In vitro activity and chemical characterization of an apolar fraction of Morus alba leaf hot water extract
White mulberry (Morus alba L.) leaf is a well known traditional medicine of type II. diabetes, a progressive disease with a broad spectrum of complications which has increasing incidency worldwide. Most typically it is taken as tea, often in combination with other phytotherapeutics. Many constituents were found to contribute to the antidiabetic activity of mulberry leaf, including iminosugars, flavonoids and related compounds, glycoproteins and ecdysteroids. Moreover, the role of phenylpropanes and megastigmane glycosides was also hypothesized by our group [1,2].
Here we report the investigation of a fraction of mulberry leaf hot water extract obtained by solvent-solvent partition between water and dichloromethane. A significant increase in the 24h glucose consumption of fully differentiated adipocytes was found when treated with 50µg/mL of fraction with 0.32µM insulin or rather 200µg/mL without it, as compared to the corresponding controls. In the latter case, the activity was similar to that of 50µg/mL rosiglitazone that was used as positive control. Chemical composition of the pleasant odour, oily fraction was investigated by using HPLC-DAD, GC-MS, GC-FID and LC-MS/MS. The main constituent (GC-FID: 56.2%) is suggested to be a chain-saturated cinnamaldehyde derivative, and benzyl alcohol, ethyl benzoate, t-cinnamic acid, p-hydroxyacetophenone, t-coniferyl alcohol and sinapyl alcohol were also identified as minor constituents.
Attempting to perform in vitro activity guided isolation, further fractionation was done by using rotational planar chromatography. All fractions obtained were found inactive, which may suggest synergy between certain constituents. In vivo investigation of antidiabetic activity is currently in process.
Acknowledgement: This project was supported by the Hungarian National Research Fund (OTKA; PD75383), the New Hungary Development Plan (TÁMOP-4.2.2–08/1–2008–0013 and TÁMOP-4.2.1/B-09/1/KONV-2010–0005) and by the grant from the National Science Council of Taiwan (NSC 982314B037011MY3).
References: 1. Hunyadi A et al. (2007) Planta Med 73: 941.
2. Hunyadi A et al. (2008) Planta Med 74: 1117.