The effectiveness of processed grapefruit-seed extract as an antibacterial agent: II. Mechanism of action and in vitro toxicity.
OBJECTIVE
Recent testimonials report grapefruit-seed extract, or GSE (Citricidal) to be effective against more than 800 bacterial and viral strains, 100 strains of fungus, and a large number of single and multicelled parasites. This study investigated GSE for antibacterial activity at varying time intervals and concentration levels and tissue toxicity at varying concentrations in an effort to determine if a concentration existed that was both microbicidal and nontoxic and in what period of time.


METHODS
Gram-negative and gram-positive isolates were introduced into graduated dilutions of GSE (twofold concentrations ranging from 1:1, through 1:512) for determination of bacterial activity. In vitro assays with human skin fibroblast cells were also performed at the same dilutions to determine toxicity.


RESULTS
These tests indicated that from the 1:1 through the 1:128 concentrations, GSE remained toxic as well as bactericidal. However, test results indicated that at the 1:512 dilution, GSE remained bactericidal, but completely nontoxic.


CONCLUSIONS
The initial data shows GSE to have antimicrobial properties against a wide range of gram-negative and gram-positive organisms at dilutions found to be safe. With the aid of scanning transmission electron microscopy (STEM), the mechanism of GSE's antibacterial activity was revealed. It was evident that GSE disrupts the bacterial membrane and liberates the cytoplasmic contents within 15 minutes after contact even at more dilute concentrations.
Heggers
John P
JP
Department of Surgery (Plastic), School of Medicine, University of Texas Medical Branch, Galveston, USA. jphegger@utmb.edu
Cottingham
John
J
Gusman
Jean
J
Reagor
Lee
L
McCoy
Lana
L
Carino
Edith
E
Cox
Robert
R
Zhao
Jian-Gang
JG
Reagor
Lana
L
D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents / Q000009:adverse effects / Q000494:pharmacology*; D002957:Citrus; D005347:Fibroblasts / Q000187:drug effects; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D006801:Humans; D066298:In Vitro Techniques; D008826:Microbial Sensitivity Tests; D008854:Microscopy, Electron; D010936:Plant Extracts / Q000009:adverse effects / Q000494:pharmacology; D012639:Seeds; D012867:Skin / Q000187:drug effects / Q000382:microbiology*; D013997:Time Factors
D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D010936:Plant Extracts