A Water-Soluble Antibiotic in Rhubarb Stalk Shows an Unusual Pattern of Multiple Zones of Inhibition and Preferentially Kills Slow-Growing Bacteria

Abstract

Organic extract of Rhubarb (Rheum officinale) roots is known to have several medicinal uses. However, not much research has been done with the rhubarb stalk. The aim of this research is to evaluate the anti-bacterial and anti-proliferative effects of the aqueous extract from rhubarb stalks. The crude aqueous extract was further purified using anion exchange and gel filtration. The purified compound demonstrated broad spectrum antibacterial activity against the Gram-negative bacteria, E. coli and Aggregatibacter actinomycetemcomitans, and Gram-positive bacteria, S. aureus. A time-kill assay demonstrated that the antibiotic has strong bactericidal activity. It also has anti-proliferative action against the breast cancer cell line MCF-7 with no cytotoxicity, although the crude extract had a significant cytotoxic effect. The antibiotic activity, as measured by the diameter of the zone of inhibition, increased by several fold in low nutrient and/or low salt agar, suggesting that the antibiotic preferentially kills slow-growing bacteria. The antibiotic also gives an unusual pattern of multiple zones of inhibition in which several zones of cell growth are seen within the zone of inhibition. In conclusion, the active component in the aqueous extract of rhubarb stalk has great potential as a strong bactericidal antibiotic and as an anti-proliferative drug.

Development and Validation of a Liquid Chromatography–Tandem Mass Spectrometry Method for Screening Potential Citrate Lyase Inhibitors from a Library of Marine Compounds

“…Its fat-soluble components like essential oils show antimicrobial activity against various bacteria [21]. Rhubarb's anthraquinones and water-soluble constituents exhibit antibacterial activities with multiple bacterial strains [22,23]. Lycium barbarum's constituents, primarily water-soluble, have antibacterial properties.…”

Bacteriostatic Effects of Yujin Powder and Its Components on Clinical Isolation of Multidrug-Resistant Avian Pathogenic Escherichia coli

“…Curcumae Radix could not only directly inhibit bacteria, but also improve the effectiveness of antibiotics on inhibiting the growth of bacteria; so, this herb was not used as the research object of this study [ 30 , 31 ]. Rhubarb demonstrated broad-spectrum antibacterial activity against the Gram-negative bacteria, E. coli , and can be used to protect the gut barrier, maintain the intestinal micro-ecological environment, and prevent bacterial translocation as well [ 32 , 33 ]. In these aspects, the concepts of clearing away heat and detoxicating in TCM and TVCM are consistent with that of antibacterial, anti-inflammatory, and diarrhea in modern pharmacological research.…”