| Summary: | 碩士 === 國立臺灣大學 === 藥學研究所 === 97 === Abstract
Diabetes mellitus is a chronic disease growing in prevalence worldwide. One of therapies to lower blood sugar level is the inhibition of α-glucosidase activity which serves the digestion of starch, oligosaccharides and disaccharides into monosaccharide.
The methanol extract of leaves of Planchonella obovata (R.Br) Pierre (Sapotaceae), an evergreen shrub, indigenous to Lanyu Island, was found to be active against α-glucosidase. Further study indicated that the n-butanol-soluble and ethylacetate fraction possessed better activity than chloroform layer (97.3 %, 87.2 %, 41.6 % inhibition at 100 μg/mL, respectively). Thus, this study focused on the chemical investigation of these two fractions.
Repeated separation of these two fractions over Sephadex LH-20, centrifugal partition chromatography and high performance liquid chromatography led to the isolation of nine compounds. They are four Iriflophenone { 2-O-β-D-glucopyranoside-(1), 2-O-(6-O-galloyl)-β-D-glucopyranoside-(2), 2-O-[6-O-(4-hydroxybenzoyl)]-β-D-glucopyranoside-(3), 2-O-(2,6-di-O-galloyl)-β-D-glucopyranoside-(7)}, and five flavonols: Kaempferol [ 3-O-β-galactopyranoside-(4) and 3-O-robinobioside-(5)], Isorhamnetin-3-O-robinobioside-(6), Quercetin [ 3-O-β-D-glucopyranoside-(8) and 3-O-α-L-arabinopyranoside-(9)]. Their structures were elucidated on the basis of elaborated spectroscopic analysis. Of these compounds, 2, 3 and 7 represent the first occurrence of such dibenzophenone natural products. Their anti-α-glucosidase activity, however, was not significant.
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