Vinay K. Sharma

Structural requirement(s) of N-phenylthioureas and benzaldehyde thiosemicarbazones as inhibitors of melanogenesis in melanoma B 16 cells

In order to define the structural requirements of phenylthiourea (PTU), a series of thiourea and thiosemicarbazone analogs were prepared and evaluated as inhibitors of melanogenesis in melanoma B16 cells. The most potent analog was 2-(4-tert-butylbenzylidene)hydrazinecarbothioamide (1u) with an IC(50) value of 2.7 microM in inhibition of melanogenesis. The structure for potent inhibitory activity of these derivatives are required with the direct connection of pi-planar structure to thiourea without steric hinderance in PTU derivatives and the hydrophobic substituent at para position in case of semicarbazones.

Structural characteristics of thiosemicarbazones as inhibitors of melanogenesis

A series of thiosemicarbazones 2(e-s) have been synthesized and studied their structure-activity relationship as melanogenesis inhibitor. Among them, (Z)-2-(naphthalen-1-ylmethylene)hydrazinecarbothioamide (2q, >100% inhibition at 10 μM, IC(50)=1.1 μM, ClogP=3.039) showed the strongest inhibitory activity. Regarding their structure-activity relationship, the hydrophobic substituents regardless the position on phenyl ring of benzaldehyde thiosemicarbazones enhance the inhibitory activity. Furthermore, the aromatic group of benzaldehydethiosemicarbazones can be replaced with sterically bulky cyclohexyl. Thus, hydrophobicity of the aryl or alkyl group on hydrazine of thiosemicarbazones is determinant factor for their inhibitory activity in melanogenesis rather than planarity.

Synthesis and evaluation of novel chromone analogs for their inhibitory activity against interleukin-5

A novel series of chromone analogs were synthesized and evaluated for their inhibitory activity against interleukin-5. Among them compounds 5-Cyclohexylmethoxy-3-(4-hydroxybenzyl)-4H-chromen-4-one (6a, 98% inhibition at 30 microM, IC50<3.0 microM) and 5-Cyclohyxylmethoxy-3-(hydroxymethyl)-4H-chromen-4-one (8a, 84% inhibition at 30 microM, IC50=7.6 microM) showed most potent activity. The structural requirement of chromone analogs possessing the inhibitory activity against IL-5 could be summarized as: (i) importance of hydrophobic group such as cyclohexylmethoxy at 5th position of ring A, (ii) requirement of ring B with small size of hydrogen bonding group with electron donating property such as phenolic hydroxyl group at 4th position and (iii) planarity of the chromen-4-one ring.

Refinement of the pharmacophore of 3,4-dihydroquinazoline-2(1H)-thiones for their anti-melanogenesis activity.

In order to define the structural requirements of quinazoline-2(1H)-thiones 1 for their inhibitory activity on melanogenesis, a novel series of 3,4-dihydroquinazoline-2(1H)-thiones (3a-h) were prepared and screened for their melanogenesis inhibition on melanoma B16 cell line under the stimulant of alpha-MSH. The anti-melanogenesis activity of 3 is mainly mediated by the hydrogen bonding ability of thioamide unit in addition to complexation ability of thione and the hydrophobic binding power of side chain substitutions at 3-position. Thus, the pharmacophore of 3,4-dihydroquinazoline-2(1H)-thiones for their anti-melanogenesis activity could be refined as 3-hydrophobic substituted quinazolinethione.

Design and synthesis of novel hydroxyalkylaminomethylchromones for their IL-5 inhibitory activity.

A series of hydroxyalkylaminomethylchromone analogs 3 were prepared and evaluated as inhibitors of interleukin-5. The most active analog 3d inhibited interleukin-5 activity with an IC₅₀ of 17.5 μM. The structural requirements of chromone analogs possessing the inhibitory activity against IL-5 could be summarized as: (i) the cyclohexylmethoxy group at 5th position of the A ring, (ii) the planarity of chromone ring, (iii) hydrophobic unit around the B ring with hydroxyl functional group, (iv) the hydrophobic unit which does not have to be a planar and (v) the length of carbon units between amino and hydroxyl group is limited to two.

Identification of novel chromenone derivatives as interleukin-5 inhibitors

A series of (E)-5-alkoxy-3-(3-phenyl-3-oxoprop-1-enyl)-4H-chromen-4-ones (4) and (E)-5-alkoxy-3-(3-hydroxy-3-phenylprop-1-enyl)-4H-chromen-4-ones (5) were synthesized and evaluated for their IL-5 inhibitory activity. Propenone analogs 4 possess some of the structurally important characteristics of isoflavone 2 and chalcone 3 previously known as potent IL-5 inhibitor. However, the inhibitory activity of 4 was weak and therefore this structural hybridization appears to be ineffective for the design of IL-5 inhibitor. Meanwhile the potent activity profile of compounds 5 was discovered. This enhanced activity of 5 compared to 4 could be due to the effective location of hydroxyl group of allylic alcohol moiety of 5 in the 3D structure. The electron withdrawing substituents at position 4 of phenyl ring of 5 enhances the activity possibly due to an increase in the strength of hydrogen bonding property of hydroxyl group of allylic alcohol moiety.

Design and synthesis of novel chromenone derivatives as interleukin-5 inhibitors

A novel series of chromenone analogs were synthesized and evaluated for their inhibitory activity against interleukin-5. Among them 5-(cyclohexylmethoxy)-3-[3-hydroxy-3-(4-hydroxyphenyl)propyl]-4H-chromen-4-one (9b, 94% inhibition at 30 μM, IC(50) = 4.0 μM) and 5-(cyclohexylmethoxy)-3-[3-hydroxy-3-(4-methoxyphenyl)propyl]-4H-chromen-4-one (9c, 94% inhibition at 30 μM, IC(50) = 6.5 μM) showed the most potent activity. According to the SAR studies introduction of propanone unit in between chromenone and ring B as in 5-(cyclohexylmethoxy)-3-[3-(4-phenyl)-3-oxopropyl]-4H-chromen-4-ones (8) moderately increased the activity. However, the reduction of these propanones 8 to propanols 9 remarkably enhanced the activity. A small substituent at position 4 of ring B in 9, especially with hydrogen bonding capability, provides favorable contribution. Disappearance of IL-5 inhibitory activity upon saturation of chroman-4-one of 9 to chroman-4-ones 10 proves the critical importance of planar chromen-4-one unit of this scaffold in the IL-5 inhibition.

Structure–activity relationship of naphthaldehydethiosemicarbazones in melanogenesis inhibition

2-(Naphthalen-1-ylmethylene)hydrazinecarbothioamide (14, IC(50)=1.1μM) was discovered as a highly potent inhibitor of melanogenesis. To define the role of hydrogens (at N1 and N3) and sulfur in 14, a series of analogs 15a-p were synthesized and evaluated for anti-melanogenic activity using melanoma B16 cells under the stimulus of α-MSH. It was observed that replacement of either of these hydrogens at N1 or N3 by substituents increases the activity significantly. Conversely, concomitant substitutions decrease the inhibitory potency. In addition, the presence of sulfur in thiosemicarbazone is essential for the activity.

Ketonethiosemicarbazones: Structure-activity relationships for their melanogenesis inhibition

A series of 2-(1-phenylalkylidene)hydrazinecarbothioamides 2, 2-(1-phenylalkyl)hydrazinecarbothioamides 3, 2-(3,4-dihydronaphthalen-1(2H)-ylidene)hydrazinecarbothioamide (4), and 2-(1-(thiophen-2-yl)ethylidene)hydrazinecarbothioamide (5) were synthesized for their melanogenesis inhibition in melanoma B16 cells. The SAR of these ketonethiosemicarbazones revealed that the benzylidene hydrogen in aldehydethiosemicarbazones 1 can be replaced by hydrophobic moiety and substitutions with alkyl group for the terminal amino hydrogen of ketonethiosemicarbazones improved the activity appreciably. In addition, the double bond in thiosemicarbazones is an important factor for the increment of hydrophobicity. Thus hydrophobic ketonethiosemicarbazones are excellent inhibitors of melanogenesis like aldehydethiosemicarbazones.

Synthesis and SAR studies of bis-chromenone derivatives for anti-proliferative activity against human cancer cells.

A novel family of 3-((4-oxo-4H-chromen-3-yl)methyl)-4H-chromen-4-one (bis-chromone) derivatives were designed, synthesized and studied for their anti-cancer activity using the XTT assay for the growth inhibition against various human cancer cells. Among them, 3-((5-(cyclohexylmethoxy)-4-oxo-4H-chromen-3-yl)methyl)-7-methoxy-4H-chromen-4-one and 3-((5-(cyclohexylmethoxy)-4-oxo-4H-chromen-3-yl)methyl)-7-hydroxy-4H-chromen-4-one showed micromolar level of in vitro anti-proliferative activity against human cancer cell lines. The SAR studies indicated bis-chromone as a basic scaffold to design anticancer agents. The 5-cyclohexylmethoxy on the first chromenone ring and electron donating group such as CH3, OCH3 or hydrogen bonding group (OH) on the other chromenone ring of bis-chromone increased the activity. However, saturation of one of chromenone to chromanone in bis-chromones decreased the activity.