Evaluation of the Behavior of Phenolic Compounds and Steviol Glycosides of Sonicated Strawberry Juice Sweetened with Stevia (Stevia rebaudiana Bertoni)

Biological activity and structural modification of isosteviol over the past 15 years

Isosteviol is a tetracyclic diterpenoid obtained by hydrolysis of stevioside. Due to its unique molecular skeleton and extensive pharmacological activities, isosteviol has attracted more and more attention from researchers. This review summarized the structural modification, pharmacological activity and microbial transformation of isosteviol from 04/2008 to 10/2023. In addition, the research history, structural characterization, and pharmacokinetics of isosteviol were also briefly reviewed. This review aims to provide useful literature resources and inspirations for the exploration of diterpenoid drugs.

Optimization and In Vitro Digestion of a Guava (Psidium guajava), Mamey (Pouteria sapota) and Stevia (Stevia rebaudiana) Functional Beverage

Guava and mamey are phenolic- and carotenoid-rich fruits with potential health benefits, but are minimally used as ingredients in functional beverages. The objectives of the present work are to optimize the content of guava and mamey pulps and a stevia solution in the formulation of a functional beverage with high content of bioactive compounds and sensory acceptability using a mixture design analysis, and to analyze its composition after in vitro digestion. The optimized formulation (17.77 and 19.23 g of guava and mamey pulps, respectively; 1% stevia solution) yielded a beverage with 418.21 mg gallic acid equivalents (GAE)/100 mL and 0.20 mg β-carotene/100 mL, and an antioxidant capacity of 213.58, 78.90 and 234.03 mg Trolox equivalents (TE)/100 mL using three methodologies. The mathematical model developed was significant (p < 0.05), according to R2 values between 0.70 and 0.75. α- and β-carotene were quantified during the oral phase of in vitro digestion. Gallic, p-coumaric, ferulic and chlorogenic acids were also identified. The beverage had a general acceptability of 6.72. We conclude that the mathematical model developed was a good predictor of the experimental data and that the optimized beverage contained high bioactive concentrations (phenolics and carotenoids) and was well-accepted by potential consumers.

Antioxidant Activity of Leaf Extracts from Stevia rebaudiana Bertoni Exerts Attenuating Effect on Diseased Experimental Rats: A Systematic Review and Meta-Analysis

Stevia (Stevia rebaudiana Bertoni) is an aromatic plant known for its high sweetening power ascribed to its glycosides. Stevia also contains several bioactive compounds showing antioxidant, antiproliferative, antimicrobial, and anti-inflammatory activities. Since inflammation and oxidative stress play critical roles in the pathogenesis of many diseases, stevia emerges as a promising natural product that could support human health. In this study we set out to investigate the way stevia affects oxidative stress markers (e.g., SOD, CAT, GPx, GSH, MDA) in diseased rats administered stevia leaf extracts or glycosides. To this end, we performed an inclusive literature search, following PRISMA guidelines, and recruited multivariate meta-analysis and meta-regression to synthesize all available data on experimental animal models encountering (a) healthy, (b) diseased, and (c) stevia-treated diseased rats. From the 184 articles initially retrieved, 24 satisfied the eligibility criteria, containing 104 studies. Our results demonstrate that regardless of the assay employed, stevia leaf extracts restored all oxidative stress markers to a higher extent compared to pure glycosides. Meta-regression analysis revealed that results from SOD, CAT, GSH, and TAC assays are not statistically significantly different (p = 0.184) and can be combined in meta-analysis. Organic extracts from stevia leaves showed more robust antioxidant properties compared to aqueous or hydroalcoholic ones. The restoration of oxidative markers ranged from 65% to 85% and was exhibited in all tested tissues. Rats with diabetes mellitus were found to have the highest restorative response to stevia leaf extract administration. Our results suggest that stevia leaf extract can act protectively against various diseases through its antioxidant properties. However, which of each of the multitude of stevia compounds contribute to this effect, and to what extent, awaits further investigation.

Steviol Glycosides from Stevia rebaudiana: An Updated Overview of Their Sweetening Activity, Pharmacological Properties, and Safety Aspects

This literature-based review synthesizes the available scientific information about steviol glycosides as natural sweeteners and molecules with therapeutic potential. In addition, it discusses the safety concerns regarding human consumption. Steviol glycosides exhibit a superior sweetener proficiency to that of sucrose and are noncaloric, noncariogenic, and nonfermentative. Scientific evidence encourages stevioside and rebaudioside A as sweetener alternatives to sucrose and supports their use based on their absences of harmful effects on human health. Moreover, these active compounds isolated from Stevia rebaudiana possess interesting medicinal activities, including antidiabetic, antihypertensive, anti-inflammatory, antioxidant, anticancer, and antidiarrheal activity. The described bioactivities of steviol glycosides deserve special attention based on their dose dependence and specific pathological situations. Further clinical research is needed to understand underlying mechanisms of action, therapeutic indexes, and pharmacological applications.

Application of Ultrasound as Clean Technology for Extraction of Specialized Metabolites From Stinging Nettle (Urtica dioica L.)

Nettle is a highly valued medicinal plant that is still largely neglected, both in terms of nutrition and use for pharmacological purposes. Tinctures, i.e., alcoholic extracts, are becoming increasingly popular nettle products, mainly because they allow better availability of phytochemicals and their stability over a longer period of time. The production of alcoholic extracts is a chemically demanding process that is still usually carried out using conventional techniques, which have numerous drawbacks. The use of green technologies such as ultrasound-assisted extraction (UAE), which is characterized by high efficiency of phytochemical extraction, shorter treatment time, and a much lower environmental footprint, is a suitable and sustainable solution. Therefore, the aim of this study is to determine the influence of the extraction method, conventional and ultrasound (by varying two ultrasound equipment systems), time and ethanol concentration on the extraction of specialized metabolites from nettle powder. Ultrasonic extraction using a probe system significantly contributed to increase the ascorbic acid yield, polyphenolic compounds, and antioxidant capacity of nettle extracts compared to conventional extraction. In addition, when a probe system was used during UAE, significantly less time was required for isolation of individual specialized metabolites compared to ultrasonic extraction in the bath. Ethanol concentration (50 and 80% v/v) also proved to be an important factor in the efficiency of extraction of specialized metabolites, with 80% ethanol being more effective for the isolation of ascorbic acid and pigment compounds (chlorophyll and carotenoids), while 50% v/v for the extraction of polyphenolic compounds. It can be concluded that extraction with the ultrasonic probe system is much more efficient in obtaining higher yields of specialized metabolites from nettle powder in a shorter time (average process duration 5-10 min) both compared to UAE in the bath and classical extraction. However, optimization of the key factors of time, solvent type, and ultrasonic power is necessary to maintain the nutritional quality of the nettle extract in order to obtain a final product with a high specialized metabolites content, antioxidant capacity, and functional value. The future application of alcoholic nettle extracts is based on the fact that these products have significant potential as functional foods and pharmacological preparations for the treatment of a number of but also to strengthen the immune system, mainly due to the rich nutritional composition and high content of various specialized metabolites. The prepared extracts can be safely taken orally by diluting the tinctures with water immediately before ingestion.

Ultrasound as a Promising Tool for the Green Extraction of Specialized Metabolites from Some Culinary Spices

Spices are a popular food of plant origin, rich in various phytochemicals and recognized for their numerous properties. The aim of the study was to evaluate the antioxidant and antimicrobial activity, as well as the content of specialized metabolites, of aqueous extracts of three spice species--garlic (Allium sativum L.), ginger (Zingiber officinalle L.) and turmeric (Curcuma longa L.)--prepared by green extraction methods. Ultrasound treatment increased the chromaticity parameter b value of turmeric and ginger extracts, thus indicating a higher yellow color predominantly due to curcuminoids characteristic of these species. Ultrasound-assisted extraction significantly increased the content of total soluble solids, phenolic compounds, total carotenoids and vitamin C. The temperature of the system was also an important factor, with the highest (70 °C) conditions in ultrasound-assisted extraction having a positive effect on thermolabile compounds (vitamin C, phenolics, total carotenoids). For example, turmeric extract treated with ultrasound at 70 °C had up to a 67% higher vitamin C content and a 69.4% higher total carotenoid content compared to samples treated conventionally at the same temperature, while ginger extracts had up to 40% higher total phenols. All different concentrations of spice extracts were not sufficient for complete inhibition of pathogenic bacterial strains of Salmonella, L. monocytogenes and S. aureus; however, only garlic extracts had an effect on slowing down the growth and number of L. monocytogenes colonies. Spice extracts obtained by ultrasonic treatment contained a significantly higher level of bioactive compounds and antioxidant capacity, suggesting that the extracts obtained have significant nutritional potential and thus a significant possibility for phytotherapeutic uses.

Two Cosmetic Properties of an Ethanol Extract of a Cultured and Edible Red Macroalga, Bangia fuscopurpurea: Moisturizing and Whitening Effects

Previous studies have focused on the role of a cultured red macroalga Bangia fuscopurpurea as a functional food; however, except for antioxidant activity, there are no reports directly regarding the potential cosmetic properties of this alga. Our present study explored the moisturizing effect of its ethanol extract (BFH1) and used the tyrosinase activity inhibition assay to evaluate its in vitro whitening effect. The in vitro moisture-retention ability of BFH1 was similar to that of glycerol (positive control), but its moisture-absorption ability was significantly higher. The overall in vivo moisturizing effect of topical application of BFH1 in mice was similar to that of glycerol, but BFH1 did not cause significant changes in the oil content of the skin, and there were no obvious side effects regarding skin appearance and external behavior during treatment. BFH1 exerted in vitro tyrosinase inhibitory activity with a half-maximal inhibitory concentration (IC50) of 48.3 μg/mL (IC50 of positive control, vitamin C: 19.6 μg/mL). The total phenolic content of BFH1 was determined as 10.8 % ± 0.07 %. Thus, BFH1 has high potential to be turned into a cosmetic ingredient with moisturizing and whitening effects.