Devil's Claw - the roots and tubers are used.
Cat's Claw - the bark, leaves and shoots are used.

I am not certain if the Devil's Claw preparations that are available in the U.S. come from a plant that is the same or related to the Kalahari Devil's Claw of South Africa and Botswana. But the latter is a popular and effective medicinal in that part of the world. The following information about the Kalahari Devil's Claw (Harpagophytum procumbens) is taken from "Medicinal Plants of South Africa" by Ben-Erik Van Wyck et al., Briza Publications, 1997. (Great reference!)

The plant is commonly used to treat rheumatism and
arthritis, and as a general health tonic. The thick,
secondary roots are sliced and dried. Infusions of
the dried root are used as a cure for digestive
disorders and as a tonic in lack of appetite.
It is also taken as an analgesic, especially during
pregnancy, and the treatment continuing after labor.
An ointment is made from the root material which is
applied to sores, ulcers and boils.

This book also provides a botanical description and information on preparation and dosage, active ingredients (complete with diagrams of their molecular structure), pharmacological effects, and distribution. By the way, the authors note that for conservation purposes, it is important that collectors take only the secondary roots without damaging the primary one.

Traditional healers in southern Africa were the original source of medicinal knowledge about this plant, and it continues to be precribed by them as well as offered for sale in traditional herbalists' shops. Commercial preparations of tablets and powders are also widely available in pharmcacies (called chemists) there. I've got a box of tablets on a shelf in my kitchen that I bought at a chemists in Swaziland as a kind of souvenir (along with a lot of medicinal plant material in their raw states that I bought from the rural herbalists). One wonderful thing about this product is that the plant is harvested by a cooperative of BaTswana women who also carry out it's preliminary processing. I have lost the insert, so I can't tell you the name of their enterprise, meaning that I unfortunately can't give them their due credit.

cranebill

P.S.: Incidentally, I'm looking for a source of viable seeds of Devil's Claw. If you know of one, I'd be grateful for the info.

Just looked at HortPlex (ought to have been my first step), and it lists the genus Proboscidea under "Devil's Claw". Harpagophytum is not listed there (yet). So it seems that the Devil's Claw that people are posting about on this forum is Proboscidea louisianica, a native to the U.S. I don't know if the Kalahari-type Devil's Claw is available in health stores as well as the native Common Devil's Claw.

cranebill

P.S.: I'm still looking for Harpogophytum seeds.

I'm trying to learn if these two items, devil's and cat's claw can be used at the same time. Anyone have any clues? thank you