficial effects in human health acting in disease prevention. In the present study, the determination of triterpenes compounds in olive leaves of six different cultivars grown at four dates was assessed in order to corroborate the influence of olive growth cycle on triterpenes content and to evaluate if the highest amounts are detected in correspondence to the olive oil production period when the leaves are one of the most important by-product. A GC-QTOF-MS methodology was optimized and validated, and five triterpenes were identified and quantified in all olive leaves samples analysed. ANOVA analyses revealed quantitative differences among sampling times and cultivars. Principal Component Analyses showed a good separation among triterpenes content for the different collecting seasons and cultivars. Picual, the most commonly grown olive today for olive oil production, was the cultivar that presented the highest concentrations of triterpenes and oleanolic acid the major triterpene in all cultivars at all sampling times (54-76.5% of total triterpenes). The triterpenes concentration is higher in June than in the other sampling times. Unfortunately, the leaves sampled at the stage that corresponded to the olive oil production were not the best one in terms of triterpenes content; however the decrease was never > 15.5%. Thus, the present results confirm olive leaves a suitable source of bioactive compounds that can be used to obtain high added-value products enriched in triterpenes.