1. Introduction
Capparis decidua (Forsk.) Edgew (Capparidaceae), locally known as Kair, is a drought resistant plant growing in dry regions of Pakistan as dense tufts [
1]. Besides many socioeconomic and ecological benefits [
2], all parts of this plant have a number of medicinal properties. The plant is traditionally used to cure toothache, arthritis, asthma, cough, inflammation, intermittent fevers, malaria, rheumatism, and swelling. It is also believed to possess laxative, astringent and vermifuge properties [
3,
4]. The alcoholic extract of fruit pulp and root bark is claimed to have anthelmintic activity. The fruits and the seeds are used to cure cholera, dysentery and urinary purulent discharges and have diuretic and antidiabetic properties [
5]. The spicy taste fruits serve as an astringent for bowels, a remedy for bad breath and is claimed to cure cardiac troubles [
4]. The green immature fruits are considered antihelminthic and laxative and are employed in the treatment of asthma, constipation, coughs, hysteria and other psychological problems [
6]. The blanched fruit is used as a vegetable [
7]. Green berries are used in food preparations such as pickles [
8]. The seeds oil is edible when processed and also used to cure skin diseases [
4].
Several chemical and pharmacological researches have been carried out on
C. decidua Sterols [
9], fatty acids [
10], flavones [
11], oxygenated heterocyclic constituents [
12], alkaloids [
13–
18], and an isothiocyanate glucoside [
19] have been reported in different parts of this plant. The nutritional value of flowers and fruits of
C. decidua was also evaluated [
20,
21].
Different extracts of the plant have been demonstrated to possess pharmacological properties. The plant has been reported for its Central Nervous System sedative and depressant [
22,
23], and antimicrobial properties [
8,
24,
25]. Methanol and water extracts of
C. decidua possessed hepatoprotective activity [
26]. The effects of extracts of the plant on human plasma triglycerides, total lipids and phospholipids have been reported [
27]. The fruit has been shown to possess anti-atherosclerotic [
28], antidiabetic [
29,
30], anti-hypertensive [
31], and anti-hyperlipidemic [
28,
32,
33] properties. The cardiovascular activity of capparidisine, a spermidine alkaloid from
Capparis decidua, has been reported [
34].
This study reports some chemical features of this plant, along with the evaluation of antioxidant, antidiabetic and antihemolytic activities of extracts of different parts of C. decidua.
2. Results and Discussion
To the best of our knowledge, there is no previous report on compositional studies of
C. decidua seeds. These were firstly subjected to proximate analysis. Results indicate presence of high amounts of carbohydrates (25.42 ± 0.26%), proteins (27.71 ± 1.39%), and lipids (29.11 ± 1.07%) (
Table 1).
Proximate composition is therefore an index of total energy content in a food and its analysis usually is the first step when evaluating its nutritional potential. Our results agree with those reported earlier for other parts of
Capparis decidua and for other
Capparis species [
35,
36]. A balanced amino acid profile is an indicator of quality of proteins and foods. The amino acid content of
C. decidua seeds (
Table 2) indicated that glutamic (24.01 ± 0.56%) and aspartic acids (11.91 ± 0.14%) were present in highest concentrations, while methionine (0.75 ± 0.62%) and cysteine (0.34 ± 0.01%) were in lowest concentrations. A similar amino acid pattern was reported for other
Capparis species [
37].
Fatty acid composition (
Table 3) showed a high content of linoleic acid (47.33 ± 1.04%), while eicosenoic acid has been found in lowest amounts (0.52 ± 0.38%). These results are similar to the data previously reported [
38,
39]. It has been reported that linoleic acid prevents cardiovascular disorders such as coronary heart disease, atherosclerosis, as well as hypertension [
40]. Fatty acid composition of
Capparis decidua seed oils can be considered an interesting point with regard to the further use of the seeds for oil purpose.
Moreover, γ-Tocopheol was found in highest amount in seed oil (
Table 4), while β-tocopheol was found in lowest amount. These results are similar to those reported for
Capparis spinosa [
41]. High amounts of tocopherols can be interesting for the stabilization of fats and oils against oxidative deterioration and for applications in dietary, pharmaceutical, or biomedical products. Sterol profile of
Capparis decidua seed oil indicated that β-sitosterol was the major constituent (
Table 5). Like other parameters, no previous study reported sterol contents of this species. Sterols are perhaps the most important class of the minor components and comprise a major portion of the unsaponifiable matter of most vegetable oils. The occurrence of Δ
5-avenasterol in the seed oil is of interest because this compound is known to act as an antioxidant and as an anti-polymerization agent in frying oils [
42]. Sterols with an ethyldiene group in the side chain are believed to be one of most effective antioxidants.
Plants producing large amounts of glucosinolates are of interest, because their derivatives can serve as natural pesticides and are under investigation as antitumoral drugs [
43]. Glucosinolate contents indicated that all parts of plant material of
C. decidua contained relatively high amounts of these anti-nutrients (
Table 6). Glucosinolates are present in highest concentration in stems (107.39 ± 1.57 μmol/g) while lowest amount was detected in roots (77.48 ± 0.59 μmol/g). Glucosinolates enzyme degradation products produced negative sensory properties in
Capparis decidua and may have harmful effects on animal health. Microorganisms invading animal gut enable glucosinolates decomposition and formation of various glucosinolates hydrolysis products, namely isothiocyanates, nitriles and thiocyanates [
44]. These compounds, depending on their type, have strong goitrogenic effects and have been frequently reported to be implicated in anti-thyroidal activity [
45]. Although glucosinolates have been detected in other
Capparis species [
41,
46,
47], to the best of our knowledge, there is no report on glucosinolate contents of
Capparis decidua.
The content of total phenolic compounds of different aerial parts of
C. decidua is shown in
Table 6. Generally, examined extracts showed prominently high levels of phenolic compounds. The highest value was obtained in fruit extract (407.72 ± 0.81 mg CE/g), and the lowest in leaves extract (286.51 ± 4.62 mg CE/g). Our results are in agreement with those found for other
Capparis species [
48,
49]. The Folin-Ciocalteu method is relatively simple; however, it is not specific. Heterogeneity of phenolic compounds and the presence of easily oxidized substances other than phenols like vitamin C and Cu(I), leading to elevated phenolic concentrations [
50]. Moreover, this method relies on reaction kinetics and not stoichiometric conversion, it is not very precise, and variations of approximately 5% are typical for replicates, depending on the temperature control and timing precision of the reagent additions and spectral measurements [
51]. Despite the undefined chemical nature of Folin-Ciocalteu Reagent (FCR), the total phenols assay by FCR is convenient, simple, and reproducible and it has become a routine assay in studying phenolic antioxidants [
52].
Three different aerial parts (leaves, flowers and fruits) were subjected to antioxidant activity screening, using different testing methods. The extracts of
C. decidua showed potent antioxidant activity, reducing different types of radicals (
Table 7). In fact, to varying extents, the tested extracts were able to reduce the stable 1,1-diphenyl-2-pictylhydrazyl (DPPH) radical, reaching IC
50 values from 69.1 ± 1.3 μg/mL, for fruit extract, to 104.17 ± 1.68 μg/mL, for leaves extract. Although DPPH and ABTS (2,2′-azinobis(3-ethylbenzo-thiazoline-6-sulphonic acid) diammonium salt) methods are based on the same principle, data obtained from ABTS assay were lower than those obtained from DPPH assay, reaching Trolox equivalent (TE) values from 341.86 ± 1.37 μmol TE/g for leaves extract, to 501.17 ± 1.34 μmol TE/g for fruit extract. This is probably due to steric factors that are one of the major factors influencing the reduction of stable DPPH radical. Moreover, results obtained from Ferric reducing antioxidant power (FRAP) and Total radical-trapping antioxidant parameter (TRAP) assays are in agreement with values obtained from the above discussed assays. The superoxide radical scavenging assay (SRSA) is said to be more relevant than those methods described above, because it utilizes a biologically relevant radical source. This radical mediates inflammatory tissue injuries in ischemia-reperfusion, arthritis, gout and gastric ulceration. Superoxide radical has a low reactivity and a low capacity to penetrate the lipidic membrane layer, but it can generate hydrogen peroxide and highly reactive hydroxyl radical, via Haber-Weiss reaction. Our findings are in the agreement with those published earlier [
29,
53].
Erythrocyte membrane, being rich in polyunsaturated fatty acids, is susceptible to free radical mediated peroxidation. Since this peroxidation is a free radical chain reaction, the erythrocyte membrane is quickly damaged leading to hemolysis. Moreover, the red blood cells hemolysis is claimed to be a more sensitive system for evaluating the antioxidant properties of the phytoceuticals [
54]. In the present study, the investigated extracts were reported to possess dose dependent inhibitory effects towards hemolysis of cow blood erythrocyte. It is possible that a high total phenol content in the extract can produce this potent antihemolytic activity, as previous studies ascribe the antihemolytic capacity to these components [
55].
Diabetes mellitus is a metabolic disorder characterized by a congenital (type I insulin-dependent diabetes mellitus) or acquired (type II noninsulin-dependent diabetes mellitus) inability to transport glucose from the bloodstream into cells [
56]. Currently, much attention is being paid to plants and their constituents for the treatment of diabetes. A possible therapeutic approach for treating diabetes is to decrease postprandial hyperglycaemia. This can be achieved by delaying the absorption of glucose through the inhibition of carbohydrate hydrolyzing enzymes, α-amylase and α-glucosidase in the digestive tract [
57]. Therefore, α-amylase and α-glucosidase inhibitors found in medicinal plants have long been studied to evaluate their antidiabetic properties. Among the extracts of
C. decidua studied, the fruit extract showed satisfactory inhibitory effect on both enzymes, followed by flowers and leaves extracts, at both concentrations tested (
Table 8). Like other parameters, enzyme inhibition activities of this plant have not been previously reported. Results obtained in the present study support the use of this plant as a dietary supplement for the treatment of diabetes. Further studies are required to find out the mode of action of these plant extracts in inhibiting α-amylase and α-glucosidase.