Xanthone glucoside from an insect pathogenic fungus Conoideocrella luteorostrata NBRC106950

Article abstract of DOI:10.1080/14786419.2021.1883607

A new compound, 3-O-(4-O-methyl-β-D-glucopyranosyl) xanthone (1) was isolated from the culture of Conoideocrella luteorostrata NBRC106950. The structure of 1 was mainly determined by ¹H, ¹³C, 2D-NMR and HREIMS spectral analyses. The absolute configuration of 4-O-methylglucopyranosyl moiety was determined by the optical rotation of aqueous layer of hydrolyzed 1 as D-configuration.

Full text of DOI:10.1080/14786419.2021.1883607

Natural Product Research
Formerly Natural Product Letters
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/gnpl20
Xanthone glucoside from an insect pathogenic
fungus Conoideocrella luteorostrata NBRC106950
Tatsuro Yoneyama, Miki Iguchi, Kento Yoshii, Abdelsamed I. Elshamy, Sayaka
Ban, Masaaki Noji & Akemi Umeyama
To cite this article: Tatsuro Yoneyama, Miki Iguchi, Kento Yoshii, Abdelsamed I. Elshamy,
Sayaka Ban, Masaaki Noji & Akemi Umeyama (2021): Xanthone glucoside from an insect
pathogenic fungus Conoideocrellaꢀluteorostrata NBRC106950, Natural Product Research, DOI:
10.1080/14786419.2021.1883607
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NATURAL PRODUCT RESEARCH
https://doi.org/10.1080/14786419.2021.1883607
BRIEF REPORT
Xanthone glucoside from an insect pathogenic
fungus Conoideocrella luteorostrata NBRC106950
Tatsuro Yoneyamaa , Miki Iguchia, Kento Yoshiia, Abdelsamed I. Elshamya,b
Sayaka Banc, Masaaki Nojia and Akemi Umeyamaa
,
b
aFaculty of Pharmaceutical Science, Tokushima Bunri University, Tokushima, Japan; Chemistry of
c
Natural Compounds Department, National Research Centre, Giza, Egypt; Medical Mycology Research
Center, Chiba University, Chiba, Japan
ABSTRACT
ARTICLE HISTORY
Received 26 October 2020
Accepted 27 January 2021
A new compound, 3-O-(4-O-methyl-b-D-glucopyranosyl) xanthone
(1) was isolated from the culture of Conoideocrella luteorostrata
1
NBRC106950. The structure of 1 was mainly determined by H, 13C,
KEYWORDS
Conoideocrella luteorostrata
NBRC106950;
Clavicipitaceae; xanthone
glucoside; 4-O-
2D-NMR and HREIMS spectral analyses. The absolute configuration
of 4-O-methylglucopyranosyl moiety was determined by the optical
rotation of aqueous layer of hydrolyzed 1 as D-configuration.
methylglucopyranose
1. Introduction
Insect pathogenic fungi which belong to the order Hypocreales, such as Cordyceps
and Conoideocrella species produce its fruiting body or perithecium from host insects.
Conoideocrella luteorostrata (which belongs to the order Hypocreales, the family
Clavicipitaceae) primarily parasite on scale insects. Insect pathogenic fungi produce an
interesting variety of metabolites, but not many of them have been studied and
reported so far, given the existence of about 500 species worldwide. From these rea-
sons, we have focused on the isolation of new compounds and bioactive compounds
from Cordyceps. (Grudniewska et al. 2014; Umeyama et al. 2014; Ganaha et al. 2016)
In this manuscript, we report the isolation and structural elucidation of a new 1,6-dihy-
droxy-8-methyl-3-O-(4-O-methyl-b-D-glucopyranosyl) xanthone (1). There are few
CONTACT Akemi Umeyama
umeyama@ph.bunri-u.ac.jp; Tatsuro Yoneyama
yoneyama@ph.bunri-u.ac.jp
Supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2021.1883607.
ß 2021 Informa UK Limited, trading as Taylor & Francis Group

2
T. YONEYAMA ET AL.
reports of glucose glucoside methylated at the hydroxy group of C-40 position, limited
to examples from some entomopathogenic fungi and other species.
2. Result and discussion
C. luteorostrata NBRC106950 was cultured with potato sucrose medium for two weeks.
Mycelium were collected by filtration and extracted with MeOH twice and CHCl3:
MeOH 2:1 once and separated by subsequential liquid-liquid extraction to yield
10.99 g of EtOAc soluble fraction. EtOAc soluble fraction was purified by silica gel col-
umn chromatography to isolate 18.3 mg of 1.
Molecular formula of 1 was determined as C21H22O10 by HR-EIMS (calculated
as 434.1213). In IR spectrum analysis, presence of hydroxy and carbonyl groups were
1
indicated due to the peaks at 3357 and 1621 cmꢀ1, respectively. In H-NMR, four aro-
matic methine protons (dH 6.90, 6.87, 6.82, and 6.79), five oxygenated methine protons
(dH 5.68, 4.36, 4.25, 3.91, and 3.45), a oxygenated methylene proton (dH 4.27 and 4.17),
a methoxy proton (dH 3.86) and a methyl proton (dH 2.89) were observed. In 13C-NMR,
21 signals were observed, including a carbonyl carbon (dC 182.6), eight aromatic
quaternary carbons (dC 164.7, 164.4, 164.2, 160.0, 157.2, 143.9, 111.9 and 105.0),
four aromatic methine carbons (dC 117.4, 101.39, 99.4 and 94.4), five oxygenated
methine carbons (dC 101.36, 80.1, 77.9, 77.7 and 74.8), an oxygenated methylene
carbon (dC 61.5), a methoxy carbon (dC 60.6), and a methyl carbon (dC 23.5) (Table S1).
HMBC correlations between H-2 (dH 6.82)/C-1 (dC 157.2), C-3 (dC 164.4), C-4 (dC 99.4)
and C-9a (dC 105.0) and H-4 (dH 6.79)/C-4a (dC 157.2) and C-9a indicated the phenol
moiety (Figure S7). In the same manner, H-10 (dH 2.89)/C-7 (dC 117.4), C-8 (dC 143.9)
and C-8a (dC 111.9) and H-5 (dH 6.87)/C-5a (dC 160.0), C-6 (dC 164.7) and C-7 (dC 117.4)
revealed the presence of m-cresol moiety. In these partial structures, chemical shift
values of aromatic quaternary carbons showed down field shift due to the presence of
oxygen (C-4a and C-5a) and carbonyl group (C-8a and C-9a). These data confirmed the
1, 6-dihydroxy-8-methyl-xanthone structure.
Glucopyranosyl moiety was successfully determined by the COSY correlations between
H-10 (dH 5.68, d, J¼ 7.7 Hz)/H-20 (dH 4.25, dd, J¼ 7.7, 8.9 Hz), H-20/H-30 (dH 4.36, dd, J¼ 8.9,
8.9 Hz), H-30/H-40 (dH 3.91, dd, J¼ 8.9, 9.7 Hz), H-40/H-50 (dH 3.95, ddd, J¼ 1.8, 4.2, 9.7 Hz),
and H-50/H-60 (dH 4.27, dd, J¼ 1.8, 12.3 Hz) and H-60 (dH 4.17, dd, J¼ 4.2, 12.3 Hz). HMBC
correlation between dH 3.86/C-40 (dC 80.1) indicated the methoxy group at position C-40.
In addition, H-10 (dH 5.68)/C-3 (dC 164.4) revealed the substitution at position C-3 by
4-O-metylglucopyranose. The b-orientation of 4-O-methylglucose was determined by ROE
correlation observed between H-10/H-30 and H-50, and H-20/H-40, and J value (7.7 Hz) of
aromatic proton at dH 5.68. The D-configuration of 4-O-methyl-b-glucopyranosyl unit was
determined with specific optical rotation of the H2O soluble layer of hydrolysate of 1.
1H-NMR analysis revealed sugar moiety was transferred to aqueous layer, while aglycone,
which has planner structure, was dissolved in EtOAc layer (Figure S8 and S9). Aqueous
21
layer of 1 showed positive value, ½aꢁD þ24.4 (c 0.17, MeOH), which correspond to the
20
reported value of 4-O-methyl-D-glucopyranose, ½aꢁD þ80 (c 1.3, MeOH). (Smith 1951) The
absolute configuration of 1 was determined as 1,6-dihydroxy-8-methyl-3-O-(4-O-methyl-
b-D-glucopyranosyl) xanthone (Figure 1).

NATURAL PRODUCT RESEARCH
3
Figure 1. Structure of 1.
Unfortunately, 1 didn’t show significant activity in anti-malarial assay (data
not shown).
3. Conclusion
In this study, we have isolated a new xanthone derivative, 1, 6-dihydroxy-8-methyl-3-
O-(4-O-methyl-b-D-glucopyranosyl) xanthone from the culture of C. luteorostrata.
Previously, compounds with 40-O-methylglucose have been isolated from some insect
pathogenic fungi, Akanthomyces novoguineensis, Metarrhizium anisopliae, Cordyceps jav-
anica, Paecilomyces cinnamomeus and Orbiocrella sp., which belong to the orders
Hypocreales or Eurotiales. (Bunyapaiboonsri et al. 2007; Isaka et al. 2007, 2014;
Kuephadungphan et al. 2017; Helaly et al. 2019; Wang et al. 2020) From the starfish
Anthenea sibogae, steroids substituted by 3-O-methyl-glucopyranose and 4-O-methyl-
glucopyranose were reported. (Kicha et al. 2018) Hydroxy group at C-60 position of
glucopyranose is more active than others because of its primary alcohol structure,
implying this methoxy group at C-40 position was not substituted artificially while the
extraction and purification steps. In addition, glycosyltransferase which is clustered
with a methyltransferase isolated from the genome DNA of Beauveria bassiana has
been demonstrated to contribute on the methylglucosylation of aromatic amino and
phenolic moieties. (Xie et al. 2018) These indicate C. luteorostrata and other insect
pathogenic fungus could have related biosynthetic enzymes for this reaction which
could be hardly found in plants and other organisms. Isolation of new compound
from Cordyceps will lead the finding of not only new compounds but also new bio-
synthetic enzymes which have new interesting metabolic functions in further study.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
Tatsuro Yoneyama
Abdelsamed I. Elshamy
http://orcid.org/0000-0001-7306-9015
http://orcid.org/0000-0003-3302-3623
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