油菜素类固醇（Brassinosteroids，BRS）又被称为芸苔素内酯（brassinolides）或是油菜内酯。以化学结构来说属于固醇类物质是一类多羟基的类固醇，已被视为第六类植物激素。

芸苔素（brassinolides）一开始的研究集中在十字花科蔬菜，他的命名也是来自于十字花科的属名（brassica）。

芸苔素内酯在植物体内扮演着促进植体成熟，开花结果，对抗逆境等角色。它会和生长素、细胞分裂素、激勃素等促进生长的贺尔蒙产生加成作用，扩大影响的效应，一般来说在农业上作为增加产量和开花数量的生长调节剂。

Brassinosteroids (BRs) are a class of polyhydroxysteroids that have been recognized as a sixth class of plant hormones. These were first explored nearly 40 years ago, when Mitchell et al. reported promotion in stem elongation and cell division by the treatment of organic extracts of rapeseed (Brassica napus) pollen. Brassinolide was the first isolated brassinosteroid in 1979, when pollen from Brassica napus was shown to promote stem elongation and cell divisions, and the biologically active molecule was isolated. The yield of brassinosteroids from 230 kg of Brassica napus pollen was only 10 mg. Since their discovery, over 70 BR compounds have been isolated from plants.