Plantago media L. | Encyclopedia MDPI

Plantago media L.: Comparison

Please note this is a comparison between Version 1 by Radu Claudiu Fierascu and Version 3 by Catherine Yang.

Belonging to the Plantaginaceae family, the hoary plantain (Plantago media L.) represents one of the lesser studied species from the Plantago genus. The potential applications of Plantago media (P. media) will be detailed in regard to other potential applications of Plantago species, in respect to recent literature data published.

Plantago media L.
composition
biomedical applications
potential uses
: Plantago media L.

1. Introduction

Accompanying the development of human civilization, plants were commonly used as food, feed or for empirical medicinal purposes [1]. The development of the modern medicine led to the loss of important ethnomedicinal data, accompanied by the disappearance or the reduction of the growing area of medicinally important plants [2]. However, the last decades led to the resurrection of alternative, plant-based medicine [3], together with a search of alternative, “bio” products [4], as well as the discovery of new potential applications of the vegetal materials [5]. Several plant-originating biomolecules have even pursued the long road from “plant to pharmacy shelf”, resulting in economically important commercial products [6]. With the identification of commercially valuable phytochemicals, the vegetal resources could become the subject of over-harvesting, producing environmental or ecological imbalances [6]. This could be avoided by continuously searching for alternative vegetal resources, and by the re-discovery of underutilized plants.

The Plantaginaceae family contains herbs or small shrubs, their habitat ranging from terrestrial to aquatic. The family contains only one genus and approximatively 270 species [7]. Plantago genus is characterized by a wide variety of component phytochemicals, but the most encountered are the iridoid glucosides, flavonoids, hydroxycinnamic acids, terpenoids, polysaccharides, unsaturated fatty acids, vitamins, alkaloids, terpenes and saponins (leaves), respectively xylose and galacturonic acid (mucilaginous seeds) ^[8][9][8,9]. The genus is world-wide represented, several species having a weedy character [7].

Belonging to the Plantaginaceae family, the hoary plantain (Plantago media L.) represents one of the lesser studied species from the Plantago genus. Native to Eurasia and introduced in most parts of the world [10], the plant is a perennial herb, characteristically growing on chalk or limestone soils, but often also encountered on heavy clay soils. Its habitat is mainly related to the presence of a calcium source, being encountered mainly on downland grassland, calcareous pasture or even in water-meadows beneficiary of calcareous water [11]. The species is morphologically characterized by the slender stalk (5 to 50 cm), basal, finely-haired elliptic to ovate leaves, developing in rosette pattern, over 3 cm wide, presenting 7–9 veins and equipped with midribs that can be easily separated from the mesophyll tissue, curly, abundant, or sparsely scattered lamina trichomes on both epidermis, a petiole shorter than the leaf lamina, delicate pink-white flowers (appearing May–September) that are pollinated by wind and insects, and contains 4 seeds per capsule ^{[12][13][14][15][16][17][18][19]}[12,13,14,15,16,17,18,19]. A tetraploid species, P. media shows treading resistance, a feature related to the resistance being represented by the strong root contraction [10]. The hoary plantain is edible (fresh young leaves being used in fresh salads or cooked as other leafy green vegetables) [20] and its uses were apparently common in the past, its seeds being encountered in the archaeological excavations from Roman period Britain ^[21][22][21,22] and even earlier [23]. Its use in folk medicine included several applications, such as antimicrobial, anti-inflammatory, anti-histaminic, hemostatic, cicatrizing, expectorant and diuretic ^[20][24][20,24]. The commonly used part for medical purposes is the leaves, used for the preparation of infusions [22].

2. Plantago media L. PoFutential Applicationure Perspectives

The potential applications of P. media will be detailed in regard to other potential applications of Plantago species, in respect to recent literature data published.

2.1. Health Applications

P. squarrosa and P. major L. exhibited anti-microbial potential ^[25][26][67,68] against several gram-positive and gram-negative bacteria or fungi, a good support of the mycostatic potential observed for P. media ^[27][37]. Another very important potential activity is represented by the antiviral potential. Chathuranga et al. ^[28][69] evaluated the antiviral potential of P. asiatica and its component verbascoside (acteoside), a compound that, as previously presented, can be found in relatively high quantities in P. media ^[27][37], against the respiratory syncytial virus, the in vivo assays suggesting a possible anti-viral path to be followed.

The anti-inflammatory potential of P. media ^[29][43] was supported by the application of P. major and P. lanceolata extracts as anti-inflammatory agents (either in vitro, in carrageenan-induced paw edema model, by determining the expression of the proinflammatory enzyme, cyclooxygenase, or on oral epithelial cells), an effect attributed to the presence of phenylethanoid compounds (in particular, verbascoside) ^{[30][31][32][33]}[70,71,72,73].

An anti-tumoral potential was observed for P. major and P. lanceolata extracts ^[34][35][36][74,75,76], as well as for the polysaccharide fraction of P. ovata ^[37][77]. All the previously presented activities for different Plantago sp. represent a good indicator, supporting the reported applications of P. media.

Other studies, in turn, would suggest potential applications of the hoary plantain that are waiting to be explored. For example, a hepatoprotective action was observed for the defatted aqueous methanolic extract obtained from the leaves of P. major (effect attributed to verbascoside) ^[30][70], P. ovata husk mucilage ^[38][78] and seed aqueous extract ^[39][79], P. asiatica seeds polysaccharide fraction ^[40][80], P. psyllium seeds ethanolic extract (for which the total phenolics and total flavonoids contents were determined as 16.17 mg gallic acid equivalents/g dried weight, respectively 1.9 mg rutin equivalents/g dried weight) ^[41][81] and P. albicans leaves aqueous extract (total phenolics content 592.75 mg gallic acid equivalents/g, total flavonoids content 116.7 mg catechin equivalents/g ^[42][82], in several hepatic damage models, Table 3). Considering the variety of extracts and fractions used, the results would suggest a hepatoprotective potential for the P. media, also.

The renoprotective effect of the P. major Soxhlet extracts (ethanol, 70%) was evaluated in Cisplatin and Adriamycin induced renal dysfunction in animal models ^[43][44][45][83,84,85], while the P. albicans leaves extract and P. asiatica and P. depressa (a species to which, according to recent phylogenetic analyses, P. media is closely related [19]) seeds extracts proved to have an anti-obesity potential, by effectively improving lipid and glucose metabolism in high-fat diet-induced obese mice ^[46][47][48][86,87,88].

The flavonoid fraction isolated and the leaves extract obtained from P. major (a species that, as previously stated ^[49][59], presents a lower total flavonoids content, compared with P. media), were evaluated as antiarrhythmic agents (by functional modulation of Na⁺ and Ca²⁺-channels in cardiomyocytes) ^[50][89], respectively as anxiolytic agents ^[51][90]. Arabinoxylan (a polysaccharide isolated from different Plantago sp.) proved to have anti-diabetic (by improvement of carbohydrate, lipid and amino acid metabolism) ^[52][91] and prebiotic (by enhancing the growth and antimicrobial activity of Lactobacillus casei) properties ^[53][92].

The Plantago asiatica L. extract and polysaccharide fraction were proved to have antihypertensive effect (trough angiotensin-converting-enzyme 46 inhibition, while simultaneously protecting organ damage against hypertension) ^[54][93], respectively to alleviates nonylphenol induced reproductive system injury (via PI3K/Akt/mTOR pathway) ^[55][94].

The whole plant extract of Plantago rugelii Decne was evaluated by Ogbiko et al. ^[56][95] in an anti-ulcer study, the results suggesting that the infusion (200 and 400 mg/kg) had a protective effect against gastric ulceration (induced by aspirin and HCl). Similar results were obtained by Bagheri et al. ^[39][79], using the aqueous P. ovata seeds extract, in an indomethacin-induced rat model, observing a reduction in microscopic and macroscopic ulcer index. Seed mucilage of P. ovata was used by Basiri et al. ^[57][96] as a potent lead biosorbent (increasing fecal excretion and decreasing lead tissue absorption) in mice models.

All these potential applications of Plantago sp. remains to be studied for P. media, as no studies in those area were performed to this date, up to theour knowledge.

2.2. Other Applications

Besides the health-related applications, Plantago sp. were evaluated for a series of industrial applications. The methanol extract of P. lanceolata could find application in fish farming, as its application was proven to promote growth, as well as to enhance immune responses and antioxidant enzyme activities in rainbow trout ^[58][97], while verbascoside and aucubin was proved to reduce NH₃ production on rumen fermentation, reducing the N losses in the urine ^[59][98].

P. lanceolata extracts were proposed for the development of natural cosmetics (due to their UV protecting activity, as well as skin regeneration stimulation) ^[60][99], while the gum isolated from P. major seeds proved to have emulsifying and foaming properties, which supports the use of the fraction as an alternative hydrocolloid for emulsion and foam-based foods ^[61][100]. Related to the food industry, P. major mucilage (extracted either by hot-water extraction or ultrasound assisted extraction) was used for the development edible and biodegradable films ^[62][63][101,102]. This could lead to the development of bioproducts for increasing the shelf-life of meat products. For example, the application of the edible film (with a 1.5% dill essential oil content) increased the shelf life of beef by 9 days ^[62][101].

The mucilage separated from Plantago sp. could also find application in other important areas, such as scaffolds for cell culture, drug delivery systems or food additives. This would involve the development of biocompatible materials, such as those proposed by Allafchian et al. ^[64][103], based on P. ovata mucilage and polyvinyl alcohol.

Correlated with their metal-uptake capacity, Plantago sp. could be used for phytoremediation potential. This application was studied, for example, for P. lanceolata and P. major for the removal of toxic heavy metals (Pb, As, Cd) ^[65][66][104,105]. The studies revealed a higher concentration of heavy metals in the roots, compared with the leaves, thus suggesting a limited mobility of the heavy metals, as a part of the resistance mechanism to heavy metals (involving an avoidance strategy, such as the immobilization of the metal at root level and in cell walls) ^[66][105]. The same plant was proved efficient in the phytoremediation of organic pollutants contaminated sites ^[67][106].

Another potential application of P. media, correlated with their metal up-take capacity could be in the improvement of mineral concentrations in the diet of livestock, to prevent the apparition of mineral deficiency, trough increasing species diversity in swards ^[68][107]. However, the hoary plantain affinity towards different metals could represent a drawback, as some studies ^[69][108] suggest a potential for P. media to up-take hazardous heavy metals. Although this aspect could be beneficial for phytoremediation strategies, it needs to be considered for other application, the control of heavy metals content in extracts should be performed before their application. The use of P. lanceolata in cattle diet was proven to reduce N₂O emissions ^[70][109] and to increase the growth performance and carcass characteristics of lambs ^[71][110], areas in which P. media could find applications.

Another environmental application of Plantago sp. is represented by its mucilage ability to remove organic pollutants. The biocomposite membrane (P. psyllium mucilage, eggshell membrane and alginate) proposed by Mirzaei and Javanbakht ^[72][111] proved to have the ability to remove cationic and anionic dyes (methylene blue and methyl orange) from aqueous solutions, reaching an adsorption capacity of 5.45 and, respectively, 3.25 mg/g. Another potential application of the Plantago sp. is represented by their chemical inhibitor potential. For example, the polysaccharide fraction of P. ovata was proposed as a green corrosion inhibitor by Mobin and Rizvi ^[73][112], their study suggesting a protective effect of the developed material for the carbon steel in hydrochloric medium, presenting a good inhibition efficiency (92.53%) accompanied by a low risk of environmental pollution. The authors assign the main corrosion inhibitor role to the highly branched polysaccharide arabinosyl (galaturonic acid) rhamnosylxylan ^[73][112].

Finally, a new and promising application of Plantago sp. is related to the nanotechnology area, in particular for the nanoparticles phytosynthesis (synthesis of materials using plant extracts). Briefly, the phytosynthesis mechanisms involve the reduction of metals from metallic salts precursors to zero-valent nanoparticles or metallic oxides, using the different plant phytoconstituents ^[74][113]. The mechanism, presented in multiple studies ^[75][114] uses the phytocomponents both as reduction and capping agents. This alternative method of nanoparticles synthesis leads to materials with enhanced properties, valuable for a series of medical and industrial applications ^[74][76][113,115], enhancing the intrinsic properties of the nanoparticles ^[77][116], as well as a potential reduction of their toxicity ^[75][114]. The application was explored for P. major aqueous leaves extracts, leading to the synthesis of silver nanoparticles (AgNPs) and iron oxide nanoparticles (IONPs—spherical, 4.6–30.6 nm) and the exploration of their environmental applications, for the enhanced phytoremediation of soil and water contaminated with the insecticide fipronil ^[78][117] and for the removal of methyl orange dye, respectively ^[79][118].