Raspberry ketone is a substance purported to be an effective natural weight loss aid. This is problematic, because a) there is no evidence it is good for anything and b) extracting raspberry ketone from actual raspberries is very expensive, so synthesizing, which is much cheaper, is usually (but not always) done instead, meaning the name is often misleading.
Raspberry ketones (if you believe some, at least) can be either toxic, deadly, pharmaceutical poisons, or safe, gentle, natural cures, depending on the method used to produce it, even though in either case, the end molecule is exactly the same. One herb company tried to find a chemical test that could distinguish between synthetic and natural raspberry ketones but failed, so they decided not to sell the stuff at all in order not to sell any "harmful" artificial chemicals. This raises the question: if you can't tell the difference, how do you know there is one?