SEARCH

SEARCH BY CITATION

Keywords:

  • antileishmanial activity;
  • chalcones;
  • chromene;
  • Leishmania major;
  • promastigotes

Abstract

  1. Top of page
  2. Abstract
  3. Experimental Section
  4. Biological activity
  5. Results and discussion
  6. Acknowledgment
  7. References

Two types of regioisomeric chromene-based chalcones namely, 1-(6-methoxy-2H-chromen-3-yl)-3-phenylpropen-1-ones and 3-(6-methoxy-2H-chromen-3-yl)-1-phenylpropen-1-ones were prepared and investigated for their antileishmanial activity against promastigotes form of Leishmania major. The obtained results from in vitro biological assays indicated that chloro-substituted 1-(6-methoxy-2H-chromen-3-yl)-3-phenylpropen-1-ones exhibited excellent activity against Leishmania major at non-cytotoxic concentrations.

Leishmaniasis comprises a group of parasitic diseases typically transmitted by the bite of female phlebotomine sandfly and manifest with visceral, cutaneous and mucutaneous forms (1). Human leishmaniasis is mainly distributed in the tropic and subtropic area with a prevalence of 12 million cases and approximate incidence of 0.5 million cases of visceral leishmaniasis and 1.5 million cases of cutaneous leishmaniasis. Overall, 350 million individuals are at risk of leishmaniasis infection in the 88 countries (2). Whereas no vaccine exists, the current chemotherapy for leishmaniasis possesses a set of problems because of the emergence of drug resistant strains, limited efficacy, long-term treatment, cost expensive and severe side effects (3–5). Thus, the necessity for the development of new, efficient, affordable and safe drug is felt. Also, because of the high toxicity associated with the currently used antileishmanial drugs, efforts are being made to identify new structures from natural and synthetic compounds.

Chalcones (1,3-diaryl-2-propen-1-ones) are natural or synthetic compounds belonging to the flavonoid family with widespread distribution in vegetables, fruits, spices and tea and are present in a variety of plant species (6). Chemically, they consist of open-chain flavonoids in which the two aromatic rings are joined by a three-carbon α,β-unsaturated carbonyl system. Chalcones have been reported to possess many pharmacological activities (7), including anti-inflammatory (8), immunomodulatory (9), antifungal (10), anticancer (11,12), antioxidant (13), antibacterial (14), antimalarial (15,16) and antileishmanial (17,18) properties.

In the past decade, synthetic or naturally occurring chalcones emerged as a new class of antileishmanial compounds. The most studied antileishmanial chalcones are licochalcone A (1) isolated from the roots of Chinese liquorice, licochalcone C (2) and oxygenated chalcones 3 (19). Recently, Narender et al. (20,21) have described the promising antileishmanial activity of few naturally occurring chromenochalcones 4, including crotaramosmin, crotaramin and crotin (Figure 1). These compounds contain a benzopyran system, which is frequently found in many natural products.

image

Figure 1.  Structures of naturally occurring and synthetic antileishmanial chalcones 1–4 and newly designed compounds (5 and 6) as chromene-based antileishmanial chalcones.

Download figure to PowerPoint

In the search for new synthetic chromene-based chalcones (22), we prepared two types of novel chromenochalcones 5a–e and 6a–e, to investigate their antileishmanial activity against promastigotes form of Leishmania major (Figure 1). The structure 5a–e possessing the carbonyl group close to chromene ring is called Type A chalcones. The structure 6a–e possessing the carbonyl group away from chromene ring is called Type B chalcones (Figure 1). The synthesis and in vitro antileishmanial activity of both regioisomeric chromene-based chalcones are reported in this article.

Experimental Section

  1. Top of page
  2. Abstract
  3. Experimental Section
  4. Biological activity
  5. Results and discussion
  6. Acknowledgment
  7. References

All chemical and solvent used in this study were purchased from Merck AG and Aldrich. Melting points were determined on a Kofler hot stage apparatus and are uncorrected. The IR spectra were obtained on a Shimadzu 470 spectrophotometer (potassium bromide disks). 1H NMR spectra was recorded using a Bruker 500 MHz spectrometer and chemical shifts are reported in parts per million (ppm) relative to tetramethylsilane as internal standard. The mass spectra were run on a Finigan TSQ-70 spectrometer (Finigan, San Jose, CA, USA) at 70 eV. Elemental analyses were carried out on CHN-O rapid elemental analyzer (Heraeus GmbH, Hanau, Germany) for C, H and N, and the results are within ±0.4% of the theoretical values. Merck silica gel F254 plates were used for analytical TLC.

Synthesis of 1-(6-methoxy-2H-chromen-3-yl) eth-anone (9)

A mixture of 5-methoxy-2-hydroxybenzaldehyde (5 mmol) and potassium carbonate (5 mmol) in 1,4-dioxane (5 mL) was treated with methyl vinyl ketone (5 mmol). The mixture was heated at 100 °C for 4 h and allowed to cool. It was then diluted with water and extracted several times with ether. The combined ether extracts were dried (Na2SO4) and evaporated to give 9 as a yellow solid, which was crystallized from ethyl acetate-hexane (23).

Synthesis of 6-methoxy-2H-chromene-3-carbal-dehyde (10)

A mixture of 5-methoxy-2-hydroxybenzaldehyde (7 mmol) and potassium carbonate (7 mmol) in 1,4-dioxane (12.5 mL) was treated with acrolein (0.5 mL). The mixture was heated at 100 °C for 8 h and allowed to cool. It was then diluted with water and extracted several times with ether. The combined ether extracts were dried (Na2SO4) and evaporated to give 10 as a yellow solid, which was crystallized from ethyl acetate-hexane (23).

General procedure for the synthesis of (E)-1-(6-methoxy-2H-chromen-3-yl)-3-phenyl prop-2-en-1-one derivatives 5a–e

To a solution of compound 9 (1 mmol) and appropriate aldehyde (1 mmol) in absolute ethanol (5 mL), NaOH solution (3.5 m, 2 mL) was added and stirred overnight in an ice-bath. The reaction mixture was diluted with water and the precipitate was filtered and crystallized from ethanol to give the corresponding chalcones 5a–e.

(E)-1-(6-Methoxy-2H-chromen-3-yl)-3-phenylprop-2-en-1-one (5a)

IR (KBr, cm−1) νmax: 1649 (C=O), 1224 (C-O). 1H NMR (CDCl3) δ: 7.74 (d, 1H, = 15.6 Hz, H3 propenone), 7.63 (dd, 2H, = 7.5 and 2 Hz, H2, H6 phenyl), 7.44 (s, 1H, H4 chromene), 7.42 (m, 3H, H3, H4 and H5 phenyl), 7.38 (d, 1H, = 15.6 Hz, H2 propenone), 6.84 (m, 2H, H7 and H8 chromene), 6.75 (d, 1H, = 2.5 Hz, H5 chromene), 5.08 (s, 2H, OCH2), 3.80 (s, 3H, OCH3). MS (m/z, %): 293 (M + 1, 38), 291 (60), 273 (38), 270 (16), 159 (38), 130 (50), 100 (98), 74 (100). Anal. Calcd for C19H16O3: C, 78.06; H, 5.52. Found: C, 77.87; H, 5.69.

(E)-3-(2-Chlorophenyl)-1-(6-methoxy-2H-chromen-3-yl)prop-2-en-1-one (5b)

IR (KBr, cm−1) νmax: 1639 (C=O), 1219 (C-O). 1H NMR (CDCl3) δ: 8.1 (d, 1H, = 15.6 Hz, H3 propenone), 7.73 (dd, 1H, = 7 and 2 Hz, H6 phenyl), 7.44 (m,1H, H4 phenyl), 7.43 (s, 1H, H4 chromene), 7.33 (d, 1H, = 15.6 Hz, H2 propenone),7.32 (m, 2H, H3 and H5 phenyl), 6.84 (m, 2H, H7 and H8 chromene), 6.74 (d, 1H, = 2.5 Hz, H5 chromene), 5.07 (s, 2H, OCH2), 3.79 (s, 3H, OCH3). MS (m/z, %): 328 (M + 2, 15), 326 (M+, 45), 309 (40), 199 (11), 185 (100), 143 (33), 137 (94), 109 (80), 73 (46). Anal. Calcd for C19H15ClO3: C, 69.84; H, 4.63. Found: C, 70.03; H, 4.77.

(E)-3-(3-Chlorophenyl)-1-(6-methoxy-2H-chromen-3-yl)prop-2-en-1-one (5c)

IR (KBr, cm−1) νmax: 1644 (C=O), 1229 (C-O). 1H NMR (CDCl3) δ: 7.81 (d, 1H, = 15.6 Hz, H3 propenone), 7.73 (m, 1H, H6 phenyl), 7.58 (m, 2H, H2 and H4 phenyl), 7.43 (s,1H, H4 chromene), 7.32 (d, 1H, = 15.6 Hz, H2 propenone), 7.18 (m, 1H, H5 phenyl), 6.84 (m, 2H, H7 and H8 chromene), 6.73 (d, 1H, = 2.5 Hz, H5 chromene), 5.08 (s, 2H, OCH2), 3.80 (s, 3H, OCH3). MS (m/z, %): 328 (M + 2, 33), 326 (M+, 90), 309 (50), 201 (8), 189 (14), 159 (60), 146 (43), 101 (100), 88 (30). Anal. Calcd for C19H15ClO3: C, 69.84; H, 4.63. Found: C, 69.71; H, 4.80.

(E)-3-(4-Chlorophenyl)-1-(6-methoxy-2H-chromen-3-yl)prop-2-en-1-one (5d)

IR (KBr, cm−1) νmax: 1649 (C=O), 1224 (C-O). 1H NMR (CDCl3) δ: 7.68 (d, 1H, = 15.6 Hz, H3 propenone), 7.56 (d, 2H, = 8.2 Hz, H2 and H6 phenyl), 7.43 (s, 1H, H4 chromene), 7.39 (d, 2H, = 8.2 Hz, H3 and H5 phenyl), 7.35 (d, 1H, = 15.6 Hz, H2 propenone), 6.84 (m, 2H, H7 and H8 chromene), 6.75 (d, 1H, = 2.5 Hz, H5 chromene), 5.07 (s, 2H, OCH2), 3.80 (s, 3H, OCH3). MS (m/z, %): 328 (M + 2, 30), 326 (M+, 90), 307 (42), 275 (17), 227 (8), 165 (50), 159 (63), 135 (67), 101 (100), 89 (58), 45 (50). Anal. Calcd for C19H15ClO3: C, 69.84; H, 4.63. Found: 69.52; H, 4.49.

(E)-3-(2,4-Dichlorophenyl)-1-(6-methoxy-2H-chro-men-3-yl)prop-2-en-1-one (5e)

IR (KBr, cm−1) νmax: 1647 (C=O), 1222 (C-O). 1H NMR (CDCl3) δ: 8.02 (d, 1H, = 15.6 Hz, H3 propenone), 7.66 (d, 2H, = 8.4 Hz H6 phenyl), 7.47 (d, 1H, = 2 Hz, H3 phenyl), 7.42 (s, 1H, H4 chromene), 7.32 (d, 1H, = 15.6 Hz, H2 propenone), 7.28 (dd, 2H, = 8.4 and 2 Hz, H5 phenyl), 6.86 (dd, 1H, = 8.8 and 2.5 Hz, H7 chromene), 6.83 (d, 1H, = 8.8 Hz, H8 chromene), 6.74 (d, 1H, = 2.5 Hz, H5 chromene), 5.07 (s, 2H, OCH2), 3.79 (s, 3H, OCH3). MS (m/z, %): 364 (M + 4, 10), 362 (M + 2, 65), 361 (M+, 21), 360 (100), 325 (58), 309 (17), 260 (8), 202 (10), 198 (35), 161 (50), 118 (62), 89 (45), 63 (20). Anal. Calcd for C19H14Cl2O3: C, 63.18; H, 3.91. Found: C, 62.96; H, 4.05.

General procedure for the synthesis of 3-(6-meth-oxy-2H-chromen-3-yl)-1-phenyl prop-2-en-1-one derivatives 6a–e

To a solution of compound 10 (1 mmol) and appropriate acetophenone (1 mmol) in absolute ethanol (5 mL), NaOH solution (3.5 m, 2 mL) was added and stirred overnight in an ice-bath. The reaction mixture was diluted with water and the precipitate was filtered and crystallized from ethanol to give the corresponding chalcones 6a–e.

(E)-3-(6-Methoxy-2H-chromen-3-yl)-1-phenylprop-2-en-1-one (6a)

IR (KBr, cm−1) νmax: 1649 (C=O), 1229 (C-O). 1H NMR (CDCl3) δ: 7.96 (d, 2H, = 7.5 Hz, H2 and H6 phenyl), 7.58 (m, 1H, H4 phenyl), 7.52 (d, 1H, = 15.6 Hz, H3 propenone), 7.50 (m, 2H, H3 and H5 phenyl), 6.86 (d, 1H, = 15.6 Hz, H2 propenone), 6.82 (s, 1H, H4 chromene), 6.80 (d, 1H, = 8.7 Hz, H8 chromene), 6.76 (dd, 1H, = 8.7 and 2.5 Hz, H7 chromene), 6.65 (d, 1H, = 2.5 Hz, H5 chromene), 5.03 (s, 2H, OCH2), 3.78 (s, 3H, OCH3). MS (m/z, %): 292 (M+, 60), 277 (30), 187 (39), 142 (23), 113 (24), 105 (75), 75 (88), 45 (100). Anal. Calcd for C19H16O3: C, 78.06; H, 5.52. Found: 78.32; H, 5.51.

(E)-1-(2-Chlorophenyl)-3-(6-methoxy-2H-chromen-3-yl)prop-2-en-1-one (6b)

IR (KBr, cm−1) νmax: 1659 (C=O), 1219 (C-O). 1H NMR (CDCl3) δ: 7.45 (m, 2H, H4, H6 phenyl), 7.41 (m, 1H, H3 phenyl), 7.36 (m, 1H, H5 phenyl), 7.18 (d, 1H, = 16 Hz, H3 propenone), 6.77 (m, 2H, H7, H8 chromene), 6.75 (s, 1H, H4 chromene), 6.61 (d, 1H, = 2.5 Hz, H5 chromene), 6.48 (d, 1H, = 16 Hz, H2 propenone), 4.97 (s, 2H, OCH2), 3.76 (s, 3H, OCH3). MS (m/z, %): 328 (M + 2, 22), 326 (M+, 66), 311 (48), 236 (11), 201 (11), 185 (100), 141 (40), 139 (80), 109 (80), 67 (38), 55 (55). Anal. Calcd for C19H15ClO3: C, 69.84; H, 4.63. Found: C, 69.83; H, 4.70.

(E)-1-(3-Chlorophenyl)-3-(6-methoxy-2H-chromen-3-yl)prop-2-en-1-one (6c)

IR (KBr, cm−1) νmax: 1654 (C=O), 1219 (C-O). 1H NMR (CDCl3) δ: 7.93 (s, 1H, H2 phenyl), 7.83 (d, 1H, = 7.75 Hz, H4 phenyl), 7.56 (m, 1H, H6 phenyl), 7.53 (d, 1H, = 15.5 Hz, H3 propenone), 7.44 (t, 1H, = 7.75 Hz, H5 phenyl), 6.84 (s, 1H, H4 chromene), 6.80 (d, 1H, J = 15.5 Hz, H2 propenone), 6.78 (m, 2H, H7, H8 chromene), 6.65 (d, 1H, = 2.5 Hz, H5 chromene), 5.02 (s, 2H, OCH2), 3.78 (s, 3H, OCH3). MS (m/z, %): 328 (M + 2, 28), 326 (M+, 84), 309 (76), 189 (11), 159 (60), 146 (45), 101 (100), 87 (28). Anal. Calcd for C19H15ClO3: C, 69.84; H, 4.63. Found: C, 69.99; H, 4.48.

(E)-1-(4-Chlorophenyl)-3-(6-methoxy-2H-chromen-3-yl)prop-2-en-1-one (6d)

IR (KBr, cm−1) νmax: 1649 (C=O), 1229 (C-O). 1H NMR (CDCl3) δ: 7.90 (d, 2H, = 8.5 Hz, H2 and H6 phenyl), 7.52 (d, 1H, = 15.6 Hz, H3 propenone), 7.47 (d, 2H, = 8.5 Hz, H3 and H5 phenyl), 6.83 (s,1H, H4 chromene), 6.80 (m, 2H, H7 and H8 chromene), 6.79 (d, 1H, = 15.6 Hz, H2 propenone), 6.65 (d, 1H, = 2.5 Hz, H5 chromene), 5.02 (s, 2H, OCH2), 3.78 (s, 3H, OCH3). MS (m/z, %): 328 (M + 2, 20), 326 (M+, 93), 323 (68), 311 (46), 308 (25), 245 (11), 202 (11), 187 (95), 184 (32), 139 (100), 111 (80), 109 (46), 75 (28). Anal. Calcd for C19H15ClO3: C, 69.84; H, 4.63. Found: C, 70.21; H, 4.49.

(E)-1-(2,4-Dichlorophenyl)-3-(6-methoxy-2H-chro-men-3-yl)prop-2-en-1-one (6e)

IR (KBr, cm−1) νmax: 1662 (C=O), 1224 (C-O). 1H NMR (CDCl3) δ: 7.47 (d, 1H, = 2 Hz, H3 phenyl), 7.40 (d, 1H, = 8 Hz, H6 phenyl), 7.35 (dd, 1H, = 8 and 2 Hz, H5 phenyl), 7.19 (d, 1H, = 16 Hz, H3 propenone), 6.77 (m, 2H, H7 and H8 chromene), 6.61 (d, 1H, = 2 Hz, H5 chromene), 6.46 (d, 1H, = 16 Hz, H2 propenone), 4.96 (s, 2H, OCH2), 3.77 (s, 3H, OCH3). MS (m/z, %): 365 (M + 4, 7), 363 (M + 2, 42), 361 (M+, 63), 325 (46), 279 (60), 261 (18), 206 (8), 189 (23), 187 (100), 149 (100), 113 (48), 71 (64), 57 (70). Anal. Calcd for C19H14Cl2O3: C, 63.18; H, 3.91. Found: C, 63.20; H, 4.04.

Biological activity

  1. Top of page
  2. Abstract
  3. Experimental Section
  4. Biological activity
  5. Results and discussion
  6. Acknowledgment
  7. References

Parasite and culture

The strain of L. major used in this study was the vaccine strain (MRHO/IR/75/ER), obtained from Pasteur Institute, Tehran (Iran). The infectivity of the parasites was maintained by regular passage in susceptible BALB/c mice. The promastigote form of parasite was grown in blood agar cultures at 25 °C. The stationary parasite inoculation was 2 × 106 cells/mL. For the experiments described here, the stationary phase of promastigotes was washed with phosphate-buffered saline and recultured in RPMI 1640 medium (Sigma, St. Louis, MO, USA) at 2 × 106 cells/mL density, supplemented with 10% of heat-inactivated fetal bovine serum, 2-mm glutamine (Sigma), pH approximately 7.2, 100 U/mL penicillin (Sigma) and 100 μg/mL streptomycin (Sigma).

In vitro antileishmanial activity

The antileishmanial evaluation of compounds 5a–e and 6a–e was performed using direct counting and MTT assay (24,25). The growth curve of the L. major strain was determined daily under light microscope and counting in a Neubauer’s chamber. Then, parasites (2 × 106/mL) in the logarithmic phase were incubated with a serial range of drug concentrations for 24 h at 25 °C. To determine 50% inhibitory concentrations (IC50), the tetrazolium bromide salt (MTT) assay was used. Briefly, promastigotes from early log phase of growth were seeded in 96-well plastic cell culture trays, containing serial dilution of drug and phenol red free RPMI 1640 medium, supplemented with 10% of FCS, 2-mM glutamine, pH approximately 7.2 and antibiotics, in a volume of 200 μL. After 24 h of incubation at 25 °C, the media was renewed with 100 μg/well of MTT (0.5 mg/mL) and plates were further incubated for 4 h at 37 °C. The plates were centrifuged (700 g × 5 min) and the pellets were dissolved in 200 μL of DMSO. The samples were read using an ELISA plate reader at a wavelength of 492 nm. Two or more independent experiments in triplicate were performed for determination of sensitivity to each drug, the IC50 was calculated by linear regression analysis, expressed in mean ± SD. Control cells were incubated with culture medium plus DMSO.

Cytotoxicity against macrophages

In vitro toxicity against mouse peritoneal macrophages was assessed with cells plated in 96-well plates at 2 × 105 cells/well. After cell adherence, the medium was removed and replaced by the media containing IC50 concentration of each compound. The plates were incubated for 24 h at 37 °C in a humidified incubator with 5% CO2. Control cells were incubated with culture medium plus DMSO. Cell viability was determined using MTT colorimetric assay.

Results and discussion

  1. Top of page
  2. Abstract
  3. Experimental Section
  4. Biological activity
  5. Results and discussion
  6. Acknowledgment
  7. References

Chemistry

As illustrated in Scheme 1, the routes to synthesis of both target compounds 5a–e and 6a–e was started from phenolic compound 7. Compound 7 was converted to salicylaldehyde derivative 8 according to the general literature method (26,27). Then, compound 8 was reacted with methyl vinyl ketone, as a Michael acceptor, in refluxing dioxane in the presence of K2CO3 to give 3-acetylchromene 9. Claisen-Schmidt condensation of 3-acetylchromene 9 with different aldehydes in ethanolic solution of NaOH yielded corresponding type A chalcones 5a–e. For obtaining type B chalcones 6a–e, a slightly different strategy was used. Treatment of salicylaldehyde 8 with acrolein in refluxing dioxane in the presence of K2CO3 afforded chromene-3-carbaldehyde 10. Subsequently, condensation of aldehyde 10 with appropriate acetophenone in ethanolic solution of NaOH afforded type B chalcones 6a–e. The structures of desired products were established with IR, NMR, mass spectrometry and elemental analysis. 1H NMR spectra showed that only (E)-isomer of chalcones were obtained. The structures and physicochemical data of target compounds are listed in Table 1.

image

Figure Scheme 1:.  Synthesis of chromene-based chalcones 5a–e and 6a–e. Reagents and conditions: (a) NaOH, CHCl3, H2O, reflux (b) methyl vinyl ketone, 1,4-dioxane, K2CO3, reflux (c) appropriate aldehyde, NaOH, EtOH, (d) acrolein, 1,4-dioxane, K2CO3, reflux (e) appropriate acetophenone, NaOH, EtOH.

Download figure to PowerPoint

Table 1.   Structures and physicochemical data of chromene-based chalcones 5a–e and 6a–eThumbnail image of

Antileishmanial activity

The life cycle of Leishmania parasites consists of two evolutionary stages: promastigotes, flagellated extracellular parasites and amastigotes, non-flagellated, non-motile stages that is more sensitive and live in macrophages. In this study, the chromene-based chalcones 5a–e and 6a–e were evaluated for their in vitro activity against the promastigote form of the Leishmania major using MTT assay. In primary screening assay, the Leishmania parasite was affected by 10 μm concentration of the synthesized compounds 5a–e and 6a–e for three consecutive days and the growth inhibitory effect of these compounds was monitored during Day 1, Day 2 and Day 3 and the results are reported in Table 2. The obtained results indicate that compounds 5b–e (Type A chalcones) exhibited excellent activity against Leishmania (100% inhibition) at the concentration of 10 μm. Compound 5a that showed no inhibition at the first day of exposure exhibited potent inhibitory activity after 3 days (% inhibition = 93%). In addition, remaining compounds (Type B chalcones) showed weak to moderate inhibitory activity at this level of concentration.

Table 2. In vitro activities of chromene-based chalcones 5a–e and 6a–e against promastigote form of L. majorThumbnail image of

The IC50 values of type A and type B chalcones against L. major in comparison with meglumine antimonate (Glucantime®, Aventis, Paris, France) are presented in Table 2. The IC50 values of the test compounds against L. major indicate that most compounds possessed good leishmanicidal activity (IC50 ≤ 50 μm) with respect to reference drugs. The most potent compounds against the promastigote form of L. major were found to be chloro-substituted Type A chalcones 5c–e with IC50 values less than 1.0 μm. The activity profile of these compounds (5c–e) against promastigotes demonstrated that there are no significant differences in their IC50 values.

The effect of positional substitution was investigated by preparing all three possible chloro-substitutions (2-Cl, 3-Cl or 4-Cl) and 2,4-dichloro-substitutions on phenyl ring attached to propenone scaffold. Although chlorine substitution on phenyl ring increases the activity in Type A chalcones, (compounds 5b–e in comparison with 5a) this alteration in Type B compounds cannot improve antileishmanial activity (compounds 6b–e in comparison with 6a). The better results were achieved with 3-chloro- or 4-chloro-containing analogues in the Type A series.

The cytotoxicity of target compounds was also assessed using MTT colorimetric assay on macrophage cells. Macrophage cells were treated with synthesized compounds at the concentration equal to IC50 values for 24h, side by side with the reference drug Glucantime® (25). The results showed that these compounds display antileishmanial activity at non-cytotoxic concentrations.

Chemically, chalcones consist of open-chain flavonoids in which the two aromatic ring A and ring B are joined by a three-carbon α,β-unsaturated carbonyl linker. Ring A is attached to the β-position respect to the carbonyl group and ring B is aryl moiety connected to the carbonyl group. Based on previous studies on antileishmanial chalcones, ring A and its substitution pattern are generally considered less important for antileishmanial activity compared to ring B (28,29). Our results with chromene-based chalcones revealed that very good antileishmanial activity was observed when ring B is 6-methoxy-2H-chromen-3-yl and ring A is 3- or 4-chlorophenyl moiety (compounds 5c–e). In this work, the mechanisms by which the chromene-based chalcones showed antileishmanial activity were not addressed but based on the literature, it can be predicted that chalcones could potentially interfere with the function of parasite mitochondria and inhibit the activity of fumarate reductase, succinate dehydrogenase, NADH dehydrogenase, or succinate- and NADH-cytochrome c reductases (30–32).

In conclusion, we prepared two types of regioisomeric chromene-based chalcones namely, 1-(6-methoxy-2H-chromen-3-yl)-3-phenylpropen-1-ones and 3-(6-methoxy-2H-chromen-3-yl)-1-phenylpropen-1-ones and investigated their antileishmanial activity against promastigotes form of Leishmania major. The obtained results from in vitro biological assays indicated that chloro-substituted 1-(6-methoxy-2H-chromen-3-yl)-3-phenylpropen-1-ones exhibited excellent activity against Leishmania major at non-cytotoxic concentrations. The marked activity and simple synthesis of these chalcones suggest that they are potential leads for the development of antileishmanial compounds and further work is in progress to improve the potency of these compounds.

Acknowledgment

  1. Top of page
  2. Abstract
  3. Experimental Section
  4. Biological activity
  5. Results and discussion
  6. Acknowledgment
  7. References

This work was supported by grants from the research council of Tehran University of Medical Sciences and Iran National Science Foundation (INSF).

References

  1. Top of page
  2. Abstract
  3. Experimental Section
  4. Biological activity
  5. Results and discussion
  6. Acknowledgment
  7. References
  • 1
    Guerin P.J., Olliaro P., Sundar S., Boelaert M., Croft S.L., Desjeux P., Wasunna M.K., Bryceson A.D. (2002) Visceral leishmaniasis: current status of control, diagnosis, and treatment, and a proposed research and development agenda. Lancet Infect Dis;2:494501.
  • 2
    Piñero J., Temporal R.M., Silva-Goncalves A.J., Jiménez I.A., Bazzocchi I.L., Oliva A., Perera A., Leonb L.L., Valladares B. (2006) New administration model of trans-chalcone biodegradable polymers for the treatment of experimental leishmaniasis. Acta Trop;98:5965.
  • 3
    Croft S.L., Coombs G.H. (2003) Leishmaniasis-current chemotherapy and recent advances in the search for novel drugs. Trends Parasitol;19:502508.
  • 4
    Hemmateenejad B., Miri R., Niroomand U., Foroumadi A., Shafiee A. (2007) A mechanistic QSAR study on the leishmanicidal activity of some 5-substituted-1,3,4-thiadiazole derivatives. Chem Biol Drug Des;69:435443.
  • 5
    Singh S., Sivakumar R.J. (2004) Challenges and new discoveries in the treatment of leishmaniasis. J Infect Chemother;10:307315.
  • 6
    Di Carlo G., Mascolo N., Izzo A.A., Capasso F. (1999) Flavonoids: old and new aspects of a class of natural therapeutic drugs. Life Sci;65:337353.
  • 7
    Go M.L., Wu X., Liu X.L. (2005) Chalcones: an update on cytotoxic and chemoprotective properties. Curr Med Chem;12:481499.
  • 8
    Hsieh H.K., Lee T.H., Wang J.P., Wang J.J., Lin C.N. (1998) Synthesis and anti-inflammatory effect of chalcones and related compounds. Pharm Res;15:3946.
  • 9
    Barford L., Kemp K., Hansen M., Kharazmi A. (2002) Chalcones from Chinese liquorice inhibit proliferation of T cells and production of cytokines. Int Immunopharmacol;2:545–555.
  • 10
    Sivakumar P.M., Muthu Kumar T., Doble M. (2009) Antifungal activity, mechanism and QSAR studies on chalcones. Chem Biol Drug Des;74:6879.
  • 11
    Nam N.H., Kim Y., You Y.J., Hong D.H., Kim H.M., Ahn B.Z. (2003) Cytotoxic 2′,5′-dihydroxychalcones with unexpected antiangiogenic activity. Eur J Med Chem;38:179187.
  • 12
    Lawrence N.J., Rannison D., McGown A.T., Ducki S., Gul L.A., Hadfield J.A., Khan N. (2001) Linked parallel synthesis and MTT bioassay screening of substituted chalcones. J Comb Chem;3:421426.
  • 13
    Yaylı N., Üçüncü O., Yaşar A., Gök Y., Küçük M., Kolaylı S. (2004) Stereoselective photochemistry of methoxy chalcones in solution and their radical scavenging activity. Turk J Chem;28:515521.
  • 14
    Sivakumar P.M., Priya S., Doble M. (2009) Synthesis, biological evaluation, mechanism of action and quantitative structure-activity relationship studies of chalcones as antibacterial agents. Chem Biol Drug Des;73:403415.
  • 15
    Xue C.X., Cui S.Y., Liu M.C., Hu Z.D., Fan B.T. (2004) 3D QSAR studies on antimalarial alkoxylated and hydroxylated chalcones by CoMFA and CoMSIA. Eur J Med Chem;39:745753.
  • 16
    Liu M., Wiliarat P., Go M.L. (2001) Antimalarial alkoxylated and hydroxylated chalones: structure-activity relationship analysis. J Med Chem;44:44434452.
  • 17
    Liu M., Wilairat P., Croft S.L., Tan A.L., Go M.L. (2003) Structure–activity relationships of antileishmanial and antimalarial chalcones. Bioorg Med Chem;11:27292738.
  • 18
    Chen M., Christensen S.B., Theander T.G., Kharazmi A. (1994) Antileishmanial activity of licochalcone A in mice infected with Leishmania major and in hamsters infected with Leishmania donovani. Antimicrob Agents Chemother;38:13391344.
  • 19
    Nowakowska Z. (2007) A review of anti-infective and anti-inflammatory chalcones. Eur J Med Chem;42:125137.
  • 20
    Kumar J.K., Narender T., Rao M.S., Rao P.S., Toth G., Balazs B., Duddeck H. (1999) Further Dihydrochalcones from Crotolaria ramosissima. J Braz Chem Soc;10:278280.
  • 21
    Narender T., Shweta, Gupta S. (2004) A convenient and biogenetic type synthesis of few naturally occurring chromeno dihydrochalcones and their in vitro antileishmanial activity. Bioorg Med Chem Lett;14:39133916.
  • 22
    Nazarian Z., Emami S., Heydari S., Ardestani S.K., Nakhjiri M., Poorrajab F., Shafiee A., Foroumadi A. (2010) Novel antileishmanial chalconoids: synthesis and biological activity of 1- or 3-(6-chloro-2H-chromen-3-yl)propen-1-ones. Eur J Med Chem; In press: doi:10.1016/j.ejmech.2009.12.046.
  • 23
    Sorkhi M., Forouzani M., Dehghan G., Abdolahi M., Shafiee A., Foroumadi A. (2008) Synthesis and evaluation of antioxidant activity of 6-methoxy-2H-chromenes. Asian J Chem;20:21512155.
  • 24
    Behrouzi-Fardmoghadam M., Poorrajab F., Ardestani S.K., Emami S., Foroumadi A., Shafiee A. (2008) Synthesis and in vitro anti-leishmanial activity of 1-[5-(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-yl]- and 1-[5-(5-nitrothiophen-2-yl)-1,3,4-thiadiazol-2-yl]-4-aroylpiperazines. Bioorg Med Chem;16:45094515.
  • 25
    Dutta A., Bandyopadhyay S., Mandal C., Chatterjee M. (2005) Development of a modified MTT assay for screening antimonial resistant field isolates of Indian visceral leishmaniasis. Parasitol Int;54:119122.
  • 26
    Nielsen A.T., Houlihan W.J. (1968) The aldol condensation. Org React;16:1438.
  • 27
    Fine S.A., Pulaski P.D. (1973) Reexamination of the Claisen-Schmidt condensation of phenylacetone with aromatic aldehydes. J Org Chem;38:17471749.
  • 28
    Nielsen S.F., Christensen S.B., Cruciani G., Kharazmi A., Liljefors T. (1998) Antileishmanial chalcones: statistical design, synthesis, and three- dimensional quantitative structure-activity relationship analysis. J Med Chem;41:48194832.
  • 29
    Kayser O., Kiderlen A.F. (2001) In vitro leishmanicidal activity of naturally occurring chalcones. Phytother Res;15:148152.
  • 30
    Chen M., Zhai L., Brogger S., Christensen S.B., Theander T.G., Kharazmi A. (2001) Inhibition of fumarate reductase in Leishmania major and L. donovani by chalcones. Antimicrob Agents Chemother;45:20232029.
  • 31
    Zhai L., Blom J., Chen M., Christensen S.B., Kharazmi A. (1995) The antileishmanial agent licochalcone A interferes with the function of parasite mitochondria. Antimicrob Agents Chemother;39:27422748.
  • 32
    Zhai L., Chen M., Blom J., Christensen S.B., Theander T.G., Kharazmi A. (1999) The antileishmanial activity of novel oxygenated chalcones and their mechanism of action. J Antimicrob Chemother;43:793803.