Protein glycation inhibitory activity and antioxidant capacity of clove extract.

Abstract

Syzygium aromaticum (L.) (clove) is one of the most widely cultivated spices in many tropical countries. The aim of this study was to determine the phytochemical content, the antioxidant properties and the antiglycation properties of aqueous extract of clove against fructose-mediated protein glycation and oxidation. The result showed that the content of total phenolics and flavonoids in clove extract was 239.58 ± 0.70mg gallic acid equivalents/g dried extract and 65.67 ± 0.01mg catechin equivalents/g dried extract, respectively. In addition, clove exhibited antioxidant properties including DPPH radical scavenging activity (IC50 = 0.29 ± 0.01 mg/ml), Trolox equivalent antioxidant capacity (4.69 ± 0.03μmol Trolox equivalents/mg dried extract), ferric reducing antioxidant power (20.55 ± 0.11μmol ascorbic acid equivalents/mg dried extract), Oxygen radical absorbance capacity (31.12 ± 0.21μmol Trolox equivalents/mg dried extract), hydroxyl radical scavenging activity (0.15 ± 0.04mg Trolox equivalents/mg dried extract), and superoxide radical scavenging activity (18.82 ± 0.50mg Trolox equivalents/mg dried extract). The aqueous extract of clove (0.25-1.00mg/ml) significantly inhibited the formation of fluorescent advanced glycation end products (AGEs) and non-fluorescent AGEs (N(ɛ)-(carboxymethyl) lysine (CML)) in glycated BSA during 4weeks of incubation. The extract also markedly prevented oxidation-induced protein damage by decreasing protein carbonyl formation and protecting against the loss of protein thiol group. These results clearly demonstrated that a polyphenol enriched clove extract, owing to its antioxidant, was capable to inhibit the formation of AGEs and protein glycation. The findings might lead to the possibility of using the clove extract for targeting diabetic complications.