Abstract
The work reports antibacterial and antifungal activity of some 3-(substituted phenyl) isocoumarins (1H-2-benzopyran-1-ones), isocarbostyrils 1(2H)-isoquinolones, the nitrogen analogues of isocoumarins and isocoumarin-1-thiones, the thio derivatives of isocoumarins. The antimicrobial activity was determined against ten different Gram positive and Gram negative bacterial strains and three fungal strains. The bacterial strains were Klebsiella pneumonae (ATCC 6633), Staphylococcus aureus (ATCC 29213), Micrococcus luteus (ATCC 9341), Pseudomonas aeruginosa (ATCC 33347), Escherichia coli (ATCC 25922), Salmonella typhi (ATCC 19430), Lactobacillus bulgaricus, (ATCC 25929), Pasteurella multocida A (ATCC 9150), Staphylococcus epidermidis (ATCC 29232) and Proteus vulgaris (ATCC 49565) and fungal strains were Aspergillus flavus, Aspergillus nigar and Aspergillus pterus. Agar well diffusion method was followed for antibacterial activity and poison plate method was adopted for antifungal assay. Chloramphenicol and fluconazole used as standard drugs for antibacterial and antifungal activity respectively. In general, these compounds exhibited high antibacterial potential than antifungal. Comparative study reveals that the 1-thio derivatives are more active than parent isocoumarins but 1(2H)-isoquinolones, are less active. Most of these compounds showed poor activity but some of these compounds exhibited moderate to good activity against Staphylococcus epidermidis, Klebsiella pneumonae, Escherichia coli and Proteus vulgaris, compared with the standard drug.
Highlights
Isocoumarins are the secondary metabolites of fungi, bacteria, plants and insect venoms and pheromones
The antibacterial activity of the 3-phenylsubstituted isocoumarins, 3-phenylsubstituted isoquinolin-1(2H)-ones and 3-phenylsubstituted 1H-isochromenes-1-thiones was determined against ten bacterial strains and reported in Tables 1-3 respectively
Among all the ten differently 3-phenylsubstituted isoquinolin-1(2H)-ones only the 3-(2,4-dichlorophenyl)1(2H) isoquinolone (18) shows moderate to potent activity against these tested microorganisms. It shows potent activity against K. pneumonae and have moderate efficacy against L. bulgaricus and P. multocida. These results indicate that in case of 1(2H) isoquinolones presence of two electronegative halogen functionality is important in showing antibacterial activity
Summary
Isocoumarins are the secondary metabolites of fungi, bacteria, plants and insect venoms and pheromones. Insect and marine organisms are the rich source of these secondary metabolites [1] [2]. They exhibit a broad range of pharmacological activities including antimalarial, antimicrobial, immunomodulatory, antifungal, anti-inflammatory, cytotoxic, antiangiogenic and antiallergic [3]-[9]. Isocoumarins are used as a lead compound for the identification of insecticides which selectively bind at the insect GABA receptor [10]. 3-Substituted isocoumarins show anti HIV activity in vitro, diuretic, antihypertensive, antiarrythmics, β-sympatholytics, anticorrosive, laxatives, asthmolytic, phytotoxic, and are useful in the treatment of emphysema [11]. Isocoumarin derivatives are potently inhibits endothelial cell proliferation, migration, sprouting, tube formation in vitro, and tumor growth in vivo [12]
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