Miltiorins A–D, diterpenes from Radix Salviae miltiorrhizae

Constituents of the anti-influenza A neuraminidase (NA) active extract from Radix Salviae miltiorrhizae were investigated, resulting in the isolation of four new diterpenes, miltiorins A–D (1–4), together with eight known diterpenes. The structures of 1–4 were assigned by spectroscopic analysis. Miltiorins A–C (1–3) were abietane diterpenes possessing a 2α-acetoxy group and a 12-hydroxy group in common, while miltiorin D (4) was a 11,12-seco-abietane diterpene with a γ-lactone ring. Miltiorin D (4) is the first example of a 11,12-seco-abietane diterpene from natural sources. Anti-NA activities of the isolated diterpenes were evaluated.

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