Sweet Bell Pepper: A Focus on Its Nutritional Qualities and Illness-Alleviated Properties

Abstract

Sweet bell pepper (SBP, Capsicum annuum L.) can be employed as a spice in many dishes and may also be eaten as a delicious fruit. These two nutritional attributes are owing to the strong, deep taste of many SBP phytochemicals. This fruit has many additional beneficial properties because it contains high concentrations of minerals and vitamins that distinguish it from other kinds of fruits. Almost every part of the SBP is thought to be an excellent source of bioactive substances that are health supporters, such as flavonoids, polyphenols, and various aromatic substances. The ability of SBP-phytochemicals to work as antioxidants, reducing the harmful effects of oxidative stress and consequently preventing many chronic illnesses, is one of their main biomedical characteristics. These phytochemicals have good antibacterial properties, mostly against gram-positive pathogenic microbes, in addition to their anti-carcinogenic and cardio-preventive effects. So, this review aims to highlight the nutritional qualities of SBP-derived phytochemicals and their illness-alleviated characteristics. Antioxidant, anti-inflammatory, antitumor, antidiabetic, and analgesic properties are some of the ones discussed.

Introduction

A well-known fruit product grown all over the world is the sweet bell pepper (SBP, Capsicum annuum L.), which is part of the Solanaceae family. Eating SBP is increasing in popularity as a result of its distinctive and unique color, flavors, and health-promoting ingredients (vitamin E, carotenoids, vitamin C, and other phytochemicals) [1]. There are some cultivars of SBP, as shown in Fig. 1, that can range in color from green to red to yellow to orange according to their level of maturity, capacity for producing carotenoids, or chlorophyll, environmental factors, and climate changes [2].

Fig. 1.

Visual overview of some SBP cultivars

Green SBP and its seeds are high in calories, dietary fiber, vitamin C, and fat [3]. Also, this green-colored cultivar is a good source of antioxidants (AOs) like vitamins C, E, and A, chlorophyll, a variety of phenolic substances, and carotenoids [4]. These types of oxidation inhibitors are known to have anti-diabetic, anti-cancer, anti-inflammatory, anti-atherosclerosis, and anti-aging properties [5]. The antioxidant levels in SBP vary depending on maturity, growing environment, cultured medium, and storage conditions [6, 7].

Damaging free radicals (DFRs) or oxidant substances can build up in human tissues as a result of both regular internal metabolism and external factors (such as radiation, medication, pollution, and cigarette smoke) [4]. A high level of DFRs causes damage through abnormal cellular oxidation in humans [5], which increases the risk of developing a number of long-term diseases, including diabetes mellitus, autoimmune diseases, cancer, and neurological disorders [8]. Because of their ability to protect cells from cellular oxidative damage and stop the spread of chronic diseases, plant-based AOs are attracting a lot of attention [9–12].

Many of the currently-available synthetic medications were derived from plants, which are highly likely sources of the AO drugs that are essential for treating diseases related to cellular oxidative stress [13, 14]. Therefore, the use of DFR removal products produced by plants and animals has become more important recently due to their widespread availability as natural products, affordability, and lack of known negative side effects [15]. Because it is abundant in beneficial substances, including capsaicinoids, phenolic compounds, and vitamins E and C, SBP can prevent/manage long-term conditions caused by oxidative overload [16, 17].

In addition to the eatable parts of SBP, the seeds serve as a possible source of nutrients and biologically active compounds, such as capsaicinoids and phenolics that have both dietary importance and pharmacological potential [18, 19]. Different types of seeds are typically regarded as commercial byproducts; however, according to numerous studies [20–22], such vegetal substances frequently represent an interesting source of biologically active substances that can be used for their biological ability and dietary value [23–27]. Since it is usually believed that people choose organic nutrients, using them in disease treatments and food additives could be an interesting approach [28, 29]. Based on that, SBP can be employed to preserve food because of its antibacterial as well as AO abilities and medication due to its biological characteristics [30–36]. So, this review aims to highlight the nutritional qualities of SBP-derived phytochemicals and their illness-alleviated characteristics.

Nutritional Significance and Phyto-derivatives of SBP

SBP is an abundant source of carbs like glucose, fructose, and sucrose [37]. A large amount of nutritional fiber was discovered in practically all SBP cultivars, and it persisted throughout the plant’s numerous growth stages. The total amount of protein found in various SBP cultivars has been reported to change. Higher CO₂ levels in the air had an adverse effect on the level of proteins, while high CO₂ levels have been shown to increase the amounts of fiber and sugars [38]. In addition, SBP contains a lot of minerals like calcium, zinc, potassium, iron, and sulfur, as well as different vitamins like vitamin C, vitamin B complex, and vitamin A [39]. Table 1 shows the primary and secondary metabolic phytochemicals detected in SBP and their relative quantities.

Table 1.

Phyto-derivatives and related variables of SBP and their quantities calculated for a 100-g sample

Phyto-derivative	Quantity	Reference(s)
Total fat	2.1 g	[39, 40]
Protein	11.22 g	[40, 41]
Carbohydrate	47.23 g	[39, 41]
Water	8.2 g	[39, 40]
Fiber	33.17 g	[39, 41]
Energy	5.724 kcal	[39, 41]
Total ash	6.26 g	[40, 41]
Monounsaturated fatty acids	0.05 g	[39, 41]
Saturated fatty acids	0.059 g	[39]
Iron	7.73 mg	[39, 40]
Calcium	80.16 mg	[40, 41]
Zinc	15.78 mg	[39]
Sodium	22.00 mg	[39]
Phosphorous	5.274 mg	[39, 41]
Cupper	0.007 mg	[39, 41]
Manganese	0.036 mg	[39, 41]
Selenium	0.158 mg	[39, 41]
Magnesium	2.736 mg	[39, 41]
Potassium	6925 mg	[39, 40]
Vitamin C	1.375 mg	[39, 41]
Vitamin B3	0.157 mg	[39, 41]
Vitamin B2	0.017 mg	[39, 41]
Vitamin B1	0.006 mg	[39, 41]
Vitamin B6	0.037 mg	[39, 41]

Nearly every cultivar of SBP is abundant in significant compounds generally and polyphenols as well as flavonoids, in particular, which are known as useful nutritional elements [42]. They also contain glycosides and aglycones, such as luteolin, quercetin, apigenin, myricetin, and kaempferol [43]. Moreover, glycosyltransferase, an enzyme naturally occur in the secondary metabolic pathways of plants, promotes the synthesis of glycosides. In SBP, glycone and aglycone are poorly connected to one another through the glycosidic bond [44]. In addition, the concentrations of different SBP-bioactive substances differ based on the genetic characteristics, species, growth phase, and stages of development, in addition to environmental factors [43].

Illness-Alleviated Properties of SBP

SBP has been used as a dried food component as well as a fruit in its raw form. But it has also been applied in medical practice to treat joint pain, wound healing, infections, sore throats, coughing, and pain in the teeth [45]. Also, SBP is utilized as a reliever for a variety of illness conditions, such as high blood pressure, a bad lipid profile, skin rash, and neuropathy pain, in addition to being employed as an appetizer, and carminative in pharmaceutical preparations [46]. A further study reports that SBP functions as an immunological modulator, an AO, and a stimulant of salivary, hepatic, intestinal, and pancreatic secretions, in addition to improving the digestive tract’s immunity [47]. Some of the biomedical properties of SBP are summarized in Fig. 2.

Fig. 2.

Graphical representation of some illness-alleviated properties of SBP

Oxidative Stress-Alleviated Property

DFRs have been linked to a number of difficult-to-treat health problems, including cardiovascular diseases, cancer, diabetes mellitus, and disorders of the nervous system [48]. A number of enzymes in the body and antioxidants obtained from food sources, such as SBP, can both collaboratively detoxify these DFRs [49]. A wide variety of second-generation metabolites with well-known DFR removal capabilities may be found in SBP [50], as recorded in Table 2. These phyto-derivatives include capsaicinoids, carotenoids [51, 52], and phenolic substances, mainly luteolin, flavonoids, and quercetin [53, 54]. Consuming SBP for four weeks has been shown to increase adult men’s and women’s serum lipoproteins’ resistance to harmful oxidation, and these AO properties provide another advantage in the treatment of heart illnesses and other chronic diseases [55–58].

Table 2.

The mechanisms involved in some illness-alleviated properties of SBP; the aforementioned ones

Medical condition	Bioactive product	Proposed mechanisms of action	Reference (s)
Pain-alleviation	C*	1. It selectively activates TRPV1, a calcium-permeable cationic ion channel in the terminals of nociceptors 2. It causes a degeneration of nerve endings that transmit the pain 3. It decreases response to noxious stimuli 4. It reduces substance P, a pain transmitter in the nerves	[59, 60]
Diabetes-alleviation	C*	1. It decreases storage glucose and lipids 2. It increases the activation of adiponectin gene expression (a protein hormone involved in regulating glucose levels) 3. It causes hepatic AMP-activated protein kinase activation that regulates lipid metabolism	[61]
		4. It reduces blood sugar by promoting the complete activation of TRPV1-expressing neurons in hyperglycemia	[62]
		5. It increases the level of cytochrome C to treat diabetes and decreases the synthesis of mitochondrial B-cell lymphoma 2 protein	[63]
Cancer-alleviation	C*	1. It increases the release of interferon 2. It promotes apoptosis 3. It decreases NADH-oxidase enzyme activity	[64]
		4. It plays a role in stopping the cell cycle at the dividing phase	[65]
		5. It aids in reducing the production and release of inflammatory mediator 6. It blocks proliferation of colon tumor cells	[66]
		7. It improves production of FOXO3	[67]
		8. It reduces the phosphorylation of paxillin and prevent extracellular signal-regulated kinase activation	[68]
		9. It inhibits the development of cells that cause cancer in the colon	[66]
		10. It decreases the growth of the kidney cancer cell	[69, 70]
Inflammatory alleviation	C*	1. It causes inhibition of the cyclooxygenase-2 enzyme activity and nitric oxide synthase expression	[71]
		2. It lowers levels of reactive oxygen generation	[72]
		3. It inhibits lipoxygenase enzyme	[73]
Oxidative stress-alleviation	C*	1. It indirectly increases the production of intracellular AO enzymes 2. It directly interacts with DFR and reduces damage caused by oxidation	[5, 38]
	Vitamin C
	Carotenoids
	Quercetin
	Luteolin
	Lycopene

C* means capsaicin

SBP has acquired a lot of popularity due to the quantity and type of AOs it contains, and due to their AO capacity, polyphenols and carotenoids stand out among AO phytochemicals. Because they contribute to the color, pungency, flavor, and bitterness of fruits, polyphenols are significant in this regard in addition to their AO activity [74]. The different types of pigments found in carotenoid compounds, which consist of vitamin A activity with beta-carotene and oxygen-rich carotene like cryptocapsin, capsorubin, and capsanthin [75] that are responsible for the desirable coloration, have AO properties. SBP also contains capsaicinoids, luteolin, and quercetin, which also contribute to its AO effect [76].

Inflammatory-Alleviated Property

Inflammation, a normal immunological reaction, is brought on by a number of objects, including damage, toxic substances, and infection [77]. If it worsens, it turns into a bodily illness [78]. The presence of bioactive substances, as recorded in Table 2, such as capsaicinoids, polyphenols, tocopherols, flavonoids, and capsinoids, gives SBP its inflammatory-alleviated property [79]. Involving several mechanisms, SBP may reduce inflammation through its ability to suppress the lipoxygenase enzyme. In this regard, green SBP has the greatest level of lipoxygenase inhibition, followed by yellow and red cultivars [38].

SBP can be applied as topical creams and gels for pain treatment owing to the fruit’s widely recognized inflammatory-relieving properties. In order to cause the anti-inflammatory response, capsaicin releases pro-inflammatory substances that consequently stimulate the capsaicin receptors (transient receptor potential cation channel subfamily V member 1), which are linked to nociception and thermoreception [80]. Also, this phytocompound reduced the synthesis of prostaglandin E2 hormones by blocking the activities of the cyclooxygenase-2 enzyme and reducing the level of the enzyme inducible nitric oxide synthase, according to a study to assess these effects in animal macrophages [81].

Cancer-Alleviated Property

SBP has been included in many kinds of traditional cancer therapeutic applications because of its apoptosis-enhancing properties, as recorded in Table 2. Also, SBP has been shown to be beneficial in displaying protective characteristics against several tumor-causing cells and mutations. This protective effect may be mediated by inhibiting the tumor-associated NADH-oxidase enzyme, a cellular growth-promoting enzyme [82–84]. Carotenes, which possess anti-carcinogenic and antimutagenic characteristics [85], are present in high concentrations in SBP. According to the research, using the SBP extract can decrease the genetically harmful function of urethane in the mammal cells, bacteria, and yeast [86]. Furthermore, a chemotherapeutic drug called cisplatin, when used with the bioactive chemicals derived from SBP, could promote cell death in human osteosarcoma tumor cells due to elevated calreticulin production [87].

It is believed that the cancer-alleviated mechanism of capsaicin is immune-stimulating cell death, which is carried out by rapid contact with the surface of calreticulin, a multifunction protein [88]. In particular, capsaicin therapy has been associated with the displacement of calreticulin from the inner membranes to the outer cell surface, increasing cell phagocytosis and stimulating interferon-gamma release [89]. As a result, the death of cells suppressed the activity of the protein sirtuin and the tumor-associated NADH-oxidase enzyme, reducing the development of cancer cells [68]. Additionally, it was found that capsaicin derived from SBP significantly decreased the production and function of many different proteins linked to the progression of cell cycles, thus lowering the extent of malignant cell migration and proliferation [90–92].

Diabetes-Alleviated Property

The alkaloids present in SBP have been shown to be helpful for controlling the level of glucose in the blood; they could ultimately be utilized to treat diabetes in elderly people [93]. According to a study, the SBP’s natural extract assisted in preventing the gastrointestinal absorption of carbohydrates and probably helped lower the level of glucose in the blood [39], as reported in Table 2. Gestational diabetes represents a serious medical danger to both expectant mothers and their unborn children in the near future, and giving this woman a SBP supplement may be useful [94]. According to study findings, supplements containing SBP may decrease hyperinsulinemia and hyperglycemia after eating [95]. In addition to fasting lipid metabolic abnormalities in women with gestational diabetes, these SBP supplementations can also dramatically decrease the occurrence of large gestational-age babies [94].

Pain-Alleviated Property

Researchers examined the pain-relieving abilities of phytocompounds that exist in SBP, as shown in Table 2, and their association with nociceptive behaviors [96]. A large body of research confirms the hypothesis that SBP can modify sensitivity to pain by inhibiting the activity of substance P, a type of neuropeptide that functions as both a neuromodulator and a neurotransmitter. So, SBP is very useful in reducing the pain that’s caused by trigeminal neuralgia as well as painful neurological conditions such as diabetes [97].

In addition to many illness-alleviated properties, SBP has recently shown its efficacy as a local analgesic. The Osteoarthritis Research Society International suggested the use of topically applied SBP as a useful or alternative preparation to anti-inflammatory drugs and oral pain relievers for the treatment of many kinds of pain and inflammation in the parts of the body where typical drugs and oral pain killers often fail to treat effectively [98]. Also, some research found that the dried SBP extract caused important local analgesic effects at doses of 5 mg/kg, 20 mg/kg, and 80 mg/kg; the last dose afforded systemic analgesic effects [99].

Microbial Growth-Alleviated Property

SBP contains polyphenolic compounds that have shown significant anti-pathogenic bacterial activity. Common types of both gram-negative and gram-positive bacteriomers were employed as samples to determine susceptibility to the anti-pathogenic bacterial effect of SBP, as recorded in Table 3. Bacillus subtilis, Salmonella enterica serovar Typhimurium, Bifidobacterium animalis, subsp. Lactis, Lactobacillus plantarum, Lactobacillus acidophilus (CECT-4529), and six wild-type strains of Staphylococcus aureus [8, 14, 26, 32] are among the bacteriomers that have been examined [100].

Table 3.

The mechanisms involved in some illness-alleviated properties of SBP; the last five aforementioned ones

Medical condition	Bioactive product	Proposed mechanisms of action	Reference (s)
Microbial growth-alleviated property	C*	1. It interferes with cell membrane integrity	[101]
		2. It interferes with the formation of biofilm in fungi	[102]
		3. It prevents cellular invasiveness	[103]
		4. It induces hemolytic activity
Cardiovascular problem-alleviated property	C*	1. It decreases total cholesterol, triglyceride, and low-densities lipoprotein levels	[104]
		2. It promotes the production of the cholesterol 7α-hydroxylase enzyme in plasma to avoid heart disease and stroke
	C**	3. It decreases cholesterol levels in cells	[72]
		4. It increases cholesterol efflux
Alzheimer-alleviated property	Green SBP	1. It aids for the memory enhancement and correction of memory impairments	[105]
		2. It improves DFRs removal
		3. It induces suppression of the AChE enzyme
		4. It causes large increase in brain glutathione levels
Skin problem-alleviated property	C*	1. It decreases blood supply to the skin lesion	[106, 107]
		2. It desensitizes nerve ending
		3. It activates nociceptors to produce a burning. sensation
Obesity-alleviated property	C*	1. It stimulates the channel’s receptor vanilloid I and thus inhibits fat production	[108]
		2. It prevents the buildup of fat in central and superficial areas of the body
		3. It causes apoptosis in adipocytes and pre-adipocytes

C* and C** refer to capsaicin and dihydrocapsaicin, respectively

Also, the growth of numerous bacterial and fungal species, including Aspergillus flavus and Listeria monocytogenes, was significantly inhibited by SBP ethanol extracts [109]. The tested fruit may have either bactericidal or bacteriostatic activity against many kinds of bacteriomers. Moreover, SBP also has action against parasites and fungal infections like Toxoplasma gondi and Candida spp., respectively [102].

Cardiovascular Problem-Alleviated Property

SBP contains capsaicinoids like dihydrocapsaicin that have been found to decrease levels of cholesterol in plasma, very low-density lipoprotein, cholesterol, low-density lipoprotein, and triglyceride [110]. Also, these phytocompounds can decrease inflammatory cytokines like tumor necrosis factor-alpha, C-reactive protein, and interleukin-1 beta. Apolipoprotein A1 and high-density lipoprotein cholesterol levels in plasma are additionally increased [111].

The results indicate that the use of capsaicinoids prevents the absorption of cholesterol, and consequently lowering plasma cholesterol levels. Due to its role in raising high-density lipoprotein levels, dihydrocapsaicin actively enhanced the opposite direction of the cholesterol transport (CRT) pathway, suppressing the development of cardiovascular disease while increasing the efflux of cholesterol in THP-1 macrophage-derived foam cells [112]. The cardiovascular problem-alleviated property and the proposed mechanisms of action concerning SBP phytochemicals are recorded in Table 3.

The metabolic syndrome, a group of conditions that includes hypertension, elevated sugar levels, dyslipidemia, and obesity, is frequently considered to be an important risk factor for the onset of cardiac diseases. Much research, in both animal and laboratory settings, has recently been done on the effects of SBP on lowering blood pressure, blood sugar levels, hyperglycemia, reducing blood cholesterol, and the incidence of cardiovascular disease [113], and the results are encouraging.

Alzheimer-Alleviated Property

Alzheimer’s disease (AZ) is a serious neurological condition that primarily affects elderly people. Although the exact causes of AZ are unrevealing, three current mechanisms, involving the termination of cholinergic synapses, the formation of beta-amyloid, and the activation of DFRs, are thought to be responsible for it [114, 115]. DFRs are produced during usual physiologic and metabolic activities in cells and tissues; according to studies published, the overproduction of DFRs may be the main cause of many oxidative stress-related disorders, such as AZ [114]. Reduced synthesis of acetylcholine, a neurotransmitter found in the brain involved in thought, memory, and making choices, further supports the idea that the degeneration of cholinergic receptors causes AZ [116]. Consequently, bioactive substances that have AO and anti-acetylcholine play an essential role in preventing the worsening of AZ [117].

SBP contains many bioactive compounds, such as vitamin C, phenolic acids, flavonoids, carotenoids, and alpha-tocopherol, that have significant health benefits and act as AO to prevent many oxidative stress-related disorders such as neurodegenerative diseases, Alzheimer, cancer, and cardiovascular disease [118]. Also, SBP can help improve memory and cognitive deficits in animal models because of its phytochemicals [119], as reported in Table 3.

Skin Problem-Alleviated Property

Some people may have severe itching that lasts for an extended period. This condition is known as chronic pruritus, and it may be generalized (affecting all the body) or localized (affecting a specific area of the body). SBP contains phytochemicals that have itching-relieving properties and are effective in treating pruritus [106], as recorded in Table 3. According to a study, patients with psoriasis, when treated for twenty-four hours with SBP phytochemicals, are effective in minimizing the blood supply to the area of the skin associated with lesions, which are characterized by redness, scaling, and pruritus to varying degrees, and relieving this symptom [39, 120]. It was shown that SBP phytochemicals work by desensitizing the ends of nerves, therefore decreasing the feeling of skin discomfort. Although the initial usage of SBP may cause feelings of burning, this can be avoided by raising the amount of SBP in the dosage form [38].

Obesity-Alleviated Property

Being overweight is a complicated health problem. Recent years have seen a rise in the number of cases of obesity, which is now considered an important health problem with significant socioeconomic effects [121–123]. Nutritional variables, hereditary factors, a sedentary lifestyle, and the environment all interact to promote a long-term healthy energy balance that results in an increase in fat in the body and so causes obesity [124]. Due to its significant effects on world morbidity, mortality, and economics, obesity is regarded as an international health problem. In addition, being overweight raises the chance of developing a number of chronic illnesses, including heart diseases, diabetes mellitus, hypertension, stroke, osteoarthritis, and many more [125].

Natural methods like using SBP for the treatment of obesity have been evaluated. Producing cheaper and more potent anti-obesity medications using natural ingredients is a great option [126]. Numerous products from nature can prevent diet-induced obesity and cause bodyweight loss and are therefore extensively utilized in the management of obesity [124]. To reduce the overall amount of body fat, several phytochemicals found in SBP may stimulate the breakdown of fat, limit the formation of fatty tissue, and induce death in pre-existing fatty tissue cells, as recorded in Table 3. Natural treatments with a focus on adipogenesis suppression are thought to hold great promise for the treatment of obesity [127].

Many natural substances in SBP, including capsaicin, genistein, linoleic acids, quercetin, and resveratrol, have apoptotic effects on mature pre-adipocytes [128–130]. One of the elements contributing to the onset of obesity is low-level chronic inflammation. According to a research study [131], eating SBP dramatically decreased the number of liposaccharides and decreased chronic low-level inflammation, resulting in anti-obesity characteristics. Moreover, consuming SBP can reduce levels of triglycerides, cholesterol, and glucose, as well as decrease the accumulation of lipid in adipose tissue and epididymal regions [132].

Conclusion

The chemical and functional characteristics of SBP have been highlighted in the writing of this review. This fruit contains many vitamins like B, C, E, and A, and minerals like iron, calcium, magnesium, zinc, sodium, and others that have a role in the benefits of SBP. It also contains a wide variety of phytochemicals and bioactive compounds that enable the use of SBP in a wide variety of applications, like food, medicine, and pharmaceuticals. So, because these bioactive compounds, SBP possesses many illness-alleviated properties that are used in the treatment of a wide range of health disorders, these include oxidative stress, cardiovascular diseases, diabetes mellitus, cancer, and Alzheimer’s disease. In the present review, an attempt was made to summarize the nutritional qualities and biological activities of SBP that have been measured in relation to its medical effects. Finally, the authors concluded that SBP can be regarded as a valuable fruit for medicinal purposes with a broad spectrum of pharmacological properties that, due to their efficacy and safety, could be used in many different medical fields.

Funding

The article is not received any fund.

Data Availability

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Declarations

Conflict of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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