Propolis: bioactive molecules with antibacterial activity

<p>Propolis is a natural substance produced by honey bees from the exudates of certain trees and plants. Ιts composition varies according to the botanical and geographical origin, the seasonal timing of collection, and extraction methods. In this investigation we performed several tests regarding the solvent, the extraction method and the bioactivity. For this purpose, propolis extracts in 95 or 70% ethanol and standard bacterial strains were used (Staphylococcus aureus ATCC 29213, Micrococcus luteus ATCC 934 and Escherichia coli ATCC 25922). Bioactivity tests were performed by Disk Diffusion Assay and Well Diffusion Assay. Applying these methods of analysis, the growth inhibition zone for S. aureus και M. luteus was 2±0,3 cm και 1,8±0,2 cm, respectively. No inhibition was observed for the bacterial strain E. coli. These results indicate that the examined propolis sample has antibacterial activity against the tested Gram-positive bacteria.</p&gt

Leaf structure and histochemistry of Ficus carica (Moraceae), the fig tree

Heavily "armed" with trichomes, the hypostomatic leaf of Ficus carica L. is investigated with light and scanning electron microscopy. Histochemical tests were also applied to trace the secondary matabolites produced in the leaf of this well known, Mediterranean tree with the delicious fruits. Numerous idioblasts with crystals, laticifers and sized lythocysts appear within the compact mesophyll. Protective trichomes are located on both surfaces while capitate secretive hairs and stomata appear only abaxially. Stomata, concerning their magnitude, can be assembled in three size-groups in which the arrangement of their parastomatal cells differs as well. Histochemical reactions proved positive only for alkaloids within the laticifers and phenolic compounds, especially for the condensed tannins accumulated within the vacuole of the epidermal cells of this simply constructed leaf with unique features among the Mediterranean herbs. Comparison of GC-MS and LC-HRMS spectra of different extracts of the nerves and, separately, the rest of the leaf, revealed that coumarines such as umbeliferone, psoralen, bergapten and xanthotoxol are probably biosynthetically produced within the nerve area where the highly differentiated, main secretive apparatus of the leaf (laticifers) resides. That is why, these metabolites, are absent from the extracts of the undifferentiated cells derived from in vitro cultures. © 2015 Elsevier GmbH

A two-season impact study on Globularia alypum: adaptive leaf structures and secondary metabolite variations

A detailed histo-anatomical and phytochemical study on Globularia alypum was carried out to investigate season-induced plant responses related to leaf morphology and content of secondary metabolites (SMs). Leaf tissue analysis by light and scanning electron microscopy showed neither morphological nor significant anatomical adaptions/variations to the coldest and the hottest seasons. Both summer and winter leaf tissue resulted amphistomatic with compact mesophyll and capitate glandular trichomes. Epidermal and mesophyll cells showed a significant accumulation of osmiophilic compounds, further characterized as phenolics by the histochemical screening. Beside the morpho-anatomical similarities in tissue arrangement, SMs production, within and among the different natural product classes, resulted seasonally dependent. In total, 24 SMs belonging to iridoids, flavonoids and phenylethanoid glycosides were tentatively assigned by UHPLC-HRMS analysis. Among iridoids, (E)-globularicisin showed to be the prevalent constituent, with content up to 70%. Total iridoid production was increased by 48.1% during summer. Similarly, flavonoid anabolism was more active during the same period, although with less remarkable seasonal variation reaching 25.6%. In contrast to the overall higher production of iridoids and flavonoids, a drastic fall (33.5%) of phenylethanoids was observed during summer. © 2018 Società Botanica Italiana

Structural and phytochemical investigation of the leaves of Ricinus communis

Ricinus communis L., also known as the castor oil plant, is a highly toxic species indigenous to the south-eastern Mediterranean. Leaf anatomy was investigated by light and electron microscopy (SEM and TEM). Histochemistry and composition of secondary metabolites, were also investigated. The amphistomatic leaves of R. communis are of simple structure with a single layered palisade parenchyma. They contain numerous idioblasts with crystals and present a strong positive reaction to histochemical reagents for terpenes, flavonoids, phenolics and alkaloids. Only a few protective trichomes appear on the adaxial epidermis. The phytochemical analysis of leaf extracts using UHPLC-HRMS and GC-MS confirmed the results of the histochemical tests and, among other metabolites, the flavonoids rutin, isoquercetin, and nicotiflorin, as well as the toxic alkaloid ricinine were detected. © CSIRO 2017

Leaf structure and histochemistry of the hardy evergreen Euphorbia characias L. (Mediterranean spurge)

The dorsiventral, hypostomatic leaf of Euphorbia characias is investigated to disclose its structural features and the chemical nature of the secondary metabolites produced. Light and scanning electron microscopy along with histochemical tests were employed to investigate the leaf of this well known perennial dwarf Mediterranean shrub. The compact leaf is characterized by numerous, rather uniform, curly, unicellular hairs on both surfaces, vaulty protrusions of the outer periclinal walls of the epidermal cells, prominent on the lower epidermis in particular, and a network of latex producing ducts (laticifers) extending in two layers within the mesophyll. Histochemical reactions proved positive only for alkaloids within the laticifers and phenolic compounds, especially for the condensed tannins accumulated within the vacuole of the epidermal cells. GC-MS and GC-FID analyses of the latex revealed the presence of several secondary metabolites, mainly belonging to the class of triterpenes. Lanosterol, butyrospermol, cycloartenol and lupeol were the major constituents in the extract examined. © 2014 Elsevier GmbH