Cancer Chemopreventive in vitro Activities of Isoflavones Isolated from Iris germanica

Abstract

Six known isoflavones were isolated from the rhizomes of Iris germanica, and were established by UV, MS and NMR techniques as irisolidone (1), irisolidone 7-O-α-D-glucoside (1a), irigenin (2), irilone (3), iriflogenin (4), and iriskashmirianin (5). These compounds were examined for their cancer chemopreventive potential. They were shown to be potent inhibitors of cytochrome P450 1A activity with IC₅₀ values in the range 0.25 - 4.9 μM. The isoflavones 2, 3 and 5 displayed moderate activity as inducers of NAD(P)H:quinone reductase (QR) in cultured mouse Hepa 1c1c7 cells, with CD values (concentration required to double the specific activity of QR) of 3.5 - 16.7 μM, whereas weak activity was observed with compounds 4 and 5 in the radical (DPPH) scavenging bioassay (IC₅₀ values 89.6 and 120.3 μM, respectively). With respect to anti-tumor promoting potential based on anti-inflammatory mechanisms, none of the compounds demonstrated significant activity in the concentration range tested.

Abbreviations

APCI:atmospheric pressure chemical ionization

CD:concentration required for doubling of the specific activity of NAD(P)H:quinone reductase

Cox:cyclooxygenase

Cyp:cytochrome P450

DAD:diode-array detector

DPPH:1,1-diphenyl-2-picrylhydrazyl

HMBC:heteronuclear multiple bond correlation

IC₅₀:half-maximal inhibitory concentration

iNOS:inducible nitric oxide synthase

NF:naphthoflavone

QR:NAD(P)H:quinone reductase

SC₅₀:half-maximal scavenging concentration

Key words

Iris germanica - Iridaceae - isoflavones - cancer chemoprevention - carcinogen metabolism

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