Prolyl Endopeptidase-inhibiting Isoflavonoids from Puerariae Flos and Some Revision of their $^{13}C-NMR$ Assignment

갈화의 Prolyl Endopeptidase 저해 활성 Isoflavonoid 및 이들의 $^{13}C-NMR$ Assignment

In order to find anti-dementia drugs from natural products, prolyl endopeptidase inhibitors were purified from Puerariae Flos by consecutive solvent partition, followed by silica gel, Sephadex LH-20, and HPLC. Four isoflavonoid inhibitors were isolated and identified as tectorigenin, genistein, 5,7-dihydroxy-4',6-dimethoxyisoflavone, and 5-hydroxy-6,7,4'-trimethoxyisoflavone by means of instrumental analyses including $^{1}H-$, $^{13}C-$, $^{2}D-NMR$ and MS and $IC_{50}$ values against PEP were 5.30 ppm$(17.7\;{\mu}M)$, 10.39 ppm$(38.5\;{\mu}M)$, 13.92 ppm$(44.3\;{\mu}M)$, and 20.61 ppm$(62.8\;{\mu}M)$, respectively. Some previous mistakes in $^{13}C-NMR$ assignment were revised by careful investigation of HMBC and HMQC data.

갈화로부터 항치매 효과를 기대할 수 있는 prolyl endopeptidase(PEP) 저해제를 분리하기 위하여 갈화의 methanol 추출물을 chloroform 및 ethyl acetate로 분배추출 후 chloroform 가용성 분획에 대하여 silica gel, Sephadex LH-20 column chromatography 및 RP-HPLC를 행한 결과, $FeCl_3$,에 양성 반음을 나타내는 4종의 화합물을 얻었다. 이들을 $^1H-$, $^{13}C-$, $^2D-NMR$ 및 MS 등을 이용하여 분석한 결과, 각각 tectorigenin, genistein, 5,7-dihydroxy-4',6-dimethoxyisoflavone, 5-hydroxy-6,7,4'-trimethoxyisoflavone으로 동정하었으며 HMBC, HMQC를 통하여 $^{13}C-NMR$ signal들을 assign함으로써 기 보고된 data들의 오류를 바로잡았다. PEP에 대한 이 화합물들의 $IC_{50}$값은 각각 5.30 ppm$(17.7\;{\mu}M)$, 10.39 ppm$(38.5\;{\mu}M)$, 13.92 ppm$(44.3\;{\mu}M)$, 20.61 ppm$(62.8\;{\mu}M)$이었다.