Houttuynoid M, an Anti-HSV Active Houttuynoid from Houttuynia cordata Featuring a Bis-houttuynin Chain Tethered to a Flavonoid Core.

Houttuynoid M (1), a new houttuynoid, and the related known compound houttuynoid A (2) were isolated from Houttuynia cordata. Their structures were defined using NMR data analysis, HR-MSn experiment, and chemical derivatization. Houttuynoid M is the first example of a houttuynoid with a bis-houttuynin chain tethered to a flavonoid core. A putative biosynthetic pathway of houttuynoid M (1) is proposed. The anti-herpes simplex virus (anti-HSV) activities of 1 and 2 (IC50 values of 17.72 and 12.42 µM, respectively) were evaluated using a plaque formation assay with acyclovir as the positive control.