Aromatase is the key enzyme responsible for catalyzing the conversion of C19steroids to estrogens. Its inhibitors are widely used in breast cancer therapy. The DCM partition of a crude ethanolic extract from the roots of Flemingia philippinensisshowed potent inhibitory activity of aromatase. The constituents of the extract were analyzed and identified by liquid chromatography tandem mass spectrometry. Five purified prenylated isoflavones were evaluated for aromatase inhibition and their IC50 values ranged between 2.98 and 58.08 μM. In kinetic studies, all tested compounds behaved as reversible competitive inhibitors and their Ki values were calculated by Dixon plots. The most potent inhibitor (6, 8-diprenylorobol) had a Kivalue of 1.42 μM. Furthermore, using UPLC and LC-MS, 6, 8-diprenylorobol was proven to be present in the native roots in high quantities.

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... flemiphilippinin A (compound 20) (purity tested by HPLC & 1 H-NMR was 98.6%, 97.4% and 97.6%, respectively) were purchased from the Biopurify Company (Chengdu, China). The organic solvents used for extraction were of analytical grade. ...