Dr. Barbra Sturm “The Good C” Vitamin C Serum. NEW! 10ml Vitamin C protects cells from damaging free radicals while working to brighten and even out your skin tone, so Dr. Barbara Sturm's 'The Good C Serum' is ideal for adding to your morning routine. It combines Kakadu Plum - a powerful plant source of Vitamin C - with a scientifically-proven fusion of stable and potent forms for maximum effect.