Protective effects of puerariae radix extract and its single compounds on methylglyoxal-induced apoptosis in human retinal pigment epithelial cells

Abstract

Ethnopharmacological relevance: In Korea, Puerariae radix is a medicinal plant traditionally used to treat various diseases including diabetes mellitus. To provide pharmacological basis for Puerariae radix in the treatment of diabetes, we investigated the protective effects of the ethanolic extract and its single compounds on apoptosis associated with glycation in human retinal pigment epithelial (RPE) cells.

Materials and methods: In the present work, a quantified ethanolic extract or single compounds of Puerariae radix were selected to determine its anti-apoptotic effect in human RPE cells cultured with methylglyoxal (MG), which is a stimulator of glycation. To assess the protective effect of the extract or single compounds, the cytotoxicity assessment was performed using an MTT assay in the human RPE cells. Selected active compounds or extracts were tested by FACS analysis with annexin V staining for apoptosis.

Results: Daidzein (1), daidzin (2), puerarin (3), 3'-hydroxy-daidzein 8-C-apiosyl (1→6) glucoside (4), and daidzein 8-C-apiosyl (1→6) glucoside (5), and pueroside B (6) were isolated from an ethanolic extract of Puerariae radix. MG-induced apoptosis was completely inhibited by Puerariae radix, ethanolic extract, and single compounds. Of the six major compounds, daidzin (2) and 3'-hydroxy-daidzein 8-C-apiosyl (1→6) glucoside (4) significantly inhibited MG-induced apoptosis.

Conclusion: Our results provide the first evidence that, due to its anti-glycation effect, Puerariae radix extract could inhibit MG-induced apoptosis in the cultured human RPE cells. These data suggest that Puerariae radix extract, especially its single compounds daidzin and 3'-hydroxy-daidzein 8-C-apiosyl (1→6) glucoside, has potential utility as a preventive agent for glycation-related diabetic retinopathy.

Keywords: Apoptosis; Human retinal pigment epithelial cells; Isoflavone; Methylglyoxal; Puerariae radix.