Sabine Krist

Characterisation of various grape seed oils by volatile compounds, triacylglycerol composition, total phenols and antioxidant capacity.

Grape seed oil (Oleum vitis viniferae) representing a promising plant fat, mainly used for culinary and pharmaceutical purposes as well as for various technical applications, was subject of the present investigation. HS-SPME-GC-MS was applied to study volatile compounds in several seed oil samples from different grape oils. The triacylglycerol (TAG) composition of these oils was analyzed by MALDI-TOF-MS/MS. In addition the total phenol content and the antioxidant capacity (using TEAC) of these oils were determined. The headspace of virgin grape oils from white and red grapes was dominated by ethyl octanoate (up to 27.5% related to the total level of volatiles), ethylacetate (up to 25.0%), ethanol (up to 22.7%), acetic acid (up to 17.2%), ethyl hexanoate (up to 17.4%) and 3-methylbutanol (up to 11.0%). Triacylglycerol composition was found to be dominated by LLL (up to 41.8%), LLP (up to 24.3%), LLO (up to 16.3%) and LOO (up to 11.7%), followed by LOP (up to 9.3%) and LOS/OOO (up to 4.3%). Total phenol content ranged between 59μg/g and 115.5μg/g GAE. Antioxidant capacity (TEAC) was analyzed to range between 0.09μg/g and 1.16μg/g.

Synthesis and evaluation of lysozyme derivatives exhibiting an enhanced antimicrobial action

In order to generate novel preservatives exhibiting a broad antimicrobial spectrum against Gram-positive as well as Gram-negative bacteria, lysozyme was modified by the covalent attachment of caffeic acid and cinnamic acid, respectively. Linkage of these organic acids to lysozyme was achieved by the constitution of amide bindings between the carboxyl group of ligands and primary amino groups of the enzyme mediated by a carbodiimide. Compared to nonmodified lysozyme, the lytic activity of all resulting conjugates was reduced. In contrast, bacterial growth of Escherichia coli (ATCC 8739) could be strongly inhibited by lysozyme-caffeic acid conjugates and to a lower degree also by lysozyme-cinnamic acid conjugates. The minimal inhibitory concentration against E. coli was 0.05% for the lysozyme derivative of the highest antimicrobial activity. However, the efficacy of lysozyme derivatives against Staphylococcus aureus (ATCC 6538) was slightly reduced. As the antimicrobial spectrum of lysozyme altogether could be substantially widened, these derivatives represent promising candidates as novel preservatives for various pharmaceutical and cosmetic formulations.