Method for the estimation of Corosolic acid content

Method for the estimation of  Corosolic acid content

Reagent Required:

Methanol L.R. Grade, acetone L.R. Grade

Glass wares and Apparatus Required:

R.B. flask, condenser, funnel, Whatman filter paper No. 1, glass rod., Evaporating dish, beaker 250mL.

Procedure:

Weigh accurately about 5gm of dry extract powder in a 250mL R.B. flask and reflux effectively with 90% alcohol for about 4 hrs. The extract is filtered and the filtrate is dried under vacuum in buchi vacuum rotary evaporator. The residue is given washing successively each of 15mL with petroleum ether, diethylether and chloroform. The insoluble mass is taken in water. To this added about 5ml of neutral lead acetate solution (20% w/v) and keep aside for few minutes. The precipitated lead salts are filtered and the filtrate freed of the lead salts by treatment with hydrogen sulphide. Subsequently filtrate is warmed on water bath to expel excessive hydrogen sulphide gas and is then evaporated under vacuum in buchi rotary evaporator to yield a residue, hygroscopic in nature. This residue is the glycosidal portion is refluxed for 6 hours in ethanol (33%v/v), taking approx. 30mL containing concentrated sulphuric acid (1.75mL) on a boiling water bath. The reaction mixture is diluted with water and extracted with ethyl acetate (3 extract). The solvent layer is washed with water, dried and freed of the solvent in a tared evaporating dish. Dry the residue to constant weight in a vacuum dessicator and weigh as crude corosolic acids.

Calculation :

Percentage of Corosolic acid content is calculated as:

             (A – B)  X  100 

         =  -------------------

                       W

A   = Weight of filter paper with Corosolic acid

B   = Weight of filter paper