This finding could explain the lower radical-scavenging activity recorded for RCO than for GCO. As regards the diterpenes, there is no consensus in the literature data regarding the decrease of kahweol and cafestol contents during coffee beans roasting, but it has been reported that dehydrocafestol and dehydrokahweol are generated by dehydration of diterpenes under heat exposure [48 ].
Source: wiktionary