Piper guineense (Piperaceae): Chemistry, Traditional Uses, and

Chapter 3

Downloaded by PRINCETON UNIV on October 8, 2013 | http://pubs.acs.org Publication Date (Web): October 4, 2013 | doi: 10.1021/bk-2013-1127.ch003

Piper guineense (Piperaceae): Chemistry, Traditional Uses, and Functional Properties of West African Black Pepper H. Rodolfo Juliani,1 A. R. Koroch,2 L. Giordano,1 L. Amekuse,3 S. Koffa,4 J. Asante-Dartey,3 and J. E. Simon*,1 1New Use Agriculture and Natural Plant Products Program, School of Environmental and Biological Sciences, and the New Jersey Agricultural Experiment Station (NJAES), Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, New Jersey 2City University of New York, Borough of Manhattan Community College, 199 Chambers Street, Science Department, New York, New York 10007 3Agribusiness in Sustainable Natural African Plant Products (ASNAPP-Ghana), Accra, Ghana 4ELWA, Paynesville, Monrovia, Liberia *E-mail: [email protected].

West African black pepper (Piper guineense) is an important plant used in traditional medicine and as spice. The fruits (the part of the plant traditionally used) are rich in a wide range of natural products including volatiles oils, lignans, amides, alkaloids, flavonoids and polyphenols. The objectives of this paper are to review the chemistry of this unique spice, to develop quality control standards for the commercialization of the fruits and to examine the traditional uses and functional properties of “West African Black Pepper”.

© 2013 American Chemical Society In African Natural Plant Products Volume II: Discoveries and Challenges in Chemistry, Health, and Nutrition; Juliani, H., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.


Introduction

The tropical family Piperaceae has offered in the past and today a rich source of natural products with a wide range of biological activities. The genus Piper includes more than 1,000 species being one of the largest genera of basal angiosperms (1). Piper species are distributed pantropically and the pattern of distribution vary from locally endemic to widespread. Species of this genus can be found in the understory of lowland wet forests as shrubs, herbs, or lianas (2). Piper species has been long known for their commercial, economical, ecological and also medicinal importance. The economic uses are mainly as spices, herbal medicines, cosmetics and insecticides. Piper guineense Schum and Thonn is locally known as West African black pepper, Ashanti pepper, Guinea pepper, Bush pepper and Guinea cubebs (3–5). West African black pepper is a climbing perennial plant distributed throughout West Africa that can reach up to 12 m high, usually found in high forest areas and has prominent nodes and clasping roots (3). The leaves are simple, opposite and ovate, the flowers are small in solitary spikes. The fruits, commonly known as peppercorns, are racemes and usually black or white depending on the time that they have been harvested (6, 7). West African black pepper is widely distributed from Guinea to Uganda. While the plant product of commerce is the fruits, other plant parts such as roots, seeds, stem bark and leaves are used in traditional medicine (5). The fruits or berries are usually sold in local markets for food coloring, as a condiment/spice to flavor for example soups or for medicinal uses (3, 8). Preparations of leaves, roots and seeds have medicinal properties (3, 6). West African pepper has been indicated to treat different medical conditions such as boils, bronchitis, catarrh, chest pains, coughs, dyspepsia, impotence, insect repellant, lumbago, rheumatism, uterine fibroid, wounds, stomach aches and discomforts (5, 8). The fruit are used also as tonic, abortifacient, to easy childbirth, oxytocic, for tumors, insecticide and for hemorrhoids (4). Traditionally, the herb is prepared in several forms including decoctions, powders or tinctures (5). Roots have been also used as aphrodisiac, colds, respiratory diseases and caries. It was reported that a mixture of leaves, roots and fruits are incorporated in preparations for the treatment of infectious diseases as antibacterial agent (3). Leaves are used for abdominal disorders, antihelmintic, chickenpox, bronchitis, cough, headache, lumbar pain, gingivitis, chest complains and diseases, intestinal colic and as antiseptic. In Cameroon, West African pepper leaves are mixed with leaves of Pentas shimperana spp. occidental to make a yellow soup that is used to treat diarrhea (9). In Southeast Nigeria the leaves are used for contraction of the womb, as a pre-labor stimulation (10). Piper species are also used in folk medicine for the treatment of coughs, intestinal diseases, bronchitis, venereal diseases, colds, rheumatism and diarrhea (3, 9, 11, 12). The objectives of this paper are to review the chemistry, develop quality control standards for the commercialization of the fruits and to review the traditional uses and functional properties of “West African Black Pepper”. 34

In African Natural Plant Products Volume II: Discoveries and Challenges in Chemistry, Health, and Nutrition; Juliani, H., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.


Material and Methods

Five samples of fruits of P. guineense which were representative of the available West African pepper were purchased at the local market in Sanniquellie (Nimba County, Liberia) in January 2011. With the proper USDA seed importation permit, the fruits were hand carried from Liberia through USDA customs to Rutgers University. The sensory, foreign matter and chemical analyses of the samples were conducted at Rutgers University (USA). Samples of black whole peppercorns from a commercial source of black pepper (Piper nigrum) were also analyzed for comparison purposes. The colors of the peppercorns were determined visually. Each subsample was weighed (2 g) and then gently placed in an oven (85°C) until constant weight was reached for the determination of moisture percent. The dried fruits were then ground (mesh 20) and total ashes, and acid insoluble ashes were determined for each sample using methods described by the Food Chemical Codex. (13). A sieve (250 μm) was used to separate the fine particles and then weighed to calculate their percentages in relation to the total mass of dried spice (10 g). Essential oil extraction and analysis: The volatile oils were isolated from the dried fruits (100 g) by water distillation using a Clevenger-type apparatus, oil yield was calculated as percent on a dry weight basis (mL of oil/100 g dry leaves). The oils were analyzed by gas chromatography (GC) coupled to a mass spectrometry (MSD) and flame ionization (FID) detectors (Agilent GC System 6890 Series, Mass Selective Detector, Agilent 5973 Network, FID detector). Each oil was run in two separate columns (HP-5, 30 m, 0.25 mm ID, 0.25 im Film), attached to the MSD and the FID. The conditions for both inlets and columns were the same: Helium constant flow was set at 1 ml/min. Inlet temperature was 220°C, temperature program, 60°C 1 min, 4°C/min, 200°C 15 min. The temperature for the FID was set at 220°C and for MSD at 280°C. Qualitative analysis was based on a comparison of retention times and indexes on both columns and mass spectra with corresponding data in the literature and mass spectral libraries (Wiley 275) (14). Samples were analyzed using an International Standard HPLC/UV method (ISO 11027: 1993 E) modified by the New Use Agriculture and Natural Plant Products Program, Rutgers University described below. Piperine (Acros organics), reference standard, was used for identification of the compound, which was performed on an Agilent 1100 HPLC equipped with a diode array detector and analyzed using MSD trap software. A Prodigy 5 μ OD3 150 x 3.20 mm (Phenomenex Co.) column was used. The various pepper seeds were sifted (2.36 mm sieve) then ground to a powder from which 125 mg were extracted in 25 ml of denatured ethanol (HPLC grade – Fischer Scientific Co.) then sonicated for 30 minutes. Approximately 2 ml aliquots per sample were centrifuged (5 min) and supernatants were transferred to amber glass auto-sampler HPLC vials. HPLC separation was performed in an isocratic condition with the mobile phase consisting of an aqueous acetic acid solution (1.0%) and formic acid acetonitrile solution (0.1%) (52 /48 - v/v). 35

In African Natural Plant Products Volume II: Discoveries and Challenges in Chemistry, Health, and Nutrition; Juliani, H., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.

Samples were run with a flow rate of 1.0 ml/min for 30 minutes and detected on UV chromatogram at 343 nm. Elution time for piperine was approximately 4.1 minutes.


Results The West African black peppercorns were characterized by variations in color and sensory characteristics. Most of Sample 1 peppercorns and to lesser extent Sample 2 showed grayish colors. Samples 3 to 5 showed black/dark brown colors, which were similar in color to the regular commercial black peppercorns (P. nigrum) (Table I). All the West African black peppercorns were characterized by pleasant spicy notes with Sample 1 also having a slight moldy note. The traditional regular black pepper (P. nigrum) samples exhibited the typical spicy and woody notes. (Table I). The West African samples 1 and 2 were characterized by very high levels of foreign materials (1.6 and 3.1%, respectively), while the commercial sample was characterized by very low levels (

Piper guineense (Piperaceae): Chemistry, Traditional Uses, and

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