Iridoid glycosides from Barleria lupulina

Phytochemical investigation of an extract of the aerial part of Barleria lupulina resulted in the identification of four new iridoid glycosides (1-4), together with 14 known analogues (5-18). The structures of 1-4 were determined through 1D and 2D NMR spectroscopic data analysis, HRMS, and acid hydrolysis. This is the first report of iridoid glycosides with a formate group. The free-radical scavenging activity of compounds 9, 12, and 15-17 was assessed using the DPPH assay. Compounds 16 and 17 scavenged DPPH radicals weakly with IC₅₀ values of 97.5 and 78.6 μg/mL, respectively.