Two new β-hydroxy amino acid-coupled secoiridoids from the flower buds of Lonicera japonica: Isolation, structure elucidation, semisynthesis, and biological activities

Two new β-hydroxy amino acid-coupled secoiridoids, named serinosecologanin (1) and threoninosecologanin (2), were isolated from an aqueous extract of the flower buds of Lonicera japonica. Their uncommon structures including absolute configurations were determined by spectroscopic data analysis, and confirmed by semisynthesis from the co-occurring secologanin (3) and secologanic acid (4). Compounds 1 and 2 exhibited resistant activity against β-glucosidase from almonds and hesperidinase from Aspergillus niger, they also showed activity against the release of glucuronidase in rat polymorphonuclear leukocytes induced by the platelet-activating factor with inhibition rates of (34.9 ± 3.1)% and (53.6 ± 2.6)%, respectively.

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