Influence of Nutrient Deprivation on the Antioxidant Capacity and Chemical Profile of Two Diatoms from Genus Chaetoceros.

The limited availability of phosphate, nitrogen and silicon in the growth media affects the growth, cellular processes, and metabolism of diatoms. Silicon deficiency primarily affects diatom morphology, while phosphate deficiency reduces the production of nucleic acids and phospholipids. Differences in pigment and protein composition are mainly due to nitrogen deficiency. In this study, Chaetoceros socialis and Chaetoceros costatus were cultured under phosphate, nitrogen, and silicon deprivation conditions. The diatom biomass was collected during the stationary growth phase and extracted with 70% ethanol under ultrasonication. The chemical profiles of the extracts were analyzed by high-performance liquid chromatography with high-resolution mass spectrometry with electrospray ionisation (UHPLC-ESI-HRMS), while the antioxidant capacity was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and oxygen radical absorbance capacity (ORAC) assays. Pigments, fatty acids, sterols, and derivatives were detected in both species. The total phenolic content in the extracts ranged from 46.25 ± 1.08 to 89.38 ± 6.21 mg of gallic acid equivalent (GAE)/L and from 29.58 ± 1.08 to 54.17 ± 1.18 mg GAE/L. for C. costatus and C. socialis, respectively. Antioxidant activity was higher in C. costatus extracts, especially those obtained from nitrogen-deprived media. The results of this study contribute to the existing knowledge and the ongoing efforts to overcome application and commercialization barriers of microalgae for wide-ranging potential in different industries.

Golden Chanterelle or a Gold Mine? Metabolites from Aqueous Extracts of Golden Chanterelle (Cantharellus cibarius) and Their Antioxidant and Cytotoxic Activities.

Cantharellus cibarius, the golden chanterelle, is the second most-collected wild edible mushroom in Europe and very frequently harvested in Croatia. Wild mushrooms have been considered a healthy food since ancient times and are today highly valued for their beneficial nutritional as well as medicinal properties. Since golden chanterelle is added to different food products to improve their nutritive value, we studied the chemical profile of aqueous extracts of golden chanterelle (at 25 °C and 70 °C) and their antioxidant and cytotoxic activities. Malic acid, pyrogallol and oleic acid were some of the main compounds identified by GC-MS from derivatized extract. p-Hydroxybenzoic acid, protocatechuic acid and gallic acid were the most abundant phenolics quantitatively determined by HPLC, with somewhat higher amounts for samples extracted at 70 °C. Antioxidant activity was determined by ferric reducing antioxidant power assay and oxygen radical absorption method, and the highest results were recorded for golden chanterelle extracted at 70 °C, being 41.54 ± 1.54 and 38.72 ± 2.47 µM TE/L, respectively. Aqueous extract at 25 °C showed the better response against human breast adenocarcinoma MDA-MB-231 (IC50 = 375µg/mL). Our results confirm the beneficial effect of golden chanterelle even under aqueous extraction conditions and highlight its significance as a dietary supplement and in the development of new beverage products.

In the Beginning Was the Bud: Phytochemicals from Olive (Olea europaea L.) Vegetative Buds and Their Biological Properties.

Even though Olea europaea L. is one of the most important and well-studied crops in the world, embryonic parts of the plants remain largely understudied. In this study, comprehensive phytochemical profiling of olive vegetative buds of two Croatian cultivars, Lastovka and Oblica, was performed with an analysis of essential oils and methanol extracts as well as biological activities (antioxidant, antimicrobial, and cytotoxic activities). A total of 113 different volatiles were identified in essential oils with hydrocarbons accounting for up to 60.30% and (Z)-3-heptadecene being the most abundant compound. Oleacein, oleuropein, and 3-hydroxytyrosol had the highest concentrations of all phenolics in the bud extracts. Other major compounds belong to the chemical classes of sugars, fatty acids, and triterpenoid acids. Antioxidant, antimicrobial, and cytotoxic activities were determined for both cultivars. Apart from antioxidant activity, essential oils had a weak overall biological effect. The extract from cultivar Lastovka showed much better antioxidant activity than both isolates with both methods (with an oxygen radical absorbance capacity value of 1835.42 µM TE/g and DPPH IC50 of 0.274 mg/mL), as well as antimicrobial activity with the best results against Listeria monocytogenes. The human breast adenocarcinoma MDA-MB-231 cell line showed the best response for cultivar Lastovka bud extract (IC50 = 150 µg/mL) among three human cancer cell lines tested. These results demonstrate great chemical and biological potential that is hidden in olive buds and the need to increase research in the area of embryonic parts of plants.