Synthetic Methods Applied in the Preparation of Coumarin-based Compounds

Retrieval of High Added Value Natural Bioactive Coumarins from Mandarin Juice-Making Industrial Byproduct

Cold pressed essential oil (CPEO) of mandarin (Citrus reticulata Blanco), a by-product of the juice-making industrial process known to contain large amounts of polymethoxyflavones, was exploited for its content in high added value natural coumarins. The study herein afforded a method referring to the evaporation of CPEO volatile fraction under mild conditions (reduced pressure and temperature below 35 °C) as azeotrope with isopropanol. This allowed the isolation of high added value coumarins from the non-volatile fragment using preparative High Performance Liquid Chromatography (HPLC). Pilot-scale application of this procedure afforded for each kg of CPEO processed the following natural bioactive coumarins in chemically pure forms: heraclenol (38-55 mg), 8-gerayloxypsoralen (35-51 mg), auraptene (22-33 mg), and bergamottin (14-19 mg). The structures of coumarins were verified by Nuclear Magnetic Resonance (NMR) spectroscopy and HPLC co-injection with authentic standards. Thus, the low market value mandarin CPEO with current value of 17 to 22 EUR/kg can be valorized through the production of four highly bioactive natural compounds worth 3479 to 5057 EUR/kg, indicating the great potentials of this methodology in the terms of the circular economy.

Coumarin functionalized molecular scaffolds for the effectual detection of hazardous fluoride and cyanide

Fluoride and cyanide contamination in drinking water imposes detrimental impacts on human health above their permissible limits. Hence, the quantitative detection of these colourless water-soluble toxins has attracted attention. Even though a plethora of chemosensors have been reported so far for the detection of fluoride and cyanide from various matrices, still their applicability is limited to a few examples. Nevertheless, recent advances in the syntheses of coumarin derivatives have shown significant impact on fluoride and cyanide detection. Therefore, this present review provides a brief overview of the application of coumarin-coupled molecular scaffolds towards the detection of perilous fluoride and cyanide along with their sensing mechanisms in order to develop more innovative, simple, sensitive, real-time responsive and cost-effective coumarin-based supramolecular chemosensors to promote next generation approaches towards the ultra-trace quantitative detection of these toxic anions.