Food as Medicine

Functional Food Plants of Africa

Maurice M. Iwu

• Verlag: CRC Press
• Jahr: 2016
• ISBN:
  9781315354385
• Auflage: 1
• Thema: Medicine
• Thema: Nutrition, Dietics & Bariatrics

This comprehensive book documents African plants used for functional and medicinal foods. It contains more than 60 detailed monographs of African foods, describing foods with various characteristics such as prebiotic, probiotic, satiety, immune modulation, stress-reduction, sports performance, mental acuity, sleep-supporting, metabolic syndrome, antioxidant, and unsaturated fats. Plant description, botanical names and synonyms, plant part used, habitat and distribution, folk use, nutritional content, and chemistry are all fully detailed. The book highlights indigenous African food processing technologies up to the modern era.

Section III

Monographs

10

Monographs of Major African Functional Foods

Introduction

This section contains monographs of 67 African food plants that are of considerable scientific interest based on literature citations as feasible candidates for the development of functional foods and/or possible sources of nutraceuticals. These are edible plants selected for their potential functionality and not necessarily by their ranking in the food table. Almost all of them are native to Africa but a few are naturalized crops that are cultivated and consumed at a significant level in Africa for many years. Some of the plants have been featured in the earlier chapters and the additional information in this section should be taken along with the information provided therein. According to Peters and others,¹ there are about 2155 African plant species that are used as food out of over 50,000 recorded species of African flora. The number of plants selected to be highlighted here represents only a tiny fraction of the food plants used in Africa and still less is the number of culinary plants that are used in traditional medicine, which are cataloged in Chapter 2 (Table 2.1). A review of the commercialized food plants by Van Wyk² showed that Africa has made a substantial contribution in the global food base, with 119 species, which compares favorably with estimates of 126 crops for Europe, 68 for Central America, and 97 for South America. The entries are not comprehensive and the objective was not to provide a universal coverage of all edible African plants that contain phytochemicals that may be useful for health optimization.

The arrangement of the monographs lists the plants by their common names to assist in their ease of recognition as food plants, followed by a short overview, and a detailed pharmacognostical profile, which includes botanical names, culinary relevance, ethno-medicinal uses, constituents, and pharmacological studies. The description of the plants has been adapted mainly from three sources: Handbook of African Medicinal Plants,³ the online database on African medicinal plants (PROTA4U),⁴ and the Lost Crops of Africa (three volumes) published by the U.S. National Academy of Sciences.⁵ Readers are encouraged to consult these references for additional information.

Alligator Pepper: Grains of Paradise

Overview

Alligator pepper (Aframomum melegueta) is an aromatic plant used as a general tonic in West and Central Africa. The flowers of the herbaceous plant are described as “handsome” aromatic, with an orange-colored lip and a rich pinkish-orange upper part. The fruits contain numerous, small, golden red-brown seeds. It yields a very spicy volatile oil and enjoys a folk reputation as an aphrodisiac agent. The fruits are used in traditional medicine for therapeutic purposes and as a ritual plant to appease the gods. The seeds are used in the food industry as an essence to spirits, wines, and beer. Laboratory studies and clinical outcome evaluation tend to support the use of grains of paradise for sexual dysfunction. The extract of the seeds and rhizome has been shown to have antioxidant and anti-inflammatory activities. The pungent and peppery taste of the seeds is caused by the presence of aromatic ketones, 1-(4-hydroxy-3-methoxyphenyl)-decan-3-one ((6)-paradol), zingiberone, 6-gingerol, and 6-shogaol. Alligator pepper has shown potential as a possible treatment for male erectile dysfunction and premature ejaculation. Aframomum melegueta seed enjoys a GRAS classification (substances regarded “generally recognized as safe”), and no side effects have been reported from its consumption or usage over the years. It is relatively easy to cultivate and has been incorporated in many dietary supplements and herbal medicines.

Pharmacognostical Profile

Botanical Name: Aframomum melegueta K. Schum.

Synonyms: Aframomum grana-paradisi (L.) K. Schum; Aframomum meleguetella K. Schum; Alexis grandiflora (Sm.) Salisb.; Alpinia grana-paradisi (L.) Moon; Amomum grandiflorum Sm.; Amomum grana-paradisi L.; Amomum melegueta Roscoe; Cardamomum grana-paradisi (L.) Kuntze; Cardamomum grandiflorum (Sm.) Kuntze; Torymenes officinalis Salisb.

Family: Zingiberaceae

Related Species: A. daniellii, A. strobilaceum, A. exscapum, A. korarim

Common Names: Grains of paradise, guinea grain, alligator pepper, melegueta pepper

Description: A. melegueta is an aromatic plant cultivated for its edible spicy fruit. It is a perennial herb growing up to 4 m high. The stem is short, marked with the encircling scars of fallen aerial leaves, and it is highly branched. The lower surface bears the roots, which are adventitious and slender. It yields an aromatic rhizome, which is horizontal and tuberous and bears scaly leaves with occasional buds in axils. The leaves are large, about 30 cm long and 12 cm wide, with close nerves below. They occur in two rows with an open or closed sheath sessile or stalked on the sheath; the blades are usually large with numerous closely parallel pinnate nerves diverging obliquely from the midrib. The bracts are few and about half overlapping. The beautiful aromatic flowers are solitary, borne separately from the leafy stem. The fruits are fleshy and indehiscent, and contain numerous small seeds embedded in pleasant-tasting aril. The seeds are golden or red-brown when fresh but darken on drying; angular and granular; and strongly aromatic and pungent.

Geographical Distribution: Aframomum occurs throughout tropical Africa but it is cultivated mainly in West and Central Africa.⁶

Ethnomedicinal Uses: The genus is employed extensively in traditional medicine in West and Central Africa. In Ewe (Ghana), the common name for the plant, megbe-dogboe, means “never lacking for the sick.” In Southern Nigeria, it is typically chewed with Kola nut as a masticatory agent. The fresh fruit is used as an aphrodisiac. The leaf is dispensed for measles and applied externally for the treatment of leprosy. The root decoction is taken by nursing mothers to check excessive lactation and to control postpartum hemorrhage. The rhizome is used as an ingredient for the preparation of remedy for infertility to promote conception and the fruit is used as a tonic for sexual stimulation. The plant is also used as a purgative, galactagogue, anthelmintic, and homeostatic (hemostatic) agent. The seeds are used with the leaves of Urera oblongifolia as an external treatment for tumors. In Senegal, the seeds are mixed with salt and rubbed to the interior of the mouth as a treatment of sleeping sickness.

Constituents: The members of the genus yield essential oil in most parts of the plants. The seeds of A. melegueta have been shown to contain the benzenoids, gingerol, shagaol, and paradol.⁷ The seeds of A. danielli obtained from Cameroon have been shown to contain labdane diterpenoids.⁸ Other constituents of the genus include flavonoids,⁹ monoterpenes,¹⁰,¹¹ and quinoids.¹² The chloroform extract of the seeds contains antioestrogenic diarylheptanoids, namely, gingerenone D, dihydrogingerenone A, dihydrogingerenone B, and dihydrogingerenone C.¹³

Pharmacological Studies: The essential oil obtained from the seeds and the benzenoids, paradol, gingerol, and shagaol have been shown to possess antimicrobial and antifungal activity.¹⁴ The alcoholic extract was found lethal to snail hosts of schistosomes.¹⁵ Extracts of the plant showed positive activity in cytotoxicity assay.¹⁶ Studies on sexual behavior in rats have shown that A. melegueta modified the sexual behavior of male rats by increasing sexual arousal. The aqueous extract of the seeds of this plant was shown to significantly increase the penile erection index, as well as the frequencies of intromission and ejaculation. The plant extract was also found to enhance the orientation of males toward females by increasing mounting and anogenital investigatory behavior.¹⁷ A review of Aframomum indicated its potential as a dietary supplement or spice for foods and as a potential source of new medicines for a variety of conditions, including inflammation, infections, and CNS disorders.¹⁸ It has been suggested that the selective inhibition of COX-2 enzyme by Aframomum constituents may be indicative of more tolerable anti-inflammatory and analgesic compounds than most conventional NSAIDs.¹⁹ The phenolic component has been shown to possess significant antiglycation and antioxidant effect,²⁰ which may be useful in its application as a dietary supplement.²¹

The potential benefit of grains of paradise in weight management has been demonstrated by the effect of extract of Aframomum and 6-paradol on the activation of thermogenesis in brown adipose tissue.²² Intragastric injection of an extract or 6-paradol enhanced the efferent discharges of the sympathetic nerves in a dose-dependent manner. The enhanced nerve discharges were sustained for as long as 3 h. The rats did not become desensitized to the stimulatory effects of these compounds on sympathetic nerve activity. The tissue temperature of brown adipose tissue showed significant increase in rats injected with 6-paradol. These results demonstrate that Aframomum may be useful for the regulation of weight loss and weight maintenance.²³

Toxicity: Aframomum is considered a safe herbal supplement and no human toxicity or allergic reaction has been reported. A 28-day subchronic toxicity study in male and female Sprague–Dawley rats to evaluate the safety of a grains of paradise extract showed a dose-related increase in absolute and relative liver weights in males and females dosed with 450 and 1500 mg/kg. There was a corresponding increase in alkaline phosphatase with no signs of steatosis or cirrhosis. At the same doses, there was a significant decrease in blood glucose in male rats.

Aloe vera

Overview

Aloe has long been used globally in food products, beverages, and cosmetics, and as an ingredient in several traditional medicine remedies. It yields a mucilaginous gel called aloe vera gel (AVG), which con...