Agar is a dried, hydrophilic, colloidal polysaccharide complex extracted from the agarocytes of algae of the Rhodophyceae. The structure is believed to be a complex range of polysaccharide chains having alternating a-(1→3) and b-(1→4) linkages. There are three extremes of structure noted: namely neutral agarose; pyruvated agarose having little sulfation; and a sulfated galactan. Agar can be separated into a natural gelling fraction, agarose, and a sulfated nongelling fraction, agaropectin^[1].

[1] 美国FDA批准药物非活性成分数据库

琼指可用作食品增稠剂、蚕丝上浆剂、缓泻剂，以及药品的胶粘剂、增稠剂和胶囊，还可作为细菌培养基、固定化酶载体、细菌的包理材料和电泳的介质。还可用于病毒，亚细胞粒子和大分子的过滤分离，以及血清抗原或抗体的观察。ADI（每日允许摄入量）不需要特殊规^[1]。

Agar is widely used in food applications as a stabilizing agent. In pharmaceutical applications, agar is used in a handful of oral tablet and topical formulations. It has also been investigated in a number of experimental pharmaceutical applications including as a sustained-release agent in gels, beads, microspheres, and tablets.It has also been reported to work as a disintegrant in tablets.Agar has been used in a floating controlled-release tablet; the buoyancy in part being attributed to air entrapped in the agar gel network. It can be used as a viscosity-increasing agent in aqueous systems. Agar can also be used as a base for nonmelting, and nondisintegrating suppositories. Agar has an application as a suspending agent in pharmaceutical suspensions.

Emulsifying agent; stabilizing agent; suppository base; suspending agent; sustained-release agent; tablet binder; thickening agent; viscosity-increasing agent^[2].

[1] 以上信息来自化工字典：http://www.cnreagent.com/source/sdict.php