Oleuropein derivatives from olive fruit extracts reduce α-synuclein fibrillation and oligomer toxicity

Aggregation of α-synuclein (αSN) is implicated in neuronal degeneration in Parkinson's disease and has prompted searches for natural compounds inhibiting αSN aggregation and reducing its tendency to form toxic oligomers. Oil from the olive tree (Olea europaea L.) represents the main source of fat in the Mediterranean diet and contains variable levels of phenolic compounds, many structurally related to the compound oleuropein. Here, using αSN aggregation, fibrillation, size-exclusion chromatography–multiangle light scattering (SEC-MALS)-based assays, and toxicity assays, we systematically screened the fruit extracts of 15 different olive varieties to identify compounds that can inhibit αSN aggregation and oligomer toxicity and also have antioxidant activity. Polyphenol composition differed markedly among varieties. The variety with the most effective antioxidant and aggregation activities, Koroneiki, combined strong inhibition of αSN fibril nucleation and elongation with strong disaggregation activity on preformed fibrils and prevented the formation of toxic αSN oligomers. Fractionation of the Koroneiki extract identified oleuropein aglycone, hydroxyl oleuropein aglycone, and oleuropein as key compounds responsible for the differences in inhibition across the extracts. These phenolic compounds inhibited αSN amyloidogenesis by directing αSN monomers into small αSN oligomers with lower toxicity, thereby suppressing the subsequent fibril growth phase. Our results highlight the molecular consequences of differences in the level of effective phenolic compounds in different olive varieties, insights that have implications for long-term human health

Responses of Commercial Olive Cultivars (Olea europaea L.) to Cold Stress Using Electrolyte Leakage Method and Measuring Total Soluble Carbohydrate

Identification and characterization of tolerant and susceptible cultivars of crop plants to cold stress is important. In this regard, in present research electrolyte leakage and Total Soluble Sugar (TSS) contents in the leaf and bark tissues in ten olive cultivars, namely, Zard, Mari, Fadak87-1, Fadak87-5, Fadak86, Fadak77, Arbequina, Mission, Blady and Coratina were measured to assess their response to cold stress during two consecutive years. Two years-old shoots from five year-old olive trees were collected in summer and winter from a commercial orchard in Qom, Central Iran and exposed to cold treatments of 0, -4, -8, -12, -16 and -20°C for 24 hours. Then LT50 was measured by electrolyte leakage. A considerable increase in cold-hardiness was observed with decreasing temperature. Leaf and bark tissues exhibited more tolerance in winter than summer and bark tissue had more tolerance than leaf in both seasons. Also TSS contents in leaf and bark tissues were greater in winter than summer and in all studied cultivars bark tissue had greater TSS content than the leaf. Results showed that cold-hardy cultivars, Zard, Arbequina and Fadak87-5 (with tolerance thresholds of -17.34°C, -17.5°C and -17.99°C, respectively) had greater TSS contents in tissues in summer and winter compared to susceptible cultivars, Coratina and Mari (with tolerance thresholds of -7.18°C and -9.13°C respectively). Although the precise mechanism in response to cold stress has not been characterized in olive tree, it can be concluded from this experiment, that the tissue TSS content is closely associated with resistance to cold stress in this tree species

Effects of antimicrobial activity of silver nanoparticles on in vitro establishment of G × N15 (hybrid of almond × peach) rootstock

In the present investigation were evaluated the antifungal and antibacterial activities of Nano-silver (NS). Two separate experiments were done to evaluate the potential of silver nanoparticles in controlling the contamination of G × N15 micro-propagation. In the first experiment, a factorial experiment based on a completely randomized design with 15 treatments including five different NS concentrations (0, 50, 100, 150 and 200 ppm) and three soaking time of explants (3, 5 and 7 min) with five replications was conducted. In the other experiment, NS was added to Murashige and Skoog (MS) medium with concentrations of 0, 50, 100, 150 and 200 ppm in a completely randomized design. Results showed that the application of 100 and 150 ppm NS both as an immersion and as added directly to the culture medium significantly reduces internal and external contaminations compared with the control group. Using NS in culture medium was more efficient to reduce fungal and bacterial contamination than immersion. High concentrations of NS had an adverse effect on the viability of G × N15 single nodes and this effect was more serious in immersed explants in NS than directly added NS ones regarding the viability of buds and plantlet regeneration. In conclusion, due to high contamination of woody plants especially fruit trees and also adverse environmental effects of mercury chloride, the NS solution can be used as a low risk bactericide in micro-propagation of G × N15 and can be an appropriate alternative to mercury chloride in the future