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In this study we purified and characterized a Protease Inhibitor (PI) from the seeds of Hibiscus acetosella (HAPI). The inhibitor was purified using ammonium sulphate fractionation, Fast Protein Liquid Chromatography using anion exchanger UNOsphere Q column and trypsin affinity chromatography. The HAPI has a subunit molecular weight of 20 kDa and inhibited trypsin to the extent of 89.81 ± 0.61% and larval gut protease activity of Spodoptera litura to the extent of 84.61 ± 0.97%. The purified inhibitor showed 5690.00 U/mg specific inhibition activity with a fold purity of 158.10 and yield of 2.2 µg per gram of seed. The HAPI was quite stable in the range of pH 7–9 with a maximum activity around pH 8–9, the pH range in the gut of lepidopteran larvae. The inhibitor was found to be stable up to a temperature of 50 C and retained an inhibition of 73.54 ± 0.83% even at 70 °C but declined beyond 80 °C. Further, detergents, oxidizing agents and reducing agents altered the inhibition activity of HAPI. The kinetic analysis revealed that HAPI is a non-competitive inhibitor of trypsin with a Ki of 52 nM. Feeding experiments on S. litura larvae with 1.16 µg of the purified inhibitor twice daily resulted in only 5.5% of the larvae emerged as adults from the treated group as against 97% the larvae emerged as adults from control group indicating its potential in pest control. [ABSTRACT FROM AUTHOR]

Abstract The objective of this work was to evaluate the performance of okra grafted onto Hibiscus spp. in the presence and absence of three root knot nematode species. The experimental design was completely randomized in a 4x4 factorial arrangement with ten replicates. The first factor consisted of the following four rootstocks: kenaf (Hibiscus cannabinus), false roselle (Hibiscus acetosella), self-grafted, and non-grafted. The second factor was the inoculation of 5,000 eggs and second-stage juveniles of Meloidogyne incognita, Meloidogyne javanica, and Meloidogyne enterolobii in okra plants, plus an uninoculated control. Vegetative development, agronomic performance, and nematode reproduction were evaluated. The grafting of okra onto Hibiscus spp. in the presence of root-knot nematodes provided a greater plant height, scion length, fresh shoot mass, number of fruits, and yield, when compared with self-grafted and non-grafted plants. The averages of the root-knot nematode reproduction factor were low in the plants grafted onto Hibiscus spp., indicating that grafting in the presence of root-knot nematodes is capable of maintaining okra vegetative development and yield.

The effects of different drying methods (freeze- and spray-drying) and carriers (gum Arabic and inulin) on the powder characterization and stability of the bioactive compounds of Hibiscus acetosella extract (HAE) during storage were evaluated. The 1H NMR spectrum of the HAE revealed characteristic signals of the caffeoyl hydroxycitric acid. The encapsulated extract powder presented different morphology according to the drying processes. The powders produced by the freeze-drying process presented higher retention of bioactive compounds due to the low temperature process. The mixture of gum Arabic and inulin as carrier resulted in the absorption of larger amount of water. The half-life time of the encapsulated extract powders ranged from 31 to 36 h (DPPH) and from 34 to 71 h (phenolic compounds). In general, the powders constituted of gum Arabic and recovered by the freeze-drying process presented better protection and retention of the bioactive compounds from the HAE. Image 1 • Caffeoyl hydroxycitric acid was confirmed in the H. acetosella tea. • Encapsulated tea powders depend on the drying processes. • Freeze-dried powders presented higher moisture content and activity water values. • Gum Arabic freeze-dried powders better protected the bioactive compounds. [ABSTRACT FROM AUTHOR]

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.

Methanolic and dichloromethane extracts from the leaves of Congolese Hibiscus species were characterised by chromatographic and spectroscopic techniques and their in vitro biochemical activities against ROS production were evaluated in cellular models and on an enzyme, myeloperoxidase (MPO), involved in inflammation. Hibiscus acetosella has a chemical fingerprint different from Hibiscus cannabinus and Hibiscus sabdariffa both having similar fingerprints. Major compounds were polyphenols, represented mainly by caffeoyl-hydroxycitric acid for H. acetosella and neochlorogenic acid for the two other species. All extracts displayed high cellular antioxidant activity with IC50 values ranging from 0.5 to 3 μg mL−1 using lucigenin on neutrophils. Dichloromethane extracts showed more efficient effects on extracellular ROS production and MPO activity. Antioxidant and anti-inflammatory activities of caffeoyl-hydroxycitric acid were significantly higher than those of neochlorogenic acid. The bioactivities of Hibiscus species were positively correlated with their phytochemical content and could justify their use as local nutraceutical resources and medicines. [ABSTRACT FROM AUTHOR]

Abstract: The major anthocyanin pigments extracted from Hibiscus acetosella flower were investigated by UV–Vis spectroscopy and multivariate curve resolution-alternating least squares (MCR-ALS). Pure spectra and kinetic of the species present at different pH values were recovered for anthocyanins transformation and degradation products, found with and without UV radiation exposure. In the absence of UV radiation, up to seven different species were detected and by UV radiation exposure, this number increased to up to nine. The species detected in the absence of radiation were also detected when pigments samples were exposed to UV radiation, where degradation occurred faster and two new species appear. The kinetic profiles obtained at different pH values allowed the proposal of a reaction mechanism and pathway. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spray drying is the main technique to encapsulate bioactive compounds of Hibiscus. • H. acetosella , H. sabdariffa and H. cannabinus are the only exploited species. • Anthocyanins from H. sabdariffa calyces are the main encapsulated compounds. • Encapsulated extracts of Hibiscus plants increased stability of food formulations. • Researches on biological effects of encapsulated extracts of Hibiscus are missing. The genus Hibiscus includes more than 250 species, and many studies showed that these plants contain bioactive compounds with technological potential to be used in the development of functional foods. However, the instability of these compounds during typical food processing conditions, such as exposure to high temperatures, pH changes and presence of light and oxygen have stimulated the use of encapsulation techniques to increase their stability and applicability. Among the existing Hibiscus species, only H. sabdariffa , H. cannabinus , and H. acetosella have been investigated in encapsulation studies, being spray drying the most common method approached. Considering the high technological potential offered by the incorporation of encapsulated bioactive compounds from plants of the genus Hibiscus in food formulations, this review discusses key information of selected encapsulation techniques, which represents promising alternatives to increase food systems' stability and stimulate the design of new functional foods. Relevant gaps in the literature were also noticed, mainly the lack of systematic studies regarding the composition of bioactive compounds after encapsulation, instead of total determinations, and biological activities in different analytical systems, such as antioxidant, antimicrobial and anti-inflammatory properties as well as bioaccessibility and bioavailability. [ABSTRACT FROM AUTHOR]

Mature seeds of diploid and tetraploid Hibiscus species were analyzed for enzyme activity (alcohol dehydrogenase, malate dehydrogenase, leucine aminopeptidase), total protein content, DNA amount and dry weight. The recently formed tetraploid, H. radiatus, generally had enzyme and protein levels very similar to the sum of its progenitors, while the more ancient species H. acetosella had several lower levels. This difference may reflect the greater amount of time H. acetosella has had to evolve dosage compensations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract Hibiscus acetosella was shown to exert beneficial effects in humans and animal models however, the effects of this plant on DNA are unknown. The aim of this study was to determine the antigenotoxic and antimutagenic effects of H. acetosella extracts on alkylating agent methyl methanesulfonate (MMS) in vivo in mice. Initially, we performed analysis of phenolic compounds in extracts of H. acetosella by high-performance liquid chromatography (HPLC). Next, mice were divided into 8 groups and treated with distilled water or plant extract (0.1 ml/10 g) by gavage for 15 days, followed by intraperitoneal (ip) administration of saline solution or MMS (40 mg/Kg b.w) on day 16. Caffeic acid, following by gallic acid, gallocatechin, coumaric acid, and 3,4-dihydroxybenzoic acid were found to be present in extracts of H. acetosella leaves. In peripheral blood analysis of groups receiving pretreatment with H. acetosella at doses of 50 or 100 mg/kg plus MMS decreased DNA damage as evidenced by comet assay and Micronucleus assays relative to MMS alone. These results suggested that H. acetosella extracts exerted protective effects dose dependent against genotoxicity and mutagenicity induced by alkylating agents.