A diketopiperazine metabolite; active against various bacteria (MICs = 125-1000 μg/ml) and fungi (MICs = 8-64 μg/ml); inhibits hydroxy radical production (IC50 = 1.8 μM); a bitter tastant that can rapidly permeate rat taste cell membranes (1 mM); a melatonin receptor agonist, inhibiting cAMP accumulation (20 μM)