Improving the drug-likeness of inspiring natural products - evaluation of the antiparasitic activity against Trypanosoma cruzi through semi-synthetic and simplified analogues of licarin A

• Published in: Scientific reports Vol. 10; no. 1; p. 5467
• Main Authors: Morais, Thiago R., Conserva, Geanne A. Alves, Varela, Marina T., Costa-Silva, Thais A., Thevenard, Fernanda, Ponci, Vitor, Fortuna, Ana, Falcão, Amílcar C., Tempone, Andre G., Fernandes, João Paulo S., Lago, João Henrique G.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 25-03-2020; Nature Publishing Group
• Subjects: 631/154/309/2144; 639/638/403; 639/638/403/977; Amastigotes; Animals; Antiparasitic agents; Antiparasitic Agents - chemical synthesis; Antiparasitic Agents - isolation & purification; Antiparasitic Agents - pharmacology; Bioavailability; Biological Products - chemical synthesis; Biological Products - isolation & purification; Biological Products - pharmacology; Chagas disease; Chagas Disease - drug therapy; Drug Discovery; Energy expenditure; Eugenol; Homeostasis; Humanities and Social Sciences; Hyperpolarization; Isoeugenol; Lauraceae - chemistry; Lignans - chemical synthesis; Lignans - isolation & purification; Lignans - pharmacology; Membrane permeability; Membrane potential; Mitochondria; multidisciplinary; Natural products; Oxidative stress; Oxidative Stress - drug effects; Parasites; Permeability; Phytotherapy; Plant Leaves - chemistry; Protozoa; Reactive oxygen species; Reactive Oxygen Species - metabolism; Science; Science (multidisciplinary); Structure-Activity Relationship; Toxicity; Trypanocidal Agents - chemical synthesis; Trypanocidal Agents - isolation & purification; Trypanocidal Agents - pharmacology; Trypanosoma cruzi; Trypanosoma cruzi - drug effects; Trypanosoma cruzi - metabolism; Trypanosomiasis; Trypomastigotes; Vanillin; Vanillyl alcohol; Vector-borne diseases
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-62352-w

Neolignan licarin A (
1
) was isolated from leaves of
Nectandra oppositifolia
(Lauraceae) and displayed activity against trypomastigote forms of the etiologic agent of American trypanosomiasis,
Trypanosoma cruzi
. Aiming for the establishment of SAR, five different compounds (
1a – 1e
) were prepared and tested against
T. cruzi
. The 2-allyl derivative of licarin A (
1d
) exhibited higher activity against trypomastigotes of
T. cruzi
(IC
50
 = 5.0 μM and SI = 9.0), while its heterocyclic derivative
1e
displayed IC
50
of 10.5 μM and reduced toxicity against NCTC cells (SI > 19.0). However, these compounds presented limited oral bioavailability estimation (<85%, Papp <1.0 × 10
−6
 cm/s) in parallel artificial membrane permeability assays (PAMPA) due to excessive lipophilicity. Based on these results, different simplified structures of licarin A were designed: vanillin (
2
), vanillyl alcohol (
3
), isoeugenol (
4
), and eugenol (
5
), as well as its corresponding methyl (
a
), acetyl (
b
), O-allyl (
c
), and C-allyl (
d
) analogues. Vanillin (
2
) and its acetyl derivative (
2b
) displayed expressive activity against intracellular amastigotes of
T. cruzi
with IC
50
values of 5.5 and 5.6 μM, respectively, and reduced toxicity against NCTC cells (CC
50
 > 200 μM). In addition, these simplified analogues showed a better permeability profile (Papp > 1.0 × 10
−6
 cm/s) on PAMPA models, resulting in improved drug-likeness. Vanillyl alcohol acetyl derivative (
3b
) and isoeugenol methyl derivative (
4a
) displayed activity against the extracellular forms of
T. cruzi
(trypomastigotes) with IC
50
values of 5.1 and 8.8 μM respectively. Based on these results, compounds with higher selectivity index against extracellular forms of the parasite (
1d
,
1e
,
3d
, and
4a
) were selected for a mechanism of action study. After a short incubation period (1 h) all compounds increased the reactive oxygen species (ROS) levels of trypomastigotes, suggesting cellular oxidative stress. The ATP levels were increased after two hours of incubation, possibly involving a high energy expenditure of the parasite to control the homeostasis. Except for compound
4a
, all compounds induced hyperpolarization of mitochondrial membrane potential, demonstrating a mitochondrial imbalance. Considering the unique mitochondria apparatus of
T. cruzi
and the lethal alterations induced by structurally based on licarin A, these compounds are interesting hits for future drug discovery studies in Chagas disease.