Bioactivities of crude caffeine: Antioxidant activity, cyclooxygenase-2 inhibition, and enhanced glucose uptake

Thousands of tons of crude caffeine are produced annually in the decaffeination of coffee. Crude caffeine is further purified to obtain pure caffeine, and the non-caffeine residue is typically discarded as waste. In the present study, we discovered that crude caffeine possessed unexpected bioactive properties. Crude caffeine had potent hydrophilic antioxidant activity (145 μmol Trolox equivalent (TE)/g) and lipophilic antioxidant activity (66 μmol TE/g). It also inhibited cyclooxygenase-2 with a higher potency (IC₅₀, 20 μg/ml) than 2-acetoxybenzoic acid (aspirin, IC₅₀, 190 μg/ml). Crude caffeine increased glucose uptake 1.45-fold in cultured human skeletal muscle cells and 2.20-fold in adipocytes. In contrast, pure caffeine, which accounts for approximately 90% of the crude caffeine mass, was found to possess negligible antioxidant activity and did not inhibit cyclooxygenase-2, nor stimulate glucose uptake. We believe crude caffeine has potential health benefits and may serve as a novel functional ingredient in the food industry.