Chemical Constituents from Aerial Parts of Houttuynia cordata and Their Inhibitory Activity against NO Production in Macrophage

Abstract

Houttuynia cordata Thunb, belonging to the family of Saururaceae, is a plant used in traditional medicine for the treatment of fever, poisoning and inflammation-related disorders. In previous phytochemical studies, it has been reported that the aerial parts of H. cordata contained various types of compounds including simple phenolic compounds, flavonoids, flavonoid glycosides, ionones and some alkaloids containing benzamide and isoquinoline moieties. Alkaloids are nitrogen-containing compounds found in plants, microorganism and marine organisms. They contain one or more nitrogen atoms, and they have various structures, including quinoline, isoquinoline, indole alkaloid and benzamide. The alkaloids in nature have been reported for diverse biological and pharmacological activities. A few alkaloids have been reported from aerial parts of H. cordata, and their anti-inflammatory activities have not been reported previously. This report investigated the alkaloids from the aerial parts of H. cordata and explored the biological activity of the isolates to determine their anti-inflammatory properties. In detail, twenty-one alkaloids were isolated and their structures were elucidated. Of which, two benzamides (1, 2) and a β-carboline alkaloid (14) were isolated from nature for the first time. The isolated alkaloids were tested for their inhibitory activity against NO production in RAW 264.7 cells stimulated by LPS. Of the tested compounds, perlolyrine (15) showed the significant inhibitory activity with an IC50 value of 8.7 μM. In addition, further isolation was performed in order to investigate the constituents of aerial parts of H. cordata. As a result, thiry-eight compounds were further isolated from a methanolic extract of aerial parts of H. cordata including 8 flavonoids, 4 megastigmanes, 8 phenylpropanoid derivatives, 3 benzoic acid derivatives, 2 lignans, 5 neolignans, a bisphenylpropanol, 5 glycosides and 2 macrolides. Among them, a neolignan (50) was firstly isolated from nature.