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Four chromone derivatives (1-4) were isolated fromthe clove buds (Syzygium aromaticum). Of these, two chromoneC-glucosides (1 and 2) showed significant PEP inhibition withIC 50 values of 1.48±0.02 and 1.74±0.03µM and K i values of0.27±0.02 and 0.50±0.05µM, respectively. They also exhibitedstrong antioxidant capacities against the 2,2'-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid diammonium salt radical systemwith EC 50 values of 4.13±0.04 and 4.79±0.03µM, respectively.Keywords antioxidant capacity · chromone C-glucoside · clovebuds · prolyl endopeptidase inhibitor ·Syzygium aromaticumCloves, the dried flower buds of Syzygium aromaticum, havehistorically been used as medicine to relieve tooth pain and healmouth and gum sores (Lee and Shibamoto, 2001). Clove extractshas antimicrobial, antiseptic, analgesic, anti-inflammatory,chemopreventive, hepatoprotective, neuroprotective, and plateletaggregation inhibition effects (Lagow, 2004). In our search forprolyl endopeptidase (PEP, EC 3.4.21.26) inhibitors as bioactiveconstituents against cognitive decline (Lee et al., 2004; Han andPaik, 2010; Yoon and Paik, 2010), we found that BuOH fractionof S. aromaticum at 8µg/mL exhibited 98% of PEP inhibitoryactivity. This paper describes four chromone components (1-4)isolated from S. aromaticum (Fig. 1) that exhibit PEP inhibitionabilities as well as antioxidant capacities against the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid diammonium salt (ABTS)radical system.Dried flower buds of S. aromaticum (2.0 kg) were extractedtwice at room temperature with 80% aqueous MeOH. Afterfiltration and evaporation of the solvent under reduced pressure,the combined crude extract was suspended in water and thensuccessfully partitioned to afford hexane-, EtOAc-, and BuOH-soluble fractions. The BuOH-soluble fraction (25 g) was subjectedto ODS column (190 mm × 30 mm) eluting with CH

Antioxidant and Prolyl Endopeptidase Inhibitory Capacities of Chromone C-glucosides from the Clove Buds (Syzygium aromaticum)