Cultivated Fruit Body of Phellinus baumii: A Potentially Sustainable Antidiabetic Resource

Abstract

Previous studies have been reported that the fruit body of wild Phellinus baumii alleviates diabetes, and antioxidants are beneficial to diabetes by protecting the β-cell from damage due to oxidative stress. Large-scale cultivation of P. baumii fruit body has been successful in the past decade. This paper aimed to investigate whether the fruit body of the cultivated P. baumii has the same analogical effects as the wild. The cultivated P. baumii fruit body was extracted by 80% of ethanol extracts, and different fractions were obtained with the successive use of petroleum ether, ethyl acetate (EtOAc), n-butanol (n-BuOH), and water, which yielded 15.98 ± 1.56, 1.74 ± 0.34, 3.31 ± 0.41, 4.12 ± 0.37, and 1.38 ± 0.26% extract recovery, respectively. Results show that the EtOAc fraction exhibits the highest inhibitory effect on α-glucosidase activity (IC₅₀ = 49.05 ± 3.14 μg mL^-1), which is an order of magnitude higher than the positive control (acarbose, IC₅₀ = 645.73 ± 7.86 μg mL^-1). It was mainly composed of phenolic compounds with a purity of 79.45% and characterized by liquid chromatography-mass spectrometry as osmudacetone, hispidin, davallialactone, 2,5-bis(4,7-dihydroxy-8-methyl-2-oxo-2H-chromen-3-yl)cyclohexa-2,5-diene-1,4-dione, hypholomin B, and inoscavin A. Furthermore, the EtOAc fraction increased the glucose consumption of insulin-resistant HepG2 cells at a concentration range of 25-100 μg mL^-1. The EtOAc fraction also demonstrated antioxidant activities by scavenging 1,1-diphenyl-2-picrylhydrazyl, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt, and hydroxyl radicals. In conclusion, the EtOAc fraction of the cultivated P. baumii fruit body exerted effective antidiabetic effects, possibly due to the high content of selective phenolic compounds. Hence, the cultivated fruit body of P. baumii can be a sustainable resource for treating diabetes, and our work also shed some light on its future utilization.

Figure 1

Extraction yield and total polyphenol contents of different fractions from the cultivated P. baumii fruit body. Results are means ± SD (n = 3). Different letters indicate a significant difference by Duncan’s multiple test at P < 0.05.

Figure 2

Major constituents of the EtOAc fraction from the fruit body of cultivated P. baumii (PB-EtOAc). (A) HPLC chromatogram of PB-EtOAc at 254 nm with peaks 1–6. (B) Chemical structures of compounds 1–6 identified from PB-EtOAc.

Figure 3

Effects of different concentrations of insulin and cultured time on glucose consumption in HepG2 cells. Results are means ± SD (n = 3). (A) Glucose consumption in HepG2 cells under different concentrations of insulin. *P < 0.05, which is compared with the control. (B) Glucose consumption in HepG2 cells under different culture times. ^#P < 0.05, which is compared with 24 h group. Different letters indicate a significant difference by Tukey test.

Figure 4

MTT assay results of EtOAc fraction from the fruit body of cultivated P. baumii at different concentrations. Results are means ± SD (n = 3).

Figure 5

Effects of the EtOAc fraction from the fruiting body of P. baumii on glucose consumption in insulin-resistant HepG2 cells. “IR” represents the insulin resistance group; “metformin” represents the positive control group of metformin. Results are means ± SD (n = 3). Different letters indicate a significant difference by Tukey test. *P < 0.05, which is compared with the control; ^#P < 0.05, which is compared with metformin; ^△P < 0.05, which is compared with IR.

Figure 6

DPPH (A), ABTS (B), and hydroxyl radical (C) scavenging activities of the EtOAc fraction from the fruiting body of P. baumii. Data are expressed as means ± SD of at least three independent experiments. Different letters indicate a significant difference according to the Tukey test. *P < 0.05, **P < 0.01, which is compared with Vc.

Figure 7

Fruit bodies of P. baumii cultivated in a greenhouse.

Figure 8

Flow chart of the fractions extracted from the fruit body of cultivated P. baumii.