In vitro evidence of phyto-synergy for plant part combinations of Croton gratissimus (Euphorbiaceae) used in African traditional healing.
OBJECTIVE
Despite the extensive traditional use of Croton gratissimus Burch. var. gratissimus for medicinal purposes, scientific studies validating the therapeutic properties of this indigenous plant are lacking. As the bark, roots and leaves of C. gratissimus are used separately as well as in combination, this study focused on determining antimicrobial efficacies of the plant parts independently and in combination to assess possible pharmacological interactions (e.g. synergy, antagonism).


METHODS
The hydro-distilled leaf essential oil and extracts of bark, root and leaf were comparatively assessed for antimicrobial activity by means of microdilution minimum inhibitory concentration (MIC). The fractional inhibitory concentrations (FIC) were determined for the leaf and root (1:1), bark and root (1:1), leaf and bark (1:1) combination. Isobolograms were plotted to demonstrate interactions between various ratios of the roots and leaves.


RESULTS
The MIC and FIC results indicated variable efficacies for the various plant part combinations, the greatest of which was noted for Cryptococcus neoformans in the root and leaf combination (MIC 0.4 mg/ml and FIC of 0.4). Isobolograms indicated the greatest synergy for Bacillus cereus, Candida albicans and Cryptococcus neoformans.


CONCLUSIONS
The observed synergistic interactions clearly indicate that the reductionist approach may often be short-sighted and that biological activity may be improved through combination therapy, where different complex metabolic pools collectively contribute to the enhanced effect.
van Vuuren
S F
SF
Department of Pharmacy and Pharmacology, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown 2193, South Africa.
Viljoen
A M
AM
D000890:Anti-Infective Agents / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects; D029802:Croton / Q000737:chemistry*; D004357:Drug Synergism; D005658:Fungi / Q000187:drug effects; D016488:Medicine, African Traditional; D008826:Microbial Sensitivity Tests; D009822:Oils, Volatile / Q000737:chemistry / Q000494:pharmacology; D008517:Phytotherapy; D024301:Plant Bark / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry
D000890:Anti-Infective Agents; D009822:Oils, Volatile; D010936:Plant Extracts