No abstract

Chili peppers (Capsicum spp.) may possess antibacterial properties and have potential to be used in foods as antimicrobial. The complete chili pepper extract should be evaluated to determine which compounds are responsible for the antimicrobial activity. Extraction of compounds from the pepper is completed using a solvent. The type of solvent used for extraction influences which compounds are isolated, therefore the best extraction method needs to be determined. The purpose of this study was to identify which solvent is most successful at extracting unknown antibacterial compounds from jalapeño peppers. Fresh jalapeño peppers were chopped, weighed, and blended with a solvent (sterilized hot water, 70% methanol, 95% methanol, 70% ethanol, or 95% ethanol) at a 1:1 ratio (g/g) until the mixture was homogenized, followed by shaking for 15 min. The slurry was centrifuged; supernatant was removed and used for antibacterial testing against Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica. The diameter of growth inhibition was measured and statistically evaluated using ANOVA to determine the extract with the greatest antimicrobial activity. Solvents were tested alone as a control. There was greater bacterial inhibition from extracts created with methanol and ethanol than hot water. Listeria monocytogenes was significantly more susceptible to the extracts than E. coli or Salmonella isolates. Each solvent extract was then analyzed using high‐performance liquid chromatography (HPLC) and fractions (A–G) were collected and used for subsequent disk diffusion analysis against L. monocytogenes. Fractions E and F (eluded between 20 and 30 min) exhibited the most antibacterial activity. There were no differences between solvents used (p = .05). Further investigation into specific compounds within these extracts will be completed in the future.

1995. HMG-CoA reductase and terpenoid phytoalexins: Molecular specialization within a complex pathway. -Phy.siol. Plant. 93: 393-400.

Capsicum annuum fruits have been investigated for antimicrobial activity in a number of studies. Capsaicin or other cinnamic acid pathway intermediates are often suggested to be the antimicrobial component, however there are conflicting results. No research has specifically fractionated jalapeño pepper (Capsicum annuum var. annuum) extract to isolate and identify compound(s) responsible for inhibition. In this study, fractions were collected from jalapeño pepper extracts using reverse‐phase HPLC and tested for antibacterial activity using the disk diffusion method. Following initial fractionation, two fractions (E and F) displayed antibacterial activity against all three pathogens (p > .05). Commercial standards were screened to determine when they elude and it was found that capsaicin elutes at the same time as fraction E. Fractions E and F were subject to further HPLC fractionation and antibacterial analysis using two methods. The only fraction to display clear inhibition using both was fraction E1, inhibiting the growth of L. monocytogenes. Fraction E1 was analyzed using HPLC‐MS. The resulting mass spectra revealed fraction E1 contained compounds belonging to a group of C. annuum‐specific compounds known as capsianosides. Limited research is available on antibacterial activity of capsianosides, and a pure commercial standard is not available. In order to confirm the potential antimicrobial activity of the compound(s) isolated, methods need to be developed to isolate and purify capsianosides specifically from jalapeño peppers.

The enzyme 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) catalyzes the conversion of 3-hydroxy-3-methylglutaryl-CoA to mevalonic acid, considered the rate-limiting step in isoprenoid biosynthesis. In plants, isoprenoid compounds play important roles in mediating plant growth and development, electron transport, photosynthesis, and disease resistance. Sequence comparisons of plant HMGR proteins with those from yeast and mammalian systems reveal high levels of sequence identity within the catalytic domain but significant divergence in the membrane domain. Mammalian HMGRs are integral membrane proteins of the endoplasmic reticulum with eight membrane-spanning regions. In contrast, the membrane domain of plant HMGRs is predicted to contain only one to two transmembrane spans. We have isolated and sequenced a clone (pCD4) encoding exon 1 of tomato hmg1. The membrane domain structures of two differentially regulated tomato HMGR isoforms, HMG1 and HMG2, were analyzed using in vitro transcription and translation systems. Microsomal membrane insertion of the tomato HMGRs is co-translational and does not involve cleavage of an N-terminal targeting peptide. HMGR membrane topography was established by protease protection studies of the HMG1 membrane domain and an analogous region of HMG2 engineered to contain a c-myc epitope tag. The data indicate that both tomato HMGRs span the membrane two times with both the C and N termini located in the cytosol. Lumenal localization of the short peptide predicted to lie within the endoplasmic reticulum was further confirmed by in vitro glycosylation of an asparagine-linked glycosylation site present in HMG2.