Name: Agar
CAS No: Agar [9002-18-0]
JP: Agar PhEur: Agar USP-NF: Agar
Agar-agar; agar-agar flake; agar-agar gum; Bengal gelatin; Bengal gum; Bengal isinglass; Ceylon isinglass; Chinese isinglass; E406; gelosa; gelose; Japan agar; Japan isinglass; layor carang.
Agar [9002-18-0]
See Section 5.
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
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.(1- 4) It has also been reported to work as a disintegrant in tablets.(5) Agar has been used in a floating controlled-release tablet; the buoyancy in part being attributed to air entrapped in the agar gel network.(6) 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.(7) Agar has an application as a suspending agent in pharmaceutical suspensions.(8)
Agar occurs as transparent, odorless, tasteless strips or as a coarse or fine powder. It may be weak yellowish-orange, yellowish-gray to pale-yellow colored, or colorless. Agar is tough when damp, brittle when dry.
See Table I.
NIR spectra see Figure 1. Solubility Soluble in boiling water to form a viscous solution; practically insoluble in ethanol (95%), and cold water. A 1% w/v aqueous solution forms a stiff jelly on cooling.
Agar solutions are most stable at pH 4–10. Agar should be stored in a cool, dry, place. Containers of this material may be hazardous when empty since they retain product residues (dust, solids).
Agar is incompatible with strong oxidizing agents. Agar is dehydrated and precipitated from solution by ethanol (95%). Tannic acid causes precipitation; electrolytes cause partial dehydration and decrease in viscosity of sols.
Agar is obtained by freeze-drying a mucilage derived from Gelidium amansii Lamouroux, other species of the same family (Gelidiaceae), or other red algae (Rhodophyta).
Agar is widely used in food applications and has been used in oral and topical pharmaceutical applications. It is generally regarded as relatively nontoxic and nonirritant when used as an excipient. LD50 (hamster, oral): 6.1 g/kg(10) LD50 (mouse, oral): 16.0 g/kg LD50 (rabbit, oral): 5.8 g/kg LD50 (rat, oral): 11.0 g/kg
Observe normal precautions appropriate to the circumstances and quantity of the material handled. When heated to decomposition, agar emits acrid smoke and fumes.
GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (oral tablets). Included in the Canadian List of Acceptable Non-medicinal Ingredients. Included in nonparenteral medicines licensed in the UK.
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The drug release mechanism of agar spherules of felodipine has been studied and found to follow Higuchi kinetics.(11) Agar has also been used to test the bioadhesion potential of various polymers.(12) The EINECS number for agar is 232-658-1.