title: In vitro antimicrobial synergism within plant extract combinations from three South African medicinal bulbs.
abstract: BACKGROUND
  Tulbaghia violacea, Hypoxis hemerocallidea and Merwilla plumbea are used in South African traditional medicine for the treatment of some infectious diseases and other ailments.
  
  
  OBJECTIVE
  The study aimed at investigating the antimicrobial efficacies of independent and various within-plant extract combinations of three medicinal bulbs to understand the possible pharmacological interactions.
  
  
  METHODS
  Bulb and leaf extracts of the three medicinal plants, independently and in combinations, were comparatively assessed for antimicrobial activity against two Gram-positive and two Gram-negative bacteria and Candida albicans using the microdilution method. The fractional inhibitory concentration indices (FIC) for two extract combinations were determined.
  
  
  RESULTS
  At least one extract combination in each plant sample demonstrated good antimicrobial activity against all the test organisms. The efficacies of the various extract combinations in each plant sample varied, with the strongest synergistic effect exhibited by the proportional extract yield combination of PE and DCM extracts in Merwilla plumbea bulb sample against Staphylococcus aureus (FIC index of 0.1). Most extract combinations demonstrated either a synergistic, additive or indifferent interaction effect against the test bacteria with only a few exhibiting antagonistic effects.
  
  
  CONCLUSIONS
  The observed antimicrobial efficacy and synergistic interactions indicate the beneficial aspects of combination chemotherapy of medicinal plant extracts in the treatment of infectious diseases.
authors.affiliation: Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa.
authors.forename: B
authors.initials: B
authors.lastname: Ncube
authors.forename: J F
authors.initials: JF
authors.lastname: Finnie
authors.forename: J
authors.initials: J
authors.lastname: Van Staden
mesh_terms: D000490:Allium; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000935:Antifungal Agents / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects; D004357:Drug Synergism; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006094:Gram-Positive Bacteria / Q000187:drug effects; D027802:Hypoxis; D019668:Liliaceae; D016488:Medicine, African Traditional; D008826:Microbial Sensitivity Tests; D010936:Plant Extracts / Q000494:pharmacology*; D018515:Plant Leaves; D018517:Plant Roots; D010946:Plants, Medicinal; D013019:South Africa
chemical_list: D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; D010936:Plant Extracts