Physicochemical properties and antimicrobial activity of Roselle (Hibiscus sabdariffa L.)

Phytochemical and antibacterial properties of calyces Hibiscus sabdariffa L.: an in vitro and in silico multitarget-mediated antibacterial study

BACKGROUND

Multidrug-resistant (MDR) bacteria pose a significant threat to human health worldwide by increasing the harmful impact of traditional synthetic antibiotics. Traditional medicinal plants have bioactive metabolites that can significantly modulate the growth rate, cell survival, and pathogenicity of antibiotic-resistant bacteria. Hibiscus sabdariffa L., known as Roselle or Karkade, belongs to the Malvaceae family. It is well-known for its edible aromatic red/purple calyces and is extensively utilized in the food industry and pharmacological applications. H. sabdariffa calyx bioactive phytocompounds have potent therapeutic activities such as antimicrobial, antidiabetic, antiobesity, antioxidant, anti-inflammatory, and anticancer properties.

METHODS

This study utilized gas chromatography-mass spectrometry (GC-MS) analysis to determine the volatile aromatic compounds that found in the hydroethanolic extract of Hibiscus sabdariffa calyces. The purpose was to verify the antibacterial properties of Roselle calyces against selective MDR clinical bacterial isolates, including A. baumanii, E. coli, K. pneumoniae, and P. aeruginosa.

RESULTS

The GC-MS spectrum profile revealed the presence of twenty-seven volatile organic components, including organic fatty acid derivatives, ester compounds, sugar derivatives, and terpene components. The major GC-MS fractionations and the main active chemical compositions of the hydroethanolic extract of H. sabdariffa flowers were (E)-10-Octadecenoic acid methyl ester (59.23%), 8,11-Octadecadienoic acid, methyl ester (11.51%), Butanedioic acid, 3-hydroxy-2,2-dimethyl-, diethyl ester (6.22%), Diethyl succinate/Butanedioic acid, diethyl ester (2.35%), and Heptadecanoic acid, 16-methyl-, methyl ester/Methyl isostearate (2.31%). The hydroethanolic extract of H. sabdariffa dried calyces demonstrated potent antibacterial properties (zones diameter of inhibition growth, MIC, MBC, and MBC/MIC) against selective MDR clinical bacterial isolates, such as A. baumanii, E. coli, K. pneumoniae, and P. aeruginosa, as determined by the phytochemical screening (TAC, TFC, and TPC) and antioxidant activity (DPPH). The surface morphological characteristics of the treated A. baumanii, E. coli, K. pneumoniae, and P. aeruginosa clinical isolates have been affected in comparison to the untreated forms by the hydroethanolic extract of H. sabdariffa calyces, as determined by scanning electron microscopy (SEM). In silico predictive investigation revealed that the volatile aromatic components of the hydroethanolic extract of Roselle calyces exhibited significant scoring functions, binding affinities, and non-covalent intermolecular interactions with the MenB lyase and DNA gyrase targets of E. coli. These interactions significantly enhanced the activities of the volatile aromatic components against the bacterial pathogenicity, cell survival, growth, and differentiation of selective MDR clinical bacterial isolates.

CONCLUSIONS

According to the in vitro and in silico findings, the hydroethanolic extract of H. sabdariffa calyces has shown potentials as an effective antioxidant and antibacterial treatment. It contains volatile aromatic compounds that can modulate selective MDR Gram-negative clinical bacterial isolates.

Natural pigments: innovative extraction technologies and their potential application in health and food industries

Natural pigments, or natural colorants, are frequently utilized in the food industry due to their diverse functional and nutritional attributes. Beyond their color properties, these pigments possess several biological activities, including antioxidant, anti-inflammatory, anticancer, antibacterial, and neuroprotective effects, as well as benefits for eye health. This review aims to provide a timely overview of the potential of natural pigments in the pharmaceutical, medical, and food industries. Special emphasis is placed on emerging technologies for natural pigment extraction (thermal technologies, non-thermal technologies, and supercritical fluid extraction), their pharmacological effects, and their potential application in intelligent food packaging and as food colorants. Natural pigments show several pharmaceutical prospects. For example, delphinidin (30 µM) significantly inhibited the growth of three cancer cell lines (B16-F10, EO771, and RM1) by at least 90% after 48 h. Furthermore, as an antioxidant agent, fucoxanthin at the highest concentration (50 μg/mL) significantly increased the ratio of glutathione to glutathione disulfide (p < 0.05). In the food industry, natural pigments have been used to improve the nutritional value of food without significantly altering the sensory experience. Moreover, the use of natural pH-sensitive pigments as food freshness indicators in intelligent food packaging is a cutting-edge technological advancement. This innovation could provide useful information to consumers, increase shelf life, and assist in evaluating the quality of packaged food by observing color variations over time. However, the use of natural pigments presents certain challenges, particularly regarding their stability and higher production costs compared to synthetic pigments. This situation underscores the need for further investigation into alternative pigment sources and improved stabilization methods. The instability of these natural pigments emphasizes their tendency to degrade and change color when exposed to various external conditions, including light, oxygen, temperature fluctuations, pH levels, and interactions with other substances in the food matrix.

Microbiological Characteristics of Beef Sausage Enriched With Roselle (Hibiscus sabdariffa L.) Sepal Extract

Adding plant extracts to sausage and other meat products is very important to improve their quality, safety, and durability. The aim of this study was to evaluate the microbiological properties of beef sausage enriched with roselle (Hibiscus sabdariffa L.) sepal extract. The total content of phenolic and flavonoid compounds in hydroalcoholic extract of Roselle sepals was measured by Folin-Ciocalteu test and aluminum chloride colorimetric method, and antioxidant activity was measured by DPPH method. Pectin was used to encapsulate the extract. The characteristics of capsules, including particle size, zeta potential, and capsule efficiency were measured. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of extracts were performed by tube dilution method. Microbial tests were performed on sausage treatment samples. Analysis of the obtained data was done using SPSS and Excel software. The study revealed that the total phenolic and flavonoid compounds in the extract were 174.6 mg of gallic acid per gram and 16.8368 mg of quercetin, respectively. The extract displayed the highest antioxidant activity at elevated concentrations. Particle size ranged from 16.833 to 640.534 μm. The zeta potential and capsule efficiency were found to be satisfactory. Compared to the encapsulated extract, the free roselle extract better inhibited Staphylococcus aureus (s. aureus), Salmonella typhimurium (S. typhimurium), and Escherichia coli (E.coli). During storage until day 20, these bacteria did not grow in the free or encapsulated extract groups. However, S. aureus appeared in the free extract group from day 25 and the encapsulated extract group from day 20. Roselle extract has antimicrobial properties that can improve the quality and safety of beef sausage during storage.

Determination of anthocyanins, organic acids, and phenolic acids in hibiscus market products using LC/UV/MS

Hibiscus sabdariffa has gained increasing attention from consumers as a natural, healthy food ingredient, leading to a myriad of available products, yet there is a lack of understanding of the quality and chemical diversity among commercially available hibiscus products. Here, we conducted a survey on the chemistry of 29 hibiscus products (calyces, beverages, and extracts). UHPLC-DAD and UHPLC-QQQ/MS methods with high sensitivity and selectivity were developed to evaluate the chemical profiles pertaining to the sensory attributes (color and taste). Two major anthocyanins (delphinidin-3-sambubioside and cyanindin-3-sambubioside), eight organic acids, and 23 phenolic acids were identified and quantified in hibiscus market products. The results showed that hibiscus samples contained < 0.001-2.372% of total anthocyanins, 0.073-78.002% of total organic acids, and 0.001-1.041% of total phenolic acids, and demonstrated significant variations in market products. This is the first time that an in-depth organic acid profiling was conducted on hibiscus products using UHPLC-QQQ/MS. This method can also be extended to chemical profiling, sensory analysis, quality control, authentication, and standardization of other natural products.

Exploring Plants with Flowers: From Therapeutic Nutritional Benefits to Innovative Sustainable Uses

Flowers have played a significant role in society, focusing on their aesthetic value rather than their food potential. This study's goal was to look into flowering plants for everything from health benefits to other possible applications. This review presents detailed information on 119 species of flowers with agri-food and health relevance. Data were collected on their family, species, common name, commonly used plant part, bioremediation applications, main chemical compounds, medicinal and gastronomic uses, and concentration of bioactive compounds such as carotenoids and phenolic compounds. In this respect, 87% of the floral species studied contain some toxic compounds, sometimes making them inedible, but specific molecules from these species have been used in medicine. Seventy-six percent can be consumed in low doses by infusion. In addition, 97% of the species studied are reported to have medicinal uses (32% immune system), and 63% could be used in the bioremediation of contaminated environments. Significantly, more than 50% of the species were only analysed for total concentrations of carotenoids and phenolic compounds, indicating a significant gap in identifying specific molecules of these bioactive compounds. These potential sources of bioactive compounds could transform the health and nutraceutical industries, offering innovative approaches to combat oxidative stress and promote optimal well-being.

In vitro antioxidative activity of Fritillaria cirrhosa D. Don straw ethanolic extract and its effect on lipid, protein oxidation, and quality of Chinese-style sausage

Fritillaria cirrhosa D. Don, which can be used for medicine and food, contains a variety of chemicals including polyphenols, alkaloids, terpenoid, and others that have beneficial biological properties like antihypertension, bacteriostasis, and anti-inflammatory. The ethanolic extract of Fritillaria straw was obtained for this study using ultrasonic-aided extraction, and the amounts of total phenols and total flavonoids were 26.56 ± 1.36 mg GAE/g dw and 18.75 ± 0.80 mg RE/g dw, respectively. Ultra-performance liquid chromatography-quadrupole time-of-flight-mass spectrometry technology was utilized to identify 50 major chemicals in the Fritillaria straw extract (FSE). Meanwhile, the antioxidative activities of FSE were evaluated by 2,2-diphenyl-1-picrylhydrazyl, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and Ferric reducing antioxidant power assays in vitro, which pointed out the antioxidative potential of FSE. Additionally, 0.1%, 0.5%, and 1% of FSE and 0.02% butylated hydroxyanisole (BHA) + butylated hydroxytoluene (BHT) (1:1) were separately added to Chinese-style sausage to study their effects on the lipid oxidation, protein oxidation, and quality of the sausage at different storage times. The study found that the effect of adding 1% FSE on carbonyl content, total volatile basic nitrogen, and TVC of sausage could achieve the effect of the 0.02% BHA + BHT (1:1) group on the 35th day, and the thiobarbituric acid reactive substances value and peroxide value of sausage were significantly lower than the control group. Therefore, as one of the candidates to replace synthetic antioxidants, the FSE can be used in the production of Chinese sausages, which has a positive effect on improving the product's quality and extending the shelf life. PRACTICAL APPLICATION: The antioxidative activities of 50 main compounds were identified after the ethanolic extraction of Fritillaria straw. This Fritillaria straw extract was added to Chinese sausage, effectively inhibiting the oxidation of lipids and proteins as well as the decomposition of proteins. Obviously, the Fritillaria straw extract, one of the choices to replace synthetic antioxidants, may be useful for future meat processing, because of its positive impact on the product's quality and shelf life.

Impact of Processing and Physicochemical Parameter on Hibiscus sabdariffa Calyxes Biomolecules and Antioxidant Activity: From Powder Production to Reconstitution

Hibiscus sabdariffa is a tropical plant with red calyxes whose anthocyanins, phenols, and antioxidant activity make it attractive to consumers both from a nutritional and medicinal standpoint. Its seasonality, perishability, and anthocyanin instability, led to the setup of stabilization methods comprising drying and powdering. However, its properties can often be altered during these stabilization processes. Treatments such as dehumidified-air-drying, infrared drying, and oven-drying, and their combination showed better quality preservation. Moreover, powder production enables superior biomolecule extractability which can be linked to a higher bioaccessibility. However, the required temperatures for powder production increase the bioactive molecules degradation leading to their antioxidant activity loss. To overcome this issue, ambient or cryogenic grinding could be an excellent method to improve the biomolecule bioavailability and accessibility if the processing steps are well mastered. To be sure to benefit from the final nutritional quality of the powder, such as the antioxidant activity of biomolecules, powders have to offer excellent reconstitutability which is linked to powder physicochemical properties and the reconstitution media. Typically, the finest powder granulometry and using an agitated low-temperature reconstitution media allow for improving anthocyanin extractability and stability. In this review, the relevant physicochemical and processing parameters influencing plant powder features from processing transformation to reconstitution will be presented with a focus on bioactive molecules and antioxidant activity preservation.

Physicochemical characteristics, antioxidant potential, and shelf stability of developed roselle-fig fruit bar

Fruit bars are prepared by combining different ingredients which are wholesome and nutrient rich. The current study was designed to develop roselle-fig (different proportions) fruit bars and further investigate their physicochemical characteristics and antioxidant potential. Moreover, the prepared fruit bars were scrutinized for microbial and sensory characteristics to assess the appropriateness of ingredients during storage (up to 90 days). It was observed that there was gradual increase in moisture content with the passage of time, while ash, fat, fiber, and protein contents did not change significantly during storage. The pH and total soluble solid contents of these fruit bars during storage were 3.54-4.07 and 1.71-1.86 Brix, respectively. According to the mean values for sensory evaluation, T ₂ was preferred over other treatments. The bars received an acceptable sensory evaluation, demonstrating that they were suitable for 90 days of storage. Phytochemical quantities significantly increased in subsequent treatments, but decreased during storage in all the treatments. Similar trend was observed regarding total antioxidant and DPPH radical scavenging activities. The mineral contents increased significantly among the treatments. The microbial analysis of fruit bars exposed that the fruit were microbiologically safe. Hence, on the basis of the results obtained in this study, it may be concluded that the developed roselle-fig fruit bar would be acceptable and nutritious regarding physicochemical characteristics, microbiological quality, and antioxidant potential.

Therapeutic Potential of Hibiscus sabdariffa Linn. in Attenuating Cardiovascular Risk Factors

Cardiovascular diseases (CVDs) represent a broad spectrum of diseases afflicting the heart and blood vessels and remain a major cause of death and disability worldwide. CVD progression is strongly associated with risk factors, including hypertension, hyperglycemia, dyslipidemia, oxidative stress, inflammation, fibrosis, and apoptosis. These risk factors lead to oxidative damage that results in various cardiovascular complications including endothelial dysfunctions, alterations in vascular integrity, the formation of atherosclerosis, as well as incorrigible cardiac remodeling. The use of conventional pharmacological therapy is one of the current preventive measures to control the development of CVDs. However, as undesirable side effects from drug use have become a recent issue, alternative treatment from natural products is being sought in medicinal plants and is gaining interest. Roselle (Hibiscus sabdariffa Linn.) has been reported to contain various bioactive compounds that exert anti-hyperlipidemia, anti-hyperglycemia, anti-hypertension, antioxidative, anti-inflammation, and anti-fibrosis effects. These properties of roselle, especially from its calyx, have relevance to its therapeutic and cardiovascular protection effects in humans. This review summarizes the findings of recent preclinical and clinical studies on roselle as a prophylactic and therapeutic agent in attenuating cardiovascular risk factors and associated mechanisms.

Green Alternatives as Antimicrobial Agents in Mitigating Periodontal Diseases: A Narrative Review

Periodontal diseases and dental caries are the most common infectious oral diseases impacting oral health globally. Oral cavity health is crucial for enhancing life quality since it serves as the entranceway to general health. The oral microbiome and oral infectious diseases are strongly correlated. Gram-negative anaerobic bacteria have been associated with periodontal diseases. Due to the shortcomings of several antimicrobial medications frequently applied in dentistry, the lack of resources in developing countries, the prevalence of oral inflammatory conditions, and the rise in bacterial antibiotic resistance, there is a need for reliable, efficient, and affordable alternative solutions for the prevention and treatment of periodontal diseases. Several accessible chemical agents can alter the oral microbiota, although these substances also have unfavorable symptoms such as vomiting, diarrhea, and tooth discoloration. Natural phytochemicals generated from plants that have historically been used as medicines are categorized as prospective alternatives due to the ongoing quest for substitute products. This review concentrated on phytochemicals or herbal extracts that impact periodontal diseases by decreasing the formation of dental biofilms and plaques, preventing the proliferation of oral pathogens, and inhibiting bacterial adhesion to surfaces. Investigations examining the effectiveness and safety of plant-based medicines have also been presented, including those conducted over the past decade.

Antioxidant, physicochemical, and sensory properties of buffalo meat patties incorporated with roselle (Hibiscus sabdariffa L.), wolfberry (Lycium barbarum L.), and beetroot (Beta vulgaris L.) purées

The present work evaluated the antioxidant, physicochemical, and sensory properties of buffalo meat patties incorporated with 2% roselle (Hibiscus sabdariffa L.), wolfberry (Lycium barbarum L.), or beetroot (Beta vulgaris L.), and chill-stored (4°C) for 11 days. 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, 2-thiobarbituric acid reactive substances (TBARS), shrinkage, cooking yield, water holding capacity, pH, colour, textural properties, and sensory evaluation of the patties were examined. Patties incorporated with roselle, wolfberry, and beetroot had increased scavenging activity, thus decreasing oxidative activity in the patties during storage. Cooking yield was improved in all treatments with significant decrease in pH in both cooked and uncooked roselle-incorporated patties. No changes were observed for the texture of all samples, while roselle-incorporated patties maintained the redness after the 11th day of storage. Sensory attributes of the modified patties were acceptable to all panellists. In conclusion, the incorporation of roselle in buffalo meat patties showed more beneficial effects than the other purées tested in improving the quality of the patties while maintaining their sensory properties.

Phenolics-Linked Antioxidant and Anti-hyperglycemic Properties of Edible Roselle (Hibiscus sabdariffa Linn.) Calyces Targeting Type 2 Diabetes Nutraceutical Benefits in vitro

Phenolics- enriched plant food sources are excellent dietary and therapeutic targets to combat the increasing prevalence of diet and lifestyle-influenced non-communicable chronic diseases (NCDs), such as type 2 diabetes (T2D). Among plant sources, edible flowers rich in health protective phenolic compounds provide novel opportunities as ingredient and nutraceutical sources. Roselle (Hibiscus sabdariffa Linn.) is a popular edible flower and consumed as part of traditional cuisines and processed foods in several countries of Asia and Africa. Red calyces of Roselle are rich in phenolic compounds, which potentially have high antioxidant and anti-hyperglycemic properties. Therefore, there is merit in screening of dried Roselle calyces as sources for functional food ingredients or nutraceuticals to counter chronic oxidative stress and chronic hyperglycemia using in vitro assays. This has led to this study to investigate and compare phenolic compounds associated antioxidant and anti-hyperglycemic functions of different organic solvent-extracted fractions of dried Roselle calyces using rapid in vitro assays-based screening strategy. Total soluble phenolic content, profile of phenolic compounds, free radical scavenging assay-based total antioxidant activity, and anti-hyperglycemic function linked α-amylase and α-glucosidase inhibitory activities of four different organic solvents (chloroform, hexane, ethyl acetate, and initial crude extraction in 100% methanol) extracted fractions of calyces of Roselle were determined using in vitro assays. Studies indicated high phenolic-linked antioxidant and anti-hyperglycemic relevant properties in red Roselle calyces, specifically in ethyl acetate and methanol solvent-based extracted fractions. Major phenolic compounds in extracted fractions of Roselle calyces were chlorogenic acid, caffeic acid, gallic acid, catechin, rutin, benzoic acid, and cinnamic acid. Additionally, moderate α-amylase (30–92%) and very high α-glucosidase (81–98%) inhibitory activities were confirmed in undiluted samples of organic solvent-extracted fractions of Roselle calyces in the in vitro assays. Taken together these in vitro screening results indicated that calyces of Roselle are excellent sources of health protective phenolic compounds with high antioxidant and anti-hyperglycemic functions and organic solvent (ethyl acetate and methanol) extracted fractions of this edible flower can be strategically utilized to design functional food ingredients and nutraceuticals.

Antimicrobial Activity of Roselle-capped​ Silver​ Nanochip on Aggregatibacter actinomycetemcomitans

OBJECTIVES

 This article aimed to study the effects of the​ roselle-capped​ silver​ nanochip​ ​(SNP-Ro​ chip)​ against Aggregatibacter actinomycetemcomitans, and the toxicity of this film on fibroblast cells to develop this SNP-Ro chip into a local chemical for the treatment of periodontitis in the future.

MATERIALS AND METHODS

 Using a microwave-assisted synthesis method, silver​ nanoparticles (SNPs) were prepared from a silver nitrate solution and roselle extract as a reducing and capping agent. Then, SNP-Ro chips were fabricated by mixing a solution of SNP-Ro with alginate gel. The antimicrobial effect of the synthesized SNP-Ro chips was performed by the disc diffusion technique and time kill assay. The cytotoxic effect was also determined by the MTS assay.

STATISTICAL ANALYSIS

 One-way analysis of variance (ANOVA) and Scheffe's method were used to analyze the data for this experiment.

RESULTS

 All three ratios of the SNP-Ro chip produced inhibition zones ranging between 18.75 ± 2.08 and 19.03 ± 2.25 mm. In studying the killing time, the three groups of the SNP-Ro chips completely eradicated A. actinomycetemcomitans within 180 minutes. The percentage of the viable SNP-Ro chip-treated human gingival fibroblasts (HGFs) were significantly increased when compared with the alginate chip-treated cells (p < 0.05).

CONCLUSION

 This study developed a new method for the deposition of SNPs in alginate gel to make a thin small chip for the sustained release of the SNPs in a periodontal lesion. Therefore, the SNP-Ro chip has the potential to be developed as an adjunctive locally delivered antimicrobial agent in periodontal therapy.

Methodologies in the Analysis of Phenolic Compounds in Roselle (Hibiscus sabdariffa L.): Composition, Biological Activity, and Beneficial Effects on Human Health

Roselle (Hibiscus sabdariffa L.), as an edible flower, has long provided an array of positive effects on human health. This benefit is a result of phenolic compounds that are naturally present mainly in the calyx. Plentiful medicinal remedies and functional foods based on this flower are available worldwide, as supported by the studies of phenolic compounds in recent decades. This paper aims to provide a comprehensive review of the composition, biological activity, and beneficial effects on human health of phenolic compounds in roselle. This review was performed in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. A structured search in the published literature for phenolics compositions in roselle was required prior to the evaluation on the validity of the reported analytical methods. Reliable identification and quantification of phenolic compounds in roselle can be achieved by employing the proper extraction and separation methods. With ample alternative analytical methods discussed here, this review provided an aid for comprehending and selecting the most appropriate method for a particular study. The applications of the analytical methods highlighted indicated that phenolic acids, flavonoids, and their derivatives have been identified and quantified in roselle with a range of biological activities and beneficial effects on human health. It was also disclosed that the composition and concentration of phenolic compounds in roselle vary due to the growth factors, cultivars, and environmental influence. Finally, apart from the research progress carried out with roselle during the last ten years, this review also proposed relevant future works.

What is food-to-food fortification? A working definition and framework for evaluation of efficiency and implementation of best practices

Food-to-food fortification (FtFF) is an emerging food-based strategy that can complement current strategies in the ongoing fight against micronutrient deficiencies, but it has not been defined or characterized. This review has proposed a working definition of FtFF. Comparison with other main food-based strategies clearly differentiates FtFF as an emerging strategy with the potential to address multiple micronutrient deficiencies simultaneously, with little dietary change required by consumers. A review of literature revealed that despite the limited number of studies (in vitro and in vivo), the diversity of food-based fortificants investigated and some contradictory data, there are promising fortificants, which have the potential to improve the amount of bioavailable iron, zinc, and provitamin A from starchy staple foods. These fortificants are typically fruits and vegetables, with high mineral as well as ascorbic acid and β-carotene contents. However, as the observed improvements in micronutrient bioavailability and status are relatively small, measuring the positive outcomes is more likely to be impactful only if the FtFF products are consumed as regular staples. Considering best practices in implementation of FtFF, raw material authentication and ingredient documentation are critical, especially as the contents of target micronutrients and bioavailability modulators as well as the microbiological quality of the plant-based fortificants can vary substantially. Also, as there are only few developed supply chains for plant-based fortificants, procurement of consistent materials may be problematic. This, however, provides the opportunity for value chain development, which can contribute towards the economic growth of communities, or hybrid approaches that leverage traditional premixes to standardize product micronutrient content.

Phenolic Compounds in Extracts of Hibiscus acetosella (Cranberry Hibiscus) and Their Antioxidant and Antibacterial Properties

Hibiscus species are rich in phenolic compounds and have been traditionally used for improving human health through their bioactive activities. The present study investigated the phenolic compounds of leaf extracts from 18 different H. acetosella accessions and evaluated their biofunctional properties, focusing on antioxidant and antibacterial activity. The most abundant phenolic compound in H. acetosella was caffeic acid, with levels ranging from 14.95 to 42.93 mg/100 g. The antioxidant activity measured by the ABTS assay allowed the accessions to be classified into two groups: a high activity group with red leaf varieties (74.71–84.02%) and a relatively low activity group with green leaf varieties (57.47–65.94%). The antioxidant activity was significantly correlated with TAC (0.933), Dp3-Sam (0.932), Dp3-Glu (0.924), and Cy3-Sam (0.913) contents (p < 0.001). The H. acetosella phenolic extracts exhibited antibacterial activity against two bacteria, with zones of inhibition between 12.00 and 13.67 mm (Staphylococcus aureus), and 10.67 and 13.33 mm (Pseudomonas aeruginosa). All accessions exhibited a basal antibacterial activity level (12 mm) against the Gram-positive S. aureus, with PI500758 and PI500764 exhibiting increased antibacterial activity (13.67 mm), but they exhibited a more dynamic antibacterial activity level against the Gram-negative P. aeruginosa.

Inhibitory Effect of Roselle Aqueous Extracts-HPMC 6000 Gel on the Growth of Staphylococcus Aureus ATCC 25923

Objectives

Roselle (Hibiscus sabdariffa L.) is a medicinal plant commonly used as a beverage and herbal medicine. Complex compounds in the aqueous extracts have provided good antibacterial activity by which the growth of gram-negative and -positive bacteria is inhibited. The aims of this research were to formulate hydroxypropyl methylcellulose (HPMC) 6000 gel containing the extract and investigate the inhibitory activity of the extract and its gel formula against Staphylococcus aureus ATCC 25923.

Materials and Methods

Thin layer chromatography (TLC) on silica gel GF254 was used for analyzing flavonoids and polyphenols using butanol: acetic acid: water (4:1:5) and chloroforms: ethyl acetate: formic acid (0.5:9:0.5) as eluent, respectively. A serial dilution of aqueous extract powder in citrate buffer was made to obtain 0.50, 0.25, 0.10, 0.05, and 0.02 mg/mL solution. The roselle aqueous extract (3%) was formulated as a component of gel containing HPMC 6000 in various concentrations (2%, 3%, and 4%). A diffusion agar method on two layers of nutrient agar media was applied using Staphylococcus aureus ATCC 25923 and gentamicin 25 ppm as bacterial test and standard, respectively. After incubation for 24 h at 37°C, the inhibitory effect was denoted by a clear zone around the hole and the inhibitory activity was measured as minimum inhibitory concentration (MIC).

Results

The aqueous extract of Hibiscus sabdariffa L. contained flavonoid and polyphenol compounds based on the TLC chromatogram profile. It was found that the gel formula containing 3% HPMC 6000 and 3% aqueous extract gave a good physical characteristic and the lowest MIC (6.0 mg/mL), equivalent to 7.58 ppm of gentamicin standard at 12.0 mg/mL concentration.

Conclusion

The HPMC 6000 at 3% (w/w) concentration in roselle aqueous extract gel preparation gave good physical characteristics. The gel preparation exhibited inhibitory activity against Staphylococcus aureus ATCC 25923 shown by MIC 6.0 mg/mL. Formula 2 is recommended and should be further investigated for implementation in topical preparations.

Characterization of Roselle calyx from different geographical origins

Roselle (Hibiscus sabdariffa L.) is considered an underexploited food crop with nutritional and large scale processing potential. Roselle can be utilized as a functional food, mainly due to being rich in vitamin C, anthocyanins, other phytochemicals, and natural color. Although Roselle has been widely planted and consumed, little is known about the composition of aroma profiles. In this study, seventeen samples of dried Roselle calyx were collected from eight countries and the aroma profiles were determined by dynamic headspace sampling and GC-MS and GC-olfactometry. Furthermore, total soluble solids, pH, and color L* a* b* were determined, and sugars and acids were measured using ion chromatography. There were significant (p < 0.05) differences in all measured variables in physicochemical properties and non-volatile compounds. A total of 135 volatiles were identified mainly terpenes, aldehydes, esters, furans, and ketones. Thirty-seven odorants were reported as potentially important aroma compounds based on GC-olfactometry. This study provides valuable information for future commercial utilization of Roselle in the food industry.

Hibiscus sabdariffa anthocyanins-rich extract: Chemical stability, in vitro antioxidant and antiproliferative activities

Hibiscus sabdariffa calyx is a rich source of anthocyanins and other bioactive compounds but no study reported the effects of experimental conditions on the extraction of these chemical compounds. Therefore, the effects of time and extraction temperature on the bioactive compounds and antioxidant activity of Hibiscus sabdariffa calyx were evaluated. In addition, the effects of copigmentation and pH on the stability of anthocyanins were assessed and the cytotoxic effects (LC₅₀, IC₅₀, and GC₅₀) of the extracts were determined in relation to tumor cell lines - Caco-2, HepG-2, HCT8, and A549. The temperature significantly influenced the total anthocyanins and flavonoids contents. The interaction between time/temperature influenced the total phenolic content and ascorbic acid. The t_1/2 and the percentage of colour retention decreased markedly at temperatures above 80 °C. Variations in pH conserved the antioxidant activity of the anthocyanins, and the protonation-deprotonation process of the extract was reversible. The treatment of cells with purified anthocyanin extract or crude extracts at 5-800 μg mL^-1 did not show significant cytotoxic effects on the cell lines, corroborating the chemical antioxidant effect of the extracts (DPPH assay). Cyanidin-3-glucoside, delphinidin-3-sambubioside, delphinidin-3-glucoside, and cyanidin-3-sambubioside were identified in the extracts by LC-ESI-MS.

Characterization of dietary constituents and antioxidant capacity of Tropaeolum pentaphyllum Lam

The aim of this study was to evaluate the nutritional content and antioxidant capacity of the tubers, leaves and, flowers of the species Tropaeolum pentaphyllum Lam. The three parts of the plant were analyzed by physicochemical methods, atomic absorption spectrometry, spectrophotometric and chromatographic techniques. The tubers, leaves, and flowers exhibited significant differences in all parameters evaluated. The leaves showed significantly higher values of protein (16.28 ± 0.02 g/100 g), total dietary fiber (27.78 ± 0.15 g/100 g) and quercetin (3798.61 ± 37.57 µg/g) when compared to the tubers and flowers. The study revealed a potential content of the protein, dietary fiber, and flavonoids the species Tropaeolum pentaphyllum, when compared with the sweet potatoes leaves (Ipomoea batatas L.). In addition, the antioxidant activities of leaves and flowers were also higher measured by ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid), DPPH (2,2-diphenyl-1-picrylhydrazyl), and TRAP (total radical-trapping antioxidant potential) methods. Tropaeolum pentaphyllum have high nutritional potential that can be exploited to improve nutritional value of various food products.

Characterization of red ginseng residue protein films incorporated with hibiscus extract

An edible film was prepared from red ginseng residue protein (RGRP) and incorporated with hibiscus extract (HE). RGRP was extracted from red ginseng residue, which is an inexpensive by-product of the red ginseng processing industry. Different concentrations of HE were added to an RGRP film-forming solution as a natural antioxidant. The prepared RGRP films without HE had a tensile strength of 16.9 MPa and an elongation at break of 25.1%. The antioxidant activity of the RGRP film increased with increasing concentration of HE. In addition, the RGRP film with 1% HE exhibited the lowest value of water vapor permeability (1.88×10^-9 g·m/m²·s·Pa), which indicates that the film has high water barrier property. The results present the production of edible films from discarded red ginseng residue, and the antioxidant activity of RGRP films as a packaging material can prevent lipid oxidation and quality loss of food products.

Validation of the AlamarBlue® Assay as a Fast Screening Method to Determine the Antimicrobial Activity of Botanical Extracts

Plant compounds are a potential source of new antimicrobial molecules against a variety of infections. Plant extracts suppose complex phytochemical libraries that may be used for the first stages of the screening process for antimicrobials. However, their large variability and complexity require fast and inexpensive methods that allow a rapid and adequate screening for antimicrobial activity against a variety of bacteria and fungi. In this study, a multi-well plate assay using the AlamarBlue® fluorescent dye was applied to screen for antimicrobial activity of several botanical extracts and the data were correlated with microbial colony forming units (CFU). This correlation was performed for three pathogenic model microorganisms: Escherichia coli (Gram negative bacteria), Staphylococcus aureus (Gram positive bacteria) and for the yeast-like fungi Candida albicans. A total of ten plant extracts from different Mediterranean plants, including several Cistus and Hibiscus species, were successfully tested. HPLC-DAD-ESI-MS/MS analysis was utilized for the characterization of the extracts in order to establish structure-activity correlations. The results show that extracts enriched in ellagitannins and flavonols are promising antibacterial agents against both Gram positive and Gram negative bacteria. In contrast, phenolic acids, anthocyanidins and flavonols may be related to the observed antifungal activity.

In vitro synergistic effect of Hibiscus sabdariffa aqueous extract in combination with standard antibiotics against Helicobacter pylori clinical isolates

Context The increasing problem of drug-resistant strains has led to the failure of current treatment regimens of Helicobacter pylori (HP) infection. Recently, a new treatment strategy has been developed to overcome the problem by using natural products in combination with antibiotics to enhance the treatment efficacy. Objective The antimicrobial combinatory effect of the aqueous extract of Hibiscus sabdariffa L. (Malvaceae) (AEHS) with antibiotics (clarithromycin, CLA; amoxicillin, AMX; metronidazole, MTZ) has been evaluated in vitro against HP strains. Materials and methods Hibiscus calyces (35 g) were brewed in 250 mL of boiled water for 30 min, and minimum inhibitory concentrations (MICs) were determined by agar dilution method. The checkerboard assay was used to evaluate the antimicrobial combinatory effect according to the sum of fractional inhibitory concentration (∑FIC) indices. Results In this study, AEHS exerted remarkable bacteriostatic effect against all HP strains tested with MICs values ranging from 9.18 to 16.68 μg/mL. Synergy effect of AEHS with CLA or MTZ was obtained against four of seven HP strains tested with ∑FIC ranging from 0.21 to 0.39. The additive effect of AEHS with AMX was obtained against five of seven HP strains tested with ∑FIC ranging from 0.61 to 0.91. Conclusion This study presents AEHS as a potent therapeutic candidate alone, or in combination with antibiotics for the treatment of HP infection.

Hibiscus sabdariffa increases hydroxocobalamin oral bioavailability and clinical efficacy in vitamin B12 deficiency with neurological symptoms

The aim of the study was to evaluate the bioavailability and clinical benefits of oral new formulation (HB₁₂ ) of hydroxocobalamin (Hdrx) with Hibiscus sabdariffa (HS). First, in an observational study, a cohort of 30 vitamin B₁₂ -deficient patients (vit B₁₂ < 200 pg/mL) with neurological symptoms received oral fixed dose of Hdrx containing 15 mg Hdrx daily for 10 days followed by 15 mg monthly. Clinical benefits were evaluated on haematological and biochemical parameters, and neurological improvement at days 10 and 90 compared to day 0. To understand the mechanism, intestinal mucosa from mice were mounted in vitro in Ussing chambers to measure Hdrx Fluxes. In the clinical study, serum vitamin B₁₂ level increased from 55.1 ± 36.9 to 1330 ± 335.5 pg/mL at day 10 and 431.0 ± 24.27 pg/mL at day 90, without overt adverse effects. In mice ileum, (i) intestinal bioavailability of Hdrx increased in dose-dependent manner with HB₁₂ . The apparent permeability of Hdrx was P_app = 34.9 ± 4.6 × 10^-6 cm/s in the presence of 3 mg/mL (HB₁₂ B) compared to the control P_app = 6.2 ± 0.7 × 10^-6 cm/s. (ii) Total transepithelial electrical conductance (G_t ) increased in dose-dependent manner with HB₁₂ , G_t = 161.5 ± 10.8 mS/cm² with HB₁₂ B (Hdrx 1 mg + HS 3 mg) compared to the control Hdrx, G_t = 28.7 ± 4.0 mS/cm². In conclusion, the clinical study suggests that injections are not required when Hdrx is given orally. Intestinal bioavailability of Hdrx increased in vitro when it was used concomitantly with HS.

Hibiscus sabdariffa (Roselle) Extracts and Wine: Phytochemical Profile, Physicochemical Properties, and Carbohydrase Inhibition

Three varieties of Hibiscus sabdariffa were analyzed for their phytochemical content and inhibitory potential on carbohydrate-digesting enzymes as a basis for selecting a variety for wine production. The dark red variety was chosen as it was highest in phenolic content and an aqueous extract partially inhibited α-glucosidase (maltase), with delphinidin 3-O-sambubioside, cyanidin 3-O-sambubioside, and 3-O-caffeoylquinic acid accounting for 65% of this activity. None of the varieties significantly inhibited α-amylase. Regarding Hibiscus sabdariffa wine, the effect of fermentation temperature (20 and 30 °C) on the physicochemical, phytochemical, and aroma composition was monitored over 40 days. The main change in phytochemical composition observed was the hydrolysis of 3-O-caffeolquinic acid and the concomitant increase of caffeic acid irrespective of fermentation temperature. Wine fermented at 20 °C was slightly more active for α-glucosidase inhibition with more fruity aromas (ethyl octanoate), but there were more flowery notes (2-phenylethanol) at 30 °C.

Infusion of Hibiscus sabdariffa L. Modulates Oxidative Stress in Patients with Marfan Syndrome

Marfan syndrome (MFS) is associated with progressive aortic dilatation, endothelial dysfunction, and oxidative stress that contribute to the early acute dissection of the vessel and can end up in rupture of the aorta and sudden death. Many studies have described that the organic acids from Hibiscus sabdariffa Linne (HSL) calyces increase cellular antioxidant capacity and decrease oxidative stress. Here we evaluate if the antioxidant properties of HSL infusion improve oxidative stress in MFS patients. Activities of extra cellular super oxide dismutase (ECSOD), glutathione peroxidase (GPx), glutathione-S-transferase (GST), glutathione reductase (GSSG-R), glutathione (GSH), lipid peroxidation (LPO) index, total antioxidant capacity (TAC), and ascorbic acid were determined in plasma from MFS patients. Values before and after 3 months of the treatment with 2% HSL infusion were compared in control and MFS subjects. After treatment, there was a significant decrease in ECSOD (p = 0.03), EGPx (p = 0.04), GST (p = 0.03), GSH (p = 0.01), and TAC and ascorbic acid (p = 0.02) but GSSG-R activity (p = 0.04) and LPO (p = 0.02) were increased in MFS patients in comparison to patients receiving the HSL treatment and C subjects. Therefore, the infusion of HSL calyces has antioxidant properties that allow an increase in antioxidant capacity of both the enzymatic and nonenzymatic systems, in the plasma of the MSF patients.

Aqueous Extracts of Hibiscus sabdariffa Calyces to Control Aichi Virus

Aqueous Hibiscus sabdariffa extracts possess antimicrobial properties with limited information available on their antiviral effects. Aichi virus (AiV) is an emerging foodborne pathogen that causes gastroenteritis. Vaccines are currently unavailable to prevent their disease transmission. The objective of this study was to determine the antiviral effects of aqueous H. sabdariffa extracts against AiV. AiV at ~5 log PFU/ml was incubated with undiluted (200 mg/ml), 1:1 (100 mg/ml) or 1:5 (40 mg/ml) diluted aqueous hibiscus extract (pH 3.6), phosphate-buffered saline (pH 7.2 as control), or malic acid (pH 3.0, acid control) at 37 °C over 24 h. Treatments were stopped by serially diluting in cell-culture media containing fetal bovine serum and titers were determined using plaque assays on confluent Vero cells. Each treatment was replicated thrice and assayed in duplicate. AiV did not show any significant reduction with 1:1 (100 mg/ml) or 1:5 (40 mg/ml) diluted aqueous hibiscus extracts or malic acid after 0.5, 1, or 2 h at 37 °C. However, AiV titers were reduced to non-detectable levels after 24 h with all the three tested concentrations, while malic acid showed only 0.93 log PFU/ml reduction after 24 h. AiV was reduced by 0.5 and 0.9 log PFU/ml with undiluted extracts (200 mg/ml) after 2 and 6 h, respectively. AiV treated with 1:1 (100 mg/ml) and 1:5 (40 mg/ml) diluted extracts showed a minimal ~0.3 log PFU/ml reduction after 6 h. These extracts show promise to reduce AiV titers mainly through alteration of virus structure, though higher concentrations may have improved effects.

An anthocyanin-rich extract from Hibiscus sabdariffa linnaeus inhibits N-nitrosomethylurea-induced leukemia in rats

A previous study reported that anthocyanins from roselle (Hibiscus sabdariffa L.) showed significant anticancer activity in human promyelocytic leukemia cells. To explore the antitumor effect of anthocyanin, a roselle bioactive polyphenol in a rat model of chemical-induced leukemia was assayed. Anthocyanin extract of roselle (Hibiscus anthocyanins, HAs) was supplemented in the diet (0.1 and 0.2%). This study was carried out to evaluate the protective effect of HAs on N-nitrosomethylurea (NMU)-induced leukemia of rats. The study employed male Sprague-Dawley rats (n = 48), and leukemia was induced by intravenous injection of 35 mg kg(-1) body weight of NMU dissolved in physiologic saline solution. The rats were divided into four groups (n = 12): control, NMU only, and HAs groups that received different doses of HAs (0.1 and 0.2%) daily, orally, after NMU injection. After 220 days, the animals were killed, and the following parameters were assessed: morphological observation, hematology examination, histopathological assessment, and biochemical assay. When compared with the NMU-only group, HAs significantly prevented loss of organ weight and ameliorated the impairment of morphology, hematology, and histopathology. Treatment with HAs caused reduction in the levels of AST, ALT, uric acid, and MPO. Also, the results showed that oral administration of HAs (0.2%) remarkably inhibited progression of NMU-induced leukemia by approximately 33.3% in rats. This is the first report to demonstrate that the sequential administration of HAs followed by NMU resulted in an antileukemic activity in vivo.