Bioactive compounds from the bark of Broussonetia papyrifera after solid fermentation with a white rot fungus Perenniporia tephropora

Abstract

In this study, potential bioactive compounds in the products of the solid fermentation of the paper mulberry tree bark (Broussonetia papyrifera) with a white rot fungus (Perenniporia tephropora) were investigated. Fractionation of methanolic extracts from the fermented products of the bark led to the isolation of 10 known compounds, namely broussonin B (1), broussonin A (2), 7,4'-dihydroxy-3'-prenylflavan (3), cathayanon H (4), broussoflavonol B (5), isoliquiritigenin (6), broussochalcone B (7), glyasperin A (8), marmesin (9), and vomifoliol (10). Their structures were determined by spectroscopic analysis (including considerations of MS, ¹H, ¹³C NMR, COSY, HMQC, and HMBC spectra) and compared with structures that had been published in the literature. Of these compounds identified, cathayanon H (4) and glyasperin A (8) were isolated for the first time from the paper mulberry tree. Vomifoliol (10) was produced from the bark only after fermentation with white rot fungi. It was observed that concentrations of marmesin (9) and vomifoliol (10) generally increased with an increase in fermentation time, whereas concentration of compounds 1‒8 in the fermented products decreased during the same period. Biological tests showed that the tyrosinase inhibitory activity of marmesin (9) (IC₅₀ = 168.0 μM) was similar to that of arbutin, a well-known tyrosinase inhibitor, whereas vomifoliol (10) exhibited no tyrosinase inhibition activity at any concentration higher than 2 mM. Accordingly, both solids and the liquid broth left after fermentation of the paper mulberry tree bark with the aforementioned white rot fungus could be developed for potential use in industrial applications.

Keywords:

• Paper mulberry tree (Broussonetia papyrifera)
• marmesin
• vomifoliol
• tyrosinase inhibitor
• white rot fungus (Perenniporia tephropora)

Acknowledgements

We would like to express our gratitude toward Instrumentation Center, National Taiwan University and Taipei Medical University for performing ¹H, ¹³C NMR, and 2D NMR (COSY, HMBC and HMQC) spectra on a Bruker 500 DRX NMR Spectrometer and Bruker AVIII 500 MHz FT NMR Spectrometer. We also would like to express our gratitude toward Institute of Plant and Microbial Biology, Academia Sinica, Taiwan for performing LC/MS.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by Ministry of Science and Technology of Taiwan under Grant number NSC96-2317-B019-005 and NSC97-2317-B019-002.