大黄素甲基化衍生物的生物活性

在实验室内以天然存在的大黄素(emodin)为原料合成了甲基化衍生物大黄素甲醚(physcion)和三甲氧基大黄素(trimethoxyemodin),并进行了杀菌和杀虫活性研究,发现3个蒽醌类化合物对黄瓜白粉病(Sphaerotheca fuliginea)的活性有明显差异,其EC90值分别为56.291、3.382、102.699mg/L,大黄素甲醚的活性远高于大黄素、三甲氧基大黄素和对照药剂三唑酮,说明大黄素母环上3-OH以甲基取代杀菌活性会显著提高,而3个羟基均被甲基取代活性会降低。在对甜菜夜蛾(Spodoptera exigua)幼虫的活性测定中,发现三甲氧基大黄素对甜菜夜蛾幼虫的生理活动具有明显的抑制作用,在4000mg/L下对2龄和3龄幼虫的体重增长抑制率分别为99.6%和99.2%,而大黄素和大黄素甲醚则对其无明显影响。

Antifeedant, antibacterial, and antilarval compounds from the South China Sea seagrass Enhalus acoroides

We investigated chemical constituents and the antifeedant, antibacterial, and antilarval activities of EtOH (ethanol) extracts of the South China Sea seagrass Enhalus acoroides. Eleven pure compounds including four flavonoids and five steroids were obtained. Among these compounds, three flavonoids were antifeedant against second-instar larvae of Spodoptera litura, two flavonoids had antibacterial activity towards several marine bacteria, and one flavonoid showed strong antilarval activity against Bugula neritina larvae. This is the first description of isolation and bioactivity of secondary metabolites from E. acoroides.