Antibacterial activity of cyclo(L-Pro-L-Tyr) and cyclo(D-Pro-L-Tyr) from Streptomyces sp. strain 22-4 against phytopathogenic bacteria

Article abstract of DOI:10.1080/14786419.2015.1095747

Two bioactive cyclic dipeptides, cyclo(L-Pro-L-Tyr) and cyclo(D-Pro-L-Tyr), were isolated from the culture broth of Streptomyces sp. strain 22-4 and tested against three economically important plant pathogens, Xanthomonas axonopodis pv. citri, Ralstonia s

Full text of DOI:10.1080/14786419.2015.1095747

Natural Product Research
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: http://www.tandfonline.com/loi/gnpl20
Antibacterial activity of cyclo(L-Pro-L-Tyr) and
cyclo(D-Pro-L-Tyr) from Streptomyces sp. strain
22-4 against phytopathogenic bacteria
Pakorn Wattana-Amorn, Waranya Charoenwongsa, Christopher Williams,
Matthew P. Crump & Busaya Apichaisataienchote
To cite this article: Pakorn Wattana-Amorn, Waranya Charoenwongsa, Christopher Williams,
Matthew P. Crump & Busaya Apichaisataienchote (2015): Antibacterial activity of cyclo(L-
Pro-L-Tyr) and cyclo(D-Pro-L-Tyr) from Streptomyces sp. strain 22-4 against phytopathogenic
bacteria, Natural Product Research, DOI: 10.1080/14786419.2015.1095747
To link to this article: http://dx.doi.org/10.1080/14786419.2015.1095747
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Date: 16 October 2015, At: 00:07

Natural Product research, 2015
ꢁꢁp://ꢂx.ꢂꢃi.ꢃꢄg/10.1080/14786419.2015.1095747
ꢀ
SHORT COMMUNICATION
Antibacterial activity of cyclo(l-Pro-l-Tyr) and cyclo(d-
Pro-l-Tyr) from Streptomyces sp. strain 22-4 against
phytopathogenic bacteria
a
a
b
Pakorn Wattana-Amorn , Waranya Charoenwongsa , Christopher Williams ,
b
c
Matthew P. Crump and Busaya Apichaisataienchote
ꢅ
Fꢅꢆꢇꢈꢁy ꢃf sꢆiꢉnꢆꢉ, dꢉpꢅꢄꢁmꢉnꢁ ꢃf cꢀꢉmiꢊꢁꢄy, cꢉnꢁꢉꢄ ꢃf exꢆꢉꢈꢈꢉnꢆꢉ fꢃꢄ Innꢃvꢅꢁiꢃn in cꢀꢉmiꢊꢁꢄy ꢅnꢂ spꢉꢆiꢅꢈ
b
rꢉꢊꢉꢅꢄꢆꢀ uniꢁ fꢃꢄ aꢂvꢅnꢆꢉꢂ Mꢅgnꢉꢁiꢆ rꢉꢊꢃnꢅnꢆꢉ, Kꢅꢊꢉꢁꢊꢅꢄꢁ univꢉꢄꢊiꢁy, Bꢅngkꢃk, tꢀꢅiꢈꢅnꢂ; sꢆꢀꢃꢃꢈ ꢃf
cꢀꢉmiꢊꢁꢄy, univꢉꢄꢊiꢁy ꢃf Bꢄiꢊꢁꢃꢈ, Bꢄiꢊꢁꢃꢈ, uniꢁꢉꢂ Kingꢂꢃm; Fꢅꢆꢇꢈꢁy ꢃf enginꢉꢉꢄing ꢅnꢂ Inꢂꢇꢊꢁꢄiꢅꢈ tꢉꢆꢀnꢃꢈꢃgy,
ꢆ
dꢉpꢅꢄꢁmꢉnꢁ ꢃf Biꢃꢁꢉꢆꢀnꢃꢈꢃgy, siꢈpꢅkꢃꢄn univꢉꢄꢊiꢁy, Nꢅkꢀꢃn Pꢅꢁꢀꢃm, tꢀꢅiꢈꢅnꢂ
ABSTRACT
ARTICLE HISTORY
rꢉꢆꢉivꢉꢂ 23 Jꢇnꢉ 2015
aꢆꢆꢉpꢁꢉꢂ 8 aꢇgꢇꢊꢁ 2015
Two bioactive cyclic dipeptides, cyclo(l-Pro-l-Tyr) and cyclo(d-
Pro-l-Tyr), were isolated from the culture broth of Streptomyces sp.
strain 22-4 and tested against three economically important plant
pathogens, Xanthomonas axonopodis pv. citri, Ralstonia solanacearum
and Clavibacter michiganensis. Both cyclic dipeptides were active
against X. axonopodis pv. citri and R. Solanacearum with MIC of
KEYWORDS
cyꢆꢈꢃ(l-Pꢄꢃ-l-tyꢄ); ꢆyꢆꢈꢃ(d-
Pꢄꢃ-l-tyꢄ); Streptomyces;
pꢀyꢁꢃpꢅꢁꢀꢃgꢉniꢆ bꢅꢆꢁꢉꢄiꢅ
31.25 μg/mL. No activity could be observed against C. michiganensis.
CONTACT Pꢅkꢃꢄn Wꢅꢁꢁꢅnꢅ-amꢃꢄn
fꢊꢆipwꢅ@kꢇ.ꢅꢆ.ꢁꢀ; Bꢇꢊꢅyꢅ apiꢆꢀꢅiꢊꢅꢁꢅiꢉnꢆꢀꢃꢁꢉ
bꢇꢊꢅyꢅꢅ@gmꢅiꢈ.ꢆꢃm
sꢇppꢈꢉmꢉnꢁꢅꢈ ꢂꢅꢁꢅ fꢃꢄ ꢁꢀiꢊ ꢅꢄꢁiꢆꢈꢉ ꢆꢅn bꢉ ꢅꢆꢆꢉꢊꢊꢉꢂ ꢅꢁ ꢀꢁꢁp://ꢂx.ꢂꢃi.ꢃꢄg/10.1080/14786419.2015.1095747.
©
2015 tꢅyꢈꢃꢄ & Fꢄꢅnꢆiꢊ

2
P. WATTANAꢀAMORN ꢁT AL.
1
. Introduction
Screening for bioactive compounds from natural resources to use for medical and agricul-
tural purposes is one of the major goals in medicinal chemistry. One of the major sources
of these compounds is Streptomyces, a large genus bacteria that produce a vast diversity of
secondary metabolites (Lucas et al. 2013), including cyclic dipeptides (Zhou et al. 2014). This
class of metabolites contains a diketopiperazine core built with d and l amino acids, that
displays a broad spectrum of biological activities including antimicrobial activity (Martins &
Carvalho 2007).
Two promising cyclic dipeptides exhibiting potent antimicrobial activity are based on the
cyclo(l-Pro-l-Tyr) (A) and cyclo(d-Pro-l-Tyr) (B) scaffolds (Figure 1). To date, only cyclo(l-Pro-
l-Tyr) has been isolated from Streptomyces and here we report the isolation and molec-
ular characterisation of both diastereomers produced by Streptomyces sp. strain 22-4.
Furthermore, we also report the first antibacterial studies of both cyclo(l-Pro-l-Tyr) and
cyclo(d-Pro-l-Tyr) against three economically important phytopathogenic bacteria.
2
. Results and discussion
2
.1. Isolation and structure determination of cyclo(l-Pro-l-Tyr)
and cyclo(d-Pro-l-Tyr)
From the culture broth of S. sp. strain 22-4, a mixture containing cyclo(l-Pro-l-Tyr) and cyclo
(d-Pro-l-Tyr) was isolated. Separation of cyclo(l-Pro-l-Tyr) and cyclo(d-Pro-l-Tyr) proved to
be difficult by HPLC as both diastereoisomers eluted at 25% MeOH/H O. However, their
2
structures were elucidated by HR-MS (Figure S1) and NMR (Figures S2–S7) in combination
with Marfey’s method (Figure S8). The structures were further confirmed by comparison
Figure 1. sꢁꢄꢇꢆꢁꢇꢄꢉꢊ ꢃf (A) ꢆyꢆꢈꢃ(l-Pꢄꢃ-l-tyꢄ) ꢅnꢂ (B) ꢆyꢆꢈꢃ(d-Pꢄꢃ-l-tyꢄ).
Table 1. anꢁibꢅꢆꢁꢉꢄiꢅꢈ ꢅꢆꢁiviꢁy ꢃf ꢆyꢆꢈꢃ(l-Pꢄꢃ-l-tyꢄ) ꢅnꢂ ꢆyꢆꢈꢃ(d-Pꢄꢃ-l-tyꢄ).
Test bacteria with MIC (μg/mL)
Compound
X. axonopodis pv. citri
R. solanacearum
cyꢆꢈꢃ(l-Pꢄꢃ-l-tyꢄ)
cyꢆꢈꢃ(d-Pꢄꢃ-l-tyꢄ)
cꢀꢈꢃꢄꢁꢉꢁꢄꢅꢆyꢆꢈinꢉ
sꢁꢄꢉpꢁꢃmyꢆin ꢊꢇꢈpꢀꢅꢁꢉ
31.25
31.25
0.12
–
31.25
31.25
–
3.91

NATURAL PROꢂUCT RꢁSꢁARCH
3
1
with the H spectra of synthetic standards (Figure S2). To our knowledge, this is the first time
that both compounds have been isolated from S. sp strain 22-4. As several cyclic dipeptides
have been previously reported from production broths (Prasad 1995), the medium alone
was extracted and carefully investigated by HPLC to confirm that neither cyclo(l-Pro-l-Tyr)
or cyclo(d-Pro-l-Tyr) were present.
2
.2. Antibacterial activity against plant pathogenic bacteria
Previously, both cyclo(l-Pro-l-Tyr) and cyclo(d-Pro-l-Tyr) have been isolated from several
micro-organisms including Haloterrigena hispanica and Bacillus sp. N strain with antifungal
and antibacterial activities (Nishanth Kumar et al. 2012; Tommonaro et al. 2012; Kumar et al.
2013). To the best of our knowledge, this is the first time that the cyclo(d-Pro-l-Tyr) has been
isolated from Streptomyces. ꢂue to the antimicrobial activity of both cyclo(l-Pro-l-Tyr) and
cyclo(d-Pro-l-Tyr), this led us to assess the biological activity on untested phytopathogenic
bacteria. Bacterial wilt and canker in particular are important diseases in commercial crop
plants, causing significant economic losses worldwide. In this work, both cyclo(l-Pro-l-Tyr)
and cyclo(d-Pro-l-Tyr) were tested against Xanthomonas axonopodis pv. citri, Ralstonia sola-
nacearum and Clavibacter michiganensis. X. axonopodis pv. citri is an extremely persistent
causative agent of bacterial canker in citrus (Brunings & Gabriel 2003), whilst R. solanacearum
and C. michiganensis cause bacterial wilt in plants of the Solanaceae family (Hayward 1991;
Gleason et al. 1993). Both compounds exhibited activity against X. axonopodis pv. citri and
R. solanacearum, albeit weak (MIC 31.25 μg/mL) when compared to standard antibacterial
agents (Table 1). No antibacterial activity was observed against C. michiganensis even at
relatively high concentrations (up to 500 μg/mL).
Although there is currently a small trade-off with potency, the broad spectrum of antimi-
crobial activity of cyclo(
l-Pro-
l-Tyr) and cyclo(
d
-Pro- -Tyr) however means these compounds
l
may have potential for use as agricultural biocontrol agents. This can be seen from a chiti-
nase-producing Streptomyces glauciniger WICC-A03 (Awad et al. 2014) or a related compound,
cyclo(4-hydroxy-
l
-Pro- -Trp), which has already been deployed as a non-toxic biopreservative
l
agent to inhibit the growth of A. flavus and A. niger on peanut kernels (Kumar et al. 2014).
With further toxicity testing and structure modification to improve the biological activity
of cyclo(Pro-Tyr), this cyclic dipeptide may be a promising biocontrol agent for use in the
agricultural industry.
3
. Experimental
ꢁxperimental information is provided in Supplementary material.
4
. Conclusion
This is the first time that both cyclo(l-Pro-l-Tyr) and cyclo(d-Pro-l-Tyr) were isolated from
S. sp. strain 22-4 and we are the first to show their antibacterial activity against economically
phytopathogenic bacteria X. axonopodis pv. citri and R. Solanacearum. With the use of toxic
chemicals in agricultural industry to prevent the crop damage, the use of cyclic dipeptides
as biological control agents may provide a sustainable approach to improve the crop quality
without damaging the environment or human health.

4
P. WATTANAꢀAMORN ꢁT AL.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by the Center of ꢁxcellence for Innovation in Chemistry (PꢁRCH-CIC), Office
of the Higher ꢁducation Commission, Ministry of ꢁducation.
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