Sustainable pathways to oxicams via heterogeneous biosourced catalysts - Recyclable and reusable materials

Abstract

The current study highlights the synthesis of Zn-enriched biosourced catalysts (BIOCATs) obtained from ryegrass (Lolium perenne L.) cultivated on contaminated soils located in the North of France (Noyelles-Godault and Auby, Hauts-de-France). These cultures were located on brownfield land, next to two former industrial sites where the zinc and lead metallurgists Metaleurop and Nyrstar were installed. Physical and morphological properties of BIOCATs were compared to heterogeneous catalysts (CATs) prepared from commercial zinc chloride and montmorillonite K10. The catalysts were thermally activated (120 °C, 280 °C or 500 °C). BIOCATs have been further compared to CATs and different commercial metal chlorides in terms of efficiency in the synthesis of anti-inflammatory agents, Piroxicam and Meloxicam, both of them being involved in the inhibition of cyclooxygenases (COX) and being the main ingredients of the Feldene® and Mobic® drugs, respectively. BIOCAT-assisted synthesis resulted in the best reaction yields (84% and 78%, respectively) among all the tested catalysts. The results indicated that ryegrass provides appropriate quantity of biomass and can be considered as a bio-ore resource to improve green metrics in an environmental context involving clean and green technologies. Furthermore, the Zn/Cd and Zn/Pb ratios obtained in the ashes of ryegrass shoots were in general comprised between 153 and 202. This result demonstrated the excellent selectivity of ryegrass for zinc at the expense of the more problematic Cd and Pb, which are carcinogenic, mutagenic and reprotoxic. Future efforts are now needed to use BIOCATs in the synthesis of other high value-added molecules.