The emphasis on the use of medicinal plants had hitherto been placed on the treatment rather than prevention of diseases. However, there exists in the literature considerable report in recent times on research work on the use of medicinal plants and their constituents in disease prevention. A World Health Organisation (WHO) Expert Group defined Traditional Medicine as the sum total of all knowledge and practices, whether explicable or not, used in diagnosis, prevention and elimination of physical, mental, or social imbalance and relying exclusively on practical experience and observation handed down from generation to generation, whether verbally or in writing (WHO, 1976). For Africa, this may be extended further by including an expression, such as ‘while bearing in mind the original concept of nature which includes the material world, the sociological environment whether living or dead and the metaphysical forces of the universe’.
Over 90% of traditional medicine recipes/remedies contain medicinal plants but this paper will address, specifically, the medicinal plants that have been implicated with preventive measures in disease control strategies. However, it must be noted that only a very thin divide exists between treatment and prevention in some cases. A quick example is the fact that by treating mild elevation of blood pressure renal disease can be prevented.
What is a medicinal plant?
A medicinal plant is any plant which, in one or more of its organs, contains substances that can be used for therapeutic purposes or which are precursors for the synthesis of useful drugs. This description makes it possible to distinguish between medicinal plants whose therapeutic properties and constituents have been established scientifically, and plants that are regarded as medicinal but which have not yet been subjected to a thorough scientific study.
A number of plants have been used in traditional medicine for many years. Some do seem to work although there may not be sufficient scientific data (double-blind trials, for example) to confirm their efficacy. Such plants should qualify as medicinal plants. The term ‘crude drugs of natural or biological origin’ is used by pharmacists and pharmacologists to describe whole plants or parts of plants which have medicinal properties. A definition of medicinal plants for the purpose of this presentation should include the following (Sofowora 2008; Evans, 2008):
plants or plant parts used medicinally in galenical preparations (e.g. decoctions, infusions, etc.) e.g. Cascara bark;
plants used for extraction of pure substances either for direct medicinal use or for the hemi-synthesis of medicinal compounds (e.g. hemi-synthesis of sex hormones from diosgenin obtained from Dioscorea yams);
food, spice, and perfumery plants used medicinally, e.g. ginger;
microscopic plants, e.g. fungi, actinomycetes, used for isolation of drugs, especially antibiotics. Examples are ergot (Claviceps purpurea growing on rye) or Streptomyces griseus; and
fibre plants, e.g. cotton, flax, jute, used for the preparation of surgical dressings.
The growing importance of medicinal plants can be appreciated from the economic stand point when the following facts are considered:
Global trade in herbs is over USD 100 Billion per annum
India and China's medicinal plant trade is about two to five billion US dollars annually
In Germany, it is over one billion US dollars annually
Rose Periwinkle which is endemic to Madagascar fetches US$100 million per annum
China trades in 7,000 species and 700,000 tons of medicinal plants per annum
India trades in 7,000 species of medicinal plants
Morocco exports 58.7 tons of medicinal plants annually
In the last 5 years, sales of medicinal plants doubled in China, tripled in India and grew by 25% in Europe.
A Presidential Initiative Committee on the Development, Promotion, and Commercialisation of Nigerian Herbal Medicinal Products was inaugurated on 30th May 2006 and was given a target of US$1billion sales of medicinal plants and its products within 10 years for Nigeria. Based on current research and financial investments, medicinal plants will, seemingly, continue to play an important role as a health aid (Hoareau and DaSilva, 1999). The use of traditional medicine and medicinal plants in most developing countries, as a normative basis for the maintenance of good health, has been widely observed (UNESCO, 1996). Furthermore, an increasing reliance on the use of medicinal plants in the industrialised societies has been traced to the extraction and development of several drugs and chemotherapeutics from these plants as well as from traditionally used rural herbal remedies (UNESCO, 1998). Moreover, in these societies, herbal remedies have become more popular in the treatment of minor ailments, and also on account of the increasing costs of personal health maintenance. Indeed, the market and public demand has been so great that there is a great risk that many medicinal plants today face either extinction or loss of genetic diversity.
Health promotion, disease prevention and chronic disease management are proactive approaches to health care that stresses prevention at different points along the health care continuum. Health promotion and disease prevention strategies focus on keeping people well and preventing diseases from occurring. These strategies are referred to as primary prevention activities. Prevention is categorised into three levels (Commission on Chronic Illness, 1957):
- Primary Prevention, which seeks to decrease the number of new cases of a disorder or illness. At this level of prevention we have:
Health promotion/education, and
Specific protective measures (such as immunisation)
Secondary Prevention, which seeks to lower the rate of established cases of a disorder or illness in the population (prevalence). This level essentially involves measures that ensure early diagnosis (such as screening) and prompt management
- Tertiary Prevention, which seeks to decrease the amount of disability associated with an existing disorder. This level involves:
Disability limitation and
The secondary and tertiary prevention activities focus on maintaining the health of individuals with chronic conditions, delaying progression of their conditions, and preventing complications.
Disease prevention should focus on strategies that reduce the risk of disease, identify risk factors, or detect disease in its early, most treatable stages. Examples of disease prevention activities include well-baby visits, immunisations, calcium and Vitamin D supplements to reduce the risk of osteoporosis, blood pressure and cholesterol assessments during annual health exams, and screening for illnesses such as breast, cervical, colorectal and prostate cancer (Family Health Teams, 2006).
Public health, diet, food production and the environment are deeply interrelated, and understanding these relationships is crucial in pursuing a liveable future. Sometimes therefore, there is only a thin line between treatment and prevention of certain diseases. For example, treatment of mild hypertension will prevent many chronic renal diseases. This is also true for obesity, cancers, coronary heart diseases (CHDs) as well as diabetes and its sequelae, though these are non-communicable diseases.
The burden of healthcare and its human and financial resources requirement
In developing countries all over the world, large numbers of people die daily of preventable or curable diseases because of the lack of even simple health care. Diseases in these countries are often associated with malnutrition. As a result, those that do survive often never recover completely from the effects. The developing world is not a homogenous entity, but is made up of a variety of widely differing countries and areas which are at different stages of development. Nevertheless, these developing countries have certain features in common, including extremely limited resources, poor communications, vast distances, low levels of education, and individual and community poverty. These factors act together to keep these countries in a perpetual state of poverty. Yet, their populations continue to rise, especially in the rural regions which usually account for about 80 per cent of the total population.
Another special characteristic of the developing world is the nomadic lifestyle of some of its people. Some 50 to 100 million nomads have been estimated to be present in the world, and 90 per cent of these live in Africa or Asia. Nomads have their own needs and problems peculiar to their lifestyle. Because of their constant movement and dispersion it is difficult for conventional health services to reach these people. The striking difference between the developed and the developing world in terms of health care is reflected in the differing life expectancy of their populations. For example, according to WHO (2012), in 2009 the life expectancy at birth was estimated at 51 years in Angola and Burkina Faso, while for Malawi it was 47 years (African countries) compared with 80 years in the United Kingdom, USA and Austria. Although the situation is improving in some African countries, this gap is still wide. Twenty-six African countries are ranked among the ‘Low Income Group’, 17 in the ‘Lower Middle Income Group’ and 9 in the ‘Upper Middle Income Group’, while only Equatorial Guinea is ranked in the ‘High Income Group’ (WHO, 2012). Several of the people in Africa earn less than US$2 per day.
Any strategy for disease prevention in the developing countries, especially in Africa, must take these socioeconomic factors into account. With the abundant biodiversity of plants in the African Region and the relative lower cost of using plant derived medicines instead of processed synthetic drugs, medicinal plants should have a role to play in disease prevention strategies in Africa.
Medicinal plants and disease prevention
Strategies for the Prevention of Communicable diseases
Three core approaches - surveillance, outbreak investigations and immunisation - are fundamental to the prevention of communicable diseases. While medicinal plants may appear to have limited role in these approaches, several medicinal plants and traditional medicines derived from them have been used to enhance immune response to several disease agents (Di Pierro et al., 2012; Ramakrishna et al., 2011).
Strategies for Prevention of Non-Communicable Diseases
The WHO 2008 to 2013 Action Plan for the Global Strategy for the Prevention and Control of NCDs articulated an intersectoral, multi-level plan to curb the rising global prevalence of NCDs with particular focus on the low and middle income countries. The overall foci of the plan were to
map the emerging NCD epidemic and ascertain their social, economic, behavioural and political determinants;
reduce the level of exposure of individuals and population to the common modifiable risk factors - tobacco use, unhealthy diet, physical inactivity, etc.; and
strengthen health care for people with non-communicable diseases through the development of evidence-based norms, standards and guidelines for cost effective interventions.
Related to the third focus above, an examination of the causal chain of risk factors for NCDs (Figure 2) is helpful in illuminating the potential role of medicinal plants in the prevention of NCDs. Medicinal plants have specific roles in strengthening health care opportunities for people with NCDs as well as in the management of the biologic risk factors for NCDs, especially in the early stage (Jung et al., 2012; Tan et al., 2010).
Causal chain of risk factors for NCDs
The ‘whole population’ and ‘high-risk’ strategies
Two main types of approaches have been advocated in tackling major public health problems. The whole-population strategy targets the community as a whole to control the occurrence of new diseases in the population. The high-risk strategy on the other hand aims to identify individuals most at risk for a disease or outcome and then target preventive efforts at that group. These were first defined by Geoffrey Rose (Rose, 1985). In promoting the use of medicinal plants in disease prevention, the whole-population strategy will have the global community as the target, whereas the high-risk strategy may focus on rural communities, especially in the developing countries. It may also on the other hand wish to focus on refining medicinal plants for use in specific disease conditions that presently defy conventional treatment, such as cancer, HIV infection and AIDS.
Utilising the Common Factor approach
The common risk factor approach aims at bringing together several health promoters working on eliminating common-risk factors as a way of preventing diseases. (Sheiham and Walt, 2000) Poor Diet for example can lead to obesity, diabetes, cancers, and dental caries. Hence, nutritionists, diabetologists, oncologists, dental practitioners can work together with diet as common theme. A modified form of this approach (Figure 3) can be a useful tool in engaging other health promoters, in tackling the different forms of disease, and in propagating the ideals of medicinal plants. Working with various groups, for example, appropriate medicinal plants can be incorporated into the diets to alleviate disease and suffering. This approach will enable those working to promote the use of medicinal plants to collaborate with other health promoters in areas such as malaria, diabetes, cancers, cardiovascular diseases, tuberculosis, HIV/AIDS, oral diseases, dermatological problems, etc.
The Primary Health Care (PHC) Approach
Primary Health Care was defined in Alma Ata (WHO, 1978) as essential care based on practical, scientifically sound and socially acceptable method and technology made universally accessible to individuals and families in the community through their full participation and at a cost they and the country can afford to maintain in the spirit of self-reliance and self-determination. The PHC philosophy recognises that each discipline contributes to health and health services delivery within a PHC model, both in a unique sense and through collaborative interdisciplinary practice.
The five core principles of the PHC approach include the following:
Community Participation (as issues that local people identify rather than predetermined services introduced by professionals, working within existing community organisations and local government structures, etc.)
Focus on Prevention
Multisectoral Approach - Emphasis should be made that the reason for the failure of many programmes is due to the fact that they operate in isolation, separate from the general health care structure and without the support of other relevant sectors. The need for programme cooperation and collaboration cannot be over-emphasised.
The elements (or components) of PHC include (but not limited to) Immunisation, Maternal and Child Health (MCH) Care, Essential Drugs, Food and Nutrition, Education, Common Illnesses and injury, Water and Sanitation, Endemic Infectious Diseases, Mental health and Oral health.
All African countries have adopted PHC as the over-arching strategy to achieve health for their citizens. Strategies for the promotion of medicinal plants for the prevention of diseases in Africa must therefore take into cognisance the PHC approach. It must essentially follow the 5-key principles outlined above and be integrated into the elements. Medicinal plants will be useful for Maternal and Child health care, as essential drugs, in food and nutrition, for common illnesses and injury, for endemic infectious diseases, mental health and oral health.
Medicinal plants also fit perfectly into the modelling for priorities in Primary Health Care as proposed by McDonald and Ollerenshaw (2011). (Figure 5)
In summary, from the above considerations of available strategies, medicinal plants can play vital roles in disease prevention and their promotion and use fit into all existing prevention strategies. However, conscious efforts need to be made to properly identify, recognise and position medicinal plants in the design and implementation of these strategies. These approaches present interesting and emerging perspectives in the field of medicinal plants.
Ethnobotanical Studies on Medicinal Plants Used in Disease Prevention
In order that a comprehensive compilation of medicinal plants that can be used in disease prevention is obtained, collation of original data from the traditional custodians of such knowledge is essential (Tan et al., 2010). This is especially so in the case of African Traditional Medicine (ATM) where information is passed on from generation to generation orally about the plants used. Unlike in Chinese Traditional Medicine (CTM) and the Indian systems of medicine (Ayurveda, Unani and Sithda) where the information is available in books (and now online), a lot of the information on African traditional medicine is yet to be documented. Efforts are, however, being made by WHO-AFRO to augment the various isolated databases on medicinal plants through the provision of guidelines for documentation of herbal recipes (WHO/AFRO 2012). Specific ethnobotanic surveys at village level using some of the methods described by Sofowora (2008) can be used. Such a survey by Biswas et al. (2011) on medicinal plants used for preventive medicinal purposes in Muktipara village, Chuadanga District of Bangladesh yielded 11 authentic plants including Azadirachta indica and Moringa oleifera which are quite common in Africa.
A similar survey conducted by Rahmatulla et al. (2011) among the Chakma residents of Hatimara (south) village of Rangamati district, also in Bangladesh, indicated that the mode of consumption of the plants differed to some extent. Some plants, like Spilanthes calva or Commelina paludosa, the leaves were boiled, mixed with crushed peppers and taken. The authors found that the addition of peppers did not serve any therapeutic purposes. Rather, peppers, particularly hot peppers, were added to make the dish more palatable and to impart flavour to the dish (Rahmatullah et al., 2009; Sofowora 2008; Abel and Busia, 2005). The juice of young leaves of Centella asiatica or juice of leaves of Solena amplexicaulis was taken in the raw state. The fruits of Gymnopetalum cochinchinense were used for prevention of ulcer, and Solanum torvum as a preventive measure against leucorrhoea, typhoid and tonsillitis. The barks and seeds of Saraca were mashed and taken in the raw state as prevention for irregular menstruation and menorrhagia.
International ethnobotanical surveys sponsored by ACCT (Agence de Cooperation Culturelle et Technique) into 17 Francophone African countries and 5 into Anglophone African countries sponsored by the African Union (AU/STRC) and most of which were led by Professor Edouard Adjanohoun (Benin now France) and Professor Laurent Ake Assi have been published. These need to be searched for plants used in disease prevention as they were general ethnobotanic surveys which probably emphasised more enquiries on the use of plants to treat disease. All the data from such surveys especially the new ones need to be stored in a database where it is not yet done and protected for only authorised access.
Medicinal plants used to prevent cancer
Yasukawa (2012) has reviewed the chemopreventive activity of natural sources, foods, supplements, crude drugs and Kampo medicines (traditional Japanese herbal prescriptions). In that review, he observed that cancer chemoprevention is currently one of the most urgent projects in public health. Cancer chemoprevention is defined as the use of specific natural and synthetic chemical agents to reverse or suppress carcinogenesis and prevent the development of invasive cancers. Recently, dietary non-nutrient compounds have demonstrated important effects as chemo-preventive agents, and considerable work on the cancer chemopreventive effects of such compounds in animal models has been undertaken. Epidemiological surveys have shown that the majority of human cancers are related to two factors, namely, diet and smoking (Banning, 2005; Hirayama, 1984). However, in the general population, daily consumption of certain foods has also been shown to have anticancer effects. This highlights the importance of environmental factors such as diet in cancer chemoprevention (Banning, 2005). An understanding of the mechanisms of carcinogenesis is essential for cancer chemoprevention. Most cancer prevention research is based on the concept of multistage carcinogenesis: initiation → promotion → progression (Pitot and Dragan (1991)]; Morse and Stoner, 1993). (Figure 6)
Stages in Cancer Prevention Research
In contrast to both the initiation and progression stages, animal studies have indicated that the promotion stage occurs over a long time period and may be reversible, at least early on. For this reason, it is expected that inhibition of tumour promotion should be an efficient approach to cancer control (Murakami, et al., 1996). Yasukawa and his team have found in the search for potential anti-tumour promoters (cancer chemopreventive agents) from edible plants and fungi, and from crude drugs, that various triterpene alcohols and sterols and their oxygenated derivatives showed inhibitory effects on mouse ear inflammation induced by 12-Otetradecanoylphorbol-13-acetate (TPA). Primary prevention of cancer aims to avoid the development of cancer. Therefore, initiation and/or promotion of carcinogenesis should be inhibited. However, the adult population bears tumour cells that cannot revert to normal cells, and thus effective strategies to prevent cancer include avoiding continuous contact between these cells and promoters and/or aggressively inhibiting the tumour promoter effects. Therefore, to prevent cancer, it is essential to find plants that contain effective compounds (anti-tumour promoters) that delay, inhibit or block tumour promotion, which is a reversible and long-term process (Yasukawa, 2012). A few examples of such plants of interest are shown below:
(Pygeum) Prunus spp (Family Rosaceae) e.g. African Prune or African Plum Tree
Prostate cancer is a very good example for chemoprevention because prostate cancer is typically slow growing and is usually diagnosed in elderly males. The extract of the bark of Pygeum africanum (Prunus Africana) has been used in Europe as a prevention and treatment of prostate disorders including benign prostatic hypertrophy (BPH). In tissue culture, ethanolic extracts (30%) of the bark inhibited the growth of PC-3 and LNCaP cells; induced apoptosis and altered cell kinetics; down-regulated ERalpha and PKC-alpha protein, and demonstrated good binding ability to both mouse uterine oestrogen receptors and LNCaP human androgen receptors. TRAMP mice fed with P. africanum showed a significant reduction (P = 0.034) in prostate cancer incidence (35%) compared to casein fed mice (62.5%). P. africanum therefore has a significant role in regulation of prostate cancer both in vitro and in vivo and therefore may be a useful supplement for people at high risk for developing prostate cancer (Shenouda et al, 2007). Katz (2002) had observed that the consumption of isoflavones found in legumes and other plants is related to lower rates of BPH and prostate cancer among Asian men (Katz, 2002). The methanol extract of Prunus jamasakura Sieb. ex Koidz. inhibited two-stage carcinogenesis by DMBA/TPA in mouse skin (Yasukawa, et al., 1998). Octacosyl ferulate, from the active fraction of the plant, inhibited tumour promotion by DMBA/TPA in mouse skin (Yasukawa, et al., 1998) (Figure 7). The compound also inhibited the phosphorylation of histone by protein kinase C (PKC) in a concentration-dependent manner.
Octacosyl ferulate from Pruni Cortex
Azadirachta indica (Family Meliaceae) Neem
Over 60 different types of biochemicals including terpenoids and steroids have been purified from this plant. The anticancer properties of the plant have been studied largely in terms of its preventive, protective, tumour-suppressive, immunomodulatory and apoptotic effects against various types of cancer and their molecular mechanisms (Paul et al, 2011). Triple-negative breast cancer (TNBC) accounts for 15–20% of all breast tumours and these breast tumours are usually aggressive and highly metastatic. Unfortunately, treatment options for TNBCs are limited. A novel compound, 2′-3′-dehydrosalannol (DHS) isolated from A. indica uncrushed leaves, inhibited growth and induced apoptosis in TNBC cell lines. Molecular analysis suggested that DHS inhibited cathepsin-mediated pro-survival signalling [pAKT: phosphorylated protein kinase B; BCL-2: B-cell lymphoma 2 and cyclin D1] and induced pro-apoptotic markers such as BAX [BCL-2-associated X protein] and cleaved caspase-3 (Boopalan et al, 2012, Malathi et al, 2002). Also, Neem leaves were found to inhibit tumour promotion by DMBA/TPA in mouse skin (Arora et al., 2011). Inhibition of carcinogenesis in response to neem treatment was accompanied by an over expression of signal transducer and activator of transcription 1 (STAT1) and activator protein 1 (AP-1) and decrease in nuclear factor-kappa B (NF-κB) expression (Arora et al., 2011). In a recent study, Bharati et al, (2012) evaluated the anticarcinogenic potential of aqueous A. indica leaf extract against N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis. They reported a significant reduction in tumour incidence (33%), tumour multiplicity (42%), and increase in survival (34%) upon administration of the aqueous extract to NDEA-abused mice. Transmission and scanning electron microscopic investigations showed severe alterations in organelle organisation, cellular arrangement, degree of differentiation, cellular metabolism, and morphology of the hepatocytes. They concluded that these changes appeared to be distinctly delayed upon supplementation with the leaf extract of the plant. The results suggest that A. indica may have anticancer potential against NDEA-induced hepatic cancer.
Rosmarinus officinalis L (Family Labiatae) Rosemary
Colorectal cancer is the second leading cause of cancer death in Australia. Ngo et al. (2011) reviewed scientific evidence from all studies published from 1996 to March 2010 and which examined the protective effects of rosemary on colorectal cancer and other types of cancer. They concluded that evidence from animal and cell culture studies demonstrates the anticancer potential of rosemary extract as well as only the following constituents of it: carnosol, carnosic acid, ursolic acid, and rosmarinic acid. The reported anticancer properties were found to arise through the molecular changes in the multiple-stage process of cancer development, which are dose related and not tissue or species specific. López-Jiménez (2013) demonstrated that the anti-angiogenic activity of carnosol and carnosic acid could contribute to the chemopreventive, antitumoral and antimetastatic activities of rosemary extracts and suggested their potential in the treatment of other angiogenesis-related malignancies. Ursolic acid and carnosol were isolated from the methanol extract of Rosemary, and inhibited DMBA/TPA-promoted two-stage carcinogenesis in mouse skin (Huang et al., 1994) (Figure 8).
Vitis vinifera L. (Family Vitaceae) Grape
Dietary intake of foods rich in antioxidant properties is suggested to be cancer protective. Foods rich in antioxidant properties include grape (Vitis vinifera). Grape skin and seed extracts exert strong free radical scavenging and chelating activities and inhibit lipid oxidation in various food and cell models in vitro. The use of grape antioxidants are promising against a broad range of cancer cells by targeting epidermal growth factor receptor (EGFR) and its downstream pathways, inhibiting over-expression of COX-2 and prostaglandin E2 receptors, or modifying oestrogen receptor pathways, resulting in cell cycle arrest and apoptosis (Zhou and Raffoul, 2012).
Filip et al. (2011) in their studies on Photoprotective effects of two natural products on ultraviolet B-induced oxidative stress and apoptosis in SKH-1 mouse skin reported that their results suggest that Calluna vulgaris and Vitis vinifera extracts might be chemopreventive candidates for reducing UV-induced risk for skin cancer.
Currants and Sultanas (Vitis vinifera L.) are dried vine products produced in Greece. Kaliora et al. (2008) investigated the gastric cancer preventive activity of methanol extracts obtained from currants from three different origins in Greece (Vostizza, Nemea, and Messinia), as well as methanol extracts obtained from Sultanas cultivated on the island of Crete as to inhibition of cell proliferation, induction of apoptosis, and inhibition of inflammation. All extracts from 500 micrograms of dried raisins studied suppressed cell proliferation, significantly those obtained from Sultanas from Crete and currants from Nemea. The French eat higher levels of animal fat, but their incidence of heart disease remains surprisingly low. This ‘French Paradox’ is thought to be due to the benefits they derive from consuming red wine. The ethanol extract of grapes inhibited tumour promotion by DMBA/TPA in mouse skin (Alam et al., 2002). Resveratrol, in a dose-dependent manner, reduced the incidence, total number and multiplicity of visible hepatocyte nodules (Bishayee and Dhir, 2009) (Figure 9).
On the other hand, grape seeds are a rich source of monomeric, dimeric and oligomeric proanthocyanidins. The polyphenolic fraction of grape seeds suppressed tumour promotion by DMBA/TPA in mouse skin (Bomser, et al., 1999; Zhao, et al., 1999).
Glycine max or G. soya (Family Leguminosae) Soya milk
Genistein, the most abundant phytoestrogen in soybeans, may bind to oestrogen receptors and perform anticancer activities. Choriocarcinoma is a malignant, trophoblastic and aggressive cancer of the placenta. Liu et al (2011) investigated the effect of genistein on the invasive potential of the choriocarcinoma cell line JAR and its underlying mechanism and found that genistein inhibited JAR cell invasion in a dose-dependent manner by a matrigel invasion assay. Their findings have significant implications for the prevention and therapy of choriocarcinoma. However, Khan et al (2012) tested the hypothesis that Soy isoflavone consumption may protect against breast cancer development. They found a lack of efficacy for breast cancer prevention and a possible adverse effect in premenopausal women. Soy milk inhibited 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanoneinduced mammary carcinogenesis in rats (Ohta et al., 2000). Soy beans contain high amounts of isoflavonoids and saponins; isoflavonoids have been shown to have phytoestrogenic activity (Moliteni et al., 1995; Katz, 2002).
Zingiber officinale Roscoe (Family Zingiberaceae) Ginger
Dehydrozingerone a pungent constituent of ginger is a vanillyl ketone. Structurally, it is representative of half the chemical structure of curcumin which is a promising phytochemical for the inhibition of malignant tumours, including colon cancer. Yogosawa et al. (2012) evaluated the antiproliferative effects of dehydrozingerone against HT-29 human colon cancer cells, and it was found that it dose-dependently inhibited growth at the G2/M phase with up-regulation of p21. Dehydrozingerone additionally led to the accumulation of intracellular ROS, although most radical scavengers could not clearly repress the cell-cycle arrest at the G2/M phase. Their results suggest that analogues of dehydrozingerone may be potential chemotherapeutic agents for colon cancer (Škrovánková, 2012). Kurapati et al. (2012) investigated the combinatorial cytotoxic effects of Curcuma longa and Zingiber officinale on the PC-3M prostate cancer cell line. The two extracts separately showed significant inhibitory effects on colony-forming ability. However, when both the agents were tested together at the same concentrations, the combined effects were much more significant than their individual ones, suggesting the role of multiple components and their synergistic mode of actions to elicit stronger beneficial effects.
Hexahydrocurcumin, extracted from Zingiber officinale, was shown to be cytotoxic to colorectal cancer cells by Chen et al. (2011). Treatment of SW480 cells with hexahydrocurcumin (100 microM) resulted in a massive accumulation of the cells in the G1/G0 phase of the cell cycle. This compound could prove useful in cancer prevention.
The protective and/or preventive activity of various spices against various cancers and gastric ulcer has been reviewed by Sumbul et al. (2011) and by Sung et al. (2012).
Topical application of an ethanol extract of ginger inhibited TPA-induced tumour promotion during two-stage carcinogenesis in mouse skin (Katiyar et al., 1996). Pre-application of an ethanol extract of ginger onto the skin of SENCAR mice resulted in significant inhibition of TPA-induced epidermal ODC, COX and lipoxygenase activities as well as ODC mRNA expression in a dose-dependent manner. Topical application of -gingerol inhibited tumour promotion by DMBA/TPA in mouse skin, and also suppressed TPA-induced epidermal ODC activity and inflammation (Park et al., 1998) (Figure 10).
Some phenolics from Zingiber officinale
Introduction and Importance of Medicinal Plants and Herbs
The term “medicinal plant” include various types of plants used in herbalism ("herbology" or "herbal medicine"). It is the use of plants for medicinal purposes, and the study of such uses.
The word “herb” has been derived from the Latin word, “herba” and an old French word “herbe”. Now a days, herb refers to any part of the plant like fruit, seed, stem, bark, flower, leaf, stigma or a root, as well as a non-woody plant. Earlier, the term “herb” was only applied to non-woody plants, including those that come from trees and shrubs. These medicinal plants are also used as food, flavonoid, medicine or perfume and also in certain spiritual activities.
Plants have been used for medicinal purposes long before prehistoric period. Ancient Unani manuscripts Egyptian papyrus and Chinese writings described the use of herbs. Evidence exist that Unani Hakims, Indian Vaids and European and Mediterranean cultures were using herbs for over 4000 years as medicine. Indigenous cultures such as Rome, Egypt, Iran, Africa and America used herbs in their healing rituals, while other developed traditional medical systems such as Unani, Ayurveda and Chinese Medicine in which herbal therapies were used systematically.
Traditional systems of medicine continue to be widely practised on many accounts. Population rise, inadequate supply of drugs, prohibitive cost of treatments, side effects of several synthetic drugs and development of resistance to currently used drugs for infectious diseases have led to increased emphasis on the use of plant materials as a source of medicines for a wide variety of human ailments.
Among ancient civilisations, India has been known to be rich repository of medicinal plants. The forest in India is the principal repository of large number of medicinal and aromatic plants, which are largely collected as raw materials for manufacture of drugs and perfumery products. About 8,000 herbal remedies have been codified in AYUSH systems in INDIA. Ayurveda, Unani, Siddha and Folk (tribal) medicines are the major systems of indigenous medicines. Among these systems, Ayurveda and Unani Medicine are most developed and widely practised in India.
Recently, WHO (World Health Organization) estimated that 80 percent of people worldwide rely on herbal medicines for some aspect of their primary health care needs. According to WHO, around 21,000 plant species have the potential for being used as medicinal plants.
As per data available over three-quarters of the world population relies mainly on plants and plant extracts for their health care needs. More than 30% of the entire plant species, at one time or other were used for medicinal purposes. It has been estimated, that in developed countries such as United States, plant drugs constitute as much as 25% of the total drugs, while in fast developing countries such as India and China, the contribution is as much as 80%. Thus, the economic importance of medicinal plants is much more to countries such as India than to rest of the world. These countries provide two third of the plants used in modern system of medicine and the health care system of rural population depend on indigenous systems of medicine.
Treatment with medicinal plants is considered very safe as there is no or minimal side effects. These remedies are in sync with nature, which is the biggest advantage. The golden fact is that, use of herbal treatments is independent of any age groups and the sexes.
The ancient scholars only believed that herbs are only solutions to cure a number of health related problems and diseases. They conducted thorough study about the same, experimented to arrive at accurate conclusions about the efficacy of different herbs that have medicinal value. Most of the drugs, thus formulated, are free of side effects or reactions. This is the reason why herbal treatment is growing in popularity across the globe. These herbs that have medicinal quality provide rational means for the treatment of many internal diseases, which are otherwise considered difficult to cure.
Medicinal plants such as Aloe, Tulsi, Neem, Turmeric and Ginger cure several common ailments. These are considered as home remedies in many parts of the country. It is known fact that lots of consumers are using Basil (Tulsi) for making medicines, black tea, in pooja and other activities in their day to day life.
In several parts of the world many herbs are used to honour their kings showing it as a symbol of luck. Now, after finding the role of herbs in medicine, lots of consumers started the plantation of tulsi and other medicinal plants in their home gardens.
Medicinal plants are considered as a rich resources of ingredients which can be used in drug development either pharmacopoeial, non- pharmacopoeial or synthetic drugs. A part from that, these plants play a critical role in the development of human cultures around the whole world. Moreover, some plants are considered as important source of nutrition and as a result of that they are recommended for their therapeutic values. Some of these plants include ginger, green tea, walnuts, aloe, pepper and turmeric etc. Some plants and their derivatives are considered as important source for active ingredients which are used in aspirin and toothpaste etc.
Apart from the medicinal uses, herbs are also used in natural dye, pest control, food, perfume, tea and so on. In many countries different kinds of medicinal plants/ herbs are used to keep ants, flies, mice and flee away from homes and offices. Now a days medicinal herbs are important sources for pharmaceutical manufacturing.
Recipes for the treatment of common ailments such as diarrhoea, constipation, hypertension, low sperm count, dysentery and weak penile erection, piles, coated tongue, menstrual disorders, bronchial asthma, leucorrhoea and fevers are given by the traditional medicine practitioners very effectively.
Over the past two decades, there has been a tremendous increase in the use of herbal medicine; however, there is still a significant lack of research data in this field. Therefore since 1999, WHO has published three volumes of the WHO monographs on selected medicinal plants.
Importance of some herbs with their medicinal values
- Herbs such as black pepper, cinnamon, myrrh, aloe, sandalwood, ginseng, red clover, burdock, bayberry, and safflower are used to heal wounds, sores and boils.
- Basil, Fennel, Chives, Cilantro, Apple Mint, Thyme, Golden Oregano, Variegated Lemon Balm, Rosemary, Variegated Sage are some important medicinal herbs and can be planted in kitchen garden. These herbs are easy to grow, look good, taste and smell amazing and many of them are magnets for bees and butterflies.
- Many herbs are used as blood purifiers to alter or change a long-standing condition by eliminating the metabolic toxins. These are also known as 'blood cleansers'. Certain herbs improve the immunity of the person, thereby reducing conditions such as fever.
- Some herbs are also having antibiotic properties. Turmeric is useful in inhibiting the growth of germs, harmful microbes and bacteria. Turmeric is widely used as a home remedy to heal cut and wounds.
- To reduce fever and the production of heat caused by the condition, certain antipyretic herbs such as Chirayta, black pepper, sandal wood and safflower are recommended by traditional Indian medicine practitioners.
- Sandalwood and Cinnamon are great astringents apart from being aromatic. Sandalwood is especially used in arresting the discharge of blood, mucus etc.
- Some herbs are used to neutralize the acid produced by the stomach. Herbs such as marshmallow root and leaf. They serve as antacids. The healthy gastric acid needed for proper digestion is retained by such herbs.
- Indian sages were known to have remedies from plants which act against poisons from animals and snake bites.
- Herbs like Cardamom and Coriander are renowned for their appetizing qualities. Other aromatic herbs such as peppermint, cloves and turmeric add a pleasant aroma to the food, thereby increasing the taste of the meal.
- Some herbs like aloe, sandalwood, turmeric, sheetraj hindi and khare khasak are commonly used as antiseptic and are very high in their medicinal values.
- Ginger and cloves are used in certain cough syrups. They are known for their expectorant property, which promotes the thinning and ejection of mucus from the lungs, trachea and bronchi. Eucalyptus, Cardamom, Wild cherry and cloves are also expectorants.
- Herbs such as Chamomile, Calamus, Ajwain, Basil, Cardamom, Chrysanthemum, Coriander, Fennel, Peppermint and Spearmint, Cinnamon, Ginger and Turmeric are helpful in promoting good blood circulation. Therefore, they are used as cardiac stimulants.
- Certain medicinal herbs have disinfectant property, which destroys disease causing germs. They also inhibit the growth of pathogenic microbes that cause communicable diseases.
- Herbal medicine practitioners recommend calmative herbs, which provide a soothing effect to the body. They are often used as sedatives.
- Certain aromatic plants such as Aloe, Golden seal, Barberry and Chirayata are used as mild tonics. The bitter taste of such plants reduces toxins in blood. They are helpful in destroying infection as well.
- Certain herbs are used as stimulants to increase the activity of a system or an organ, for example herbs like Cayenne (Lal Mirch, Myrrh, Camphor and Guggul.
- A wide variety of herbs including Giloe, Golden seal, Aloe and Barberry are used as tonics. They can also be nutritive and rejuvenate a healthy as well as diseased individual.
- Honey, turmeric, marshmallow and liquorice can effectively treat a fresh cut and wound. They are termed as vulnerary herbs.
As our lifestyle is now getting techno-savvy, we are moving away from nature. While we cannot escape from nature because we are part of nature. As herbs are natural products they are free from side effects, they are comparatively safe, eco-friendly and locally available. Traditionally there are lot of herbs used for the ailments related to different seasons. There is a need to promote them to save the human lives.
These herbal products are today are the symbol of safety in contrast to the synthetic drugs, that are regarded as unsafe to human being and environment. Although herbs had been priced for their medicinal, flavouring and aromatic qualities for centuries, the synthetic products of the modern age surpassed their importance, for a while. However, the blind dependence on synthetics is over and people are returning to the naturals with hope of safety and security. It’s time to promote them globally.
- PUBLISHED DATE : May 20, 2016
- PUBLISHED BY : Zahid
- CREATED / VALIDATED BY : Dr. Mahtab Alam Khan
- LAST UPDATED ON : May 20, 2016
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