Method of synthesizing custard apple peel nanoparticles

A pharmaceutical composition comprising an effective amount of custard apple (Annona reticulata) peel nanoparticles in combination with a pharmaceutically-acceptable carrier, wherein the custard apple (Annona reticulata) nanoparticles are synthesized by:

• (a) dissolving about 450 mg of custard apple peel (epicarp) powder in a solvent comprising ethanol under stirrer to produce a solution;
• (b) spraying the solution dropwise into about 40 ml of boiling water at a flow rate of about 0.2 ml per minute in 5 minutes under ultrasonic conditions including an ultrasonic power of about 750 W and a frequency of 20 kHz to produce an aqueous solution;
• (c) sonicating the aqueous solution for about 10 minutes;
• (d) stirring the solution at 200-800 rpm at room temperature for 20 minutes;
• and
• (e) drying the solution of step (d) to obtain the custard apple peel nanoparticles.