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Food Science & Technology
The genus Cajanus (Family: Fabaceae) consists of approximately 37 species, and Cajanus cajan (C. cajan) is a significant member of the genus. It is a commercial legume crop widely grown in sub-tropical and semi-arid tropical areas of the world. C. cajan is well known for its folk medicinal uses to treat various disorders, such as toothache, dizziness, diabetes, stomachache, female ailments and chronic infections. These properties have been linked to the presence of several value-added nutritional and bioactive components.
- legumes
- Cajanus cajan
- bioactive compounds
- nutraceuticals
1. Botanical Description
1.1. Geographical Distribution and Taxonomy
C. cajan is a perennial drought resistance legume commonly cultivated in the sub-tropical and semi-arid tropical areas of the world [12,13]. India is the prime producer, corresponding to approximately 90% of the total global production. It has also been found since ancient times in Africa, Caribbean, Southeast Asia, and Egypt and has been grown at a wide range of altitudes (up to 3000 m) [8]. C. cajan is from the Genus Cajanus, Family Fabaceae, Order Rosidae, Class Magnoliopsida, and Kingdom Plantae [7].
1.2. Cytology
The cytological analysis of C. cajan showed that it is diploid having 2n = 2x = 22 chromosomes with an average length of 5.73 ± 1.15 µm up to 10.92 ± 2.69 µm and dominantly metacentric in shape, consisting of 14 metacentric and 4 submetacentric chromosomes [14]. C. cajan has a genome of size 858 mega-base pairs [15]. In the comparative genetic characterization of wild and cultivated C. cajan genotypes, the cultivated species present maximum polymorphic loci [6].
1.3. Morphology
From a morphological point of view, C. cajan is a short-lived shrub with erect stems of 1–2 m height [16]. Its roots are finely nodulated, lateral and deep rooted of up to 3 m, possessing a root system having a central taproot with several secondary and lateral branches. The branching pattern in C. cajan is determined based on the habitat, spacing and plant genotype. The leaves are lanceolate to elliptical in shape and size, ranging from 6 to 17 cm in length and are around the same breadth. The flowers are usually, yellow to orange in color, present a long peduncle of 1–8 cm long and terminal or axillary racemes (4–12 cm). Calyx: gamosepalous with 5 lobes, Corolla: zygomorphic and bright yellow, Androecium: 10 stamens (4 with short filaments and 6 with long filaments), Gynoecium: ovary (superior, pubescent, 2–9 ovules and monocarpellary), style (long, filiform and glabrous), stigma (incurved & thickened), Seeds: spherical or lens shaped [8].
2. Biological Applications
With the growth of world’s economy and enhancement in people’s living standard, several chronic diseases, like neurological, metabolic, inflammatory, cerebrovascular and cardiovascular disorders have increased rapidly [46]. Natural products are widely recognized for their biological or pharmacological potential since ancient times, and recently the interest in their study has re-emerged as upcoming drug candidates. Globally, around 50,000 plants have shown potent therapeutic potentialities [47]. According to pharmacological studies, C. cajan leaves have various bioactivities, including antioxidant, antiplasmodial, anticancer, hypoglycemic, insecticidal, neuroprotective and antimicrobial activities [37,48]. Moreover, the molecular regulatory mechanism of few biological applications/activity are briefly summarized in Table 8. The most relevant therapeutic applications of C. cajan briefly described below and presented in Figure 2.
Figure 2. Different biological applications of Cajanus cajan.
Table 8. Molecular regulatory mechanism of few biological activities of Cajanus cajan.
| S. No. | Biological Activity | Isolated Compounds/Extracts | Biological Activity | Reference |
|---|---|---|---|---|
| 1 | Hypocholesterolemic | Methanolic extract | ↑ LDRL; ↓PCSK9 mRNA | [49] |
| 2 | Antidepressant | Cajanin stilbene acid | ↓ Kynurenine pathway | [50] |
| 3 | Neuroprotective | AgNP | ↑ Proline; ↑ Glyoxalase; ↑ Pyrroline-5-carboxylate synthetase gene. | [51] |
| 4 | Antidepressant | Fluoride exposure | ↓ Growth and membrane stability index; ↑ Reactive oxygen species; ↑ Malondialdehyde; ↑ Glutathione; ↑ Lipoxygenase. | [51] |
| 5 | Antioxidant | Hexane extract | ↓ AChE; ↓ BChE; ↓ α-AMYLASE; ↓ α-glucosidase. | [52] |
| 6 | Antidiabetic | Methanolic extract | ↓ Fasting blood sugar | [53] |
| 7 | Anticancer | Betulinic acid, genistin, orientin and vitexin | ↓ Inhibit the Histone deacetylases enzyme | [54] |
| 8 | Antimitotic | - | ↓ Decrease the percentage of Sea urchin embryonic cells | [55] |
| 9 | Anticancer | Cajanin stilbene acid | ↓ Inhibit several human kinases, ↓ serine/threonine-protein kinase WNK3 | [56] |
LDRL = Low density lipoprotein receptor; PCSK9 = Proprotein convertase subtilisin/kesin type 9; AgNP = Silver nanoparticles; AChE = Acetyl cholinesterase; BChE = Butyryl cholinesterase; ↑: Increased; ↓: Decreased.
2.1. Antimicrobial Activity
The antimicrobial activity of plants varies pronouncedly depending on chemical constituents presents, hence it is difficult to classify single antimicrobial mechanisms, as they rely on the phytochemical properties of the plant [57]. Dinore and Farooqui (2022) [58] investigated the antimicrobial activity of C. cajan leaves methanol extract against Escherichia coli and Candida albicans, and the results indicated a remarkable ability to inhibit the growth of the microorganisms, with minimum inhibitory concentrations (MIC) of 50 µg/mL and minimum fungicidal concentrations (MFC) of 250 µg/mL. Cajanuslactone, one of the most abundant phytoconstituents present in C. cajan leaves is expected to be the responsible for the marked antimicrobial properties [22]. The antifungal potential of C. cajan roots were examined by microdilution method to demonstrate the use of plant extract as a novel therapeutic source [59]. The ethanolic extract of the roots showed antifungal activity in terms of MIC (Candida albicans 512 µg/mL, Candida krusei 512 µg/mL and Candida tropicalis 512 µg/mL) [59].
In another study, Qi et al. [45] extracted the essential oil from C. cajan leaves by solvent free microwave extraction and reported antimicrobial properties to the extracted oil. The essential oil revealed an effective antimicrobial potential, addressed through determination of MIC and minimum bactericidal concentration (MBC), against Bacillus subtilis (1.06 and 2.12 mg/mL, respectively), and Propionibacterium acnes (0.13 and 0.26 mg/mL, respectively).
2.2. Antioxidant Activity
Different studies also have been performed to assess the antioxidant potential of different parts of C. cajan. Aggarwal et al. (2015) reported the antioxidant potential of C. cajan ethanol seed extract using ferric reducing antioxidant power (FRAP) assay. The results obtained revealed a concentration-dependent antioxidant activity (concentration 25 to 450 µg, 4.4 to 43.0 µM) [64].
The HPLC-FRAP analysis of C. cajan stem bark extract, revealed that it consists of 12 phenolic compounds with notable antioxidant activity [52]. Yang et al. (2020) performed DPPH (2,2-diphenyl-1-picrylhydrazyl), NO (Nitric Oxide) scavenging, ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and FRAP (Ferric reducing antioxidant power) assays for determining the antioxidant potential of leaves, seeds and roots of C. cajan. Among them, C. cajan roots showed high antioxidant efficiency than seeds and leaves [30].
2.3. Anti-Diabetic Activity
The antidiabetic potential of C. cajan methanol root extract was addressed by Nahar et al. (2014) in alloxan-induced diabetic Swiss albino mice. The experimental mice were treated with C. cajan extract up to 5 days (200 and 400 mg/kg bw, orally). Glucose tolerance test and hyperglycemic effect studies (involving diabetes induction in mixed sex Swiss albino mice by injection of aqueous alloxan monohydrate, 55 mg/kg, intravenously) were carried out on tested animals, along with determination of the antioxidant activity. The results showed a rapid decline in fasting serum glucose level (p < 0.001) and blood glucose level (p < 0.001) in 5 days. On the basis of these results, the plant extract evidenced potent hypoglycemic and antioxidant properties compared to other species (e.g., Tamarindus indica seeds) [65].
2.4. Tyrosinase Inhibitory Activity
C. cajan root, stems and seeds were also addressed for its ability to inhibit tyrosinase activity, and for that water, dichloromethane and methanol extracts were prepared. The IC50 values of the extracts varied from 3.55–12.43 mg/mL, whereas the maximum inhibitory capacity was reported for methanol root extract (IC50 = 3.55 mg/mL) [38].
2.5. Neuroprotective Activity
A variety of naturally-occurring bioactive compounds are currently being explored for their therapeutic potential in neurodegenerative diseases, but only a few are known to have benefits [68]. The use of plant extracts and their bioactive constituents are one of the promising approaches for the treatment of neurological diseases [69]. C. cajan was also exploited for their neuroprotective abilities. The presence of stilbenoids is able to induce apoptotic neuronal death by Aβ25–35 injection in mice and cause elevation in choline acetyltransferase (ChAT) and superoxide dismutase (SOD) activity in the cortex and hippocampus [70]. In a study with injured larvae of zebrafish, cajanin stilbene acid (CSA) and its derivative were found to decline the migration and production of primitive macrophages and neutrophiles [71], being thus proposed that C. cajan may be a promissory source of biomolecules with neuroprotective abilities.
2.6. Other Bioactivities
In addition to the above listed bioactive effects of C. cajan, other bioactivities, such as hepatoprotective [26,72,73,74,75], anthelminthic [76], anticancer [77], and anti-inflammatory [78] effects have been documented by other researches. Moreover, the C. cajan is also used in paper-making, cosmetic industries and multi-purposely in dietary supplements for human and animals.
This entry is adapted from the peer-reviewed paper 10.3390/molecules27206877
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