Antimicrobial activity of flavonoids

School of Pharmacy, The Robert Gordon University, Schoolhill, Aberdeen AB10 1FR, UK
International Journal of Antimicrobial Agents (Impact Factor: 4.26). 12/2005; 26(5):343-56. DOI: 10.1016/j.ijantimicag.2005.09.002
Source: PubMed

ABSTRACT Flavonoids are ubiquitous in photosynthesising cells and are commonly found in fruit, vegetables, nuts, seeds, stems, flowers, tea, wine, propolis and honey. For centuries, preparations containing these compounds as the principal physiologically active constituents have been used to treat human diseases. Increasingly, this class of natural products is becoming the subject of anti-infective research, and many groups have isolated and identified the structures of flavonoids possessing antifungal, antiviral and antibacterial activity. Moreover, several groups have demonstrated synergy between active flavonoids as well as between flavonoids and existing chemotherapeutics. Reports of activity in the field of antibacterial flavonoid research are widely conflicting, probably owing to inter- and intra-assay variation in susceptibility testing. However, several high-quality investigations have examined the relationship between flavonoid structure and antibacterial activity and these are in close agreement. In addition, numerous research groups have sought to elucidate the antibacterial mechanisms of action of selected flavonoids. The activity of quercetin, for example, has been at least partially attributed to inhibition of DNA gyrase. It has also been proposed that sophoraflavone G and (-)-epigallocatechin gallate inhibit cytoplasmic membrane function, and that licochalcones A and C inhibit energy metabolism. Other flavonoids whose mechanisms of action have been investigated include robinetin, myricetin, apigenin, rutin, galangin, 2,4,2'-trihydroxy-5'-methylchalcone and lonchocarpol A. These compounds represent novel leads, and future studies may allow the development of a pharmacologically acceptable antimicrobial agent or class of agents.

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    ABSTRACT: To determine the effect of flavonoids in conjunction with antibiotics in methicillin resistant Staphylococcus aureus (MRSA) a study was designed. The flavonoids included Rutin, Morin, Qurecetin while antibiotics included ampicillin, amoxicillin, cefixime, ceftriaxone, vancomycin, methicillin, cephradine, erythromycin, imipenem, sulphamethoxazole/trimethoprim, ciprofloxacin and levolfloxacin. Test antibiotics were mostly found resistant with only Imipenem and Erythromycin found to be sensitive against 100 MRSA clinical isolates and S. aureus (ATCC 43300). The flavonoids were tested alone and also in different combinations with selected antibiotics. Antibiotics and flavonoids sensitivity assays were carried using disk diffusion method. The combinations found to be effective were sifted through MIC assays by broth macro dilution method. Exact MICs were determined using an incremental increase approach. Fractional inhibitory concentration indices (FICI) were determined to evaluate relationship between antibiotics and flavonoids is synergistic or additive. Potassium release was measured to determine the effect of antibiotic-flavonoids combinations on the cytoplasmic membrane of test bacteria. Antibiotic and flavonoids screening assays indicated activity of flavanoids against test bacteria. The inhibitory zones increased when test flavonoids were combined with antibiotics facing resistance. MICs of test antibiotics and flavonoids reduced when they were combined. Quercetin was the most effective flavonoid (MIC 260 μg/ml) while morin + rutin + quercetin combination proved most efficient with MIC of 280 + 280 + 140 μg/ml. Quercetin + morin + rutin with amoxicillin, ampicillin, cephradine, ceftriaxone, imipenem, and methicillin showed synergism, while additive relationship was indicated between morin + rutin and amoxicillin, cephradine, ceftriaxone, imipenem, and methicillin. Quercetin alone had an additive effect with ampicillin, cephradine, ceftriaxone, imipenem, and methicillin. Potassium leakage was highest for morin + rutin + quercetin that improved further in combination with imipenem. Morin and rutin alone had no activity but in combination showed activity against test bacteria. The flavonoids when used in combination with antibiotics were found to increase each other activity against test bacteria. The relationship between the flavonoids and antibiotics in most of the cases was additive. However in a few cases synergism was also observed. Flavonoids alone or in combinations also damaged bacterial cell membrane.
    BMC Complementary and Alternative Medicine 12/2015; 15(1):580. DOI:10.1186/s12906-015-0580-0 · 1.88 Impact Factor
  • Food and Nutrition Sciences 01/2013; 04(08):197-203. DOI:10.4236/fns.2013.48A024
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    ABSTRACT: Bunchosia armeniaca (B. armeniaca) is a native plant to America, and popularly called “cafezinho”, “ciruela” or “falso-guaraná”. In traditional medicine is used to treat different pathologies including infectious and inflammatory diseases. From ethanolic extract of B. armeniaca leaves (Malpighiaceae) afforded a flavonoid mixture consisting of rutin 1 (83.5%), isoquercitrin 2 (5.6%) and afzelin 5 (10.9%), which were identified and individually quantified as helpful for capillary electrophoresis and 1H and 13C NMR spectroscopy. The ethanolic extract showed an excellent antibacterial activity against Staphylococcus aureus (S.aureus) and moderate activity against Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa). The flavonoid mixture showed antibacterial activity, mainly against the gram negative bacteria. Moreover, this plant demonstrated significant anti-inflammatory action, inhibiting the leukocyte influx and exudate formation in pleural cavity caused by carrageenan. The inflammation mediators involved in this model study, myeloperoxidase, nitric oxide and tumor necrosis factor alpha were significantly inhibited by ethanolic extract and flavonoid mixture of B. armeniaca. The results show that B. armeniaca has a significant antibacterial and anti-inflammatory effects and that these effects is due, at least in part, to the presence of rutin, isoquercetrin and afzelin in large amounts. Hence, these compounds have potential as novel lead compounds for the future development of therapeutic interventions for the treatment of patients with infectious and inflammatory disorders.
    Records of Natural Products 01/2015; 9(3):419. · 1.02 Impact Factor

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