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Seasonal variability of the contents of total polyphenols and tannins of Laurus nobilis L. (Lauraceae) from Croatia

INTRODUCTION AND OBJECTIVE Bay laurel (Laurus nobilis L., Lauraceae) is a large shrub or tree up to 15 m high, often grown in coastal areas as an ornamental and spicy plant. Laurel has moderate antibacterial activity but is very active against fungi. It also acts as a spasmolytic, analgesic and expectorant. In order to monitor the seasonal variability of the content of bioactive polyphenolic substances during the 12 months (from May 2015 to April 2016), and consequently to monitor the phytotherapeutic potential of laurel, a quantitative analysis of the content of total polyphenols (TP) and tannins (T) from laurel leaves from the Croatian coast (Lovran population) was performed. METHODS Quantitative analysis of TP and T was performed by UV-Vis spectrophotometric method with Folin-Ciocalteu phenolic reagent (A720nm, according to the original method ; A748nm, maximum absorption). RESULTS The content of TP in the sample of laurel leaf was the highest for the September 2015 (9.08%, A720nm and 9.12%, A748nm), while the lowest content was recorded for the May 2015 (5.67%, A720nm and 5.80%, A748nm). By analogy with the results obtained for TP, the highest amount of T in the laurel leaves was also recorded in the September 2015, amounting to 4.91% (A720nm) and 4.87% (A748nm), while the lowest content of T was determined for the sample from May 2015 (2.31%, A720nm and 2.37%, A748nm). Among these results, the high content of polyphenolic substances in February 2016 stands out, in contrast to the other winter months in the observed period: TP (8.53%, A720nm ; 8.68%, A748nm) and T (3.89%, A748nm ; 3.94%, A748nm). This could be explained by the above-average air temperature for that time of the year and the large amount of precipitation, which was confirmed by the weather forecast in Lovran for 2016 (data from the Croatian Meteorological and Hydrological Service). CONCLUSIONS This quantitative analysis represents a contribution to scientific study of polyphenols and tannins in the leaves of Laurus nobilis and completes the previous knowledge about laurel’s phytotherapeutic potential, especially in relation to the content of bioactive phenolic substances.

total polyphenols, tannins, bay laurel

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