Further New Xenicanes from a Chinese Collection of the Brown Alga Dictyota plectens

Abstract

Four new xenicanes, namely 4α-hydroxyisodictyohemiacetal (1), 4α-hydroxyisodictyoacetal (2), 13,18-diacetoxy-4-hydroxyisodictyo-19-al (3), and 4α-hydroxypachylactone (8), were isolated from a Chinese collection of the brown alga Dictyota plectens, along with four known analogues (4–7). The structures of the new diterpenes were determined by extensive spectroscopic data analysis. All compounds were evaluated for their antiviral activities against human immunodeficiency virus type 1 (HIV-1) and the highly pathogenic avian influenza A (H5N1) virus, and inhibitory effects on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in mouse peritoneal macrophages (PEMΦ).