In vitro formation of the anthranoid scaffold by cell-free extracts from yeast-extract-treated Cassia bicapsularis cell cultures

► Cassia bicapsularis cell cultures accumulate tetrahydroanthracenes. ► Addition of yeast extract resulted in 35-fold increase in octaketide synthase activity. ► Identified enzymatic products were torosachrysone (tetrahydroanthracene) and emodin anthrone. ► Confirmation of the products came from 13C incorporation.