Trees and shrubs with medicinal and nutritional potentials abound in different parts of the world. Vegetables are indispensable constituents of human diets. They supply the body with minerals, vitamins and certain hormone precursors in addition to proteins and energy. The medicinal values of plants and vegetables are dictated by their phytochemical and other chemical constituents.
The use of plant materials to prevent and treat infectious diseases successfully over the years has attracted the attention of scientist’s worldwide (Falodun et al., 2006). Many investigations are being conducted on medicinal plants based on information supplied by the local populations with the object of finding out phytochemical constituents for application in the prevention and treatment of infectious diseases and other diseases of non-microbial etiology. Several studies have been conducted to provide scientific basis for the efficacy of plants in herbal medicines .
There has been a revival of interest in herbal medicine. This is due to increased awareness of the limited ability of synthetic pharmaceutical products to control major diseases and the to discover new molecular structures as lead compounds from the plant kingdom. Plants are the basic source of knowledge of modern medicine. The basic molecular and active structures for synthetic fields are provided by rich natural source. The relatively lower incidence of adverse reaction to plant preparation compared to modern conventional pharmaceuticals, coupled with there reduced cost, is encouraging both the consuming public and health care institutions to consider plant medicines as alternatives to synthetic drugs.
According to world health organization (WHO), more than 80% of the world’s population relies on traditional medicines for their primary health care needs. The medicinal value of plants lies in some chemical substances that produce a definite physiologic action on thehuman body. The most important of these bioactive compounds of plants are alkaloids, flavonoids, tannins and phenolic compounds. The phytochemical research based on ethno-pharmacological information is generally considered an effective approach in the discovery of new anti-infective agents from higher plants.
Primitive people have used plants to cure a variety of human ailments. Even today, 85% of Indians use higher plants as effective anti-microbials for the treatment of various diseases. A large number of anti-microbial agents derived from traditional medicinal plants are available for treating various diseases caused by microorganisms They are used to eliminate the infecting micro-organisms. The therapeutically useful novel agents should inhibit the germs and exhibit greater selective toxicity towards the infecting germ than the host cells. The mode of action for plant-derived agent should target biochemical features of the invading pathogens that are not possessed by the normal host cell. Some of the factors important for anti-microbial treatment include methods such as sensitivity of the infecting micro-organism to a particular agent.
Medicinal plants are also used for flavours and fragrances in various industries such as bakery, confectionery, alcholic beverages, foods, soft drinks and pharmaceuticals. Added to the appetizers, biscuits, bread, butter, cakes, cheese, forcemeat, dessert, drinks, egg dishes, fish dishes, meat, puddings, salads, sances, seasonings, soups, teas, vegetables, and vinegars. Flavour of food makes the food palatable, added in pastes, powders of dentrifrices, mouthwashes, and gargles, breath fresheners and denture cleaners. There is also need to develop better institutional research & development support & public polices for the development of essential oil industry .
Traditionally used medicinal plants produce a variety of compounds of known therapeutic properties.The substances that can either inhibit the growth of pathogens or kill them and have no or least toxicity to host cells are considered candidates for developing new antimicrobial drugs. In recent years, antimicrobial properties of medicinal plants are being increasingly reported from different parts of the world (Saxena and Sharma 1999). It is expected that plant extracts showing target sites other than those used by antibiotics will be active against drug-resistant microbial pathogens. However, very little information is available on such activity of medicinal plants.
Plants remain the most common source of antimicrobial agents. Their usage as traditional health remedies is the most popular for 80% of world population in Asia, Latin America and Africa and is reported to have minimal side effects. In recent years, pharmaceutical companies have spent a lot of time and money in developing natural products extracted from plants, to produce more cost effective remedies that are affordable to the population. The rising incidence in multidrug resistance amongst pathogenic microbes has further necessitated the need to search for newer antibiotic sources.
Plants have an almost limitless ability to synthesize aromatic substances, most of which are phenols or their oxygen-substituted derivatives. Most are secondary metabolites, of which at least 12,000 have been isolated, a number estimated to be less than 10% of the total. In many cases, these substances serve as plant defense mechanisms against predation by microorganisms, insects, and herbivores. Some, such as terpenoids, give plants their odors; others (quinones and tannins) are responsible for plant pigment. Many compounds are responsible for plant flavor .
Plants with possible antimicrobial activity should be tested against an appropriates microbial model to confirm the activity and to ascertain the parameters associated. The effect of plant extracts on bacteria have been studied by very large number of researchers in different parts of the world. Much work has been on ethnomedicinal plants in the world. Interest in a large number of traditional natural products has increased. It has suggested that aqueous and alcoholic extracts from plants used in allopathic medicine are potential source of antiviral, antitumoral and antimicrobial agents. The selection of crude plant extracts for screening programs has the potential of being more successful in initial steps than the screening of pure compounds isolated from natural products.
Numerous studies have shown that aromatic and medicinal plants are sources of diverse nutrient and non nutrient molecules, many of which display antioxidant and antimicrobial properties which can protect the human body against both cellular oxidation reactions and pathogens. Thus it is important to characterize different types of medicinal plants for their antioxidant and antimicrobial potential (Mothana and Lindequist 2004; Bajpai et al., 2005; Wojdylo et al., 2007). Aromatic and medicinal plants are known to produce certain bioactive molecules which react with other organisms in the environment, inhibiting bacterial or fungal growth (antimicrobial activity). The substances that can inhibit pathogens and have little toxicity to host cells are considered candidates for developing new antimicrobial drugs.
The preservative effect of many plant species and herbs suggests the presence of antioxidative and antimicrobial constituents. Many medicinal plants contain large amounts of antioxidants other than vitamin C, vitamin E, and carotenoids. Antioxidants have been reported to prevent oxidative damage caused by free radical and may prevent the occurrence of disease, cancer and aging. The medicinal properties of plants have been investigated in the recent scientific developments throughout the world, due to their potent antioxidant activities, no side effects and economic viability. Flavonoids and phenolic compounds widely distributed in plants which have been reported to exert multiple biological effect, including antioxidant, free radical scavenging abilities, anti-inflammatory, anticarcinogenic etc. Recently there has been an upsurge of interest in the therapeutic potentials of medicinal plants as antioxidants in reducing such free radical induced tissue injury.
