In vitro antimicrobial activity of a new series of 1,4-naphthoquinones

Abstract

The antibacterial activity of a series of 1,4-naphthoquinones was demonstrated. Disk diffusion tests were carried out against several Gram-positive and Gram-negative bacteria. The compound 5-amino-8-hydroxy-1,4-naphthoquinone was the most effective, presenting inhibition zones measuring 20 mm against staphylococci, streptococci and bacilli at 50 µg/ml. Methicillin-resistant Staphylococcus aureus and several clinical isolates of this bacterium were also inhibited. Naphthazarin, 5-acetamido-8-hydroxy-1,4-naphthoquinone, and 2,3-diamino-1,4-naphthoquinone were the next most active compounds. The minimal inhibitory concentration of the active compounds was determined against S. aureus, ranging from 30 to 125 µg/ml. All compounds presented a minimal bactericidal concentration higher than 500 µg/ml, indicating that their effect was bacteriostatic. The EC 50 , defined as the drug concentration that produces 50% of maximal effect, was 8 µg/ml for 5-amino-8-hydroxy-1,4-naphthoquinone against S. aureus, S. intermedius, and S. epidermidis. These results indicate an effective in vitro activity of 5-amino-8-hydroxy-1,4-naphthoquinone and encourage further studies for its application in antibiotic therapy.

Toxicity of <I>Fusarium solani</I> Strains on Brine Shrimp (<I>Artemia salina</I>)

“…nHexane soluble fraction was obtained only in three strains which showed mild toxicity. Antimicrobial naphthoquinones are widely distributed in plants, fungi and some animals (Riffel et al, 2002) are also reported from F. solani (Ammar et al, 1979;Baker et al, 1990). Besides naphthoquinones, F. solani is also known to produce diterpene and paclitaxel (Chakravarthi et al, 2008), and has been used alone or in combination with other chemotherapeutic agents for the treatment of variety of cancers, as well as AIDS-related Kaposi sarcoma (Brown, 2003;Croom, 1995 Means of 3 replicates.…”

Anti-infectious activity in plants of the genus Tabebuia

“…The ethyl acetate extract obtained from the inner bark of Tabebuia ochracea and Tabebuia rosea inhibits Staphylococcus aureus growth at concentrations ranging between 1.25 and 10 mg/well. This characteristic may be attributed to the presence of quinone-type compounds that have displayed activity against Staphylococcus aureus strains (Riffel et al 2002). However, no inhibitory activity was found against Escherichia coli and Pseudomonas aeruginosa by Tabebuia ochracea and Tabebuia rosea in the ethyl acetate extract (Franco Ospina et al 2013).…”

Computational Study of Electronic Effects from β-Substituents on the Tautomerism of Naphthazarin Derivatives

“…These compounds are frequently found in plants and on a smaller scale in inferior animals, exhibiting a broad scope of applications, such as drugs and dyes. [1][2][3][4][5][6][7][8][9] 5,8-Dihydroxy-1,4-naphthoquinone (1), naphthazarin, and its derivatives are particularly important due to their biological and pharmacological activities [10][11][12][13][14][15] and versatility as intermediates in the synthesis of more diversified chemical structures. 9,[16][17][18][19][20][21][22][23][24] One of their features is the presence of tautomerism.…”