The present study shows that the Mizo people harbor significant knowledge on traditional use of medicinal plants. In India, particularly in northeastern region, Asteraceae is the most dominant family of medicinal plants [29]. However, members of Solanaceae family are very important medicinal plants used by the people of Mizoram [30]. Local people not only collect medicinal plants but also collect large number of wild edible fruits and vegetables to supplement their domestic nutritional requirements. They use different parts of these plants as medicine for different ailments where leaves and fruits are used for medicine preparation, in the form of a decoction, or as powders. The traditional knowledge of ethnobotanical uses of plants among the Mizo people requires documentation for preserving it for the future generations. The present investigation will add significantly to the knowledge on the importance of Solanaceae plants that are used for various purposes.
The preliminary qualitative phytochemical analysis of edible plants of Solanaceae revealed the presence of various bioactive compounds which are reported to have different biological and therapeutic properties. Alkaloids are nitrogenous compounds having antioxidant potential and have been used in folk medicine [31]. Saponin is commonly used as natural antioxidant and also promotes apoptosis in tumor cells [32, 33]. Tannins are well known antimicrobial agents [34], have antioxidant potential and have been used as active ingredients in medicine and beverages [35]. Likewise, flavonoids have antioxidant properties and prevent cell damage, providing anticancer and anti-inflammatory activities [36, 37]. Similarly, it has been reported that the presence of terpenoids influence antimicrobial properties [38], and have been used as a protective agent against oxidative stress-induced diseases [39].
Plants are the diverse source of phenolic compounds with different functions and majority are bioactive compounds with anti-cancer, anti-viral, antioxidant and anti-bacterial potentials [40]. The total amount of phenol observed in the extracts was in comparison with the previous reports by Elekofehinti et al. [41], Oyeyemi et al. [42], Yousaf et al. [43]. Among the extracts, S. anguivi has the highest amount of phenol and this might be the reason that the plant is being used for the treatment of various skin diseases. Flavonoids are bioactive compounds belonging to polyphenolic class and constitute the major antioxidant in fruits, plants and have advantageous effects on human health. Due to their high antioxidant properties, flavonoids are important sources of human diet [44]. They have high potential in antimicrobial, anticancer, anti-inflammatory and anti-allergic activities due to their ability to scavenge reactive oxygen species (ROS) consisting free radicals [45]. In our study, total flavonoid obtained was slightly higher than previous report [46–48]. Even a positive correlation of flavonoid and phenol content with high antioxidant potential of the extracts was recognized (Table 4). Thus, the extracts, filled with high phenol and flavonoids, could be good sources of antioxidants thereby lowering the risk of diseases triggered by oxidative stress and also improving overall antioxidant capacity. Anthocyanins are involved in enzymatic reaction in the flavonoid biosynthesis pathway [49]. Anthocyanins also provide protection against certain chronic diseases such as hyperglycemia [50], inhibit growth of tumour cells in human [51, 52], and also improve vision [53]. Anthocyanin have high antioxidant potential, antibacterial properties and are used as natural food colorants [54]. The total anthocyanin content was found the highest in L. esculentum (0.91 mg/g) followed by P. angulata (0.75 mg/g). C. annuum showed the lowest total anthocyanin content (Table 3). In our findings, the TAC was found higher than previous work in S. nigrum, S. tuberosum, S. lycopersicon, S. melongena, N. tabacum, P. hybrida and Withania somnifera extraction [55, 56]. Recent reports have suggested that Solanaceae plants are promising resources for anthocyanin extraction [49]. The demand for anthocyanins is increasing in commercial industries and in pharmaceuticals for treatment of various diseases and also in beverage industries [57]. So, Solanaceae plants could be good sources of anthocyanins for various pharmaceutical and other commercial industries.
Antioxidants present in food are gaining prominence due to their significant function in maintaining human health by preventing diseases through inhibiting free radicals that are responsible for the spread of various diseases such as cancer, neurodegenerative disorders etc. The IC50 for DPPH of L. esculentum was lowest among the studied plants indicating strong antioxidant potential while S. torvum showed the highest DPPH. The phenol and flavonoids are multifunctional bioactive compounds which are antioxidant, antimicrobial, anti-inflammatory and anti-cancer agents. Several studies concluded that these multifunctional bioactive compounds are the major contributors on antioxidant potential of plant extracts [58]. Hence, free radical scavenging capacity observed in our study could be due to high levels of phenol and flavonoid in the extracts. This is in agreement with a report, showing higher free radical scavenging activity with higher overall phenolic and flavonoid content [59]. Hence, the present study reveals that L. esculentum has a strong antioxidant potential. This property may be due to higher phenol, flavonoid and anthocyanin content, which are required for scavenging activity, in L. esculentum. It is also known that the amount of phenolic and flavonoid content in plants are responsible for the free radical scavenging activity. Our study suggests that the extracts of edible plants of Solanaceae display high antioxidant capacity. Environmental conditions like extreme temperature, water stress, high light intensity can cause oxidative damage by over-production of toxic ROS [60]. However, plants can protect themselves against oxidative damage by antioxidant system such as anti-oxidative enzymes and non-enzymatic compounds [61]. Plants contain various anti-oxidative enzymes including SOD, CAT, APX etc. [62]. SOD converts superoxide radicals into hydrogen peroxide, APX uses ascorbate as an electron donor to reduce hydrogen peroxide to water, CAT dismutates hydrogen peroxide into water and oxygen [62]. Living organisms are able to protect themselves from toxic effects of ROS. SOD, APX and CAT are enzymes that help in detoxifying ROS. Increased level of SOD, APX and CAT can clearly lead to enhanced oxidative stress protection [63]. Previous reports have also shown that Solanaceae plants have potential activities of SOD, APX and CAT [64, 65, 55]. Our investigation thus indicates that the Solanaceae plants are good sources of SOD, APX and CAT that have significant value in reducing stress oxidative reaction. Owing to their high antioxidant capacity, these plants can serve as good sources of antioxidants in pharmaceutical and nutraceutical formulations.
The carbohydrate content was much higher than the previous work reported by Akoto et al. [66] in S. torvum (7.033 mg/g). The protein content in the plant extracts was also found to be higher than a previously reported value of 2.32 mg/g of the plant extract [67]. High values of protein and carbohydrate indicate rich in essential nutrients that could be utilized for enhancing nutrition. The mineral ion compositions of the plants were also relatively high in all the studied samples. Dietary intake of potassium has significant effect on coronary heart diseases by reducing blood pressure [68]. Calcium is essential mineral ion for human diet and is involved in cell differentiation, muscle and bone formation [69]. Sodium is required for physiological processes, body fluid balance and cellular homeostasis [70]. Magnesium is essential for circulatory system and is important for metabolism [71]. Our study also showed the presence of micronutrients such as Fe, Cu, Mn, Zn. These micronutrients are required for metabolic processes like respiration and DNA synthesis [72]. Thus, the findings also suggest the effective utilization of these plants as source of minerals or nutrient supplement.
Antibiotic resistance is an epidemic that continues to plague the healthcare system in both developing and developed countries around the world. The appearance and dissemination of multidrug-resistant pathogens has significantly jeopardized conventional antibacterial therapy. This has led to a hunt for new antimicrobial sources preferably plants that contain various bioactive compounds with established therapeutic properties. The present study was undertaken to assess the antimicrobial efficacy of edible plants of Solanaceae against multi-resistant bacterial strains- B. subtilis, E. coli and P. aeruginosa. Results indicated that the plant extracts exhibited significant antibacterial activities towards the tested bacterial isolates. L. esculentum extract showed maximum activity against all the three pathogens. The inhibition was even higher than one reported on methanol extracts of other Solanaceae plants [73]. One of the most serious challenges to humanity is the rise of multidrug resistance by pathogens. Application of effective plant extracts might be a valuable option in combating this phenomenon. Hence, the plants under current investigation could be useful in combating antidrug resistance in the tested bacterial strains. However, further investigations are sought to evaluate anti-viral, anti-fungal and anti-parasitic activities in order to harness the potentials of the plants.
Another important aspect of our study was to identify the functional groups found in the plant extracts using FTIR. This analysis helps in the identification of chemical composition, elucidation of chemical structure and to understand the importance of functional groups as bioactive compounds for phyto-pharmaceutical formulations. The plants have shown similar infra-red spectrum and some intense bands at various frequencies which define the presence of O-H (hydroxyl), O-H stretch (carboxylic acid), O-H bend (phenol or tertiary alcohol) C-H stretch (alkanes), C = C-C (aromatic compounds), C = C stretch (ketone), N-O (nitro compound), C-O (ether), C-N (aromatic primary amines), N-H (amines), C ≡ C (carbonyl), C-Br (aliphatic bromo compounds) (Table 7) groups. The presence of these functional groups indicates different metabolites such as aldehydes, alkanes, alkenes, alkynes, alkyl halides, aliphatic amines, primary and secondary amines, alcohols, aromatics, carboxylic acids, esters, ethers, glycogen, hydroxyl, lipid, organic halogen compounds, nitro compounds, phenols and tryglycerides, that are integral parts of most of the secondary metabolites such as alkaloids, flavonoids, tannins, terpenoids and polyphenol [74]. Functional groups in the plants can be used in different pharmaceutical products such as for anti-cancers, anti-ulcers, jaundice, headache, stomach ache and anti-inflammatory drugs; or as sources of antimicrobial, antioxidant compounds etc. [75–77]. This may also be the reason why traditionally these plants are used by the locals in treatment of stomach ache, as anti-inflammatory medicine etc. (Table 1). The phytochemical screening and FTIR analysis showed that various bioactive compounds were found in the plant extracts that can be used as active antioxidant and anti-microbial agents of plant origin. The current study also revealed clear discrimination between the plants parts tested (leaf, fruit whole plant etc.), displaying significant heterogeneity for identification of bioactive phytochemicals that can be used as herbal medicines. However, further studies are necessary to evaluate in vivo biological activities of the bioactive phytochemicals for designing effective phyto-pharmaceutical formulations.
Table 7
Evaluation of FT-IR spectra of Solanaceae plants.
Frequency range (cm-1) | Peak wavenumber (cm-1) | Functional group |
3870 − 3550 | C. annuum L. | C. frutescens L. | L. esculentum Mill. | P. angulata L. | S. Americanum Mill. | S. anguivi L. | S. betaceum Cav. | S. incanum L. | S. melongena L. | S. torvum L. | O-H stretch alcohol |
3500 − 3200 | 3750 | 3672 | 3672.5 | 3865 | 3742 | 3865 | 3834 | 3741.9 | | 3672 | O-H stretch vibration presence of alcohols, phenols |
3300 − 2850 | 3441 | 3441 | 3387 | 3441 | 3449 | 3649 | 3487 | 3417.9 | 3364 | 3325 | O-H stretch vibration, carboxylic acids |
2500 − 2300 | | 2916 | | 2924 | 2924 | 3225 | | 3302.1 | 2924 | | C-H stretch vibration, alkenes |
2260 − 2100 | | | 2330 | 2307 | | | 2446 | | | 2484 | C = C stretch vibration, alkynes |
1990 − 1739 | | 2160 | 2152.6 | 2137 | 2207 | 2160 | | 2237.4 | | 2237 | Ester C = O stretch, lipid, triglycerides |
1700 − 1600 | | 1836 | 1743.7 | | 1983 | 1921 | 1844 | 1975.1 | | 1975 | C = C stretch vibration, alkenes |
1550 − 1475 | | 1605 | | | 1643 | 1651 | | | 1620 | | N-O asymmetric stretch, nitro compounds |
1470 − 1400 | | | | | 1520 | | | 1543.1 | | | C-C stretch vibration, aromatics |
1400 − 1320 | | | 1458.2 | | 1458 | 1458 | 1420 | | | 1458 | N-O stretch vibration, nitro compounds |
1300 − 1290 | | 1319 | | 1319 | | | | | 1319 | 1319 | C-O stretch vibration, alcohol, carboxylic acids, esters,ether |
1275 − 1150 | | | | | | | | | | | C-H wag stretch vibration, alkyl halides |
1020 − 1000 | | 1219 | 1219 | 1219 | 1219 | 1219 | | 1219 | 1242 | 1219 | C-N stretch vibration, aliphatic amines |
990 − 800 | | 1026 | | | 1034 | 1034 | | | 1034 | 1034 | N-H wag stretch vibration, primary & secondary amines |
790 − 690 | | | | | | | | | | | C(triple bond)C-HC-H bend stretch vibration, alkynes |
680 − 510 | 772 | 772 | | 771.5 | | | 77.5 | 741.53 | 779 | 772 | C-Br stretch vibration, alkyl halides, glycogen |
490 − 400 | 556 | 517 | 640.37 | 671.2 | 594.1 | 617 | 664 | 616.92 | 556 | 617 | Halogen compound |