Aqueous extract of Hibiscus sabdariffa inhibits pedestal induction by enteropathogenic E. coli and promotes bacterial filamentation in vitro.

Diarrheic diseases account for the annual death of approximately 1.9 million children under the age of 5 years, and it is a major cause of work absenteeism in developed countries. As diarrheagenic bacteria, enteropathogenic Escherichia coli (EPEC) attach to cells in the small intestine, causing local disappearance of microvilli and inducing the formation of actin-rich pedestals that disrupt the intestinal barrier and help EPEC adhere to and infect intestinal cells. Antibiotics and other bioactive compounds can often be found by analyzing traditional medicines. Here a crude aqueous extract of Hibiscus sabdariffa, which typically grows in subtropical and tropical areas and is a popular medicinal tisane in many countries, was analyzed for antibacterial activity against EPEC. In standard microdilution assays, the extract showed a minimum inhibitory concentration of 6.5 mg/ml against EPEC growth. Time-kill kinetics assays demonstrated significant 24 h bactericidal activity at 25 mg/ml. The extract is able to impede pedestal induction. Not only did the extract inhibit preformed pedestals but it prevented pedestal induction as well. Remarkably, it also promoted the formation of EPEC filaments, as observed with other antibiotics. Our results in vitro support the potential of Hibiscus sabdariffa as an antimicrobial agent against EPEC.

Amino Acid Induced Modification of Self-Assembled Monoglyceride-Based Nanostructures.

Self-assembled phases based on monoglycerides are promising candidates for drug delivery systems. Alterations of these phases need to be performed by addition of substances which are biocompatible. Inverse bicontinuous cubic phases are altered by the addition of five amino acids, namely, glycine, phenylalanine, alanine, glutamine, and tryptophan. These natural molecules have a diversity of side chains which predicts their polarity and subsequently their interaction with the interfacial region. Whereas polar amino acids cause a slight shrinking of the fully hydrated phase, amino acids with a nonpolar side chain expand it. Tryptophan is also able to provoke a growth of inverse hexagonal, micellar cubic, and micellar structures. Amino acid concentrations in the aqueous phase, even above the amino acid's solubility, further affect all aforementioned structures and cause a significant enlargement of up to 26%. Besides the amino acids' impact on the structural sizes, they also affect the phase transition temperatures.