heres what wiki says:
Spice:
Spice was claimed by the manufacturers to contain a mixture of traditionally used medicinal herbs, each of which supposedly produces mild effects with the overall blend resulting in the cannabis-like intoxication produced by the product. Herbs listed on the packaging include Canavalia maritima, Nymphaea caerulea, Scutellaria nana, Pedicularis densiflora, Leonotis leonurus, Zornia latifolia, Nelumbo nucifera and Leonurus sibiricus. However when the product was analysed by laboratories in Germany and elsewhere, it was found that many of the characteristic "fingerprint" molecules expected to be present from the claimed plant ingredients could not be located, and also there were large amounts of synthetic tocopherol present. This suggested that the actual ingredients might not be the same as what was listed on the packet, and a German government risk assessment of the product conducted in November 2008 concluded that it was unclear what the actual plant ingredients were, where the synthetic tocopherol had come from, and whether the subjective cannabis-like effects were actually produced by any of the claimed plant ingredients or instead might possibly be caused by a synthetic cannabinoid drug.
JWH-18 :
JWH-018 (1-pentyl-3-(1-naphthoyl)indole) is an analgesic chemical from the aminoalkylindole family, which acts as a cannabinoid agonist at both the CB1 and CB2 receptors, with some selectivity for CB2.[1][2][3] It produces effects in animals very similar to those of THC itself, but with a longer duration of action, and is currently being researched as a potential analgesic to be administered by transdermal patch.