Lipoxygenase inhibitors and antioxidants from green coffee-mechanism of action in the light of potential bioaccessibility

Inhibition of lipoxygenase (LOXI) and antioxidant capacity of potentially bioaccessible, and bioavailable phytochemicals from different green coffee beans (GCB) were studied. The major compounds identified in the coffee samples were 5-caffeoylquinic, 4-caffeoylquinic, 3-feruoylquinic and 5-feruoylquinic acids. The highest level of total phenolics was found in extract of GCB from Ethiopia, whereas the lowest in extract prepared from Kenyan GCB. Unexpectedly, digestion in vitro did not increase the total content of phenolic compounds. Potentially bioaccessible phenolics were bioavailable in vitro. All raw extracts demonstrated comparable LOXI activity (EC50 from 2.75 to 2.94 mg DW/mL). Water-extractable and potentially bioaccessible phytochemicals from all samples acted as competitive inhibitors of LOX. Interestingly, potentially bioavailable compounds from Kenyan GCB acted as acompetitive inhibitors, whereas in the other cases the mixed inhibition was found. Reducing powers of raw extracts from Kenyan, Columbian and Brazilian GCB were comparable (EC50 values averaged from 47.90 mg DW/mL to 53.44 mg DW/mL). The antiradical activity of raw extracts of GCB was relatively low; EC50 averaged from 151.48 mg DW/mL to 84.58 mg DW/mL for Ethiopian and Kenyan coffee, respectively. Digestion in vitro drastically increased both activities. Importantly, compounds able to prevent lipids against oxidation from all samples were characterized by high bioavailability in vitro. In conclusion, GCB consists excellent source of potentially bioaccessible and bioavailable compounds with multidirectional antioxidant activity. Particular attention should be paid to the results concerning the inhibition of LOX, because the associated action of LOX and free radicals is the underlying diseases of civilization. (C) 2014 Elsevier Ltd. All rights reserved.