Halophytic Grasses, a New Source of Nutraceuticals? A Review on Their Secondary Metabolites and Biological Activities

Identification of Polyphenols in Sea Fennel (Crithmum maritimum) and Seaside Arrowgrass (Triglochin maritima) Extracts with Antioxidant, ACE-I, DPP-IV and PEP-Inhibitory Capacity

Sea fennel and seaside arrowgrass are two abundant but underutilized halophytes along the Atlantic and Mediterranean coasts. This study investigated the antioxidant capacity and the potential antihypertensive (Angiotensin Converting Enzyme I, ACE-I inhibition), hypoglycaemic (Dipeptidyl Peptidase IV, DPP-IV inhibition), and nootropic (Prolyl Endopeptidase, PEP inhibition) activity of their polyphenol extracts. They had a high phenol content (21-24 mEq GA/g), antioxidant capacity evaluated using the ABTS (17-2 mg ascorbic acid/g) and FRAP (170-270 mM Mohr's salt/g) assays, and effective ACE-inhibiting properties (80-90% inhibiting activity at final concentration of 0.5 mg/mL). Additionally, the sea fennel extract displayed high DPP-IV inhibitory capacity (73% at 1 mg/mL), while the seaside arrowgrass extract exhibited potent Prolyl endopeptidase inhibitory capacity (75% at 1 mg/mL). Fractionation by HPLC concentrated the bioactive molecules in two fractions, for which the composition was analyzed by LC-MS/MS. Different chlorogenic acids seemed to play an important role in the bioactivity of sea fennel extract, and different flavonoids, mainly apigenin, luteolin and chrysoeriol, in the bioactivity of the seaside arrowgrass extract. Given their potential health benefits, these extracts could serve as valuable bioactive ingredients and could potentially encourage the cultivation of these species in regions where traditional crops face challenges in growth.

Harnessing the Value of Tripolium pannonicum and Crithmum maritimum Halophyte Biomass through Integrated Green Biorefinery

Bioactive extracts are often the target fractions in bioprospecting, and halophyte plants could provide a potential source of feedstock for high-value applications as a part of integrated biorefineries. Tripolium pannonicum (Jacq.) Dobrocz. (sea aster) and Crithmum maritimum L. (sea fennel) are edible plants suggested for biosaline halophyte-based agriculture. After food production and harvesting of fresh leaves for food, the inedible plant fractions could be utilized to produce extracts rich in bioactive phytochemicals to maximize feedstock application and increase the economic feasibility of biomass processing to bioenergy. This study analyzed fresh juice and extracts from screw-pressed sea aster and sea fennel for their different phenolic compounds and pigment concentrations. Antioxidant and enzyme inhibition activities were also tested in vitro. Extracts from sea aster and sea fennel had phenolic contents up to 45.2 mgGAE/gDM and 64.7 mgGAE/gDM, respectively, and exhibited >70% antioxidant activity in several assays. Ethanol extracts also showed >70% inhibition activity against acetylcholinesterase and >50% inhibition of tyrosinase and α-glucosidase. Therefore, these species can be seen as potential feedstocks for further investigations.

Halophytes as new model plant species for salt tolerance strategies

Soil salinity is becoming a growing issue nowadays, severely affecting the world's most productive agricultural landscapes. With intersecting and competitive challenges of shrinking agricultural lands and increasing demand for food, there is an emerging need to build resilience for adaptation to anticipated climate change and land degradation. This necessitates the deep decoding of a gene pool of crop plant wild relatives which can be accomplished through salt-tolerant species, such as halophytes, in order to reveal the underlying regulatory mechanisms. Halophytes are generally defined as plants able to survive and complete their life cycle in highly saline environments of at least 200-500 mM of salt solution. The primary criterion for identifying salt-tolerant grasses (STGs) includes the presence of salt glands on the leaf surface and the Na⁺ exclusion mechanism since the interaction and replacement of Na⁺ and K⁺ greatly determines the survivability of STGs in saline environments. During the last decades or so, various salt-tolerant grasses/halophytes have been explored for the mining of salt-tolerant genes and testing their efficacy to improve the limit of salt tolerance in crop plants. Still, the utility of halophytes is limited due to the non-availability of any model halophytic plant system as well as the lack of complete genomic information. To date, although Arabidopsis (Arabidopsis thaliana) and salt cress (Thellungiella halophila) are being used as model plants in most salt tolerance studies, these plants are short-lived and can tolerate salinity for a shorter duration only. Thus, identifying the unique genes for salt tolerance pathways in halophytes and their introgression in a related cereal genome for better tolerance to salinity is the need of the hour. Modern technologies including RNA sequencing and genome-wide mapping along with advanced bioinformatics programs have advanced the decoding of the whole genetic information of plants and the development of probable algorithms to correlate stress tolerance limit and yield potential. Hence, this article has been compiled to explore the naturally occurring halophytes as potential model plant species for abiotic stress tolerance and to further breed crop plants to enhance salt tolerance through genomic and molecular tools.

Salt-Tolerant Plants, Halophytes, as Renewable Natural Resources for Cancer Prevention and Treatment: Roles of Phenolics and Flavonoids in Immunomodulation and Suppression of Oxidative Stress towards Cancer Management

Halophytes and xerophytes, plants with adequate tolerance to high salinity with strong ability to survive in drought ecosystem, have been recognized for their nutritional and medicinal values owing to their comparatively higher productions of secondary metabolites, primarily the phenolics, and the flavonoids, as compared to the normal vegetation in other climatic regions. Given the consistent increases in desertification around the world, which are associated with increasing salinity, high temperature, and water scarcity, the survival of halophytes due to their secondary metabolic contents has prioritized these plant species, which have now become increasingly important for environmental protection, land reclamation, and food and animal-feed security, with their primary utility in traditional societies as sources of drugs. On the medicinal herbs front, because the fight against cancer is still ongoing, there is an urgent need for development of more efficient, safe, and novel chemotherapeutic agents, than those currently available. The current review describes these plants and their secondary-metabolite-based chemical products as promising candidates for developing newer cancer therapeutics. It further discusses the prophylactic roles of these plants, and their constituents in prevention and management of cancers, through an exploration of their phytochemical and pharmacological properties, with a view on immunomodulation. The important roles of various phenolics and structurally diverse flavonoids as major constituents of the halophytes in suppressing oxidative stress, immunomodulation, and anti-cancer effects are the subject matter of this review and these aspects are outlined in details.

Halophytes as Medicinal Plants against Human Infectious Diseases

Halophytes have long been used for medicinal purposes. However, for many decades, their use was entirely empirical, with virtually no knowledge of the bioactive compounds underlying the different applications. In recent decades, the growing problem of antibiotic resistance triggered the research on alternative antimicrobial approaches, and halophytes, along with other medicinal plants, regained attention as an underexplored pharmacological vein. Furthermore, the high nutritional/nutraceutical/pharmacological value of some halophytic species may represent added value to the emerging activity of saline agriculture and targeted modification of the rhizosphere, with plant-growth-promoting bacteria being attempted to be used as a tool to modulate the plant metabolome and enhance the expression of interesting metabolites. The objective of this review is to highlight the potential of halophytes as a valuable, and still unexplored, source of antimicrobial compounds for clinical applications. For that, we provide a critical perspective on the empirical use of halophytes in traditional medicine and a state-or-the-art overview of the most relevant plant species and metabolites related with antiviral, antifungal and antibacterial activities.

Population Dynamic of the Annual Halophyte Salicornia ramosissima in Salt Pans: Towards a Sustainable Exploitation of Its Wild Populations

Halophyte species growing under stressful conditions, such as the annual species of the Salicornia genus, have been recognized as a source of metabolites of pharmacological and nutraceutical interest. Therefore, planning the extraction of individual plants from wild populations in a sustainable way is especially important in the case of annual species. We studied the environmental matrix and population dynamic of four Salicornia ramosissima populations growing at two elevations in salt pans under a Mediterranean climate. In elevated areas, S. ramosissima populations presented maximum plant densities of between 628–6288 plants m⁻² that remained almost constant until fruiting. In contrast, populations in depressed zones presented five-times greater soil-seed-bank densities and maximum plant densities than populations in elevated zones. In this context, populations in depressed zones lost c. 60% of their maximum plant densities from the end of spring and through summer. In whatever way the environmental matrix seemed to control the population dynamic of S. ramosissima in depressed zones, the effects of a stressful environment would interact with plant densities. In this sense, we recorded the density-dependent mortality for the densest population (max. 51,558 plants m⁻²). Our results are useful for planning a sustainable harvesting of natural populations of S. ramosissima.

Phytochemical Compositions of Some Red Sea Halophyte Plants with Antioxidant and Anticancer Potentials

The aim of this study was to determine the compositions of carbohydrates, phenolic compounds, fatty acids (FAs), and amino acids (AAs) of four Rea Sea halophytes: Anabasis ehrenbergii, Suaeda aegyptiaca, Suaeda monoica, and Zygophyllum album. The results showed that S. aegyptiaca and S. monoica were rich in gallic acid with 41.72 and 47.48 mg/g, respectively, while A. ehrenbergii was rich in naringenin with 11.88 mg/g. The polysaccharides of the four species were mainly composed of galactose (54.74%) in A. ehrenbergii, mannose (44.15%) in S. aegyptiaca, glucose and ribose (33 and 26%, respectively) in S. monoica, and arabinose and glucose (36.67 and 31.52%, respectively) in Z. album. Glutamic acid and aspartic acid were the major AAs in all halophyte species with 50–63% and 10–22% of the total AAs, respectively. The proportion of unsaturated fatty acids (UFA) of the four species was 42.18–55.33%, comprised mainly of linolenic acid (15.54–28.63%) and oleic acid (5.68–22.05%), while palmitic acid (23.94–49.49%) was the most abundant saturated fatty acid (SFA). Phytol and 9,19-cyclolanost-24-en-3β–ol represented the major unsaponifiable matter (USM) constituents of S. monoica and A. ehrenbergii with proportions 42.44 and 44.11%, respectively. The phenolic fraction of S. aegyptiaca and S. monoica demonstrated noteworthy antioxidant activity with IC₅₀ values of 9.0 and 8.0 μg/mL, respectively, while the FAs fraction of Z. album exhibited potent cytotoxic activity against Huh-7, A-549, and Caco-2 cancer cell lines with IC₅₀ values of 7.4, 10.8, and 11.8 μg/mL, respectively. Our results indicate that these plants may be considered a source of naturally occurring compounds with antioxidant and anticancer effects that could be suitable for future applications.

Halophytes.tn: an innovative database for Tunisian halophyte plant identification, distribution and characterization

Halophytes.tn (http://halophytes.rnrt.tn/) is a web-based database of Tunisian halophyte species. Halophytes are salt-tolerant plants able to grow above 85 mM of salt, even up to 2 M as for Tecticornia spp. Tunisia, a North African country located on the Mediterranean border, covering ∼165 000 km², harbors several types of saline habitats and biotopes where halophytes preferably vegetate. With ∼6000 worldwide and over 420 Tunisian species, halophytes represent a huge potential in several fields, including desalination, phytoremediation, agrofarming, medicinal use, industrial applications, pharmacology and even nanotechnology. We describe the practical and technical steps followed and bioinformatics tools used to conceive and design the first Tunisian halophytes database, enabling species identification and characterization. As a first version, information about botany, morphology, ecophysiology and biochemistry were provided for the identified species with their sites of growing in Tunisia, first step of biodiversity conservation, management and valorization. The database will be regularly maintained, updated and enriched to achieve the goal of whole Tunisian halophyte species and fit the needs of scientists and all category of users.Database URL: http://halophytes.rnrt.tn/

Sea Purslane as an Emerging Food Crop: Nutritional and Biological Studies

Halophyte plants are highly adapted to salt marsh ecosystems due to their physiological and ecological characteristics. Halimione portulacoides (L.) Aellen is one abundant halophyte shrub that belongs to a Chenopodiaceae family and Caryophyllales order and is found on sandy or muddy coastlines and salt marshes. In this study, the leaves of sea purslane (H. portulacoides) grown in Figueira da Foz (Portugal) were characterized at nutritional and mineral concentration. Moreover, different methanolic extracts were obtained from the leaves, and the antioxidant activity was assessed by several methods. From a nutritional point of view, this halophyte plant may be considered a good source of dietary fiber, protein, natural minerals such as calcium, magnesium, manganese, copper, and potassium. The primary sugar found in leaves of sea purslane is maltose, followed by sucrose, glucose, and fructose. Finally, leaves showed a high content of phenolic compounds and considerable antioxidant activity. The novel products butter and pasta enriched with powder dried leaves of H. portulacoides revealed the plant’s potential to be used as a salt substitute and a good alternative to enhance the sensory characteristics of products, with additional health benefits. The nutritional characteristics and the phytochemical value highlight H. portulacoides as a potential candidate crop in saline agriculture and to be used as a new vegetable, especially as a premium food in the novel “salty veggies” market or as a kitchen salt substitute.

Metabolomic profiling and biological properties of six Limonium species: novel perspectives for nutraceutical purposes

The genus Limonium includes important halophyte plants containing a variety of bioactive compounds of therapeutic interest. In the present work, the untargeted phytochemical profiles of both aerial part and root extracts from six Limonium species namely, L. bellidifolium, L. globuliferum, L. gmelinii, L. lilacinum, L. sinuatum and L. iconicum from Turkey were determined. Furthermore, several biological activities (in vitro antioxidant and enzyme inhibitory effects) were investigated. Overall, significant amounts of total phenolics (43.64-238.18 mg g-1) and flavonoids (1.61-129.69 mg g-1) were recorded. Particularly, the root extracts of L. gmelinii, L. iconicum and L. globuliferum showed the highest total phenolic content (204.13-238.18 mg g-1), whilst the highest total flavonoid content was recorded in the root extracts of L. gmelinii (129.69 mg g-1). Overall, the tested extracts demonstrated potent radical scavenging activities in both DPPH (2,2- diphenyl-1-picrylhydrazyl) and ABTS (3-ethylbenzothiazoline-6-sulphonic acid) (90.10-507.94 mg g-1 and 163.39-1175.34 mg g-1, respectively). However, the highest scavenging potential (p < 0.05) was displayed by the root extracts of L. iconicum. Conversely, the metal chelating ability assay revealed that L. lilacinum root extract showed the highest activity (21.03 mg g-1). Interestingly, all the extracts were found to be active inhibitors of cholinesterases (AChE (acetylcholinesterase): 4.20-5.11 mg GALAE (galantamine equivalent) per g; BChE (butyrylcholinesterase): 3.89-10.75 mg GALAE per g), amylase (0.52-1.09 mmol ACAE (acarbose equivalent) per g) and tyrosinase (119.41-155.67 mg KAE (kojic acid equivalent) per g), unlike for glucosidase (2.31-2.41 mmol ACAE per g). Taken together, these findings demonstrated a diverse chemical profiles and biological of the extracts, to be potentially considered as phytotherapeutic or functional ingredients due to their antioxidant properties and inhibition of key enzymes involved in several diseases.

Imperata cylindrica: A Review of Phytochemistry, Pharmacology, and Industrial Applications

Imperata cylindrica is a medicinal plant native to southwestern Asia and the tropical and subtropical zones. To date, 72 chemical constituents have been isolated and identified from I. cylindrica Among these compounds, saponins, flavonoids, phenols, and glycosides are the major constituents. Investigations of pharmacological activities of I. cylindrica revealed that this edible medicinal herb exhibits a wide range of therapeutic potential including immunomodulatory, antibacterial, antitumor, anti-inflammatory, and liver protection activities both in vivo and in vitro. The purpose of this review is to provide an overview of I. cylindrica studies until 2019. This article also intends to review advances in the botanical, phytochemical, and pharmacological studies and industrial applications of I. cylindrica, which will provide a useful bibliography for further investigations and applications of I. cylindrica in medicines and foods.

Tecticornia sp. (Samphire)-A Promising Underutilized Australian Indigenous Edible Halophyte

Salinization is gradually increasing over cropping soils and is challenging Governments in many countries, including Australia. There has been a high demand for utilizing arid and semi-arid land for sustainable food production. Currently, the main crops and forage plants are salt sensitive, while halophytes can tolerate a wide range of salinities. Samphire is an Australian indigenous edible halophyte and belongs to the genus Tecticornia. It is an underutilized, succulent plant growing on arid or semi-arid land. Most samphire species have a long history of use as food, but also as non-food (fodder and medicine), among indigenous communities in Australia, while scientific information is limited on their nutritional composition and potential bioactivity. The present study reports, for the first time, the nutritional composition, bioactive compounds (phytochemicals) and antioxidant capacity of six Australian grown samphire from different locations. The results showed that celosianin II and isocelosianin II could be identified as the predominant betalains (phytochemicals) in pigmented samphire species. Proximates and fiber varied significantly (p < 0.05) between the samphire species with a highest value of fiber of 46.8 g/100 g dry weight (DW). Furthermore, samphire could be identified as a valuable source of essential minerals and trace elements, such as iron (41.5 mg/100 g DW), magnesium (1.2 g/100 g DW) and sodium (16.7 g/100 g DW). The fatty acid profile, mainly palmitic, stearic, oleic, linoleic and α-linolenic acid, was similar among the studied species. Total phenolic content and DPPH-radical scavenging capacity were different (p < 0.05) between the six samphire samples. These initial results are very promising and indicate that Australian grown samphire may have the potential to be utilized as a functional food ingredient.