Guggulsterone - a potent bioactive phytosteroid: synthesis, structural modification, and its improved bioactivities

Guggulsterone is a phytosteroid derived from the oleo-gum resin of the critically endangered plant Commiphora wightii. This molecule has attracted increasing attention due to its excellent biochemistry potential and the compound has consequently been evaluated in clinical trials. With a low concentration in natural resources but wide medicinal and therapeutic value, chemists have developed several synthetic routes for guggulsterone starting from various steroid precursors. Moreover, numerous studies have attempted to modify its structure to improve the biological properties. Nowadays, green and sustainable chemistry has also attracted more attention for advanced chemical processes and reactions in steroid chemistry. The present review aimed to summarize the literature and provide an update about the improvements in the chemical synthesis and structural modification of guggulsterone from the view of green chemistry. Moreover, this review encompasses the improved activities of structurally modified guggulsterone derivatives. We expect that the information provided here will be useful to researchers working in this field and on this molecule.

Advances and Challenges in Plant Sterol Research: Fundamentals, Analysis, Applications and Production

Plant sterols (PS) are cholesterol-like terpenoids widely spread in the kingdom Plantae. Being the target of extensive research for more than a century, PS have topped with evidence of having beneficial effects in healthy subjects and applications in food, cosmetic and pharmaceutical industries. However, many gaps in several fields of PS's research still hinder their widespread practical applications. In fact, many of the mechanisms associated with PS supplementation and their health benefits are still not fully elucidated. Furthermore, compared to cholesterol data, many complex PS chemical structures still need to be fully characterized, especially in oxidized PS. On the other hand, PS molecules have also been the focus of structural modifications for applications in diverse areas, including not only the above-mentioned but also in e.g., drug delivery systems or alternative matrixes for functional foods and fats. All the identified drawbacks are also superimposed by the need of new PS sources and technologies for their isolation and purification, taking into account increased environmental and sustainability concerns. Accordingly, current and future trends in PS research warrant discussion.

Recent advances in the enzymatic synthesis of lipophilic antioxidant and antimicrobial compounds

Due to the increase in the consumption of highly processed food in developed countries, as well as, a growing number of foodborne diseases, exploration of new food additives is an issue focusing on scientific attention and industrial interest. Functional compounds with lipophilic properties are remarkably desirable due to the high susceptibility to the deterioration of lipid-rich food products. This paper in a comprehensive manner provides the current knowledge about the enzymatic synthesis of lipophilic components that could act as multifunctional food additives. The main goal of enzymatic lipophilization of compounds intentionally added to food is to make these substances soluble in lipids and/or to obtain environmentally friendly surfactants. Moreover, lipase-catalyzed syntheses could result in changes in the antioxidant and antimicrobial activities of phenolic compounds, carbohydrates, amino acids (oligopeptides), and carboxylic acids. The review describes also the implementation of a new trend in green chemistry, where apart from simple and uncomplicated chemical compounds, the modifications of multi-compound mixtures, such as phenolic extracts or essential oils have been carried out.

A comprehensive review on polarity, partitioning, and interactions of phenolic antioxidants at oil-water interface of food emulsions

There has been a growing interest in developing effective strategies to inhibit lipid oxidation in emulsified food products by utilization of natural phenolic antioxidants owing to their growing popularity over the past decades. However, due to the complexity of emulsified systems, the inhibition mechanism of phenolic antioxidants against lipid oxidation is rather complicated and not yet fully understood. In order to highlight the importance of polarity of phenolic antioxidants in emulsified systems according to the polar paradox, this review covers the recent progress on chemical, enzymatic, and chemoenzymatic lipophilization techniques used to modify the polarity of antioxidants. The partitioning behavior of phenolic antioxidants at the oil-water interface, which can be influenced by the presence of synthetic surfactants and/or antioxidant emulsifiers (e.g., polysaccharides, proteins, and phospholipids), is discussed. In addition, the emerging phenolic antioxidants among phenolic acids, flavonoids, tocopherols, and stilbenes applied in food emulsions are elaborated. As well, the interactions of polar-nonpolar antioxidants are stressed as a promising strategy to induce synergistic interactions at oil-water interface for improved oxidative stability of emulsions.

A review on chemical and physical modifications of phytosterols and their influence on bioavailability and safety

Phytosterols have been shown to lower cholesterol levels and to have antioxidant, anti-inflammatory and other biological activities. However, the high melting point and poor solubility limit their bioavailability and practical application. It is advantageous to modify phytosterols chemically and physically. This article reviews and discusses the chemical and physical modifications of phytosterols, as well as their effects on the bioavailability and possible toxicity in vivo. The current research on chemical modifications is mainly focused on esterification to increase the oil solubility and water solubility. For physical modifications (mainly microencapsulation), there are biopolymer-based, surfactant-based and lipid-based nanocarriers. Both chemical and physical modifications of phytosterols can effectively increase the absorption and bioavailability. The safety of modified phytosterols is also an important issue. Phytosterol esters are generally considered to be safe. However, phytosterol oxides, which may be produced during the synthesis of phytosterol esters, have shown toxicity in animal models. The toxicity of nanocarriers also needs further studies.

Phytochemical profile, aldose reductase inhibitory, and antioxidant activities of Indian traditional medicinal Coccinia grandis (L.) fruit extract

Coccinia grandis (L.) fruits (CGFs) are commonly used for culinary purposes and has several therapeutic applications in the Southeast Asia. The aim of this work was to evaluate phytochemical profile, aldose reductase inhibitory (ARI), and antioxidant activities of CGF extract. The CGFs were extracted with different solvents including petroleum ether, dichloromethane, acetone, methanol, and water. The highest yield of total extractable compounds (34.82%) and phenolic content (11.7 ± 0.43 mg of GAE/g dried extract) was found in methanol extract, whereas water extract showed the maximum content of total flavonoids (82.8 ± 7.8 mg QE/g dried extract). Gas chromatography-mass spectroscopy (GC-MS) analysis of methanol and water extract revealed the presence of flavonoids, phenolic compounds, alkaloids, and glycosides in the CGFs. Results of the in vitro ARI activity against partially purified bovine lens aldose reductase showed that methanol extract of CGFs exhibited 96.6% ARI activity at IC₅₀ value 6.12 µg/mL followed by water extract 89.1% with the IC₅₀ value 6.50 µg/mL. In addition, methanol and water extracts of CGF showed strong antioxidant activities including ABTS^*+ scavenging, DPPH* scavenging, and hydroxyl radical scavenging. Our results suggest that high percentage of both flavonoids and phenolic contents in the CGFs are correlated with the ARI and antioxidant activities. The fruits of C. grandis are thus potential bifunctional agents with ARI and antioxidant activities that can be used for the prevention and management of DM and associated diseases.

Investigation of the antioxidant and aldose reductase inhibitory activities of extracts from Peruvian tea plant infusions

In the present study, the antioxidant and aldose reductase inhibitory activities of 24 Peruvian infusion tea plants were investigated by 2,2'-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and aldose reductase assays. Phoradendron sp. showed the highest inhibition of aldose reductase (IC₅₀, 1.09±0.06μg/mL) and considerable antioxidant (IC₅₀ of DPPH, 58.36±1.65μg/mL; IC₅₀ of ABTS, 9.91±0.43μg/mL) effects. In order to identify the antioxidants and aldose reductase inhibitors of Phoradendron sp., DPPH-high performance liquid chromatography (HPLC) and ultrafiltration-HPLC assays were performed. Chlorogenic acid, 3,5-di-O-caffeoylquinic acid, and 1,3,5-tri-O-caffeoylquinic acid were identified as the antioxidants and aldose reductase inhibitors; apigenin was identified as the antioxidant. Finally, Phoradendron sp. and its aldose reductase inhibitors also showed a dose-dependent anti-inflammatory effect without cellular toxicity. These results suggested that Phoradendron sp. can be a potent functional food ingredient as an antioxidant, aldose reductase inhibitor and anti-inflammatory agent.

Synthesis and in vitro antioxidant and antimicrobial studies of novel structured phosphatidylcholines with phenolic acids

Novel phenoylated phosphatidylcholines were synthesized from 1,2-dipalmitoyl phosphatidylcholine/egg 1,2-diacyl phosphatidylcholine and phenolic acids such as ferulic, sinapic, vanillic and syringic acids. The structures of phenoylated phosphatidylcholines were confirmed by spectral analysis. 2-acyl-1-lyso phosphatidylcholine was synthesized from phosphatidylcholine via regioselective enzymatic hydrolysis and was reacted with hydroxyl protected phenolic acids to produce corresponding phenoylated phosphatidylcholines in 48-56% yields. Deprotection of protected phenoylated phosphatidylcholines resulted in phenoylated phosphatidylcholines in 87-94% yields. The prepared compounds were evaluated for their preliminary in vitro antimicrobial and antioxidant activities. Among the active derivatives, compound 1-(4-hydroxy-3,5-dimethoxy) cinnamoyl-2-acyl-sn-glycero-3-phosphocholine exhibited excellent antioxidant activity with EC₅₀ value of 16.43μg/mL. Compounds 1-(4-hydroxy-3-methoxy) cinnamoyl-2-acyl-sn-glycero-3-phosphocholine and 1-(4-hydroxy-3,5-dimethoxy) cinnamoyl-2-palmitoyl-sn-glycero-3-phosphocholine exhibited good antioxidant activity with EC₅₀ values of 36.05 and 33.35μg/mL respectively. Compound 1-(4-hydroxy-3-methoxy) cinnamoyl-2-palmitoyl-sn-glycero-3-phosphocholine exhibited good antibacterial activity against Klebsiella planticola with MIC of 15.6μg/mL and compound 1-(4-hydroxy-3-methoxy) benzoyl-2-acyl-sn-glycero-3-phosphocholine exhibited good antifungal activity against Candida albicans with MIC of 15.6μg/mL.

Identification of tyrosinase specific inhibitors from Xanthium strumarium fruit extract using ultrafiltration-high performance liquid chromatography

In this study, a strategy based on ultrafiltration-high performance liquid chromatography coupled with diode array detection (UF-HPLC-DAD) was proposed for screening tyrosinase specific inhibitors in Xanthii fructus. The false negatives were distinguished by optimizing the UF-HPLC-DAD parameters to reduce the background noise; the false positives were distinguished by introducing a blocked tyrosinase in the control group for comparison. To obtain the best blocker, the competitive experiments were performed using various known ligands. Using this strategy, three competitive inhibitors (protocatechuic acid; 3,5-di-O-caffeoylquinic acid; and 1,5-di-O-caffeoylquinic acid) and one mixed-type inhibitor (chlorogenic acid) were identified. These results were verified using tyrosinase inhibition assay, kinetic analysis, and structural simulation of the complex. Our experimental results suggest that the proposed strategy could be useful for high-throughput identification of tyrosinase specific inhibitors in natural products.