Aside from serving as a main source of food and nutrition, plants have long been exploited as a major source of medicine in most parts of the world. According to WHO, eighty-five percent of the world's population, mostly those in developing countries, depends on plants for medicine and at least twenty-five percent of prescription drugs have an active ingredient derived from a plant or herb1. These Herbal medicines are used to treat a variety of ailments such as dysentery, cardiovascular diseases, infertility and asthma. One such plant that is used medicinally is Xylopia aethiopica. This herb is an important plant in traditional west African culture and researchers are currently seeking to investigate its many medicinal properties and their effects on an array of health care issues.
Xylopia aethiopica commonly known as Negro pepper or in Nigeria as Uda by the Igbo tribe, Chimba by the Hausa tribe and Eeru alamo by the Yoruba tribe is a tall evergreen aromatic tree belonging to the Annonaceae family. Although this plant was first discovered in Ethiopia, it is mostly grown and prominent through out West Africa especially in Ghana. The fruit of this plant is used as a spice or condiment in many traditional African dishes such as stews, meats, and sauces. Apart from its culinary benefits, X. aethiopica also possess a wide array of uses in traditional African medicine. Negro pepper is said to contain chemical constituents such as flavonoids, alkaloids, cineol, phytosterols, tannins, saponins, glycosides, carbohydrates, β-pinene, paradol, α-terpineol, terpinene-4-ol, terpenes, cryptone, verbenone, β-phellandrene, spathulenol, bisabolene, trans-pinocarveol, limonene, linalool, and myrtenol.2 Due to these varying chemical constituents and their varying properties and functions, X. aethiopica is frequently used in decoction to make tonics that aid in childbirth as well as treat a plethora of ailments including but not limited to, cancer, bronchitis, diabetes mellitus, skin infection, male and female fertility.
According to the American cancer society, one in seven men will be diagnosed with prostate cancer in his lifetime. Additionally, in 2017 there was about 161,360 new cases of prostate cancer diagnosed.3 Conversely, according to the world cancer research fund international one in eight women will be diagnosed with breast cancer in her lifetime and there were 1.7 million new cases diagnosed in 2017.4 Given the high prevalence and mortality rate of cancer and the lack of access to modern medication and adequate healthcare in Nigeria, identifying low cost and effective ways for optimal treatment is of the utmost importance. To this end, researchers in Nigeria conducted a preliminary study investigating the anti-proliferative effects of X. aethiopica on cell lines of breast and prostate cancer in vitro. The researchers extracted ethanolic acid from the fruit of the Negro pepper plant and tested it, in vitro, against prostate cancer (LNCaP) and breast cancer (MDA-MB231and MCF7) cell lines. The results from this study showed a dose-dependent anti-proliferative activity against LNCaP, MDA-MB231and MCF7 cell lines after treatment for 48 and 72 hours. According to the researchers, the extract induced a 16.96 per cent and 93.5 per cent inhibition on MDA-MB231 cells, 29.76 per cent and 94.03 per cent on the MCF7 cells and a 9.15 per cent and 94.61 per cent inhibition on the LNCaP cells at the lowest (1μg/ml) and highest (100μg/ml) dose respectively after 48 hours. Moreover, after 72 hours The extract induced a 12.26 per cent and 91.8 per cent cell growth inhibition on the MDA-MB231 cells, 3.35 per cent and 87.36 per cent growth inhibition on the MCF7 cells and 2.28 per cent and 92.42 per cent cell growth inhibition on the LNCaP cells at the lowest (1μg/ml) and highest (100μg/ml) doses respectively.5 These findings demonstrating the growth inhibition in the cancer cell lines indicate that X. aethiopica has some anti-proliferative effects on prostate and breast cancer cells lines. The aforementioned findings also highlight the usefulness of this plant and the need for more research that will further investigate the mechanism of action of this pepper as well as the potential for the development of new cancer interventions that can work in conjunction with other conventional cancer treatments or interventions that can be used independently to target these specific cancers.
Aside from cancer research, scientist have researched the use of X. aethiopica on other aspects of health such as contraception. Gold standard contraceptive techniques have varying side effects ranging from weight gain to blood clots. For this reason, it is worthwhile to explore the use and efficacy of herbs and other natural products as alternatives to conventional medication. According to H.M. Burkill6 in, “The useful plants of west tropical Africa”, X. aethiopica has been used for centuries as an effective natural contraceptive. This herb is believed to cause temporary adverse effects on the reproductive system of men. Woode et al7 conducted a research study evaluating the effects of Xylopic acid, a kaurane derivative extracted from the plant, on serum sex hormones and spermatogenesis in male rats. The Xylopic acid was administered orally to the mice at varying doses (10, 30, 100 mg) over a 28 day period. Blood samples were collected at the 7 day and 28 day period. Xylopic acid was shown to cause a decrease in sperm count, motility and viability. Furthermore, the results showed a significant decrease in serum testosterone levels at 28 days as well as damage to the seminiferous tubules of the male mice. Normal seminiferous tubules cells and serum levels returned 2 weeks after use was discontinued. Therefore, it can be hypothesized that X. aethiopica’s primary mechanism of action as a contraceptive is through Xylopic acid and this acid may work primarily by directly disrupting the function of cells in the testes that are primarily used to make spermatocytes and androgens. Ultimately, the temporary antifertility properties that X. aethiopica possess is evidence that this herb can be an effective and viable alternative contraceptive method. However, more research needs to be conducted into the effects of this in Humans.
X. aethiopica also has abortifacient properties that are exploited to aid with child birth and menstrual problems. In eastern Nigeria, the Igbo tribe traditionally use X. aethiopica in addition to other medicinal plants to make a postpartum herbal tonic. This tonic is said to help to clear blood clots in the womb and to aid in placental discharge after childbirth. Unknown chemicals in this herb causes the smooth muscle of the uterine lining to contract consequently causing shedding of the uterine lining. This mode of action of this herb is said to also aid in stimulating menstrual flow in those with irregular menstrual cycles or amenorrhea. Additionally, when trying to induce labor, this same mode of action can be exploited when X. aethiopica is taken in small doses, although there is not a wealth of information on an exact safe dose or how safe this herb is for the mother or the fetus.
Despite the supposed positive medicinal effects of X. aethiopica use, a research study conducted on albino rats by Obembe et al8 revealed a potentially serious negative side effect associated with the use of this herb. The results from the study showed a significant dose dependent (100 mg/kg body weight and 200 mg/kg per body weight) decrease in hemoglobin, white blood cells and mean corpuscular hemoglobin concentration at 28 days of continuous ingestion. Additionally, usage during this 28 day period was shown to disrupt clotting factors therefore prolonging bleeding time irrespective of dosage. Given this information, individuals should be mindful of this side effect when consuming or using this herb medicinally.
Appropriately, given the information from the aforementioned animal and in vitro studies, X. aethiopica is shown to have great potential medicinally in the treatment of various ailments and conditions even though there is not a wealth of published data on the use of this herb in humans. It is important to continue to conduct research into the uses of X. aethiopica to ascertain its safety and efficacy in humans as this herb may prove to be a great alternative and/ or great adjuvant to modern medication.