Hot and Cold Water Infusion Aroma Profiles of Hibiscus sabdariffa: Fresh Compared with Dried

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.

GC-MS-Olfactometric Characterization of Volatile and Key Odorants in Moringa (Moringa oleifera) and Kinkeliba (Combretum micranthum G. Don) Herbal Tea Infusions Prepared from Cold and Hot Brewing

Herbal teas are a popular global drink and are widely used in many traditional medicines. Key odorants are one of the main parameters to elucidate the final herbal tea’s overall quality and consumer acceptance. In the present study, for the first time, the brewing effect on volatile, key odorants, total phenolic contents, and antioxidant potential of Moringa (Moringa oleifera) and Kinkeliba (Combretum micranthum G. Don) herbal teas was comprehensively investigated. Two different infusions were studied and labeled as 25 °C/24 h (room temperature) and 98 °C/10 min (hot temperature). A total of 45 and 44 aroma compounds were detected in Moringa cold and hot teas, respectively, whereas 39 volatiles were determined in both infusion techniques for Kinkeliba herbal teas. The total amount of volatile compounds in both cold-infused herbal teas was higher than those in the hot-infused ones. Based on GC-MS-Olfactometry results, 19 and 21 key odorants in total were found in Moringa and Kinkeliba teas, respectively. The principal key odorants in Moringa teas with the highest flavor dilution (FD) factors were (E)-2-hexen-1-ol (herbal/fresh aroma), 3-hexanol (green/grassy), 2-phenyl ethanol (floral/rose), while in Kinkeliba teas they were 2-hexanol (herbal/green) and 3-penten-2-ol (green/fresh). The total phenolic content and antioxidant potential in Moringa and Kinkeliba teas increased using hot infusion. Principal component analysis showed that each tea infusion was clearly discriminated in terms of its volatile profiles. Our findings demonstrated that the brewing procedures had a significant impact on the key odorants of Moringa and Kinkeliba infusions.

Medicinal plants with anti-colorectal cancer bioactive compounds: Potential game-changers in colorectal cancer management

Development and identification of molecular compounds capable of killing or inhibiting transformed cells promoting carcinogenesis without inducing toxic effects to the normal cells are of utmost significance. A systematic review was conducted in screening for important literature was extensively performed by searching the Web of Science, Ovid, BMC Springer, Elsevier, Embase, and MEDLINE databases for optimum selectivity. Google Scholar was also used to supplement information. Pharmacotherapeutic biomolecules active against colon cancer carcinogenesis in Musa acuminata and Musa balbisiana (bananas), Punica granatum L (pomegranate), Glycine max (Soybean), Brassica oleracea L var. italica Plenck (Broccoli), and Hibiscus rosa-sinesis and Hibiscus sabdariffa (hibiscus) were evaluated. Signaling pathways like phosphatidylinositol 3-kinase (PI3K), mitogen-activated protein kinase (MAPK), protein kinase B (AKT), and nuclear factor-kappa B (NFκB) correlate the mediation of COX-2 expression. Increased levels of COX-2 are correlated with the occurrence and progression of colon cancer. Natural antioxidants in herbal plants including polyphenols and carotenoids inhibit the oxidation of lipids, proteins, and nucleic acids and thereby preventing the initiation of oxidizing chain reactions. These bioactive compounds should be considered an important dietary supplement.

Bioprospecting for Anti-COVID-19 Interventions From African Medicinal Plants: A Review

The emergence of the novel coronavirus (SARS-CoV-2) that emanated from Wuhan in China in 2019 has become a global concern. The current situation warrants ethnomedicinal drug discovery and development for delivery of phytomedicines with potential for the treatment of COVID-19. The aim of this review is to provide a detailed evaluation of available information on plant species used in African traditional medicines with antiviral, anti-inflammatory, immunomodulatory, and COVID-19 symptoms relieving effects. Literature from scientific databases such as Scopus, PubMed, Google scholar, African Journals OnLine (AJOL), Science Direct, and Web of Science were used for this review. A total of 35 of the 38 reviewed plants demonstrated a wide range of antiviral activities. Bryophyllum pinnatum, Aframomum melegueta, Garcinia kola, Sphenocentrum jollyanum, Adansonia digitata, Sutherlandia frutescens, Hibiscus sabdariffa, Moringa oleifera, and Nigella sativa possess a combination of antiviral, immunomodulatory, anti-inflammatory, and COVID-19 symptoms relieving activities. Nine, 13, and 10 of the plants representing 23.7%, 34.2%, and 26.3% of the plants studied had antiviral activity with 3 other activities, antiviral activity with 2 other activities, and antiviral with one pharmacological activity alone, respectively. The plants studied were reported to be relatively safe at the subchronic toxicity level, except for 2. The study provides baseline information on the pharmacological activities, toxicity, and chemical components of 9 African medicinal plants with antiviral, immunomodulatory, anti-inflammatory, and symptoms relieving activities, thereby making the plants candidates for further investigation for effectiveness against COVID-19.

Influence of keeping the calyces during fermentation on physicochemical and sensory properties of Hibiscus sabdariffa wines

Hibiscus (Hibiscus sabdariffa) wines are usually made through the fermentation of its calyces extracts. However, the exhausted calyces could still contain a considerable amount of extractable bioactive compounds. This work analyzed the effect of keeping the hibiscus calyces during fermentation on the physicochemical and sensory characteristics and acceptance of its wines. Hibiscus wines Filtered-Ch and Filtered-C were generated by fermentation of filtered musts of China and Colima varieties, respectively, while Unfiltered-Ch and Unfiltered-C were obtained by fermentation of musts from calyces that were kept for 120 days. Unfiltered-C and Unfiltered-Ch wines had higher contents of total monomeric anthocyanins (32.5 mg/L in Unfiltered-C and 48.5 mg/L in Unfiltered-Ch), condensed tannins (around 200 mg_CE/L), total phenolic compounds (800 mg_GAE/L), and antioxidant activity (8.4-8.8 mM_TE/L), as well as a higher concentration of tartaric, citric and malic acids (0.26, 0.32 and 2.25 g/L, respectively) than Filtered-C and Filtered-Ch wines (P < 0.05). Moreover, Unfiltered-C and Unfiltered-Ch wines had darker red colors, evidenced by lower lightness, chroma and hue values, than those observed in Filtered-C and Filtered-Ch wines (P < 0.01). Furthermore, Unfiltered-Ch and Unfiltered-C wines were more appreciated, having a more intense taste and smell according to the descriptions obtained from consumers by applying the Check-All-That-Apply technique. Sensory attributes observed in hibiscus wines were statistically correlated with the physicochemical characteristics. Keeping hibiscus calyces during fermentation allows for the production of wines with acceptable sensory characteristics and a higher concentration of bioactive compounds than producing wines from filtered musts.

Changes in Physicochemical Properties and Volatile Compounds of Roselle (Hibiscus sabdariffa L.) Calyx during Different Drying Methods

Fresh roselle are high in moisture and deteriorate easily, which makes drying important for extending shelf-life and increasing availability. This study investigated the influence of different drying methods (oven-drying, freeze-drying, vacuum-drying, and sun-drying) on the quality of roselle calyx expressed as physicochemical properties (moisture content, water activity, soluble solids, color), volatile compounds, and microstructure. Oven-drying and freeze-drying reduced moisture content most while vacuum-drying and sun-drying were not as efficient. All drying methods except sun-drying resulted in water activities low enough to ensure safety and quality. Vacuum-drying had no impact on color of the dry calyx and only small impact on color of water extract of calyx. Drying reduced terpenes, aldehydes, and esters but increased furans. This is expected to reduce fruity, floral, spicy, and green odors and increase caramel-like aroma. Sun-drying produced more ketones, alcohols, and esters. Scanning electron microscopy revealed that freeze-drying preserved the cell structure better, and freeze-dried samples resembled fresh samples most compared to other drying techniques. The study concludes that freeze-drying should be considered as a suitable drying method, especially with respect to preservation of structure.

The Digestibility of Hibiscus sabdariffa L. Polyphenols Using an In Vitro Human Digestion Model and Evaluation of Their Antimicrobial Activity

Hibiscus sabdariffa L. (H.s.) is a polyphenolic-rich plant commonly consumed either as a beverage or spice. The aim of the present study was to evaluate the in vitro digestibility of H.s. polyphenols using an in vitro model of digestion which simulates the human stomach and small intestine. The bioaccessible polyphenols released in the digested samples were analyzed by liquid chromatography coupled to photodiode array and mass spectrometry detection. H.s. anthocyanins (cyanidin-3-O-sambubioside and delphinidin-3-O-sambubioside) content drastically dropped during the digestion process from 2.91 ± 0.03 µg g⁻¹ and 8.53 ± 0.08 µg g⁻¹ (w/w) CG (Cyanidin-glucoside) in the raw extract, respectively, to 0.12 ± 0.01 µg g⁻¹ 0.12 ± 0.01 µg g⁻¹ (w/w) CG at the end of duodenal digestion. Total polyphenols also have shown a decrease from 1192.65 ± 30.37 µg g⁻¹ (w/w) in the raw extract to 282.24 ± 7.21 µg g⁻¹ (w/w) by the end of gastric digestion, in contrast to their increase by the end of duodenal digestion 372.91 ± 3.97 µg g⁻¹ (w/w). On the other hand, the decrease in certain compounds (e.g., caffeoylquinicandcoumaroylquinic acids) was observed during gastric digestion resulting in an increase of quinic acid in the duodenal aliquots, thus suggesting that this compound was derived from the degradation of the more complex hydroxycinnamic acids. H.s. extract also exhibited a bacteriostatic effect against Staphylococcus aureus ATCC 6538 (MIC of 2.5 mg mL⁻¹) and a bactericidal effect against a food isolate of Listeria monocytogenes (MBC of 2.5 mg mL⁻¹). The undigested polyphenols of H.s. in the upper gastrointestinal tract enters the colon, where they are metabolized by the gut microbiota. The present study results showed that resistance of H.s. polyphenols during gastrointestinal digestion might affect their uptake, resulting in a decrease in their digestibility.

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.

Hibiscus sabdariffa Extract Inhibits Adhesion, Biofilm Initiation and Formation in Candida albicans

Microbial biofilms act as reservoirs for pathogenic sessile microbes which reside inside the three dimensional matrix of the biofilm, and are thus protected against anti-microbial drugs. Most of the anti-microbial drugs fail to completely abolish the biofilm associated infections. In the present study, we provide evidence of Hibiscus sabdariffa (Hs) extract having possible anti-microbial activity, with emphasis on Candida albicans biofilm. The Hs extract was shown to be effective against C. albicans pre-formed biofilm at 3.125 mg/ml and was able to inhibit the hyphae initiation and adherence of cells. Furthermore, Hs extract was able to reduce the C. albicans load in C. elegans by effectively killing the Candida cells thereby reducing the viable colony count and effectively increasing the lifespan of worms. The percentage of viable hatched progeny of worms exposed to Hs extract (both at conc. 1.5 mg/ml and 6.25 mg/ml), was also comparable to that of the control untreated eggs. The Hs extract was also found to be significantly effective against fluconazole resistant C. albicans isolated from patients. Thus, we, for the first time, propose Hs extract as a prospective drug candidate and substitute for eradicating pre-formed biofilm and inhibiting the growth of C. albicans.

Elucidation of Infusion-Induced Changes in the Key Odorants and Aroma Profile of Iranian Endemic Borage ( Echium amoenum) Herbal Tea

Infusion-induced changes in the aroma and key odorants and their odor activity values of Iranian endemic herbal (Gol-Gavzaban) tea obtained from shade-dried violet-blue petals of borage ( Echium amoenum) were studied for the first time. Two hot teas and one cold tea were investigated and coded as 4MN (4 min/98 °C), 16MN (16 min/98 °C), and 24HR (24 h/ambient temperature), respectively. Aromatic extracts of the tea samples were isolated by the liquid-liquid extraction method and analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O) for the first time. According to the results of the aroma profiling, a total of 35 common aroma compounds comprising alcohols, acids, volatile phenols, lactones, aldehydes, ketone, pyrroles, and furans were identified and quantified in the tea samples. Indeed, it is worth noting that the aroma profiles of the borage teas were similar. However, the effects of the infusion techniques were clearly different as observed on the content of each individual and total compounds in the samples. The highest mean total concentration was detected in 24HR (266.0 mg/kg), followed by 16MN (247.1 mg/kg) and 4MN (216.1 mg/kg). 1-Penten-3-ol was the principal volatile component in all borage teas. On the basis of the result of the flavor dilution (FD) factors, a combined total of 22 different key odorants was detected. The potential key odorants with regard to FD factors in all samples were prevailingly alcohols, acids, and terpenes. The highest FD factors were observed in 2-hexanol (2048 in 4MN and 24HR; 1024 in 16MN) and 1-penten-3-ol (2048 in 24HR; 1024 in 4MN and 16MN) in samples providing herbal and green notes. Principal component analysis (PCA) showed that the tea samples could clearly be discriminated in terms of their aroma profiles and key odorants. The findings of the current study demonstrate that the tea preparation conditions have a significant impact on the organoleptic quality of borage tea.

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.

Volatiles and primary metabolites profiling in two Hibiscus sabdariffa (roselle) cultivars via headspace SPME-GC-MS and chemometrics

Hibiscus sabdariffa (roselle) is a plant of considerable commercial importance worldwide as functional food due to its organic acids, mucilage, anthocyanins, macro and micro-nutrients content. Although Hibiscus flowers are emerging as very competitive targets for phytochemical studies, very little is known about their volatile composition and or aroma, such knowledge can be suspected to be relevant for understanding its olfactory and taste properties. To provide insight into Hibiscus flower aroma composition and for its future use in food and or pharmaceutical industry, volatile constituents from 2 cultivars grown in Egypt, viz. Aswan and Sudan-1 were profiled using solid-phase microextraction (SPME) coupled to GCMS. A total of 104 volatiles were identified with sugar and fatty acid derived volatiles amounting for the major volatile classes. To reveal for cultivar effect on volatile composition in an untargeted manner, multivariate data analysis was applied. Orthogonal projection to latent structures-discriminant analysis (OPLS-DA) revealed for 1-octen-3-ol versus furfural/acetic acid enrichment in Aswan and Sudan-1 cvs., respectively. Primary metabolites contributing to roselle taste and nutritional value viz. sugars and organic acids were profiled using GC-MS after silylation. The impact of probiotic bacteria on roselle infusion aroma profile was further assessed and revealed for the increase in furfural production with Lactobacillus plantarum inoculation and without affecting its anthocyanin content. This study provides the most complete map for volatiles, sugars and organic acids distribution in two Hibiscus flower cultivars and its fermented product.

Comparative study of anthocyanin and volatile compounds content of four varieties of Mexican roselle (Hibiscus sabdariffa L.) by multivariable analysis

Anthocyanins are a group of water-soluble pigments that provide red, purple or blue color to the leaves, flowers, and fruits. In addition, benefits have been attributed to hypertension and cardiovascular diseases. This study compared the content of total anthocyanins and volatile compounds in aqueous and ethanolic extracts of four varieties of Mexican roselle, with different levels of pigmentation. The multivariable analysis of categorical data demonstrated that ethanol was the best solvent for the extraction of both anthocyanins and volatile compounds. The concentration of anthocyanin in pigmented varieties ranged from 17.3 to 32.2 mg of cyanidin 3-glucoside/g dry weight, while volatile compounds analysis showed that geraniol was the main compound in extracts from the four varieties. The principal component analysis (PCA) allowed description of results with 77.38% of variance establishing a clear grouping for each variety in addition to similarities among some of these varieties. These results were validated by the confusion matrix obtained in the classification by the factorial discriminate analysis (FDA); it can be useful for roselle varieties classification. Small differences in anthocyanin and volatile compounds content could be detected, and it may be of interest for the food industry in order to classify a new individual into one of several groups using different variables at once.