Antifungal activity of cinnamic acid and benzoic acid esters against Candida albicans strains

Article abstract of DOI:10.1080/14786419.2017.1317776

Candida albicans is an important opportunistic fungal pathogen capable of provoking infection in humans. In the present study, we evaluated the antifungal effect of 23 ester derivatives of the cinnamic and benzoic acids against 3 C. albicans strains (ATCC-76645, LM-106 and LM-23), as well as discuss their Structure–Activity Relationship (SAR). The antifungal assay results revealed that the screened compounds exhibited different levels of activity depending on structural variation. Among the ester analogues, methyl caffeate (5) and methyl 2-nitrocinnamate (10) were the analogues that presented the best antifungal effect against all C. albicans strains, presenting the same MIC values (MIC?=?128?μg/mL), followed by methyl biphenyl-2-carboxylate (21) (MIC?=?128, 128 and 256?μg/mL for C. albicans LM-106, LM-23, and ATCC-76645, respectively). Our results suggest that certain molecular characteristics are important for the antifungal action.

Full text of DOI:10.1080/14786419.2017.1317776

Natural Product Research
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: http://www.tandfonline.com/loi/gnpl20
Antifungal activity of cinnamic acid and benzoic
acid esters against Candida albicans strains
Tamires C. Lima, Alana R. Ferreira, Daniele F. Silva, Edeltrudes O. Lima &
Damião P. de Sousa
To cite this article: Tamires C. Lima, Alana R. Ferreira, Daniele F. Silva, Edeltrudes O. Lima &
Damião P. de Sousa (2017): Antifungal activity of cinnamic acid and benzoic acid esters against
Candida albicans strains, Natural Product Research, DOI: 10.1080/14786419.2017.1317776
To link to this article: http://dx.doi.org/10.1080/14786419.2017.1317776
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Date: 20 April 2017, At: 03:11

Natural Product research, 2017
http://dx.doi.org/10.1080/14786419.2017.1317776
SHORT COMMUNICATION
Antifungal activity of cinnamic acid and benzoic acid esters
against Candida albicans strains
Tamires C. Limaa, Alana R. Ferreirab, Daniele F. Silvab, Edeltrudes O. Limab and
Damião P. de Sousab
adepartment of Pharmacy, Federal university of sergipe, são cristóvão, Brazil; bdepartment of Pharmaceutical
sciences, Federal university of Paraíba, João Pessoa, Brazil
ABSTRACT
ARTICLE HISTORY
received 22 January 2017
accepted 2 april 2017
Candida albicans is an important opportunistic fungal pathogen
capable of provoking infection in humans. In the present study, we
evaluated the antifungal effect of 23 ester derivatives of the cinnamic
and benzoic acids against 3 C. albicans strains (ATCC-76645, LM-106
and LM-23), as well as discuss their Structure–Activity Relationship
(SAR). The antifungal assay results revealed that the screened
compounds exhibited different levels of activity depending on
structural variation. Among the ester analogues, methyl caffeate (5)
and methyl 2-nitrocinnamate (10) were the analogues that presented
the best antifungal effect against all C. albicans strains, presenting the
same MIC values (MIC = 128 μg/mL), followed by methyl biphenyl-2-
carboxylate (21) (MIC = 128, 128 and 256 μg/mL for C. albicans LM-106,
LM-23, and ATCC-76645, respectively). Our results suggest that certain
molecular characteristics are important for the antifungal action.
KEYWORDS
antimicrobial activity;
ester; structure–activity
relationship; natural
products
O
O
n
R
n = 0 or 1
1. Introduction
Many systemic fungal diseases are resulting from immunosuppression, long-term broad-spec-
trum antimicrobials, endocrinopathies, organ transplantation and use of indwelling catheters
(Hazen et al. 2003; Tangarife-Castaño et al. 2011). Candida albicans is considered the most
CONTACT damião P. de sousa
sousadam@yahoo.com
supplemental data for this article can be accessed at http://dx.doi.org/10.1080/14786419.2017.1317776.
© 2017 Informa uK limited, trading as taylor & Francis Group

2
T. C. LIMA ET AL.
important fungal pathogen capable of causing disease in humans, being normally respon-
sible for 90–100% of the mucosal infections, and 50–70% of the candidemia episodes (Pfaller
et al. 2006). The problems associated with the treatment and management of Candida infec-
tions, such as limited therapeutic choices and antifungal resistance, have attracted great
interest of the scientific community. Thus, several studies have been conducted in order to
discover new, safe and effective therapeutic options for Candida species, as well as to
decrease the incidence of resistant strains to available antifungal agents (Noumi et al. 2010;
Sardi et al. 2013). Methyl esters from cinnamic and benzoic acids are commonly found in
nature (Widhalm & Dudareva 2015) and exhibit interesting antifungal activity (Woodward
et al. 1993; Farias et al. 2016). Many studies have investigated the bioactivity of cinnamic
and benzoic acid derivatives and found that some of these analogues possess antifungal
properties (Korošec et al. 2014; Seelolla et al. 2014). Based on these facts, we selected a series
of 23 benzoic and cinnamic acid derivatives (Figure S1) for evaluation of their antifungal
effects against three C. albicans strains (ATCC-76645 (standard strain), LM-106 and LM-23
(clinical strains)). Further, using compounds with several modifications from benzoic acid
and cinnamic acid structures, we explored the relationship between the structure and the
antifungal effect of the compounds.
2. Results and discussion
The antifungal assay results revealed that assayed compounds exhibited differential levels
of activity depending on structural variation. Among the 23 ester analogues of the cinnamic
and benzoic acids (Table S1), methyl caffeate (5) and methyl 2-nitrocinnamate (10) were the
derivatives that presented the largest antifungal effect against all C. albicans strains (ATCC-
76645, LM-106 and LM-23), exhibiting the same MIC values (MIC = 128 μg/mL), followed by
methyl biphenyl-2-carboxylate (21) (MIC = 128, 128 and 256 μg/mL for C. albicans LM-106,
LM-23 and ATCC-76645, respectively). The compounds methyl cinnamate (1), methyl 3,4,5-tri-
methoxycinnamate (9), methyl gallate (14), methyl p-toluate (17), methyl vanillate (18),
methyl 4-methylsalicylate (19) and methyl biphenyl-3-carboxylate (22) could not prevent
the fungal growth, thus being considered inactive (MIC values could not be determined).
To investigate whether the introduction of a hydroxyl group on the aromatic ring influences
the antifungal activity, methyl cinnamate (1) was compared to methyl o-coumarate (2),
methyl m-coumarate (3) and methyl p-coumarate (4), and methyl benzoate (12) was com-
pared to methyl 4-hydroxybenzoate (13). Compounds 2, 3 and 4 (equal MIC = 1024 μg/mL)
were more efficient than 1 (MIC values not determined), and the compound 13 (equal
MIC = 512 μg/mL) was more active than 12 (equal MIC = 1024 μg/mL), suggesting that the
addition of a hydroxyl group on the benzene ring improves the antifungal activity. Similar
result was observed after the addition of a second hydroxyl group on the ring, since the
methyl caffeate (5) (equal MIC = 128 μg/mL) was eight-fold more potent than methyl p-cou-
marate (4) (MIC = 1024 μg/mL). However, the introduction of three hydroxyl groups appears
to decrease the antifungal effect, once that the methyl benzoate (absence of hydroxyl group)
(12, equal MIC = 1024 μg/mL) was more bioactive than methyl gallate (presence of three
hydroxyl groups) (14, MIC values not determined).
Furthermore, to ascertain if the position of hydroxyl substituent on the ring influences in
the bioactivity, the compounds 2, 3 and 4 were compared. In 2, the hydroxyl group is at the
ortho position, whereas in 3 this substituent is at the meta position and in 4 at the para

NATURAL PRODUCT RESEARCH
3
position. All the three compounds were found to exert similar activities (equal MIC = 1024 μg/
mL), indicating that the disposition of the hydroxyl group on the aromatic ring does not
affect the antifungal effect. To examine whether the introduction of a phenyl substituent
on the aromatic ring affects the antifungal action, methyl benzoate (12) was compared to
biphenyl-2-carboxylate (21) and biphenyl-4-carboxylate (23). Compounds 21 (MIC = 128–
256 μg/mL) and 23 (MIC = 256–512 μg/mL) were more potent than 12 (equal MIC = 1024
μg/mL), indicating that the introduction of a phenyl on the benzene ring increases the
antifungal activity. Moreover, the disposition of phenyl group on the ring appears to influence
the antifungal activity, since the compound 21 (ortho-phenyl; MIC = 128–256 μg/mL) was
more bioactive than the compounds 22 (meta-phenyl; MIC values not determined) and 23
(para-phenyl; MIC = 256–512 μg/mL).
In order to investigate if the introduction of electron-withdrawing groups on the aromatic
ring, such as nitro or chlorine, contributes for the antifungal effect, compound 1 was com-
pared to methyl 2-nitrocinnamate (10) and 4-chlorocinnamate (11), and methyl 3-methyl-4-ni-
trobenzoate (20) was compared to methyl p-toluate (17). Compounds 10 (equal MIC = 128
μg/mL) and 11 (equal MIC = 256 μg/mL) were more bioactive than 1 (MIC values not deter-
mined), and 20 (equal MIC = 256 μg/mL) was more efficient than 17 (MIC values not deter-
mined). These results suggest that the decrease in electron diversity, provoked by
electron-withdrawing substituents (nitro or chlorine), resulted in enhancement of the anti-
fungal activity. Likewise, compounds having electron-donating groups (like methyl) showed
worst antifungal effect, since the methyl p-toluate (17; MIC values not determined) was
inactive whereas its corresponding methyl benzoate presented weak activity (12; equal
MIC = 1024 μg/mL). Replacement of two hydroxyl or methoxy groups located at the carbons
C-3 and C-5 by tert-butyl groups (bulky alkyl substituents) remarkably increased the anti-
fungal activity, since the compound methyl 3,5-di-tert-butyl-4-hydroxybenzoate (16; two
tert-butyl groups) was more potent (equal MIC = 256 μg/mL) than 14 (MIC values not deter-
mined) and 15 (equal MIC = 1024 μg/mL). This improvement in the antifungal effect probably
occurs due to an increase in overall lipophilicity of the molecule. The lipophilicity parameter
has been frequently studied and is one of the most important properties which influence
the antifungal action (Sánchez-Maldonado et al. 2011; Krátký & Vinšová 2012). To investigate
the effect of the replacement of a hydroxyl group by a methoxy substituent on the benzene
ring, the compound methyl caffeate (5) was compared to methyl ferulate (7), and methyl
sinapate (8) was compared to methyl 3,4,5-trimethoxycinnamate (9). The compound 5 (equal
MIC = 128 μg/mL) was 4-fold more bioactive than 7 (equal MIC = 512 μg/mL) and 8 (equal
MIC = 1024 μg/mL) was more efficient than 9 (MIC values not determined), suggesting that
the replacement of a hydroxyl by a methoxy substituent results in reduction in the antifungal
effect.
3. Conclusion
Among the 23 ester derivatives screened, methyl caffeate and methyl 2-nitrocinnamate were
the compounds with the highest antifungal activity on the three C. albicans strains assayed.
A preliminary study of the SAR revealed that certain structural features are important for
antifungal action, thus yielding the information for a further optimization of these classes
of phenolic compounds as potential antifungal agents.

4
T. C. LIMA ET AL.
Supplementary material
Experimental details relating to this paper are available online, alongside Figure S1 and Table S1.
Acknowledgements
This research was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico
(CNPq).
Disclosure statement
No potential conflict of interest was reported by the authors.
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