Yellow crystalline form of Aloe Vera; its technical name is 3-hydroxymethylanthraquinone. Best known for its laxitive effects, it also possesses certain infection-fighting qualities related to many anthraquinones. Tested individually (along with Chrysophanic Acid) for their abilities to inhibit Staph aureus microbes, aloe emodin and emodin failed. Tested in context with the leaf-gel, they proved bacteriostatic against a broad range of bacteria.
ref: Silent Healer (pg. 51) by Bill Coats R.Ph., with robert Ahola