Significance of Carotenoids in Traditional Medicines in the Republic of Suriname (South America)

Abstract

Carotenoids are pigments that produce bright yellow, red, orange, and purple colors in some vegetables and fruits. These compounds play major roles in various critical functions of plants. Carotenoids are also indispensable for humans, exerting antioxidant effects and sustaining both low-light and color vision. The more than 700 different types of carotenoids can be divided into two classes: the carotenes (e.g., β-carotene and lycopene) which do not contain oxygen, and the xanthophylls (e.g., lutein and zeaxanthin) which contain oxygen. In addition, some carotenoids such as β-carotene and α-carotene can be converted by the human body into vitamins A; lutein, zeaxanthin, and lycopene are non-provitamin A carotenoids. The Republic of Suriname (South America) is renowned for its relatively high plant diversity which comprises about 5100 species of higher plants. Several of these plants have a relatively high content of carotenoids and are widely consumed and used as traditional medicines. In this chapter, the traditional uses of eight Surinamese fruits and vegetables rich in carotenoids have been addressed, and the pharmacological support for their traditional uses has comprehensively been dealt with. The chapter concludes with the scientific evidence to justify the traditional uses of the carotenoids in these plants.

1. Introduction

Carotenoids are natural pigments belonging to the class of terpenoids that produce many of the bright yellow, orange, red, and purple colors of fruits, flowers, and tubers of certain plants such as citrus fruits, peppers, tomatoes, carrots, and sweet potatoes [1]. So far, over 700 structurally different carotenoids have been identified [1], and they play several major roles in plants [2, 3]. Firstly, these compounds are essential to photosynthesis by absorbing light in the blue-green region of the solar spectrum and transferring the absorbed energy to chlorophylls, thus expanding the wavelength range of light that enables photosynthesis [2, 3]. Furthermore, carotenoids help protect plants from photo-oxidative damage by scavenging singlet molecular oxygen and peroxyl radicals [2, 3]. These compounds also help protect plants from predation by repelling predators and attracting insects, birds, and small mammals to assist in the pollination of flowers and the dispersal of seeds [4, 5].

In addition to plants, carotenoids are produced by various other organisms including (heterotrophic) bacteria, fungi, algae, aphids, and spider mites [6]. These compounds are also responsible for the pinkish-red colors of some birds, fish, crustaceans, and insects which feed on organisms that contain carotenoids such as the red flamingo; salmon, red trout, and red sea bream; as well as shrimp, krill, crab, lobster, and crayfish [6].

Humans are unable to synthesize these compounds de novo and rely on the diet as a source of carotenoids [7]. As mentioned in greater detail below, these compounds play major roles in human health by functioning as precursors of vitamins A [8, 9]. Carotenoids are also important by functioning as crucial components of the exogenous defense system against reactive oxygen-derived species (ROS) [10, 11]. This chapter provides some information about the biochemistry, classification, and biosynthesis of carotenoids, gives some background on the Republic of Suriname, and then comprehensively addresses eight well-known Surinamese fruits and vegetables that are rich in carotenoids, highlighting the involvement of these compounds in the beneficial and health-promoting effects of the plants.

2. Biochemistry, classification, and biosynthesis

Carotenoids are polyunsaturated lipid-soluble tetraterpenoids consisting of a C-40 polyene backbone that is made up of eight isoprene units connected head-to-tail, except for the central unit, which has a reverse connection [6, 12]. Carotenoids can be classified into two main groups, namely carotenes and xanthophylls [6, 12]. Carotenes are unoxygenated carotenoids which typically contain only carbon and hydrogen (and are therefore placed in the subclass of unsaturated hydrocarbons), and include, among others, β-carotene, lycopene, and α-carotene [6, 12]. These compounds have in general an orange-red color [13, 14, 15]. Xanthophylls are oxygenated derivatives of these hydrocarbons, containing hydroxyl, methoxyl, carboxyl, keto, or epoxy groups, and include, among others, lutein, zeaxanthin, β-cryptoxanthin, and neoxanthin, and often have a yellow color [6, 12].

Important sources of orange-colored β-carotene are carrots (Daucus carota L.; Apiaceae), ripe tomato fruit (Solanum lycopersicum L.; Solanaceae), and ripe paprika fruit (Capsicum annuum; Solanaceae) [3, 16]. Lycopene contributes to the red color of ripe tomato fruit, and the xanthophyll capsanthin to that of paprika fruit (Capsicum annuum; Solanaceae) [3, 16]. Carrots also contain α-carotene, as does the beetroot (Beta vulgaris L.; Amaranthaceae) as well as mandarins (Citrus reticulata Blanco; Rutaceae) and oranges (Citrus × sinensis (L.) Osbeck; Rutaceae) [3, 16]. Fresh, dark-green, leafy vegetables such as spinach (Spinacia oleracea L.; Amaranthaceae), lettuce (Lactuca sativa L.; Asteraceae), as well as kale and broccoli (cabbage cultivars from Brassica oleracea L.; Brassicaceae) also contain relatively high levels of β-carotene, in addition to lutein and zeaxanthin [3, 16]. Only a relative handful of foods contain fairly high concentrations of β-cryptoxanthin [17]. A few examples are tangerines (Citrus tangerina Tanaka; Rutaceae) as well as yellow and orange maize (Zea mays L.; Poaceae) [18]. And the pink/red coloration of marine animals such as crustaceans, shellfish, and salmon is caused by the xanthophyll astaxanthin in the plants and small animals they feed on [3, 16].

In plants, carotenoids are synthesized in the chloroplasts in the leaves through a highly conserved and ubiquitous metabolic pathway reviewed in Ref. [19]. Briefly, the pathway starts with the fusion of two C20 geranylgeranyl pyrophosphate molecules (from the upstream methylerythritol pathway) to produce the C40 tetraterpene 15-cis-phytoene (the tetraterpene skeleton). This step is catalyzed by phytoene synthase, a rate-limiting enzyme for the pathway. Next, phytoene is transformed into ζ -carotene and then into lycopene by the enzymes ζ-carotene desaturase, phytoene desaturase, and carotenoid isomerase.

The formation of lycopene represents a branch point in the pathway after which two series of products can be formed: catalysis by lycopene β-cyclase and lycopene ε-cyclase results in carotenoids with two β-rings (for example, β-carotene), and catalysis by the simultaneous actions of the lycopene cyclases generates carotenoids with one β-ring and one ε-ring (for example, α-carotene). Hydroxylation of α-carotene and β-carotene by the action of carotenoid hydroxylases results in the formation of xanthophylls such as zeinoxanthin and α-cryptoxanthin (both of which can be transformed into lutein), as well as zeaxanthin and β-cryptoxanthin, respectively. These compounds can be further converted into other xanthophylls.

3. Health benefits and applications of carotenoids

About forty structurally different carotenoids are present in a typical human diet [20]. As mentioned above, carotenoids function as precursors of vitamins A and as powerful antioxidants in the body [10, 11]. The vitamins A include vitamin A alcohols (retinols), vitamin A aldehydes (retinals), retinyl acids (retinoic acids), and retinyl esters [21]. The body obtains these preformed vitamins A through the consumption of animal products such as meat, fish, poultry, and dairy foods [22]. The body is also able to synthesize vitamins A from the provitamin A carotenoids β-carotene, β-cryptoxanthin, and α-carotene [21]. Lycopene as well as lutein and zeaxanthin are non-provitamin A carotenoids that cannot be converted into vitamins A [21]. Both latter compounds are found in the retina where they help absorb blue light and have been associated with a meaningful reduction in the risk for cataract and age-related macular degeneration [23].

In addition to their role as precursors of vitamins A, carotenoids constitute important components of the body’s exogenous defenses against ROS along with several vitamins, a variety of phenolic compounds, essential minerals, small peptides, and fatty acids [10, 11]. The exogenous antioxidant defenses complement the endogenous mechanisms which comprise enzymatic antioxidant systems such as superoxide dismutase, catalase, and glutathione peroxidase [13]. Both carotenes and xanthophylls contribute to the antioxidant defenses by efficiently quenching singlet molecular oxygen and potently scavenging other ROS such as peroxyl radicals, both alone and together with other antioxidants such as vitamins A [14, 15], protecting the body against diseases associated with oxidative stress such as cancer [24], cardiovascular disease [17], and diabetes mellitus [25]. This hypothesis is supported by observational epidemiological studies mentioning that foods rich in carotenoids and antioxidant vitamins are associated with a reduced risk of these and other chronic conditions [26, 27].

Furthermore, the antioxidant properties of carotenoids are believed to improve the immune system by stimulating lymphocyte activities and cytokine production [28]; fight skin aging, skin damage by UV light, and skin cancer by increasing density, elasticity, and firmness of the epidermis [29]; and lower the risk of dementia [30], in addition to maintaining the health of cornea and conjunctiva as well as the capacity of both low-light vision and color vision [31]. Carotenoids also elicit anti-inflammatory activities, presumably by interfering with the nuclear factor κB pathway following blockade of the translocation of nuclear factor κB to the nucleus [32]. This results in inhibition of the downstream production of inflammatory cytokines such as interleukin-8 or prostaglandin E2 [32] and is generally believed to contribute to the beneficial effects of carotenoids against the above-mentioned diseases [33].

Due to the various pharmacological activities of carotenoids, these compounds are often incorporated into dietary supplements, fortified foods, and nutraceuticals; skin care cosmetics as well as anti-aging and skin repair compounds; colorants in foods; pharmaceuticals and cosmetics; as well as animal feed additives [9, 34, 35]. For example, carotenes or β-carotene (E160a), capsanthin and capsorubin from paprika or paprika oleoresin (E160c), lycopene or tomato extract or tomato concentrate (E160d), lutein (E161b), and astaxanthin (E161j) are used as food additives in, among others, soft drinks and juices, dairy products, breakfast cereals, jams and jellies, snacks and confectionaries, as well as animal feeds [34, 35].

4. The Republic of Suriname

The Republic of Suriname is a small independent constitutional democracy located just north of the Amazon delta, bordering the Atlantic Ocean to the north, French Guiana to the east, Brazil to the south, and Guyana to the west. More than three-quarters of the country’s land surface of about 165,000 km² is part of the Amazon Basin, but Suriname is culturally considered a Caribbean rather than a Latin American country and is a member of the Caribbean Community [36]. Suriname’s population is among the most varied in the world, comprising Amerindians (the original inhabitants of the country) as well as descendants from enslaved Africans, indentured laborers from Asia, and European settlers, as well as immigrants from various Latin American and Caribbean counties [37].

All ethnic groups of Suriname have preserved much of their original culture and identity, still practicing the religion they were raised with, speaking the language from their country of origin, maintaining their specific perceptions of health and disease, and adhering to their ethnopharmacological traditions [38]. As a result, the use of various forms of traditional medicine is deeply rooted in the country, despite the broad availability of affordable modern health care [38, 39]. This inclination, together with the easy access to raw plant material from Suriname’s rich biodiversity, probably accounts for the frequent use of traditional herbal medications in the country, either alone or in conjunction with prescription medicines [38, 39].

5. Carotenoids in eight well-known Surinamese fruits and vegetables

Hereunder, eight vegetables and fruits with a relatively high carotenoid content that are abundantly consumed in Suriname, are in detail addressed for their traditional use. The plants include the mango Mangifera indica L. (Anacardiaceae), the papaya Carica papaya L. (Caricaceae), the water spinach Ipomoea aquatica Forssk. (Convolvulaceae), the sweet potato Ipomoea batatas L. (Convolvulaceae), the pumpkin Cucurbita moschata Duchesne ex Poir. (Cucurbitaceae), the avocado Persea americana Mill. (Lauraceae), the Suriname cherry Eugenia uniflora L. (Myrtaceae), and the inkplant Renealmia alpinia (Rottb.) Maas (Zingiberaceae). The traditional medical uses of these plants are addressed, as well as the possible pharmacological (and phytochemical) support for these uses. The relevant characteristics of the plants are given in Table 1.

Plant family	Plant species (vernacular name in English; Surinamese)	Carotenoid-containing plant part(s): major carotenoid(s) [References]	Pharmacological activities possibly related to the presence of carotenoids [References]
Anacardiaceae	Mangifera indica L. (mango; manya)	Fruit: β-carotene [40, 41]	Antioxidant [42, 43, 44], eye health-promoting [45], immuno-stimulatory [46]
Caricaceae	Carica papaya L. (papaya; papaya)	Fruit: lycopene, zeaxanthin [47, 48]	Antioxidant [47, 48], anti-inflammatory [49, 50], anti-hyperlipidemic [51], antidiabetic [52, 53], eye health-promoting [54]
Convolvulaceae	Ipomoea aquatica Forssk. (water spinach; dagublad)	Aerial parts: β-carotene, lutein, and violoxanthin [55]	Antioxidant [56, 57, 58, 59], anti-inflammatory [56, 57, 58, 59, 60], antidiabetic [57, 61, 62], laxative and purgative [63], central nervous system depressant activity [64, 65], antibacterial [66]
Convolvulaceae	Ipomoea batatas L. (sweet potato; switi patata)	Tuber: β-carotene [67, 68]	Antioxidant [69, 70, 71], anti-inflammatory activity [69, 70, 71], eye health-promoting [71], immuno-stimulatory [69, 70, 71], ulcer protective [72], skin health promoting [72]
Cucurbitaceae	Cucurbita moschata Duchesne ex Poir. (pumpkin; pampun)	Fruit: β-carotene, lutein [73]	Antioxidant [74, 75], anti-inflammatory [76], eye health-promoting [74], anticancer [77, 78]
Lauraceae	Persea americana Mill. (avocado; afkati)	Fruit: β-carotene, lutein, and zeaxanthin [79, 80]	Cardiovascular [81], anti-osteoarthritic [82], anti-hyperlipidemic [83, 84], appetite-depressant and weight-reducing [85], antioxidant [84, 86, 87, 88], antimicrobial [84], anti-inflammatory [84, 86, 87, 88], anticancer [89], eye health-promoting [90]
Myrtaceae	Eugenia uniflora L. (Suriname cherry; monkimonki kersi)	Fruit: lycopene, γ-carotene, and β-cryptoxanthin [91]	Antioxidant [92, 93], anti-inflammatory [94], antidiabetic [92, 95], anti-hyperglycemic and anti-hyperlipidemic [92], anti-aging [93]
Zingiberaceae	Renealmia alpinia (Rottb.) Maas (inkplant; bigi masusa)	Fruit: β-carotene [96]	Antioxidant [96, 97]

Table 1.

Carotenoid-containing plants in Suriname and their relevant characteristics.

5.1 Anacardiaceae: Mangifera indica L.

The fruit of the mango tree M. indica has a yellow-orange-colored, juicy, and very fragrant flesh surrounded by green, yellow, or red skin depending on the variety. The color of the fruit’s flesh is due to carotenoids, particularly β-carotene, while those of the peel are mainly caused by anthocyanins [98]. M. indica fruit contains carotenoids (mainly β-carotene), vitamins A and C, phenolic compounds (including flavonoids other than anthocyanins), volatile terpenoids, as well as various minerals [40, 41]. Preparations from M. indica fruit are traditionally used in Suriname for treating cardiovascular diseases such as hypertension; diabetes mellitus; respiratory ailments; gastrointestinal diseases such as worm infections and bleeding piles; parasitic infections; uterus disorders; skin problems such as warts and bleeding; varicose veins; oral and dental problems; syphilis; and poor eyesight [99].

The abundant amount of β-carotene in M. indica fruit represents a substantial source of vitamin A, supporting its traditional use to benefit vision [99, 100] and to lower the risk for age-related macular degeneration [45]. Some of the other traditional medical claims of the fruit (such as its positive effect on the immune system and efficacy against cardiovascular and diabetic disease) have also been attributed to the antioxidant activity of the carotenoids [42, 43, 44]. However, these health benefits have also been associated with the antioxidant activities of the phenolic compounds and vitamins A and C in the fruit [42, 43, 44, 46] and that of the phenolic compound mangiferin [101].

5.2 Caricaceae: Carica papaya L.

The unripe fruit of the papaya Carica papaya L. (Caricaceae) is renowned for its white latex that contains papain for meat tenderizing, clarifying American beer, and as an ingredient of detergents [102]. The latex as well as extracts from both ripe and unripe C. papaya fruit are also traditionally used in Suriname against hypertension; diabetes mellitus; various gastrointestinal problems including constipation, colic, intestinal worms, dyspepsia, gastritis, and gastroenteritis; hemorrhoids; to stimulate breast feeding; to maintain eye health; and/or as an abortifacient [103, 104]. Externally, fruit preparations are used for treating infected wounds and abscesses; toothache; warts, calluses, and corns; athlete’s foot and ringworm; hair loss; and as a facial mask [104, 105].

Some of the ethnopharmacological uses of C. papaya fruit may be associated with the powerful antioxidant activities of its relatively high content of carotenoids (particularly lycopene) along with those of vitamins A, C, E, and K [47, 48]. As mentioned before, these compounds are able to neutralize ROS and reduce oxidative stress [10, 11], while lycopene also has the capacity to remove excess iron required for the production of ROS in the Haber-Weiss and Fenton reactions [106]. Thus, C. papaya preparations would particularly be beneficial against conditions driven by chronic inflammation such as neoplastic, cardiovascular, and diabetic disease [107]. Indeed, the consumption of C. papaya fruit led to a reduction of inflammatory markers including C-reactive protein in human subjects [49, 50].

These considerations may account for the reduction in oxidative stress and the beneficial effects of C. papaya fruit products in preventing or slowing down heart disease [108] and improving plasma HDL-to-LDL ratio [51] as well as markers of diabetes mellitus [52] and prediabetes [52, 53]. The relatively high content of zeaxanthin, along with lutein, in C. papaya fruit may be related to a lower risk for age-related macular degeneration [54]. And the powerful antioxidant effects of vitamin C and lycopene in C. papaya fruit may help prevent, delay, and repair skin damage [109].

5.3 Convolvulaceae: Ipomoea aquatica Forssk.

The water spinach Ipomoea aquatica Forssk. (Convolvulaceae) I. aquatica has a relatively high content of carotenoids including β-carotene, lutein, and violoxanthin [55]. The plant contains, furthermore, abundant amounts of phenolic antioxidants including flavonoids; vitamins A, C, and B-complex group; some alkaloids; as well as several minerals [110]. Preparations from the aerial parts of the plant are traditionally used in Suriname against diabetes mellitus; gastrointestinal problems such as constipation, jaundice, and parasitic worms; skin conditions including hemorrhoids and furuncles; heart conditions, hypertension, and anemia; as well as stress, nervousness, agitation, sleep disturbances, and psychological problems [111, 112].

Some of these traditional uses are supported by the antidiabetic effects of I. aquatica preparations in various preclinical models [61, 62] as well as type II diabetic patients who had been subjected to a glucose challenge [61]; their potent laxative and purgative properties [63]; and their notable central nervous system depressant [64] and anxiolytic activity in various laboratory models [65]. Furthermore, I. aquatica preparations displayed anti-inflammatory effects, inhibiting in vitro prostaglandin synthesis [60] and carrageenan-induced edema in a rat paw model [66], and showed in vitro antibacterial effect [66].

The potential involvement of several carotenoids in some of the pharmacological activities of I. aquatica is supported by the potent preclinical free radical scavenging, anti-inflammatory, and/or hypoglycemic activities of several carotenoids in preparations from its leaf and stem [56, 57, 58, 59]. So far, however, there are no studies that firmly associate the carotenoids in I. aquatica with these and the other pharmacological activities of preparations from the plant. Notably, flavonoids have also been implicated in the antioxidant activities of I. aquatica preparations [113, 114], suggesting that the presumed beneficial effects of the plant are attributable to the combined actions of carotenoids and other classes of bioactive phytochemicals.

5.4 Convolvulaceae: Ipomoea batatas L.

The sweet potato Ipomoea batatas L. (Convolvulaceae) develops yellow- to brown-colored and orange- to purple-colored starchy and sweet-tasting tubers with white through pink, violet, red, and purple flesh, depending on the cultivar. The different colors reflect different ratios of carotenoids versus anthocyanins in the tubers [67]. The cultivars with dark orange flesh have more β-carotene than those with light-colored flesh [67]. I. batatas tuber is also rich in dietary fiber, vitamins A, C, and E, as well as manganese and potassium [68]. Preparations from several parts of I. batatas including the tuber are also traditionally used in Suriname for treating, among others, ophthalmological disorders such as macular degeneration and catarrh; respiratory conditions; diabetes mellitus; hypertension; gastrointestinal conditions including dysentery and constipation; abscesses; inflammation as well as arthritis and rheumatoid diseases; and cancer [104].

Particularly the orange-fleshed tuber of I. batatas is an important source of β-carotene [67, 68]. It is converted into vitamins A in the body [21] and all these compounds elicit antioxidant, anti-inflammatory, eye health-stimulating, immune-promoting, and other meaningful pharmacological activities [69, 70, 71, 115]. For instance, tuber preparations seem beneficial against night blindness [116] and potentially prevented ethanol-induced gastric ulceration and stimulated wound healing [72]. These observations give some weight to several of the traditional uses of I. batata tuber [104].

However, the exact involvement of β-carotene in I. batatas (and perhaps other carotenoids) in these activities is not certain. Firstly, these compounds might cooperate with anthocyanins in decreasing the risk of colorectal cancer [117] and control blood sugar, lower LDL cholesterol, and the risk of cardiovascular diseases [69, 116]. Secondly, the antidiabetic properties of I. batatas preparations [118], and the inhibitory effects of “sweet potato protein” purified from the fresh tuber on the proliferation, migration, and/or invasion of human colorectal cancer in preclinical models might be attributable to certain flavonoids [119].

5.5 Cucurbitaceae: Cucurbita moschata Duchesne ex Poir

The fruit of the pumpkin Cucurbita moschata Duchesne ex Poir. or Cucurbita pepo L. var. moschata (Duchesne) Lam. (Cucurbitaceae) is rich in β-carotene, lutein, α-carotene, and ζ-carotene; vitamins A, B, and C; essential amino acids; and various minerals [73]. It is traditionally used in Suriname for treating poor eyesight and eye inflammation; various types of tumors; as well as hepatitis, intestinal worms, and disturbed bowel movement [104, 112, 120]. Many pharmacological studies support some of the health claims of C. moschata preparations such as those regarding its anti-inflammatory, antibacterial, anticancer, and deworming properties [121, 122]. Some of these studies support the involvement of carotenoids in the apparent health-promoting effects of the fruit [73]. For instance, its relatively high content of β-carotene as a source of vitamin A would provide meaningful protection of visual function and eye health [74].

The potent antioxidant activity of the carotenoids in C. moschata fruit [74, 75] also suggests that these preparations may be beneficial against diseases associated with oxidative stress and inflammatory processes, tentatively explaining the claims of usefulness of these substances against cancer [74]. Support for this suggestion came from the increased production of Th1 cytokines by mouse splenocytes and RAW 264.7 macrophage cells isolated from mouse spleen which had been exposed to C. moschata fruit preparations and β-carotene [76], and the reduction of the risk of cancer of stomach, intestine, lung, breast, and prostate by increasing the intake of C. moschata fruit and in this way, of several carotenoids [77, 78]. However, it should be taken into account that the results from various studies contradict this claim [122, 123, 124].

5.6 Persea americana Mill (Lauraceae)

The avocado tree Persea americana Mill. produces fruit with smooth, creamy, and golden-green flesh when ripe and a green-, brown-, purplish-, or black-colored skin depending on the cultivar. The fruit contains carotenoids, vitamins A, B, D, and E, potassium, phytosterols including β-sitosterol, as well as an unusually high amount of fat (mostly oleic acid but also palmitic acid and linoleic acid) [125]. The fruit pulp yields an edible oil that is used for salads and dips but also in the cosmetic industry for the production of soaps, hair care products, and skin moisturizers [126]. The seed can also be processed into an oil for the bath and body care industry [127].

Preparations from P. americana fruit pulp and fruit peel (but also from its seed, leaf, fresh shoots, and bark) are used in Suriname against cancer, gastrointestinal diseases, ailments of the respiratory tract, hypertension and hypercholesterolemia, menstrual problems, high uric acid levels, skin afflictions and poor hair growth, as an aphrodisiac, and as an abortifacient [99, 104, 111, 128]. These claims are partially supported by the results from clinical studies showing that fruit pulp preparations decreased the risk of cardiovascular disease and coronary heart disease [81], produced relief in symptomatic osteoarthritis of the knee and hip [82], improved the LDL to HDL ratio in (mildly) hypercholesterolemic patients [83], and had appetite-depressant and weight-reducing properties [85].

Some of these activities have been attributed to the presence of a variety of carotenoids including β-carotene, lutein, and zeaxanthin, in the samples [79, 80]. These carotenoids displayed substantial antioxidant, antimicrobial, and anti-inflammatory activities in vitro [84, 86, 87, 88]. In addition, lutein seemed to play a role in the growth inhibitory effect of a P. americana fruit in cultured prostate cancer cell lines [89] and in the protection against eye diseases such as cataract and macular degeneration [90]. However, various reports have mentioned that phenolic compounds as well as vitamins A, D, and E in the fruit pulp [86, 125] might also contribute to its pharmacological activities [84, 86, 87, 88].

5.7 Eugenia uniflora L. (Myrtaceae)

Depending on the variety, the pitanga or Suriname cherry Eugenia uniflora L. (Myrtaceae) produces orange, bright red, or dark purple fruit with juicy, sweet-sour-tasting flesh that is very rich in lycopene, γ-carotene, and β-cryptoxanthin, as well as phenolic compounds including anthocyanins and flavonoids, vitamin C, calcium and phosphorus, and pectin [91]. Preparations from the fruit are traditionally used in Suriname against high blood pressure and heartburn; diabetes mellitus; headaches, chest colds, flu, influenza, bronchitis, a sore throat, coughs, and fevers; microbial infections; skin irritations, itching, and measles; anemia and hyperuricemia; and colics and stomachache [104, 128, 129]. Preclinical studies with E. uniflora fruit extracts partially supported these uses, showing meaningful antioxidant [92, 93], anti-inflammatory [94], α-glucosidase inhibitory [95], anti-hyperglycemic and anti-hyperlipidemic [92], and anti-aging activities [93].

These pharmacological activities have mainly been attributed to phenolic compounds in the fruit preparations—particularly anthocyanins—which are believed to help mitigate the oxidative damage associated with cardiovascular disease, diabetes mellitus, the metabolic syndrome, and skin aging [130, 131]. Furthermore, certain flavonoids in fruit extracts [91] displayed antibacterial and antifungal activity [132, 133], supporting their traditional use against microbial infections [104, 128, 129]. Unfortunately, data on the involvement of carotenoids in the pharmacological activities of E. uniflora fruit preparations are scant, despite the relatively high content of carotenoids in this part of the plant [91, 134]. However, at least the antidiabetic activity of these preparations may be attributable to combinations of carotenoids and anthocyanins [95].

5.8 Zingiberaceae: Renealmia alpinia (Rottb.) Maas

The inkplant Renealmia alpinia (Rottb.) Maas also known as Renealmia exaltata L. f. produces fruit with a red-colored peel when immature and turns purple-black when mature, and then contains numerous seeds embedded in a yellow-brown-colored pulp. R. alpinia fruit pulp contains carotenoids such as β-carotene, phenolic compounds such as flavonoids and anthocyanins, and vitamin C, as well as a variety of volatile terpenoids [96]. The carotenoids contribute to the distinctive colors of the fruit pulp and peel [96, 97], and the terpenoids are mainly responsible for the characteristic flavor and fragrance of preparations from the fruit [135].

Preparations from R. alpinia fruit pulp (as well as those from various other parts of the plant) are traditionally used in Suriname against eye diseases; the symptoms of snake bites; microbial infections; gastrointestinal ailments; cardiovascular conditions; hematologic disorders; obstetric and gynecological problems; and convulsions during, for instance, epileptic seizures [104, 136]. Unfortunately, pharmacological studies with either crude R. alpinia fruit extracts or (partially) purified carotenoid-rich preparations are scant. The meaningful antioxidant activities of the carotenoids [96, 97] suggest that they may be beneficial against conditions involving oxidative stress such as cardiovascular ailments [17, 26, 27], but this remains to be proven. Furthermore, when considering the role of β-carotene as a vitamin A precursor [21], R. alpinia fruit may be useful for treating eye diseases [21, 23], but this has also not been established yet. As well, it must be determined whether and to which extent the carotenoids collaborate with the flavonoids, anthocyanins, and vitamin C to accomplish the potential health effects of R. alpinia fruit [96, 97].

6. Concluding remarks

Carotenoids have two fundamental pharmacological properties which are at the basis of their many health benefits, namely their roles as precursors of vitamins A and as powerful antioxidants [10, 11]. Therefore, these compounds are involved in proper vision, fetal development and male and female reproductive health, skin health, and immune function [28, 29, 30, 31] as well as the protection of the body from oxidative stress and various associated chronic diseases [17, 24, 25, 26, 27]. For these reasons, the intake of carotenoid-rich foods is generally recommended for maintaining and improving health. These considerations also apply to the eight carotenoid-rich plants addressed in this chapter, namely M. indica, C. papaya, I. aquatica, I. batatas, C. moschata, P. americana, E. uniflora, and R. alpinia. The fruit, leaf, or tuber from these plants are abundantly used as highly nutritious foods in Suriname and, in addition, as important traditional medicines. Notably, besides carotenoids and vitamin A, these plant parts contain relatively high amounts of phenolic compounds such as flavonoids and anthocyanins, vitamins C and E, as well as essential minerals. Clearly, these phytochemicals substantially contribute to both the nutritional value and the pharmacological activities of the plants including their provitamin A as well as their antioxidant and anti-inflammatory activities. Therefore, it is not always clear to which degree carotenoids are involved in the latter activities and, consequently, in the potential benefits of the plants against chronic diseases. This particularly holds true for preparations from I. batatas tuber, E. uniflora fruit, and R. alpinia fruit. This is an unfortunate paucity when considering the widespread use of these plants as foods and traditional medicines. For these reasons, comprehensive studies about the precise involvement of carotenoids in these plants (as well as others with a relatively high content of carotenoids) are mandatory.