Unexpected Secoiridoid Glucosides from Manulea corymbosa

From an extract of Manulea corymbosa were isolated four known secoiridoid glucosides (1–4), 10 new monoterpenoid esters of secologanol, namely, manuleosides A–I (5–11, 13, and 14) and dimethyl rhodanthoside A (12), and four new phenylpropanoid esters of carbocyclic iridoid glucosides, manucorymbosides I–IV (15–18). Also, the caffeoyl phenylethanoid glycoside verbascoside was isolated. The presence of secoiridoids apparently derived from loganic acid in the family Scrophulariaceae is unprecedented and greatly unexpected.