Abstract: The chemical constituents in stems and leaves of Syzygium jambos with α-glucosidase inhibitory active were investigated in this paper in order to lay a foundation for future study of Syzygium jambos.Effect of extract and compounds of Syzygium jambos on α-glucosidase inhibitory activity was determined by pNPG method.The constituents of active fraction were isolated and purified by various chromatography techniques such as column chromatography on silica gel,Sephadex LH-20,and preparative-HPLC.Their structures were identified by physicochemical properties and spectral data.The results indicate that ethyl acetate fraction (IC₅₀=6.96±0.82 mg/L) and n-butyl alcohol fraction (IC₅₀=5.27±0.26 mg/L) exhibited the stronger inhibitory active of α-glucosidase than positive control drug Acarbose (IC₅₀ = 2840.61±6.44 mg/L) (P<0.05).Eleven compounds (1-11) were isolated and identified as bergenin (1),2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethyldihydrochalcone (2),2′,4′-dihydroxy-6′-methoxy-3′-methylchalcone (3),5,7-dihydroxy-6,8-dimethyl-4′-methoxyflavone (4),6-desmethylsideroxylin (5),p-hydroxybenzaldehyde (6),quercitrin (7),ellagic acid (8),syringin (9),glucosyringic acid (10),and adenosine (11).All of these compounds were isolated from this plant for the first time.In addition,compounds 2-5 and 7-8 showed α-glucosidase inhibitory activity.

Key words: Syzygium jambos, isolation and identification, chemical constituents, α-glucosidase inhibitor