Lemon Juice and Cream of Tartar
Mix equal parts of each into a paste. Apply to stained area and let sit for 30 minutes. Use a damp cloth to remove the paste. Lemon juice and cream of tartar have a mild bleaching effect so only use this on light-colored leather.
Once you have gotten your purse clean, apply leather conditioner to keep it from drying out and cracking, and to make it resistant to future stains. You can buy a commercial leather conditioner or make your own by mixing 1 part vinegar to 2 parts linseed oil. Apply to leather, let sit for about 15 minutes and buff with a soft cloth till the leather shines. Knowing how to clean a leather purse will keep yours looking great and lasting a long time.