I do not think so. I dug up an old interesting article
http://www.erowid.org/pl...e/syrian_rue_info1.shtmlIt says here "to get as high as smoking one ounce of syrian rue, would require smoking 12 ounces of caapi, or over two kilograms of passion flower."
Passion flower seems to have a very low beta-carboline content of 0.1-0.05% . Out of the top of my head, if you want to reach a dose of 50mg harmalas you will need to have extracted it from 500g of passionflower. I doubt the common pharmacies are this ambitious in their passionflower capsules. The effects from such a capsule are most likely based on other alkaloids in the plant or pure placebo. (I am convinced it are other alkaloids).
All theory aside. It might work. Why won't you just give it a shot? If it fails. You will now know that for future reference.