A new cineol derivative, polyphenols and norterpenoids from Saharan myrtle tea (Myrtus nivellei): Isolation, structure determination, quantitative determination and antioxidant activity

The phytochemical profile of decoction and infusion, obtained from the dried leaves of M. nivellei, consumed as tea in Saharan region, was characterized by UHPLC-PDA-HRMS. Fourteen compounds were characterized and, to confirm the proposed structures a preparative procedure followed by NMR spectroscopy was applied. Compound 3 (2-hydroxy-1,8-cineole disaccharide) was a never reported whereas a bicyclic monoterpenoid glucoside (2), two ionol glucosides (1 and 12), a tri-galloylquinic acid (4), two flavonol glycosides (5 and 9), and a tetra-galloylglucose (7), were reported in Myrtus spp. for the first time. Five flavonol O-glycosides (6, 8, 10–11, and 14) togheter a flavonol (13) were also identified. Quantitative determination of phenolic constituents from decoction and infusion has been performed by HPLC-UV-PDA. The phenolic content was found to be 150.5 and 102.6 mg/g in decoction and infusion corresponding to 73.8 and 23.6 mg/100 mL of a single tea cup, respectively. Myricetin 3-O-β-D-(6″-galloyl)glucopyranoside (5), isomyricitrin (6) and myricitrin (8) were the compounds present in the highest concentration. The free-radical scavenging activities of teas and isolated compounds was measured by the DPPH assay and compared with the values of other commonly used herbal teas (green and black teas). Decoction displayed higher potency in scavenging free-radicals than the infusion and green and black teas.