On fluorescent sensing of metal ions using water extracts of Salvia officinalis

Sensing of metal ions using fluorometric tools has wide applications in chemical, biological and environmental analysis. Plant phytochemicals, like flavonoids, exhibit intense fluorescence upon excitation by UV light. Leaves sage (Salvia officinalis), which is rich in polyphenolic and flavonoids compounds, were extracted using Soxhlet and microwave-assisted extractors. The extraction methods led to variations in the phytochemical composition of the extracts, which in turn affected their interaction with metal ions. Despite the variations in the composition, both of the extracts gave high fluorescence emissions when excited at 365 nm. Variations in fluorescence emissions of the extracts were studied in upon addition of each metal ion;  i.e., Li⁺, Na⁺, K⁺, Cs⁺, Be²⁺, Mg²⁺, Sr²⁺, Ba²⁺, Al³⁺, Tl³⁺, Ge⁴⁺, Sn⁴⁺, Pb²⁺, Sb³⁺, Bi³⁺, Se⁴⁺, Cu²⁺, Ag⁺, Zn²⁺, Cd²⁺, Ti⁴⁺, Cr³⁺, Cr⁶⁺, Mo⁶⁺,  W⁶⁺, Mn²⁺, Fe³⁺, Ni²⁺, Co²⁺ and Pd²⁺. When they were added into the Soxhlet extract, some ions (Cr³⁺, Pb²⁺, Co²⁺) induced intense fluorescence and some (Ge⁴⁺, Mg²⁺, K⁺, Na⁺) ions quenched the fluorescence emission. As for microwave-assisted extract, the addition of Sr²⁺, Mg²⁺ and Co²⁺ ions enhanced the fluorescence emission of the extract, but Fe³⁺, Be²⁺ and Cs⁺ lowered the fluorescence intensity. However, the results of the study should be considered as introductory and further selectivity and sensitivity studies should be done for each extract if they are used for sensing of metal ions. Yet, this study demonstrated that sage extracts has a potential for fluorescent sensing of certain metal ions.