An Interactive Antimicrobial Activity of Embelica officinalis Gaertn. Fruit Extracts and Conventional Antibiotics against Some Bacterial Triggers of Autoimmune Inflammatory Diseases

Abstract

Background: Embelica officinalis Gaertn. is an Indian plant which is known for its therapeutic properties. It is especially well known as a component of the Ayuverdic medicine Triphala. This study focuses on the growth inhibitory activity of E. officinalis fruit extracts against some bacterial triggers of autoimmune inflammatory diseases, both alone and in combination with conventional antibiotics. Methods: E. officinalis fruit powder was extracted with solvents of varying polarity and screened for bacterial growth inhibition by disc diffusion assay. The minimum inhibitory concentration (MIC) was quantified by both liquid dilution and disc diffusion techniques. To screen for combinatorial effects, the E. officinalis fruit extracts were combined with a range of conventional antibiotics and tested against each bacteria using a liquid dilution assay. Toxicity was examined using Artemia nauplii and HDF bioassays. Results: The ethyl acetate E. officinalis fruit extract displayed the strongest growth inhibitory activity against all of the bacterial triggers of autoimmune inflammatory disease. This extract was a particularly potent inhibitor of P. aeruginosa growth, with an MIC values as low as 264 μg/mL. The ethyl acetate extract was also a moderate to strong growth inhibitor of P. mirabilis, K. pneumonia and A. baylyi, with MIC values generally 1000-1500 μg/mL. The methanolic and aqueous extracts also inhibited the growth of all bacteria, although generally with only moderate to low activity. Whilst no synergistic interactions were detected in combinations containing the E. officinalis fruit extracts and conventional antibiotics, a number of combinations produced additive effects. These combinations are beneficial as they provide enhanced antibacterial efficacy compared to treatment with the antibiotic or extract components alone. No antagonistic interactions were detected. Therefore, use of the extracts in combination with conventional antibiotics would not compromise the antibiotics efficacy. All extracts were nontoxic in the Artemia nauplii and HDF toxicity assays, further indicating their potential for medicinal use. Conclusion: The E. officinalis fruit extracts were moderate inhibitors of the bacterial triggers of selected autoimmune inflammatory diseases. Furthermore, the extracts potentiated the activity of chloramphenicol and tetracycline against otherwise resistant bacterial strains. Isolation of the active compounds and the potentiating agents may be beneficial in antibiotic drug design.

Interactive Antimicrobial and Toxicity Profiles of Scaevola spinescens R.Br. Extracts with Conventional Antibiotics

“…antibiotics that are otherwise ineffective against resistant bacterial strains. Several studies investigating combinations of conventional antimicrobialswith African, [3][4] Asian [5][6] and Australian traditional medicinal plants 7 have recently been published, highlighting the increased efficacy of some combinational antibiotic therapies. Several of these studies have identified plant extracts which synergistically enhance the activity of conventional antimicrobials, even when the plant extracts do not possess antimicrobial activity in isolation.…”

Interactive Antimicrobial Profiles of Astragalus membranaceus (Fisch.) Bunge Extracts and Conventional Antibiotics against Pathogenic and Non-pathogenic Gastrointestinal Bacteria

“…Interactions between the Astragalus root extracts and the conventional antibiotics were examined by determination of the sum of fractional inhibitory concentrations (ΣFIC) for each combination. 39 The FIC values for each component (a and b) were calculated using the following equations where a represents the plant extract sample and b represents the conventional antibiotic:…”

Interactive antimicrobial and toxicity profiles of Pittosporum angustifolium Lodd. extracts with conventional antimicrobials

“…Combinational approaches may prove to be more effective in overcoming antibiotic resistance and may even allow conventional antibiotics to again be effective against resistant bacterial strains. Several studies have already investigated combinations of natural product and conventional antimicrobials and have reported promising results [3][4][5][6][7][8][9]. Several plant species have been identified that substantially potentiate the activity of conventional antimicrobials, even when the plants do not possess antimicrobial activity alone [2,3,8].…”