Synthesis and antimicrobial and antioxidant activities of simple saccharin derivatives with N-basic side chains

A new class of N-basic side chains was obtained from 2,3-dihydro-2H-3-oxobenzo[d]isothiazole and aliphatic or aromatic aldehydes. Secondary amines (morpholine, N-methylpiperazine and ethyl isonipecotate) afforded tertiary N-basic side chains (4–6), while dibasic secondary amines (such as piperazine) gave bis-tertiary N-basic side chains (2). On the other hand, the use of mono- or dibasic primary amines namely; aniline, anisidine, phenyl hydrazine, o-hydroxy benzoic acid hydrazide, hydrazine hydrate, and ethylenediamine (instead of secondary amines) afforded secondary N-basic side chain as mono component or as bis component 7a-c, 9a-c, 11 and 12a-c. In addition, secondary Mannich base was synthesized via Michael addition to the corresponding aldimine. The new compounds were investigated for antioxidant and antimicrobial activities. Compounds 2, 7c and 12a exhibited significant antimicrobial activity, whereas compounds 7a, 7b, 9b, 9c and 11 exhibited high antioxidant activity as compared to ascorbic acid, These compounds showed the best protective effect against DNA damage induced by bleomycin.     

Synthesis, antimicrobial and antioxidant activity of some oxindoles

The present work describes the synthesis and spectral analysis of some new 3(Z)-{4-[4-(arylsulfonyl)piperazin-1-ylbenzylidene)-1,3-dihydro-2H-indol-2-one (5a-j). Ten of the synthesized compounds were screened in vitro against six species of microorganisms, Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa, Asperigellus niger and Asperigellus clavatus. Most of the compounds exhibited significant antimicrobial activity. All of these compounds were also screened in vitro for the antioxidant activity using DPPH assay. Most of them have shown very significant antioxidant activity.     

Synthesis of fatty acid Schiff base esters as potential antimicrobial and chemotherapeutic agents

Schiff base {4-[(pyridine-3-ylmethylimino)-methyl] phenol} was prepared by reacting 4-hydroxybenzaldehyde with 3-aminomethylpyridine in ethanol for 6 h (85 % yield) followed by their esterification via reaction with fatty acids of varying chain lengths. The structure of these Schiff base esters were elucidated using chromatographic and spectroscopic techniques like GC–MS, ¹H NMR, ¹³C NMR, and ESI–MS. Schiff base esters with shorter chain heptanoic (2a) and decanoic acid (2c) showed good activity against all the tested bacterial and fungal strains. The synthesized esters were also studied for cytotoxicity toward different human tumor cell lines like HeLa, HepG2, A549, MDA-MB-231, and MCF 7 and Neuro2a; however, Schiff base esters with shorter chain (2a, 2b) and medium chain fatty acids (2d, 2i) exhibited good anticancer activity and selectively toward MDA-MB-231 and MCF 7, while long chain fatty acid (2g) Schiff base ester exhibited good anticancer activity selectively toward MDA-MB-231 as compared to the parent molecule, Schiff base (1).     

Synthesis and evaluation of antioxidant and antimicrobial properties of thymol containing pyridone moieties

Various derivatives of 1,2-dihydro-6-(4-hydroxy-5-isopropyl-2-methylphenyl)-2-oxo-4-arylpyridine-3-carbonitrile (IVa–m) were synthesized and characterized. Their antioxidant and antimicrobial properties were evaluated by measuring their activity in vitro. Among the newly synthesized derivatives IVg, IVh, IVi, IVj, IVk, IVl, and IVm showed good antioxidant activity. However, all derivatives show better antibacterial and antifungal properties than that of parent thymol. The probable mechanism, particularly for antioxidant properties of these compounds is proposed.     

Synthesis, antimicrobial evaluation, QSAR and in Silico ADMET studies of decanoic acid derivatives

Various derivatives of decanoic acid (CD) have been synthesized and evaluated against Gram positive B. subtilis, S. aureus and Gram negative E. coli bacteria as well a sagainst fungi C. albicans and A. niger. Quantitative structure activity relationship (QSAR) models for antimicrobial activities were developed using multiple linear regression and cross validated by leave one out (LOO) approach. QSAR studies indicated that activity against Gram positive bacteria was governed by lipophilicity of the compounds while topologicalsteric nature of the molecule was deciding factor for antifungal activity. Further, in silico ADMET studies showed that compounds CD12, 19, 20 and 23 could be explored further for other activities.     

Synthesis,antimicrobial evaluation,ot-QSAR and mt-QSAR studies of 2-amino benzoic acid derivatives

A series of 2-amino benzoic acid derivatives (1–28) were synthesized and evaluated for their in vitro antimicrobial activity against the panel of Gram positive, Gram negative bacterial and fungal strains. The results of antimicrobial studies indicated that, in general, the synthesized compounds were found to be bacteriostatic and fungistatic in action. QSAR studies performed by the development of one target and multi target models indicated that multi-target model was effective in describing the antimicrobial activity as well demonstrated the effect of structural parameters viz. LUMO, ³χ^v and W on antimicrobial activity of 2-amino benzoic acid derivatives.     

Synthesis and antimicrobial evaluation of piperic acid amides and their lower homologues

Seven piperic acid amides along with their lower homologs (12) were synthesized using HATU-DIPEA coupling reagent. All the synthesized derivatives were evaluated for their antibacterial activities against Staphylococcus aureus, Pseudomonas aeruginosa, and vancomycin-resistant P. aeruginosa. They were found to be more active on P. aeruginosa than on S. aureus. However, they did not exhibit potent activity on Vancomycin resistant P. aeruginosa. Among the tested compounds, methylenedioxycinnamic acid amide of anthranilic acid (MDCA-AA, 2a) was found to be most active against S. aureus with MIC of 3.125 μg/ml. The PAS and INH amides of piperic acid were screened against Mycobacterium tuberculosis H37R_a strain. They were found to be most active among all the tested compounds but were found to be less active than the standard drug, isoniazid.     

Synthesis of phenolic acid conjugated chitooligosaccharides and evaluation of their antioxidant activity

In this study, eight kinds of phenolic acid conjugated chitooligosaccharides (PA-c-COSs) with different substitution groups, including p-hydroxyl {hydroxybenzoic acid-c-COS (HBA-c-COS), p-coumaric acid-c-COS (PCA-c-COS)}, 3,4-dihydroxyl {protocatechuic acid-c-COS (PTA-c-COS), caffeic acid-c-COS (CFA-c-COS)}, 3-methoxyl-4-hydroxyl {vanillic acid-c-COS (VNA-c-COS), ferulic acid-c-COS (FRA-c-COS)} and 3,5-dimethoxyl-4-hydroxy {syringic acid-c-COS (SRA-c-COS), sinapinic acid-c-COS (SNA-c-COS)}, were prepared by amide coupling reaction. Their antioxidant properties were evaluated using several in vitro models such as 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl (OH) and nitric oxide (NO) radicals scavenging and reducing power assays. The structures of the synthesized compounds were confirmed by UV, FT-IR and (1)H NMR data. CFA-c-COS showed 81.6% and 89.8% scavenging against DPPH and NO radical formation, respectively. CFA-c-COS also showed higher reducing power and hydroxyl radical scavenging activity compared to those of other compounds. Hence, CFA-c-COS can be a potential antioxidant compound.     

Synthesis and evaluation of B-, C-, and D-ring-substituted estradiol carboxylic acid esters as locally active estrogens

We have synthesized derivatives of estradiol that are structurally modified to serve as "soft" estrogens and act within a geographically limited area of the body; estrogens without systemic action. We have previously shown with 16alpha-substituted analogues of estradiol that carboxylates proximal to the steroid ring neither bind to the estrogen receptor nor activate estrogen-responsive genes. However, when the carboxylic acid is masked as an ester, they bind to the receptor and stimulate estrogenic responses. Enzymatic hydrolysis through nonspecific esterases can inactivate these estrogens and thereby limit their area of action. Here, we describe our continued studies to design "soft" estrogens by synthesizing carboxylic acid esters of estradiol at the 7alpha-, 11beta-, and 15alpha-positions in the steroid nucleus at which bulky substituents are accommodated by the estrogen receptor. These compounds were tested for estrogen receptor binding (estrogen receptors alpha and beta), stimulation of an estrogen sensitive gene in Ishikawa cells in culture, and as substrates for enzymatic hydrolysis. Likely candidates were tested in in vivo assays for systemic and local estrogenic action. The biological studies showed that regardless of the point of attachment, all of the short-chain carboxylic acids, C-1 to C-3, were devoid of hormonal action, while many of the esters were estrogenic. The site on the steroid nucleus had great influence on hormonal activity and esterase hydrolysis. Formate esters at 7alpha and 15alpha were good estrogens, but lengthening the chain to acetate dramatically decreased hormonal activity. However, the 7alpha-formate esters were not enzymatically hydrolyzed. At 11beta, the acetate (methyl ester) was an effective estrogen, but increasing the chain length to propionate dramatically reduced hormonal activity. In general, the length of the alcohol from methyl to butyl had only a small effect on receptor binding, and as the size of the alcohol increased, so did esterase hydrolysis. One exception was the 11beta-acetate esters where increasing the alcohol moiety from methyl to ethyl eliminated estrogenic activity (Ishikawa cells) without affecting estrogen receptor binding. Several of the esters were tested in vivo, and two, the methyl and ethyl esters of estradiol-15alpha-formate, appeared to have the requisite properties (high local and low systemic activity) of superior "soft" estrogens.     

Dodecanoic acid derivatives: Synthesis, antimicrobial evaluation and development of one-target and multi-target QSAR models

In this study a series of dodecanoic acid derivatives (1–30) were synthesized and evaluated for in vitro antimicrobial activity against the panel of Gram positive, Gram negative bacterial and fungal strains. 4-Nitro phenyl dodecanoate (4) and quinolin-8-yl dodecanoate (5) emerged as most effective antibacterial agents, and 1-(4-benzylpiperazin-1-yl) dodecan-1-one (15) was found to be the most effective antifungal agent amongst the synthesized dodecanoic acid derivatives. Quantitative structure activity relationship (QSAR) studies performed by the development of one-target and multi-target models indicated that multi-target model was effective in describing the antimicrobial activity of dodecanoic acid derivatives as well demonstrated the importance of topological parameter, zero-order molecular connectivity index (⁰χ).