A concise total synthesis and PPAR activation activity of hericerin from Hericium erinaceum

Article abstract of DOI:10.1038/s41429-020-0303-8

Hericerin is an isoindolinone meroterpenoid alkaloid isolated from medicinal mushroom Hericium erinaceum with some bioactivities. Herein, a concise total synthesis of hericerin was described, with four steps and 30percent overall yield starting from commercially available methyl 3-hydroxy-5-methoxybenzoate and geranyl bromide. A comprehensive effect of hericerin on HepG2 cell line was observed and confirmed by transcriptomic analysis. Furthermore, hericerin was found to be a new PPARγ agonist.

Full text of DOI:10.1038/s41429-020-0303-8

The Journal of Antibiotics
https://doi.org/10.1038/s41429-020-0303-8
BRIEF COMMUNICATION
A concise total synthesis and PPAR activation activity of hericerin
from Hericium erinaceum
Zhongyong Zheng1,2 Baosong Chen1,2 Kai Wang3 Li Bao1,2 Zhengdi Wang4 Liping Xie4 Changbin Guo4
Hongwei Liu1,2
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Received: 5 December 2019 / Revised: 12 February 2020 / Accepted: 9 March 2020
© The Author(s), under exclusive licence to the Japan Antibiotics Research Association 2020
Abstract
Hericerin is an isoindolinone meroterpenoid alkaloid isolated from medicinal mushroom Hericium erinaceum with some
bioactivities. Herein, a concise total synthesis of hericerin was described, with four steps and 30% overall yield starting from
commercially available methyl 3-hydroxy-5-methoxybenzoate and geranyl bromide. A comprehensive effect of hericerin on
HepG2 cell line was observed and confirmed by transcriptomic analysis. Furthermore, hericerin was found to be a new
PPARγ agonist.
Isoindolinone, featured as benzo-fused five-membered N-
heterocyclic skeleton, are widely present in an array of
biologically active natural products, such as stachyflin with
antiviral activity [1], stachybotrylactam I with HIV-1 pro-
tease inhibition activity [2], stachybotrin with neuritogenic
properties [3], and staurosporine with inhibition activities
against PKC, GSK-3, PKA, PKG, and TPK kinases [4].
Secondary natural products derived from fungi provide a
wealth of lead compounds for drug development [5, 6].
Hericerin, an isoindolinone isolated from the well-known
edible and medicinal mushroom Hericium erinaceum [6],
shows various bioactivities such as anti-inflammation,
cytotoxicity, and inhibitory activity against pine pollen
germination and tea pollen growth [6–9]. Recently, we and
other groups found that hericerin was a strong α-glucosidase
inhibitor, which may play a beneficial role in the treatment
of diabetes [10, 11]. However, the lower yields of hericerin
in the fruiting body of H. erinaceum along with the multi-
step chemical synthesis routes [12–14] limit the further
research and development of hericerin as an important
leading compound.
Hericerin was first synthesized by Kobayashi et al.
employing the geranylated lactone as the starting material that
was synthesized by CuBr2-mediated multistep reactions, with
a relatively low yield (∼3%) [12], and the structure of her-
icerin was revised to be identical with that of isohericerin
based on this total synthesis. In a following report, hericerin
was synthesized with a 34% overall yield from commercially
available 2-hydroxy-4-methoxybenzaldehyde by employing a
ether–phenol rearrangement and a Pd(OAc)2-catalyzed car-
bonylative ring closure reactions [13]. However, the harsh
reaction conditions and the use of environmentally unfriendly
CO gas limits the application of this synthetic route [13]. In
2017, Mun et al. used a Mannich reaction and one-pot lac-
tamization to establish the common isoindolinone core
structure from the commercially available hydroxybenzoate.
Hericerin was further obtained by a Suzuki–Miyaura coupling
reaction to link isoindolinone unit with geranyl boronate [14].
In our study, we developed a new route to total synthesis of
hericerin.
Supplementary information The online version of this article (https://
doi.org/10.1038/s41429-020-0303-8) contains supplementary
material, which is available to authorized users.
* Hongwei Liu
liuhw@im.ac.cn
1
State Key Laboratory of Mycology, Institute of Microbiology,
Chinese Academy of Sciences, No. 1 Beichenxi Road, Chaoyang
District, 100101 Beijing, PR China
2
Savaid Medical School, University of Chinese Academy of
Sciences, 100049 Beijing, PR China
3
Department of Physiology and Pathophysiology, School of Basic
Medical Sciences, Peking University, and the Key Laboratory of
Molecular Cardiovascular Science, Ministry of Education, 100191
Beijing, PR China
4
Scheme 1 describes the total synthesis of hericerin (1).
According to a previous report by the Lee group [14], the
Department of chemistry, Capital Normal University, 100048
Beijing, PR China

Z. Zheng et al.
OH
OH
O
N
K3PO4(2.5 M)
CH2O:Phenylethylain
NaH, 0 °C, 10 min
O
N
O
Toluene, 85 °C
reflux, 12 h
81% Yield
MeCN, 100 °C
reflux, 12 h
98% Yield
O
O
Geranyl Bromide (5), 65 °C
THF, 3 h
O
O
O
O
99% Yield
4
2
3
Ytterbium (II) Triflate
OH
O
N
O
MeCN, 85 °C
reflux, 36 h
38% Yield
N
O
O
O
6
Hericerin (1)
Scheme 1 Concise total synthesis of hericerin
Table 1 Optimization of
Entry
Catalyst
Time(h)
Reagent
Temperature (°C)
Yield (%)
reaction conditions for the
ether–phenol rearrangement
a
1
Montmorillonite
Montmorillonite
Montmorillonite
Montmorillonite K10
Montmorillonite K10
Montmorillonite K10
Montmorillonite K10
Montmorillonite KSF
Montmorillonite KSF
Montmorillonite KSF
Montmorillonite KSF
DIBAL-H
24
24
24
8
Toluene
DMF
Reflux
–
2
130
–
3
CH2Cl2
Toluene
DMF
Reflux
–
4
Reflux
–
5
24
24
12
24
24
24
12
12
24
8
130
–
6
CH2Cl2
CH2Cl2
Toluene
DMF
Reflux
–
7
0
–
8
Reflux
–
9
130
–
10
11
12
13
14
15
16
17
18
19
20
21
22
23
CH2Cl2
CH2Cl2
CH2Cl2
benzene
CH2Cl2
CH2Cl2
CH2Cl2
Toluene
MeCN
MECN
MeCN
MeCN
DMSO
DMF
Reflux
–
0
–
0
–
DMA
AlMe3 + H3O+
Reflux
–
−20
–
AlMe3
8–12
8–12
24
24
24
24
72
72
72
From −20 to reflux
From −20 to reflux
Reflux or R.T.
Reflux
–
AlCl3
–
Bi(OTf)3
–
Bi(OTf)3
–
Yb(OTf)3
From –20 to R.T.
Reflux
–
Yb(OTf)3
23%
38%
15%
–
Yb(OTf)3
Reflux
Yb(OTf)3
130
Yb(OTf)3
130
aReaction product not obtained
aromatic precursor isoindolinone 4 was synthesized. Due to
the strict conditions for the Pd(dppf)Cl2-catalyzed C–C bond
coupling reaction, we performed an alkylation reaction with
the geranyl bromide 5 and 4 under KOH-basic phase transfer
conditions to provide the phenol ether 6. Next, we attempted a
[1,3]-sigmatropic rearrangement of geranyl ethers to ortho-
and para-phenols, unfortunately, the target product was not
obtained by frequently used rearrangement agents including
montmorillonite and its derivatives, DIBAL-H, and DMA
[13, 15–17]. The eletrophilicity of the amide group in 6 might
not favor the [1,3]-sigmatropic rearrangement reaction. After
exploring a range of metal salts AlCl3, Bi(OTf)3, or Yb(OTf)3
as stronger Lewis acids [18], Yb(OTf)3 was found to trans-
form compound 6 into 1 with a satisfactory yield (38%,
Table 1). Herein, Yb(OTf)3 was reported as a [1,3]-sigma-
tropic rearrangement reagent for geranyl ether while it
has been used as a [3,3]-sigmatropic rearrangement reagent
in the synthesis of β-amino-α,β,ε,ζ-unsaturated-γ,δ-dis-
ubstituted esters [19]. Thus, a concise four-step total synthesis
of hericerin was performed, with 30% overall yield
starting from commercially available methyl 3-hydroxy-5-
methoxybenzoate (2) and geranyl bromide (5).

A concise total synthesis and PPAR activation activity of hericerin from Hericium erinaceum
Fig. 1 Transcriptome analysis of the gene expression profile in hericerin-
treated HepG2 cell line. a Gene expression changes. b Volcano Plots.
c KEGG pathway enrichment analyses of regulated genes. d Hierarchical
clustering of the differentially expressed genes by heatmap. N = 3
per group
Transcriptomic analysis of hericerin on
HepG2 cell
hericerin treatment significantly decreased the expression of
genes participating in lipogenesis (Was, Acpp, Cd74, Ear2,
Wisp1, Trp, Lima1, Top2a, and Aif1l). These data confirmed
the beneficial effect of hericerin on lipid metabolism.
Notably, mRNA expression of genes involved in PPARγ
signaling pathway including Tca1, Cd79b, Camk1g, Cdh1,
Ptprn, and Hs3st1 was upregulated (Fig. 1d and Supple-
mentary information). PPARγ, one of the members of
PPAR family, functions as a regulator of fat gene programs
and plays an important role in the control of lipid and
glucose homeostasis [20]. Above results indicated that
hericerin be a potential PPARγ agonist. To verify the effect
on PPARγ, hericerin was assayed in vitro for PPARγ
transactivation activity. As shown in Fig. S9, hericerin
showed dose-dependent activation of GAL4-PPARc by
~7.47-fold with an EC50 of 2.17 μM. Thus, hericerin is
defined as a strong PPARγ agonist with potential hypo-
glycemic and hypolipidemic effects.
To explore new bioactivities of hericerin (1), we analyzed
transcriptome alterations using high-depth next generation
sequencing with an Illumina HiSeq 4000 on HepG2 cell
lines. Among the 26,432 genes detected by RNA-seq,
hericerin significantly altered the levels of 242 genes (p <
0.05; Fig. 1a). Of these, 107 upregulated genes and 135
downregulated genes were differentially expressed by
twofold or more (Fig. 1b). A Kyoto Encyclopedia of Genes
and Genomes (KEGG) analysis of these genes showed
biological pathways involved in the lipid and glucose
metabolism (e.g., regulation of lipolysis in adipocyte, per-
oxisome proliferator-activated receptor (PPAR) signaling
pathway, PI3K-Akt signaling pathway, MAPK signaling
pathway, fatty acid biosynthesis, and fatty acid biosynth-
esis; Fig. 1c). Further gene analysis also revealed that

Z. Zheng et al.
In summary, a revised concise total synthesis route for
hericerin was reported with four-step and 30% overall yield.
The transcriptomic analysis on HepG2 cell line together
with the PPARγ activation assay confirmed hericerin to be a
new PPARγ agonist with a new scaffold.
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Acknowledgements This study was supported by the National Natural
Science Foundation of China (21472233 and 21877124).
Compliance with ethical standards
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Conflict of interest The authors declare that they have no conflict of
interest.
Publisher’s note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional affiliations.
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