Effect of squalene on the structure and function of fungal membranes

From Sharks to Yeasts: Squalene in the Development of Vaccine Adjuvants

Squalene is a natural linear triterpene that can be found in high amounts in certain fish liver oils, especially from deep-sea sharks, and to a lesser extent in a wide variety of vegeTable oils. It is currently used for numerous vaccine and drug delivery emulsions due to its stability-enhancing properties and biocompatibility. Squalene-based vaccine adjuvants, such as MF59 (Novartis), AS03 (GlaxoSmithKline Biologicals), or AF03 (Sanofi) are included in seasonal vaccines against influenza viruses and are presently being considered for inclusion in several vaccines against SARS-CoV-2 and future pandemic threats. However, harvesting sharks for this purpose raises serious ecological concerns that the exceptional demand of the pandemic has exacerbated. In this line, the use of plants to obtain phytosqualene has been seen as a more sustainable alternative, yet the lower yields and the need for huge investments in infrastructures and equipment makes this solution economically ineffective. More recently, the enormous advances in the field of synthetic biology provided innovative approaches to make squalene production more sustainable, flexible, and cheaper by using genetically modified microbes to produce pharmaceutical-grade squalene. Here, we review the biological mechanisms by which squalene-based vaccine adjuvants boost the immune response, and further compare the existing sources of squalene and their environmental impact. We propose that genetically engineered microbes are a sustainable alternative to produce squalene at industrial scale, which are likely to become the sole source of pharmaceutical-grade squalene in the foreseeable future.

Antifungal Activity and Phytochemical Screening of Vernonia amygdalina Extract against Botrytis cinerea Causing Gray Mold Disease on Tomato Fruits

Gray mold disease caused by Botrytis cinerea is a damaging postharvest disease in tomato plants, and it is known to be a limiting factor in tomato production. This study aimed to evaluate antifungal activities of Vernonia amygdalina leaf extracts against B. cinerea and to screen the phytochemical compound in the crude extract that had the highest antifungal activity. In this study, crude extracts of hexane, dichloromethane, methanol, and water extracts with concentration levels at 100, 200, 300, 400, and 500 mg/mL were shown to significantly affect the inhibition of B. cinerea. Among the crude extracts, dichloromethane extract was shown to be the most potent in terms of antifungal activities. The SEM observation proved that the treatment altered the fungal morphology, which leads to fungal growth inhibition. For the in vivo bioassay, the fruits treated with dichloromethane extract at 400 and 500 mg/mL showed the lowest disease incidence with mild severity of infection. There were 23 chemical compounds identified in V. amygdalina dichloromethane extract using GCMS analysis. The top five major compounds were dominated by squalene (16.92%), phytol (15.05%), triacontane (11.31%), heptacosane (7.14%), and neophytadiene (6.28%). Some of these significant compounds possess high antifungal activities. This study proved that V. amygdalina from dichloromethane extract could be useful for inhibiting gray mold disease on tomato fruit and has potential as a natural antifungal agent.

Itraconazole versus terbinafine in the management of onychomycosis: an overview

Ever since the introduction of itraconazole and terbinafine in the management of onychomycosis, there has been a revival of interest in the latter. In order to comprehend the intricate emerging scenario, an endeavor has been made to form a distinct outline in the shape of an overview on several of their facets. The review, therefore, envisages forming and facilitating instant decision-making.

Squalene promotes the formation of non-bilayer structures in phospholipid model membranes

A study of the lipid polymorphism of aqueous dispersions of stearoyloleoylphosphatidylethanolamine and palmitoyloleoylphosphatidylchloline (95:5, mol/mol) in the presence of the hydrophobic molecule squalene, an intermediate in the biosynthesis of sterols, has been performed. With increasing concentration of squalene the main transition temperature was decreased from 29.8 degrees C for the pure phospholipid system to 28.1 degrees C for samples containing 5 mol% squalene without considerable changes in the phase transition enthalpy as detected by high precision differential scanning calorimetry. The structure of the phospholipid aggregates was determined by small- and wide-angle X-ray diffraction experiments showing only a minor increase of the lamellar repeat distance of the liquid-crystalline phase for the squalene containing samples. By far more pronounced was the effect of squalene on the lamellar-to-inverse-hexagonal phase transition, which was shifted from 64 degrees C to about 36 degrees C in the presence of 6 mol% squalene, thereby overlapping with the main transition. X-ray data showed that the size of the tubes of the inverse hexagonal phase are increasing linearly up to 6 mol% squalene. Experiments performed in the presence of 10 mol% squalene did not further change the phase behaviour, indicating the limiting partition of this hydrophobic molecule into the membrane. The high efficiency of squalene to promote the formation of the inverse hexagonal phase is discussed along the lines of argument based on the model of Kirk et al. (Kirk, G.L., Gruner, S.M. and Stein, D.E. (1984) Biochemistry 23, 1093-1102).