Analysis of Anti-Bacterial Properties and Cytological Location of Allelochemicals in Several Varieties of Hosta

Rebecca Smith, Matthew Burns

Abstract


Plants have three classes of secondary metabolites called allelochemicals: Terpenes, Phenolics, and Alkaloids. There is evidence that Hosta plants are a source of allelochemicals, possibly essential oils and other flavonoids. Petioles of several varieties were sectioned and stained with colorometric indicators: Vanillin HCl and the Hoepfner-Vorsatz test for phenolic compounds, and FeCl3 and Henna for terpenoids. Plant Defense Mechanisms are both physical and chemical. The cuticle is a hydrophobic physical barrier but was also positive for Resorcinol (a phenolic compound). Plants have defense mechanisms that may deter herbivores. Barriers are: 1) Physical by a laminated waxy cuticle and by raphid crystals that score the digestive track of herbivores, 2) Chemical defense mechanisms were cited in the cuticle and in the subcuticular layer of the epidermis. The distal primary walls of the collenchyma and in the hypodermal parenchyma primary walls also stained. Partially purified Hosta extract of three different varieties were macerated with methanol and combined. This extract was initially used in a bioassay against various bacterial species to determine which of these species was inhibited by the extract. It was shown that the methanolic Hosta extract inhibited the common soil bacteria Bacillus subtilis and to a lesser extent Bacillus cereus. This was followed by silica gel chromatographic separation of the extract and identification by fluorescently labeled TLC plates. Two peaks were identified. In the bioassay, peak two showed the major inhibitory activity against B. subtilis. This fraction was analyzed by gas chromatography-mass spectrometry (GC-MS). The GC-MS analysis identified two compounds that represented the closest spectrum within the MS database. These two compounds were menthol and linolenate-methyl ester. In animals, there are two types of defense mechanisms, passive and active immune systems. In this study, an immune-like system in plants, analogous to that found in animals (physical) passive and (chemical) defenses were demonstrated through chemical extraction and by cytohistochemical localization.

Keywords


Hosta, Allelochemicals , Bacillus subtilis,

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