I am not sure what nature sunshine sells but if it is capsules don't waste your money, Pau d'arco must be taken as a "tea" to be effective, you have to buy a good grade of inner bark in the correct cut form and boil it for 20 mins for it to be effective. The traditional method of drinking Essiac is in the same "tea" form with slightly different brewing instructions, I take both in tea form, I beleive the more a herb/botanical etc is refined the more you lose the synergistic effects (many of which are too complicated for us to fathom). When I still showed tumors I was taking 6 or 7 cups of Pau d'arco per day and 6 oz of Essiac split into 3 2oz doses per day, I am now on the maintenance dose of 2 cups Pau per day and 4 oz essiac. I was given 6 months to live almost 3 years ago and my last scan from Jan 5th showes I am still Cancer Free !! My story is posted on this site if your interested.
herb-care.com sells premium quality herbals and Pau-d-arco.com has a lot of information.