Experimental Planning for Extraction of Secondary Metabolites from Tithonia diversifolia (Hmsl.) A. Gray/Asteraceae Leaves: Biological and Chemical Characterization by Synchronous Fluorescence and Phosphorescence Spectroscopy and FTIR

S. Tomé and Principe (STP) islands have been studied in recent years for their wide range of medicinal plants which exhibit several biological activities of great medicinal interest for some diseases. Experimental planning for optimization of several parameters was carried out by a full factorial of two levels of three factors for secondary metabolite extraction from Tithonia diversifolia leaves by using water and hexane at 25 and 40 ºC and 150 rpm for 0 and 5 days of incubation. The best conditions for highest extraction of phenolic compounds (i.e 72.16 mmoles gallic acid equivalent/g leaves)) was obtained at 40ºC, in H20 and 5 days of incubation. Several phytochemical assays were performed for characterization of these plant extracts and the highest levels for extraction of reducing power, ABTS and DPPH were obtained at 25 ºC, H20 and 5 days of incubation whereas highest levels of SOD activity were extracted at 40ºC, H20 and 5 days of incubation. The present report consists of a novel and intrinsic synchronous fluorescence and phosphorescence characterization of secondary metabolites from this plant extract. Intrinsic and non-destructive synchronous fluorescence was carried out in the range of 250 to 750 nm with a Δλ range of 5–30 nm which exhibited peaks at 290, 320, 345, 400, 490 and 675 nm in hexane plant extracts whereas aqueous extracts revealed only peaks at 490, 560 and 675 nm. On the other hand, intrinsic and non-destructive synchronous phosphorescence was also performed which exhibited peaks at 325, 400, 490, 550, 675 nm and 500, 560 nm, respectively. 3-D spectra of secondary metabolites confirmed the peaks at 290, 320, 345, 400, 490 and 675 nm in plant extracts. FTIR spectroscopy was selected to investigate the structural properties of secondary metabolites in these plant extracts. Therefore, the present work describes a novel characterization of secondary metabolites by a non-destructive and intrinsic synchronous fluorescence techniques for plant extracts.