Vernonia Amygdalina, commonly known as bitter leaf, is a shrub that grows up to 3 meters high in the African tropics and other parts of Africa, particularly, Nigeria, Cameroon and Zimbabawe.
Indeed, fruits and plants are rich sources of phenolic compounds and have been recognized to possess a wide range of properties including antioxidant, antibacterial, anti-inflammatory, hepatoprotective and anticarcinogenic actions. Many of the biological functions of flavonoids and phenolic compounds have been attributed to their free radical scavenging, metal ion chelating and antioxidant activities. Antioxidant phenolic agents have been implicated in the mechanisms of chemoprevention which refers to the use chemical substances of natural origin or synthetic to reverse, retard or delay the multistage carcinogenesis process.
It is reputed to have several health benefits. The organic fraction extracts of the plant was shown to possess cytotoxic effects towards human carcinoma cells of the nasopharynx. It is effective against amoebic dysentery], gastrointestinal disorders, and has antimicrobial and antiparasitic activities.
Recently, considerable attention has been focused on dietary and medicinal phytochemicals that inhibit, reverse or retard diseases caused by oxidative and inflammatory processes. Vernonia amygdalina is a perennial herb belonging to the Asteraceae family. Extracts of the plant have been used in various folk medicines as remedies against helminthic, protozoal and bacterial infections with scientific support for these claims. Phytochemicals such as saponins and alkaloids, terpenes, steroids, coumarins, flavonoids, phenolic acids, lignans, xanthones, anthraquinones, edotides and sesquiterpenes have been extracted and isolated from Vernonia amygdalina.
The antioxidant activity of Vernonia amygdalina has been attributed to the presence of flavonoids, as reported by Igile et al. Using spectroscopic techniques, the study had isolated and characterized the flavonoids occurring in Vernonia amygdalina. Three flavones were identified with chemical and spectroscopic techniques namely: luteolin, luteolin 7-O-β-glucuronoside, and luteolin 7-O-β-glucoside. Determination of the antioxidant activity of the three flavones had shown that luteolin showed greater activity than the other two. Since flavonoids are established as possessing antioxidant activity. It can be speculated that the antioxidant properties of Vernonia amygdalina can be attributed to the presence of these flavonoids. The advantage of this antioxidant property has been revealed in neurotoxic studies since it has been established that flavonoids can traverse the blood brain barrier. In this connection, there was a reported neuroprotection of the cerebellum by the methanolic extract of Vernonia amygdalina leaves on the gamma-irradiated brain of Wistar rats.
Many chemicals including hydrogen peroxide are known to generate DNA damage through an oxygen radical mechanism and can induce chromosomal aberrations, gene mutations and DNA strand breaks. Flavonoid compounds possessing antioxidant and antiradical activities are capable of quenching free radicals, which may promote mutations and DNA damage. This provided evidence that Vernonia amygdalina extracts represent a DNA-damaging anti-cancer agent against breast cancer and its mechanisms of action functions, at least in part, through minimal DNA damage and moderate toxicity in tumors cells. In mechanistic terms studies have shown that V. amygdalina extract acts as a monofunctional inducer in MCF-7 breast cancer cells.
A number of chemical compounds including edotides, and sesquiterpene lactones have been isolated form the leaf of Vernonia amygdalina. Similarly, the bioflavonoid complex otherwise known as kolavion have been characterized from the seed of Garcinia kola. These compounds elicit remarkable antioxidant and chemopreventive properties in cell cultures and rodent models. Prominent among the biochemical and molecular mechanisms of action of these compounds are elevation of phase II enzymes, inhibition of cell proliferation and suppression of pro-inflammatory mediators. These mechanisms play pivotal role in chemoprevention which appears to be a more pragmatic and rational approach to prevention of cancer. Cancer chemoprevention has received a phenomenal attention in the last three decades by several investigators with focus on evaluating the efficacy of well defined phytochemicals from dietary substances and plant origin in various experimental models. There is also the need to source for new and novel chemopreventive agents from natural origin.
In this review, the chemopreventive properties of novel compounds from Vernonia amygdalina and Garcinia kola have been presented. Their striking underlying and molecular mechanisms support the idea that supplements of these compounds may be considered in strategies of using natural products in cancer prevention and therapy. Necessary long-term clinical trials are therefore warranted in order to showcase potential benefits of Vernonia amygdalina and Garcinia kola-derived phytochemicals as chemopreventive agents. Also important is bioavailability of the compounds in Vernonia amygdalina and Garcinia kola. However, the biflavanones of Garcinia are pharmacologically active with several pharmacokinetic advantages over simple monomeric flavonoids; for instance, the bifavonoids have been shown to survive first-pass metabolism which inactivates most flavonoids and they have been proved to possess very high thera-peutic potentials.
Scientific Reference Studies: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3138040/