Major Sterol Research Articles

Role of Squalene Epoxidase Gene (SQE1) in the Response of the Lichen Lobaria pulmonaria to Temperature Stress.

Currently, due to the increasing impact of anthropogenic factors and changes in solar activity, the temperature on Earth is rising, posing a threat to biodiversity. Lichens are among the most sensitive organisms to climate change. Elevated ambient temperatures can have a significant impact on lichens, resulting in more frequent and intense drying events that can impede metabolic activity. It has been suggested that the possession of a diverse sterol composition may contribute to the tolerance of lichens to adverse temperatures and other biotic and abiotic stresses. The major sterol found in lichens is ergosterol (ERG); however, the regulation of the ERG biosynthetic pathway, specifically the step of epoxidation of squalene to 2,3-oxidosqualene catalyzed by squalene epoxidase during stress, has not been extensively studied. In this study, we used lichen Lobaria pulmonaria as a model species that is well known to be sensitive to air pollution and habitat loss. Using in silico analysis, we identified cDNAs encoding squalene epoxidase from L. pulmonaria, designating them as LpSQE1 for the mycobiont and SrSQE1 for the photobiont Symbiochloris reticulata. Our results showed that compared with a control kept at room temperature (+20 °C), mild temperatures (+4 °C and +30 °C) did not affect the physiology of L. pulmonaria, assessed by changes in membrane integrity, respiration rates, and PSII activity. An extreme negative temperature (-20 °C) noticeably inhibited respiration but did not affect membrane stability. In contrast, treating lichen with a high positive temperature (+40 °C) significantly reduced all physiological parameters. Quantitative PCR analysis revealed that exposing thalli to -20 °C, +4 °C, +30 °C, and +40 °C stimulated the expression levels of LpSQE1 and SrSQE1 and led to a significant upregulation of Hsps. These data provide new information regarding the roles of sterols and Hsps in the response of lichens to climate change.

In-Vitro Cytotoxic and Anti-Inflammatory Potential of Asparagus Densiflorus Meyeri and its Phytochemical Investigation.

Genus Asparagus is well known for its pharmacological activities and ethnopharmacological applications. In folk medicine, it is used in the management of several diseases such as diabetes, inflammations, and rheumatism. This work aimed to investigate the potential of Asparagus densiflorus meyeri root & aerial parts extracts as cytotoxic and anti-inflammatory and the investigation of their chemical profile. GC analysis & Folin-Ciocalteu and gravimetric methods were used respectively to estimate the lipoidal, phenolic, and saponin contents. MTT assay was conducted using two cell lines (MCF-7 & HepG2) to investigate the cytotoxic and anti-inflammatory activity using TNF-α stimulated MCF-7 cells through monitoring the level of nitric oxide release and NF-κB gene expression. Preliminary phytochemical investigation indicated that both extracted parts are equally rich in saponins, flavonoids, carbohydrates and/or glycosides, and sterols and/or triterpenes. Palmitic acid and β sitosterol represented the major saturated fatty acids and sterol, respectively. A significant cytotoxic activity against MCF-7 cells was recorded for DCM extract (IC50 26.13 μg/ml). All tested extracts showed a significant decrease in NO release and NF-κB gene expression thus it possesses a potential anti-inflammatory activity. A. densiflorus meyeri is considered a good candidate as a food supplement for protection from malignancy.

In vivo functional analysis of the cotton bollworm Helicoverpa armigera 24-dehydrocholesterol reductase (HaDHCR24) in phytosterol metabolism.

Insects have to obtain sterols from food due to the inability to synthesize this essential nutrient de novo. For lepidopteran insects, they can convert a variety of phytosterols into cholesterol to meet their growth needs. The final step of the cholesterol biosynthesis is the metabolism of desmosterol catalyzed by 24-dehydrocholesterol reductase (DHCR24). In this study, we identified a DHCR24 homolog in the cotton bollworm Helicoverpa armigera, designated as H. armigera 24-dehydrocholesterol reductase (HaDHCR24)-1. The quantitative expression analyses indicated that HaDHCR24-1 was highly enriched in the midgut where dietary sterol uptake occurs. Compared to the control, the DHCR24-1 mutant larvae generated by clustered regularly interspaced palindromic repeats (CRISPR) / CRISPR-associated nuclease 9 technology accumulated more desmosterol in the gut, while the content of cholesterol was significantly reduced. A similar phenomenon was observed when the DHCR24 inhibitor, amiodarone, was applied to the insects. Moreover, DHCR24-1 played an important role for the usage of β-sitosterol, a major sterol in plants, in H. armigera, and loss of function of DHCR24-1 resulted in higher mortality on β-sitosterol. However, the DHCR24 homolog does not necessarily exist in the genomes of all insects. The loss of this gene occurred more frequently in the insects feeding on animals, which further support the role of DHCR24-1 in using phytosterols. This gene may have important potential in developing new strategies to control herbivory pests in Lepidoptera and other insect orders.

Metabolic Profile of Leaves and Pulp of Passiflora caerulea L. (Bulgaria) and Their Biological Activities.

At present, there are no data in the scientific literature on studies aimed at characterizing Passiflora caerulea L. growing in Bulgaria. The present study aimed to investigate the metabolic profile and elemental composition of the leaves and pulp of this Passiflora, as well as to evaluate the antioxidant, antimicrobial and anti-inflammatory activities of its leaf and pulp extracts. The results showed that the pulp predominantly contained the essential amino acid histidine (7.81 mg g-1), while it was absent in the leaves, with the highest concentration being tryptophan (8.30 mg g-1). Of the fatty acids, palmitoleic acid predominated both in the pulp and in the leaves. A major sterol component was β-sitosterol. Fructose (7.50%) was the predominant sugar in the pulp, while for the leaves, it was glucose-1.51%. Seven elements were identified: sodium, potassium, iron, magnesium, manganese, copper and zinc. The highest concentrations of K and Mg were in the pulp (23,946 mg kg-1 and 1890 mg kg-1) and leaves (36,179 mg kg-1 and 5064 mg kg-1). According to the DPPH, FRAP and CUPRAC methods, the highest values for antioxidant activity were found in 70% ethanolic extracts of the leaves, while for the ABTS method, the highest value was found in 50% ethanolic extracts. In the pulp, for all four methods, the highest values were determined at 50% ethanolic extracts. Regarding the antibacterial activity, the 50% ethanolic leaf extracts were more effective against the Gram-positive bacteria. At the same time, the 70% ethanolic leaf extract was more effective against Gram-negative bacteria such as Salmonella enteritidis ATCC 13076. The leaf extracts exhibited higher anti-inflammatory activity than the extracts prepared from the pulp. The obtained results revealed that P. caerulea is a plant that can be successfully applied as an active ingredient in various nutritional supplements or cosmetic products.

Sterols of the aberrant plastid, Kareniacean dinoflagellate Asterodinium gracile: Chemotaxonomic overlap with amphisterol‐producing Amphidinium carterae

SUMMARYDinoflagellates have a rich history of characterization of their membrane‐reinforcing sterols because of a structural diversity and chemotaxonomic utility uncommon to other classes of algae. The Kareniaceae are no exception in that they produce sterols, often containing a Δ8(14) nuclear unsaturation, which are rare in most other dinoflagellate groups. A continuing goal of our laboratory is to examine the sterols of previously uncharacterized dinoflagellates to assess their sterol‐based chemotaxonomy compared to other members of the Dinophyceae. Asterodinium gracile, a member of the Kareniaceae, has not been commercially available for study until recently. To this end, our objective was to characterize the sterols of A. gracile to determine whether they match the 4α‐methyl‐substituted, Δ8(14)‐nuclear‐unsaturated sterols, such as (24R)‐4α‐methyl‐5α‐ergosta‐8(14),22‐dien‐3β‐ol (gymnodinosterol; C29:2) and 27‐nor‐(24R)‐4α‐methyl‐5α‐ergosta‐8(14),22‐dien‐3β‐ol (brevesterol; C28:2), of most species within the canonical genera Karenia, Karlodinium and Takayama, or instead the 4‐desmethyl sterols, such as 27‐nor‐(24R)‐23‐methyl‐ergosta‐8(14),22‐dien‐3β‐ol (C28:2), of its chemotaxonomically atypical, yet closest phylogenetic relative, Karenia papilionacea. We have observed A. gracile to produce two 4α‐methyl‐substituted sterols with the suggested structures of 4α‐methyl‐5α‐ergosta‐8(14)‐en‐3β‐ol (C29:1) and 4α‐methyl‐5α‐ergosta‐8(14),24(28)‐dien‐3β‐ol (amphisterol, C29:2), as major sterols amongst five other minor sterols, which included the common dinoflagellate sterol cholest‐5‐en‐3β‐ol (cholesterol, C27:1), but did not include gymnodinosterol or brevesterol (as in most canonical Kareniaceae) or 27‐nor‐(24R)‐23‐methyl‐ergosta‐8(14),22‐dien‐3β‐ol (as found in K. papilionacea). Detection of amphisterol and 4α‐methyl‐5α‐ergosta‐8(14)‐en‐3β‐ol is notable because they are sterols associated with some species of Amphidinium, such as Amphidinium carterae, and, to our knowledge, have not been observed in a member of the Kareniaceae before. Discovery of these major sterols in A. gracile expands our knowledge of the range of sterols produced by the Kareniaceae and indicates a shared chemotaxonomy with some species of Amphidinium.

Physicochemical Properties and Bioactive Compounds of Three Varieties of Melon (Cucumis melo) Seed Oils

The physicochemical composition of the oil extracted from three different melon seed varieties (named Uzbek-Russian, Soski, and Soski Green), which were collected from three various geographical parts of Iran (north, northeast, and center), was determined in 2021 and 2022. The macronutrient components, fatty acid profile, sterol compounds, phenolic compounds, tocopherols, and oxidative stability of the melon seed oils were determined. The oil content of melon seeds ranged from 43.3% to 47.3%. Linoleic (54.48% to 60.35%), oleic (24.35% to 28.03%), and palmitic acids (10.15% to 12.65%) were the predominant fatty acids. No significant differences were observed between the three cultivars and between the 2 years of the study in terms of macronutrient components and fatty acid profiles (p > 0.05). Twelve different phenolic compounds were identified, of which caffeic acid was the major compound, ranging from 39.74% ± 1.70% (Soski Green) to 63.45% ± 1.25% (Uzbek-Russian). The amounts of caffeic acid and oxidative stability of Uzbek‐Russian were significantly higher than those in the two other cultivars. β‐Sitosterol (approximately 60%) and γ‐tocopherol (71.6 to 84.07 mg/100 g) were the major sterol and tocopherol compounds, respectively. The results indicated that the physical and chemical specifications of the three investigated melon seed oils were stable for two consecutive years. Therefore, melon seed oil is a rich source of bioactive compounds and could be introduced as a healthy oil for human consumption.

Nutritional Potential of Ziziphus lotus (L.) Lam. Almonds as Compared to Some Oilseeds from Morocco: Evidence from Proximate Composition, Mineral Profiling, and Oil Physicochemical Traits

Nowadays, there is a great interest in the search for new sources of vegetable oils, natural bioactive compounds, and essential nutrients for human health. Oleaginous fruits and seeds are a good source of nutrients such as oil, carbohydrates, fatty acids, sterols, tocopherols, fibers, vitamins, minerals, and proteins for the human diet. The main objective of this study was to compare the nutritional composition of Ziziphus lotus almonds (ZLA) with some well‐known seeds (argan kernel, nigella seed, cactus seed, and sesame seed) and to classify them by the mean of principle component analysis (PCA). The samples’ proximate composition, mineral profiling, and some physicochemical parameters of extracted oil were evaluated. Our results revealed that ZLA composition was as follows: oil yield (26.99 ± 1.52 g/100 g), proteins (30.79 ± 0.07 g/100 g), ash (6.5 ± 0.06 g/100 g), and moisture (3.62 ± 0.10 g/100 g). The mineral profile of ZLA consists mainly of P, K, Mg, and Ca. The main fatty acids in ZLA oil were oleic acid (60.73 ± 0.10 g/100 g), linoleic acid (18.75 ± 0.10 g/100 g), and palmitic acid (9.86 ± 0.10 g/100 g). β‐Sitosterol (67.92 ± 0.46 g/100 g) was the major sterol in ZLA, followed by stigmasterol (15.34 ± 0.35%) and campesterol (8.75 ± 0.12%). Total tocopherols were present at 523 ± 9.23 mg/kg in the oil. PCA analysis demonstrated that the ZLA composition was found to be close to that of sesame seeds. In conclusion, ZLA could be considered an alternative source of vegetable oils and protein as well as other various applications.

LAMinar Flow: Sterol Transport in a Pathogenic Yeast.

Cryptococcus neoformans is an important fungal pathogen, responsible for over 140,000 deaths per year worldwide. Like other yeasts, C. neoformans relies on ergosterol as its major membrane sterol and carefully regulates its synthesis and distribution. Ergosterol is also targeted by two of the three compound classes currently used to treat cryptococcal infection. We recently reported the discovery and characterization in C. neoformans of a single retrograde ergosterol transporter of the LAM family, Ysp2. Here we review these findings and discuss directions for future research, including the connections between processes that are perturbed by the absence of Ysp2 (which also abrogates cryptococcal virulence) and possible roles for Ysp2 and other, as yet unknown, lipid transport proteins in this organism.

Comprehensive characterization of physicochemical, thermal, compositional, and sensory properties of cold-pressed rosehip seed oil

In this study, cold-pressed rosehip seed oil was fully characterized. Acidity and oxidation levels were near the limit values or slightly exceeded them and improvement in the storage conditions was suggested. The oil started to crystallize at -45.25 °C, and melt at -25.56 °C. Linoleic acid (51.1%), β-sitosterol (84.6%), γ-tocopherol (773.76 µg/g) and rosmarinic acid (31.38 µg/g) were determined as major fatty acid, sterol, tocopherol and phenolic compound, respectively. For the first time, aromatic volatile compounds and sensory descriptive terms were determined for cold-pressed rosehip seed oil. Sixty-seven volatile compounds were detected and L-limonene was found to be a major volatile compound. According to the sensory analysis, timber/kindling and raw vegetable tastes/aromas were found to be relatively dominant. Consequently, it is thought that rosehip seeds can be used as a raw material for edible and nutritionally-rich cold-pressed oil production and/or as source oil for functional food preparations.

Common origin of sterol biosynthesis points to a feeding strategy shift in Neoproterozoic animals

Steranes preserved in sedimentary rocks serve as molecular fossils, which are thought to record the expansion of eukaryote life through the Neoproterozoic Era ( ~ 1000-541 Ma). Scientists hypothesize that ancient C27 steranes originated from cholesterol, the major sterol produced by living red algae and animals. Similarly, C28 and C29 steranes are thought to be derived from the sterols of prehistoric fungi, green algae, and other microbial eukaryotes. However, recent work on annelid worms–an advanced group of eumetazoan animals–shows that they are also capable of producing C28 and C29 sterols. In this paper, we explore the evolutionary history of the 24-C sterol methyltransferase (smt) gene in animals, which is required to make C28+ sterols. We find evidence that the smt gene was vertically inherited through animals, suggesting early eumetazoans were capable of C28+ sterol synthesis. Our molecular clock of the animal smt gene demonstrates that its diversification coincides with the rise of C28 and C29 steranes in the Neoproterozoic. This study supports the hypothesis that early eumetazoans were capable of making C28+ sterols and that many animal lineages independently abandoned its biosynthesis around the end-Neoproterozoic, coinciding with the rise of abundant eukaryotic prey.

Quantitative data of up to thirty sterols in vegetable oils and fats

Sterols are known for a plethora of 250 different structures. Between 5 and 10% of them usually occur with varying abundance ratios (~ four orders of magnitude) and total amounts (0.4–1000 mg/100 g oil) in samples. Yet, quantitative data are mostly restricted to the few major sterols which are available as reference standards. Here, we developed a gas chromatography with mass spectrometry method operated in selected ion monitoring mode (GC/MS-SIM) that enabled the quantitation of 30 (silylated) sterols although only ten were available as reference standards. This could be obtained by studying the full-scan mass spectra of these ten sterol standards and 20 additional sterols measured in seven oils. In the next step, sterols were assigned to different groups. Values for quantification were then selected on the premise that response factors were constant within a sterol group. The deviation of the response factors within one sterol group was frequently below ± 10% and otherwise about ± 11–12%. Using mean response factors for all sterols, the novel GC/MS-SIM quantification method was superior to GC/FID which was exemplarily applied to two oils. Between eight and 21 of the 30 studied sterols and pentacyclic triterpenols were detected and quantified in 18 vegetable oils and two vegetable fats. The much higher number of sterols that could be quantified resulted in higher sterol amounts and the method and data may be useful for food authentication.

Effect of cultivar and environment on chemical composition and geographical traceability of Spanish olive oils

AbstractThis study aimed to investigate the influence of cultivar and environment on the chemical composition of Arbequina and Empeltre olive oils, and their contribution to geographical identification of olive oils from Aragon. A total of 260 olive oil samples from different cultivars (Arbequina, Empeltre, Royal de Calatayud, Alquezrana, and Royeta de Asque) from the three main oil‐producing areas of Aragon, located in northeast Spain, were selected. Fatty acid and sterol composition were analyzed in the course of three crop years (2017, 2018, and 2019). Cultivar was found the main factor influencing the variability of palmitic, palmitoleic, and linolenic fatty acid content, whereas geographic origin was the main contributor to variation in oleic and linoleic fatty acids in Arbequina and Empeltre olive oils. Cultivar also had a significant impact on sterol composition, although the effect of the production area also showed a significant effect on these oils. Crop year showed limited relevance, except for oleic and linoleic fatty acids. The interaction between the environment (e.g., crop year and geographical factors) and the cultivar (Arbequina and Empeltre) exerted a significant influence on oleic/linoleic (O/L) ratio and Δ7‐stigmastenol content, particularly in the southeast area of Aragon during the crop year with higher temperatures and drier conditions. Principal component analysis (PCA) and discriminant analysis (DA) confirmed the discriminative potential of the geographic production zone as a factor enabling the differentiation of olive oils from Aragon based on the major fatty acids and sterols.

Ergosterol distribution controls surface structure formation and fungal pathogenicity.

Ergosterol, the major sterol in fungal membranes, is critical for defining membrane fluidity and regulating cellular processes. Although ergosterol synthesis has been well defined in model yeast, little is known about sterol organization in the context of fungal pathogenesis. We identified a retrograde sterol transporter, Ysp2, in the opportunistic fungal pathogen Cryptococcus neoformans. We found that the lack of Ysp2 under host-mimicking conditions leads to abnormal accumulation of ergosterol at the plasma membrane, invagination of the plasma membrane, and malformation of the cell wall, which can be functionally rescued by inhibiting ergosterol synthesis with the antifungal drug fluconazole. We also observed that cells lacking Ysp2 mislocalize the cell surface protein Pma1 and have abnormally thin and permeable capsules. As a result of perturbed ergosterol distribution and its consequences, ysp2∆ cells cannot survive in physiologically relevant environments such as host phagocytes and are dramatically attenuated in virulence. These findings expand our knowledge of cryptococcal biology and underscore the importance of sterol homeostasis in fungal pathogenesis. IMPORTANCE Cryptococcus neoformans is an opportunistic fungal pathogen that kills over 100,000 people worldwide each year. Only three drugs are available to treat cryptococcosis, and these are variously limited by toxicity, availability, cost, and resistance. Ergosterol is the most abundant sterol in fungi and a key component in modulating membrane behavior. Two of the drugs used for cryptococcal infection, amphotericin B and fluconazole, target this lipid and its synthesis, highlighting its importance as a therapeutic target. We discovered a cryptococcal ergosterol transporter, Ysp2, and demonstrated its key roles in multiple aspects of cryptococcal biology and pathogenesis. These studies demonstrate the role of ergosterol homeostasis in C. neoformans virulence, deepen our understanding of a pathway with proven therapeutic importance, and open a new area of study.

Structural Characterization and Anti-Inflammatory Effects of 24-Methylcholesta-5(6), 22-Diene-3β-ol from the Cultured Marine Diatom Phaeodactylum tricornutum; Attenuate Inflammatory Signaling Pathways

In the present investigation, 24-methylcholesta-5(6), 22-diene-3β-ol (MCDO), a major phytosterol was isolated from the cultured marine diatom, Phaeodactylum tricornutum Bohlin, and in vitro and in vivo anti-inflammatory effects were determined. MCDO demonstrated very potent dose-dependent inhibitory effects on the production of nitric oxide (NO) and prostaglandin E2 (PGE2) against lipopolysaccharide (LPS)-induced RAW 264.7 cells with minimal cytotoxic effects. MCDO also demonstrated a strong and significant suppression of pro-inflammatory cytokines of interleukin-1β (IL-1β) production, but no substantial inhibitory effects were observed on the production of cytokines, including tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) at the tested concentrations against LPS treatment on RAW macrophages. Western blot assay confirmed the suppression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expressions against LPS-stimulated RAW 264.7 cells. In addition, MCDO was assessed for in vivo anti-inflammatory effects using the zebrafish model. MCDO acted as a potent inhibitor for reactive oxygen species (ROS) and NO levels with a protective effect against the oxidative stress induced by LPS in inflammatory zebrafish embryos. Collectively, MCDO isolated from the cultured marine diatom P. tricornutum exhibited profound anti-inflammatory effects both in vitro and in vivo, suggesting that this major sterol might be a potential treatment for inflammatory diseases.

PROXIMATE COMPOSITION OF WILD EDIBLE MUSHROOMS FROM THE BATAK MOUNTAIN, BULGARIA

Aim: The aim of the study was to be thoroughly examined the chemical and lipid composition of three species of wild edible mushrooms (Boletus pinophilus, Cantharellus cibarius and Craterellus cornucopioides) grown in Bulgaria as well as performing a principal component analysis in order to clarify specific relationships between the species and their nutritional compositions. Methods: Standard methods following the ISO procedures were used for determination of the components. Results: Moisture, crude fat, proteins, total carbohydrates, crude fibre and ash were determined in the examined mushroom species. Potassium and phosphorus were the essential elements in the mushrooms. Unsaturated fatty acids predominated in the lipid fraction of triacylglycerols, and oleic acid was the main one. Ergosterol was the major sterol in the lipid fraction of all mushrooms (42.4 – 72.8%). Phospholipid composition of the mushrooms differed, and phosphatidic acids were the main class in B. pinophilus and C. cibarius, while in C. cornucopioides all phospholipid classes were present in similar quantities. Fatty acid composition of the main phospholipid classes of the mushrooms was determined for the first time and was observed that saturated fatty acids (51.2 – 73.3%) predominated in all main phospholipids except in phosphatidic acids from C. cornucopioides, where unsaturated fatty acids prevailed (54.9%). Conclusion: Some key differences were observed in the chemical and lipid composition of the examined mushroom species but all of them were abundant in valuable fat-soluble biologically active components which made them suitable for possible application as food additives in many products and functional foods.

Phyto-chemical and bioactive compounds of pumpkin seed oil as affected by different extraction methods

Pumpkin (Cucurbita moschata Duch.) seeds of KH (Kashi Harit) cultivar were chosen for oil extraction by three different methods cold press extraction (CPE), soxhlet extraction (SE) and mechanical shaking extraction (MSE) method. SE method showed highest oil yield (38.03%) followed by CPE (33.25%) and MSE (26.36%) methods. Peroxide and acid value were found to be least in the CPE pumpkin seed oil (PSO) whereas oil stability index was highest in this oil. PSO is a good source of essential fatty acids as it contains significant amount (p < 0.05) of linoleic acid in the range of 44.38–44.47%. PSO also contains major sterols like campesterol, stigmasterol, β-sitosterol, ∆7,22,25-Stigmastratrienol, ∆7,25-Stigmastadienol, ∆5-Avenasterol, etc. CPE oil showed higher values for tocopherols (α, β, γ and δ) (4.01, 0.77, 12.51 and 6.42 mg/100 g, respectively), β-carotene (3.86 mg/kg), TPC (19.26 mg GAE/g), DPPH (46.35%) and squalene (352.63 mg/100 g). Thermal analysis of all oil samples revealed that no endothermic reaction occurred beyond 27.5 °C and remains at liquid state at room temperature. 1HNMR fingerprinting of PSO was carried out to determine the composition of major and minor oil constituents like mono and di-glycerides, aliphatic chains and fatty acids.

Sterol Composition of the Peridinin-Containing Dinoflagellate Gertia stigmatica, a Member of the Kareniaceae without a Canonical Haptophyte-Derived Plastid

Gertia stigmatica is a recently described member of the Kareniaceae with a peridinin-containing plastid rather than the aberrant, haptophyte-derived, tertiary plastid found in canonical Kareniaceae genera such as Karenia, Karlodinium, and Takayama. G. stigmatica provides a unique opportunity to compare biochemical traits, such as sterol composition, between these two fundamentally different types of Kareniaceae. To this point, canonical members of the Kareniaceae have been observed to typically produce a set of 4α-methyl-substituted, Δ8(14)-nuclear-unsaturated major sterols, such as (24R)-4α-methyl-5α-ergosta-8(14),22-dien-3β-ol (gymnodinosterol) and 27-nor-(24R)-4α-methyl-5α-ergosta-8(14),22-dien-3β-ol (brevesterol), which are very uncommon throughout other members of the class Dinophyceae. Our objective was to compare the sterols of G. stigmatica to canonical Kareniaceae to elucidate whether these same distinctive sterols are found, with our hypothesis being that they would because G. stigmatica is indeed a member of the Kareniaceae. Contrary to our hypothesis, G. stigmatica lacks gymnodinosterol and brevesterol, with its sterols instead dominated by 4-desmethyl sterols, such as cholesterol, 24-methylcholesta-5,22E-dien-3β-ol, and the unusual tri-unsaturated sterols ergosta-5,8(14),22E-trien-3β-ol and cholesta-5,8(14),22E-trien-3β-ol. No sterols were found to possess a 4α-methyl substituent or a single Δ8(14) nuclear unsaturation. Thus, G. stigmatica's sterol composition as a member of the Kareniaceae is atypical.

Extraction and Quantitation of Phytosterols from Edible Brown Seaweeds: Optimization, Validation, and Application.

Brown seaweeds are known as important marine food sources, from which phytosterols have been recognized as functional food components with multiple health-beneficial effects. However, studies on phytosterol extraction and quantitation from edible brown seaweeds are limited. In the present work, extraction methods for seaweed phytosterols were compared and optimized by one-factor-at-one-time method and response surface methodology. Moreover, the quantitation method of total sterols and major sterol components, including fucosterol, saringosterol, and ostreasterol, was established and validated using 1H NMR. Furthermore, the developed extraction and determination methods were applied to investigate three common edible seaweeds from Japan (Hijiki, Wakame, and Kombu). As a result, the finally optimized conditions were ultrasound-assisted extraction with CHCl3-MeOH 2:3 for 15 min followed by saponification with 1.65 mL of 1.85 M KOH for 14.5 h. Based on the developed methods, phytosterols in three seaweeds were compared, and Hijiki showed an abundant total sterol amount (2.601 ± 0.171 mg/g DW), significantly higher than Wakame (1.845 ± 0.137 mg/g DW) and Kombu (1.171 ± 0.243 mg/g DW). Notably, the composition of the sterol components varied in different seaweeds. These findings might help the nutritional investigation and functional food development concerning phytosterols from seaweeds.

Structural Role of Plasma Membrane Sterols in Osmotic Stress Tolerance of Yeast Saccharomyces cerevisiae.

Yeast S. cerevisiae has been shown to suppress a sterol biosynthesis as a response to hyperosmotic stress. In the case of sodium stress, the failure to suppress biosynthesis leads to an increase in cytosolic sodium. The major yeast sterol, ergosterol, is known to regulate functioning of plasma membrane proteins. Therefore, it has been suggested that the suppression of its biosynthesis is needed to adjust the activity of the plasma membrane sodium pumps and channels. However, as the sterol concentration is in the range of thirty to forty percent of total plasma membrane lipids, it is believed that its primary biological role is not regulatory but structural. Here we studied how lowering the sterol content affects the response of a lipid bilayer to an osmotic stress. In accordance with previous observations, we found that a decrease of the sterol fraction increases a water permeability of the liposomal membranes. Yet, we also found that sterol-free giant unilamellar vesicles reduced their volume during transient application of the hyperosmotic stress to a greater extent than the sterol-rich ones. Furthermore, our data suggest that lowering the sterol content in yeast cells allows the shrinkage to prevent the osmotic pressure-induced plasma membrane rupture. We also found that mutant yeast cells with the elevated level of sterol accumulated propidium iodide when exposed to mild hyperosmotic conditions followed by hypoosmotic stress. It is likely that the decrease in a plasma membrane sterol content stimulates a drop in cell volume under hyperosmotic stress, which is beneficial in the case of a subsequent hypo-osmotic one.

Allylamines, Benzylamines, and Fungal Cell Permeability: A Review of Mechanistic Effects and Usefulness against Fungal Pathogens.

Allylamines, naftifine and terbinafine, and the benzylamine, butenafine, are antifungal agents with activity on the fungal cell membrane. These synthetic compounds specifically inhibit squalene epoxidase, a key enzyme in fungal sterol biosynthesis. This results in a deficiency in ergosterol, a major fungal membrane sterol that regulates membrane fluidity, biogenesis, and functions, and whose damage results in increased membrane permeability and leakage of cellular components, ultimately leading to fungal cell death. With the fungal cell membrane being predominantly made up of lipids including sterols, these lipids have a vital role in the pathogenesis of fungal infections and the identification of improved therapies. This review will focus on the fungal cell membrane structure, activity of allylamines and benzylamines, and the mechanistic damage they cause to the membrane. Furthermore, pharmaceutical preparations and clinical uses of these drugs, mainly in dermatophyte infections, will be reviewed.