Traditional medicinal system of United Arab Emirates utilizes many native plants, and increasing amounts of evidence has revealed the presence of potent antioxidant activity in herbal extracts [1, 2]. Crude extracts of UAE plants showed many medicinal properties including antioxidant effects, so there will be vast potential of medicinal plants as source of new drugs [2, 3]. Scientific evidence supports that rationale of using native plants and traditional formulations in health care. In this modern era, all medical systems rely on synthetic medicine, but the plant materials remain an important resource for combating illnesses, including infectious diseases. Out of the native plants used in traditional medical systems, many have been investigated for potential drugs, alternative medicine, food additives, agrochemicals and industrial chemicals [4].

According to World Health Organization (WHO) 80% of the population of developing countries still relies on traditional medicines, mostly plant derived drugs, for their primary health care needs [5, 6]. Phytochemicals are naturally occurring bioactive compounds present in plants, which acts as agents for protection of tissues from stress, diseases and other deleterious effects. Phytochemicals can be primary or secondary metabolites, they may be pigments, proteins, sugars, terpenoid, alkaloids and phenolic compounds [7]. Medicinal plants are a major natural alternative to synthetic drugs, and nowadays, native plant usage in traditional as well as modern medicine is gaining a lot of attention [8].

Tephrosia apollinea (Delile) DC. is a perennial shrub and legume species, and one of the most common plants in the lower mountains of the UAE [9]. There are many traditional medical uses for this plant, e.g. leaves for relieving earache and pain from fractures, bark for removing ticks from camel ears [9]. The plant possesses insecticidal and anti-cancer properties [10, 11]. The plant possesses medicinal properties and has significant anti-bacterial properties; the leaves and the root have been used to treat bronchitis, cough, earache, wounds and bone fractures by herbalists in countries like Oman [9, 12].

Tephrosia purpurea extracts showed the presence of isoflavones, flavanones, flavanols and flavones [13]. The leaves of Tephrosia contains semiglabrin, semigalbrinol, and a flavanone named apollineanin [14]. Recently, there are reports indicating that a number of species of Tephrosia possess medicinal properties [15]. These studies help in identification and scientific validation of Tephrosia. Reactive oxygen species (ROS) are responsible for many diseases of cardiovascular systems, neurodegenerative disorders, diabetes mellitus and cancer. Antioxidants obtained from natural resources gained high research interest to face diseases generated by ROS [16]. In this regard, it seems important to estimate the natural antioxidant and phytochemical contents of native plants used in the traditional medical systems of UAE. This study aims to investigate the scientific basis for the use of T. apollinea plant by analyzing the phytochemical constituents, proximate and mineral compositions and the free radical scavenging activity from the aerial plant parts.

Total phenolics and flavonoids contents of methanolic extract of T. apollinea were 12.36 mg GAE/g and 4.18 mg QE/g respectively.

The reducing power of extract is given in Table 4, at each concentration, in the range of 10–50 µg/ml compared to GAE. The methanolic extract of T. apollinea exhibited a significant dose dependent inhibition of reducing power-scavenging activity. The reducing power of extract of T. apollinea was very potent and the reducing power of the extract and was increased with quantity of sample. The plant extract could reduce the most Fe³⁺ ions, which had a lesser reductive activity than the standard of GAE. The reducing power shows good linear relationship in both standard gallic acid (R² = 0.956) and T. apollinea extract (0.984). Therefore, ferric reducing antioxidant activities of methanol extract of T. apollinea indicating the ability of plant extract to reduce Fe³⁺ to Fe^2+. The methanolic extract of T. apollinea exhibited a significant dose dependent inhibition of reducing power activity.

Medicinal plants are a pool of drugs of traditional systems of medicine, also modern medicines relies a lot in traditional plants. United Arab Emirates has a wide variety of medicinal plants in its relatively desert and arid flora [1–3]. Many synthetic drugs are being replaced by herbal plants due to their nutraceuticals values, and are often without side effects [29]. The medicinal and nutritional potentials of the aerial parts of T. apollinea were assessed in this study through qualitative and quantitative assays of the phytochemicals and the proximate composition and minerals content from this plant.

Phenolics are important plant metabolite playing a remarkable protective role against several health disorders [30]. Phenolics possess various biological activities, for different types of ailments [31]. There are scientific reports showing relationship between phenolic content and antioxidative activity of the methanolic extract of different plants. In this study also, we can correlate the antioxidative activity with the presence of phenolics and other compounds. Presence of phenolics is one of the mechanisms of the overall antioxidant activities in plant samples and is mainly due to their redox properties [32].

Terpenoids exhibit pharmacological activities like anti-inflammatory, anticancer, antihyperglycemic, antipasmodic anti-malarial, inhibition of cholesterol synthesis, anti-viral and anti-bacterial activities [33]. Additionally, terpenoids can be used as protective substances in storing agriculture products as they are known to have insecticidal properties as well [34]. Due to the presence of gallic and diagallic acids, tannins have the oxidation inhibiting activity [35]. Flavonoids, on the other hand are potent water-soluble antioxidants and prevent oxidative cell damage, with considerable anticancer activity [36]. It also helps in managing diabetes induced oxidative stress. Here in this study, we report significant flavonoid contents in the extract of T. appollinea.

The alkaloids are the class of nitrogenous compounds and a diverse array of which are produced by numerous plants as secondary metabolites [37]. They are usually produced by plants for protective functions like from stresses or defense toward herbivory or pathogenic organisms and insects [37]. They have been reported to be active against many metabolic disorders like hypertension, arrhythmia, malaria, cancer and cardiovascular problems [38]. Saponin’s natural tendency to destroy microbes makes them good candidates for treating fungal, yeast infections, and serve as natural antibiotics, which help the body to fight infections and microbial invasion [39].

The aerial parts of T. apollinea contains crude fibre, all fall in the range of recommended dietary allowance (RDA) for fibre in children, adults, pregnant and lactating mothers [40]. But due to the reported toxicity of this plant [41, 42], it cannot be recommended to consume as such. Crude fibre can decrease serum cholesterol levels, which is the main risk of coronary heart disease, hypertension, diabetes, colon and breast cancer [40]. Ash content is generally taken to be a measure of the mineral content of the original food. Natural food products should have a general ash content of about 5% while processed food can have ash content ranging over 10%. According to A.O. A.C, this study shows that Tephrosia species have acceptable levels of ash content as natural food products. Wild edible plants high in carbohydrate are helpful for the body to meet up with daily activities, and most of them contains antioxidant compounds [43]. In this plant high carbohydrate content are more advantageous than those with excess protein because the body does not require too much of protein and fat. Moisture content determination is one of the most fundamental and important analytical procedure. According to Yisa et al. [44] high moisture content increases perishability as the fruits are more susceptible to microbial infections.

Minerals such as calcium and sodium are essential in maintaining a good health. Besides that, zinc plays quite a crucial role as well. There has also been an increasing concern in the amount of minerals in food as human’s fundamental minerals [45]. In the presence, micro and macro elements are vital for the overall mental and physical well being; and are important constituent of bones, teeth, tissues, muscles, blood and nerve cell and can help in acid–base balance [46]. Deficiency of vital and trace elements in human can occur even under the most practical dietary conditions and in many diseased statuses. The aerial parts of T. apollinea had significantly higher potassium concentrations. Potassium content in the body was reported to increase iron utilization and beneficial to control hypertension through body fluid [47]. While the remaining nutrients like Ni, Pb and Cr had negligible concentration levels in T. apollinea. Cr is considered toxic even at 5 mg/l and due to this reason, most of the plants shows lesser concentration of Cr as compared to that of recommended level for toxicity in plants. The deficiency of Mg causes semi coma, diabetes mellitus and neurological disturbances [48].

The function of DPPH assay method is that the antioxidants respond with the stable free radical. During the free radical effect, DPPH (α,α-diphenyl-β-picrylhydrazyl) is converted into α,α -diphenyl- β-picrylhydrazine with colour change. The rate of colour change slowly decreases to indicate the scavenging potentials of the sample antioxidant. The methanolic extracts of T. apollinea contain flavonoid, saponins, tannins, phenolics and aromatic compounds. Shehab et al. [31] showed the ethanolic and methanolic extracts of herbs showed noticeable DPPH radical-scavenging activity as compared to ascorbic acid. All these bioactive compounds were able to discolour DPPH solution by their hydrogen donating ability [49]. T. apollinea possesses significant reducing power property in methanol extract. It means, most of the compounds derived from this plant are electron donors, and therefore it can reduce the oxidized intermediates of lipid peroxidation process, so that they can act as primary and secondary antioxidants [32]. The maximum DPPH radical scavenging activity in fresh pulp can be attributed to the richness of the total phenolic components. Energy and nutrient values of medicinal plant samples are mainly used to translate medicinal samples intakes as intakes of food components.

In this study, the aerial parts of the T. apollinea showed considerable phytochemicals and thus the plant extract can be used as an efficient free radical scavenger. The study also demonstrated post harvest storage quality of plant material because of low level of moisture content, indicative of its prolonged shelf life. The antioxidant qualities are also significant, thus making it an excellent ingredient of traditional medicine and can be useful in the synthesis of active medicinal compound for modern medicine. However, individual active compound isolation and characterization is needed in order to elucidate the structure of phyto-active principles compounds, which could be used for pharmaceutical use, which is the next step in our study.