Determination of hydroxytyrosol and tyrosol by liquid chromatography for the quality control of cosmetic products based on olive extracts

Hydroxytyrosol permeability comparisons and strategies to improve hydroxytyrosol stability in formulations

There has been a growing interest in hydroxytyrosol (HT) due to its powerful antioxidant and free-radical scavenging properties when added to formulations such as pharmaceuticals and cosmetics. To study the stability and transdermal properties of hydrogels and creams (HT-based formulations), a high-performance liquid chromatography method was developed for determining HT. In the Franz diffusion cell system, both hydrogel and cream show a rapid and similar penetration profile through the Bama miniature pig skin. However, the Strat-M® membrane exhibits slightly lower permeability and is selective to different formulations; that is, the cream has a permeability value of 10.69%, while the hydrogel has a value of 5.27%. The dynamics parameters from the permeation assays indicate that the model using the Strat-M® membrane can be used as a screening tool to evaluate the skin uptake and permeation efficacy of different formulations. Adding 3-O-ethyl-L-ascorbic acid to HT-based formulations can effectively prevent discoloration under prolonged high-temperature storage, while combining multiple antioxidants delays degradation most effectively. This study provides novel ideas for functional formulation optimization to enhance the realism and reproducibility of cosmetic products containing HT and provides scientific evidence for the production, packaging, shelf life, storage, and transportation of products.

Comparison among Different Green Extraction Methods of Polyphenolic Compounds from Exhausted Olive Oil Pomace and the Bioactivity of the Extracts

The use of by-products as a source of bioactive compounds with economic added value is one of the objectives of a circular economy. The olive oil industry is a source of olive pomace as a by-product. The olive pomace used in the present study was the exhausted olive pomace, which is the by-product generated from the air drying and subsequent hexane extraction of residual oil from the olive pomace. The objective was to extract bioactive compounds remaining in this by-product. Various types of green extraction were used in the present study: solvent extraction (water and hydroalcoholic); ultrasound-assisted extraction; Ultra-Turrax-assisted extraction; and enzyme-assisted extraction (cellulase; viscoenzyme). The phenolic profile of each extract was determined using HPLC-DAD and the total phenolic content (TPC) and antioxidant activity (ABTS, DPPH, and ORAC) were determined as well. The results showed significant differences in the yield of extraction among the different methods used, with the enzyme-assisted, with or without ultrasound, extraction presenting the highest values. The ultrasound-assisted hydroethanolic extraction (USAHE) was the method that resulted in the highest content of the identified phenolic compounds: 2.021 ± 0.29 mg hydroxytyrosol/100 mg extract, 0.987 ± 0.09 mg tyrosol/100 mg extract, and 0.121 ± 0.005 mg catechol/100 mg extract. The conventional extraction with water at 50 °C produced the best results for TPC and antioxidant activity of the extracts. The extracts from the USAHE were able to inhibit Gram-positive bacteria, especially Bacillus cereus, showing 67.2% inhibition at 3% extract concentration.

Hydroxytyrosol recovery from olive pomace: a simple process using olive mill industrial equipment and membrane technology

In this work, pilot-scale nanofiltration was used to obtain aqueous solutions rich in hydroxytyrosol and tyrosol from olive oil by-products. A large-scale simple process involving olive mill standard machinery (blender and decanter) was used for the olive pomace pre-treatment with water. The aqueous extract was then directly fed to a nanofiltration unit and concentrated by reverse osmosis. Final concentration factors ranged between 7 and 9 for hydroxytyrosol and between 4 and 7 for tyrosol. The final aqueous solution, obtained as retentate stream of reverse osmosis, was highly concentrated in hydroxytyrosol and tyrosol and their concentrations remained stable over at least 14 months.

An Efficient Prephenate Dehydrogenase Gene for the Biosynthesis of L-tyrosine: Gene Mining, Sequence Analysis, and Expression Optimization

L-tyrosine is a key precursor for synthesis of various functional substances, but the microbial production of L-tyrosine faces huge challenges. The development of new microbial chassis cell and gene resource is especially important for the biosynthesis of L-tyrosine. In this study, the optimal host strain Bacillus amyloliquefaciens HZ-12 was firstly selected by detecting the production capacity of L-tyrosine. Subsequently, the recombinant expression of 15 prephenate dehydrogenase genes led to the discovery of the best gene, Bao-tyrA from B. amyloliquefaciens HZ-12. After the overexpression of Bao-tyrA, the L-tyrosine yield of the recombinant strain HZ/P43-Bao-tyrA reach 411 mg/L, increased by 42% compared with the control strain (HZ/pHY300PLK). Moreover, the nucleic acid sequence and deduced amino acid sequence of the gene Bao-tyrA were analyzed, and their conservative sites and catalytic mechanisms were proposed. Finally, the expression of Bao-tyrA was regulated through a promoter and 5'-UTR sequence to obtain the optimal expression elements. Thereby, the maximum L-tyrosine yield of 475 mg/L was obtained from HZ/P43-UTR3-Bao-tyrA. B. amyloliquefaciens was applied for the first time to produce L-tyrosine, and the optimal prephenate dehydrogenase gene Bao-tyrA and corresponding expression elements were obtained. This study provides new microbial host and gene resource for the construction of efficient L-tyrosine chassis cells, and also lays a solid foundation for the production of various functional tyrosine derivatives.

Exploring Olive Pomace for Skincare Applications: A Review

The cosmetic industry is continuously searching for new active ingredients in an effort to attend to consumer demands which, in recent years, are focused on more natural and environmentally friendly products, obtained from sustainable resources. Nevertheless, they are required to provide cosmetologically appealing skincare products, ultimately with the purpose of improving skin appearance. The olive oil industry generates a large amount of liquid and semi-solid by-products such as olive pomace. Their phytotoxicity impairs safe disposal, so valorization strategies that promote by-product reuse are needed, which may include skincare products. Hydroxytyrosol is the main phenolic compound present in olive pomace and possesses biological effects that make it a desirable active compound for cosmetic formulations such as antioxidant and anti-aging activities as well as photoprotector, depigmenting, antimicrobial and anti-inflammatory actions. Other compounds present in olive pomace can also have functional properties and skin-related benefits. However, the application of this by-product can be a challenge in terms of formulation’s design, stability, and proven efficacy, so appropriate methodologies should be used to validate its incorporation and may include extraction and further encapsulation of bioactive compounds in order to achieve effective and aesthetic appealing skincare products.

Multi-modular engineering of Saccharomyces cerevisiae for high-titre production of tyrosol and salidroside

Tyrosol and its glycosylated product salidroside are important ingredients in pharmaceuticals, nutraceuticals and cosmetics. Despite the ability of Saccharomyces cerevisiae to naturally synthesize tyrosol, high yield from de novo synthesis remains a challenge. Here, we used metabolic engineering strategies to construct S. cerevisiae strains for high-level production of tyrosol and salidroside from glucose. First, tyrosol production was unlocked from feedback inhibition. Then, transketolase and ribose-5-phosphate ketol-isomerase were overexpressed to balance the supply of precursors. Next, chorismate synthase and chorismate mutase were overexpressed to maximize the aromatic amino acid flux towards tyrosol synthesis. Finally, the competing pathway was knocked out to further direct the carbon flux into tyrosol synthesis. Through a combination of these interventions, tyrosol titres reached 702.30 ± 0.41 mg l-1 in shake flasks, which were approximately 26-fold greater than that of the WT strain. RrU8GT33 from Rhodiola rosea was also applied to cells and maximized salidroside production from tyrosol in S. cerevisiae. Salidroside titres of 1575.45 ± 19.35 mg l-1 were accomplished in shake flasks. Furthermore, titres of 9.90 ± 0.06 g l-1 of tyrosol and 26.55 ± 0.43 g l-1 of salidroside were achieved in 5 l bioreactors, both are the highest titres reported to date. The synergistic engineering strategies presented in this study could be further applied to increase the production of high value-added aromatic compounds derived from the aromatic amino acid biosynthesis pathway in S. cerevisiae.

Efficacy of topical antioxidants in the skin hyperpigmentation control: A clinical study by reflectance confocal microscopy

BACKGROUND

Some in vitro studies have reported the potential of antioxidants for the reduction of melanogenesis. However, it is important to assess the clinical efficacy of these substances in reducing skin hyperpigmentation. Thus, the aim of this study was to evaluate the clinical efficacy of dermocosmetic formulations based on antioxidants using Reflectance confocal microscopy (RCM).

METHODS

Thirty-two healthy females aged 39-55 years were enrolled and divided into four groups: Vehicle (V), V with ascorbyl tetraisopalmitate (ATIP), V with Spirulina sp., and V with hydroxytyrosol-titrated olive extract. Imaging analyses by high-resolution methods and RCM were performed in the malar region of the face before and after a 42-day period of application of the studied formulations.

RESULTS

Reflectance confocal microscopy imaging analyses showed a significant reduction of number of hyperreflective pixels and basal layer brightness after 42 days of application of formulations containing the antioxidants compared to vehicle and baseline values, suggesting an improvement of the skin pigmentation pattern.

CONCLUSION

Reflectance confocal microscopy permitted the identification of skin hyperpigmentation and the assessment of the clinical efficacy of dermocosmetic formulations based on antioxidants in a noninvasive way. All formulations containing antioxidants significantly reduced skin hyperpigmentation after the period of application.

Antioxidant Effects of a Hydroxytyrosol-Based Pharmaceutical Formulation on Body Composition, Metabolic State, and Gene Expression: A Randomized Double-Blinded, Placebo-Controlled Crossover Trial

Hydroxytyrosol (HT) plays a significant role in cardiovascular disease (CVD) protection, and its metabolites are able to protect from the endothelial dysfunction commonly present in atherosclerosis. This randomized double-blinded, placebo-controlled crossover trial determined the effect in healthy volunteers of two gastroresistant capsules containing 15 mg/day of HT, for a 3-week period (HTT). Evaluation of nutritional status, serum metabolites, oxidative stress biomarkers, and gene expression of 9 genes related to oxidative stress, inflammation, and CVDs was performed. Oxidation biomarkers like thiol group (p = 0.001), total antioxidant status (TAS) (p = 0.001), superoxide dismutase 1 (SOD1) (2^-ΔΔCt = 3.7), and plasma concentration of HT (2.83 μg·mL^-1) were significantly increased, while nitrite (p = 0.001), nitrate (p = 0.001), and malondialdehyde (MDA) (p = 0.02) were drastically reduced after HTT. A significant reduction of body fat mass percentage (p = 0.01), suprailiac skinfold (p = 0.01), and weight (p = 0.04; Δ% = -0.46%) was observed after HTT. This study shows that regular intake of 15 mg/day of HT changed body composition parameters and modulated the antioxidant profile and the expression of inflammation and oxidative stress-related genes. However, it is advisable to personalize HT doses in order to exert its health benefits in CVD prevention and protection of LDL-C particles from oxidative damage. This trial is registered with ClinicalTrials.gov NCT01890070.

Optimization and validation of a rapid liquid chromatography method for determination of the main polyphenolic compounds in table olives and in olive paste

A high performance liquid chromatography method, coupled to diode-array and fluorescence detectors, with a previous solid-liquid extraction, has been developed for the simultaneous detection and quantification of polyphenolic compounds in table olives and in olive paste. The effects of extraction variables have been studied by response surface methodology. The best conditions were extraction with 100% methanol (2mM NaF) during 30min for table olives, and 91% methanol (2mM NaF) during 40min for olive paste. Chromatographic separation of 26 polyphenols from different families was optimized. This method provides high linearity, in all cases higher than 98.65%, and high sensitivity whose detection limits ranged between 0.08 and 1.11μg/mL. The validated method has been applied for the determination of polyphenols in table olive and olive paste samples. The intra-day and inter-day assay repeatability, in the analysis of real samples was less than 7.6 and 11%, respectively.