Apparently, synthetic compounds analogous to those found in Khat. From what I gather, there are several compounds that qualify as "cathinones" and I expect they have varied effects. Drugs often have different effects on different people, too (see alcohol intolerance). Also, with any home-cooked organic chemistry, there will be a lot of variance in the product. Also, with any street supply, you never know what it's cut with (even if it appears to be beautiful dank nugs).
https://www.drugabuse.gov/publications/drugfacts/synthetic-c...