In recent years, there has been a marked increase in the amount of research and publications providing scientific evidence to support the hypotheses that phytochemicals in foods and in isolated form might provide health benefits to the consumer. This fact has impacted the food, health food and pharmaceutical industries, among others (Laufenberg et al., 2003).
The concept of growing crops for health rather than for food is slowly changing plant biotechnology and medicine (Raskin et al., 2002). The rediscovery of the connection between plants and health is responsible for launching a new generation of botanical therapeutics which may include plant-derived pharmaceuticals, multicomponent botanical drugs, dietary supplements, functional foods, plant-produced recombinant proteins and plant-based cosmetics. Many of these products will soon complement conventional pharmaceuticals in the treatment, prevention and diagnosis of diseases, while at the same time adding value to agriculture.
Plant extracts have been widely used as topical applications for wound-healing, anti-ageing and disease treatments. Examples of these include ginkgo biloba, echinacea, ginseng, grape seed, green tea, lemon, lavender, rosemary, thuja, sarsaparrilla, soy, prickly pear, sagebrush, jojoba, aloe vera, allantoin, feverwort, bloodroot, apache plume, papaya and many others (Hulse, 2004).
This chapter does not pretend to detail 'all' the plant-derived compounds that have the potential to be used in the pharmaceutical and cosmetic fields, but to focus on three important groups of plant-derived components, namely: plant polysaccharides, phenolic compounds and plant-derived oils.
Actually, the incorporation of plant-derived 'bioactive' components in pharmaceutical and cosmetic products is a great focus of interest (Montgomery, 2004). Many studies have found enough scientific evidence to confirm the health-promoting properties of plant extracts. This fact combined with the perception that a number of common synthetic preservatives might have hazardous effects has led to multiple investigations in the field of plant-based natural compounds (Aburjai and Natsheh, 2003). There are considerable amounts of data that suggest the benefits of such ingredients in pharmaceutical and/or cosmetic formulations. Thus, the objective of this chapter is to review recent published data that support the usefulness and potential benefits of incorporating plant polysaccharides, phenolic compounds and plant oils in pharmaceutical and/or cosmetic products.
Over the last decades, there has been considerable scientific interest in the active components of herbal drugs and/or medicinal plants and there is increasing evidence that many polysaccharides of plant origin are responsible for their bioactive properties. A wide range of bioactivities has been identified including anti-tumour activity, anti-viral activity, anti-bacterial activity, anti-complementary activity, anti-inflammatory activity, hypogly-caemic activity, anti-coagulatory activity, phagocytotic activity, anti-throm-botic activity, anti-ulcer activity and wound-healing properties.
Although most 'bioactive' plant polysaccharides have been utilised due to their pharmacological properties, their use in cosmetics as emollient natural remedies is also common. In general, products containing plant polysaccharides are capable of relieving dryness and providing a soothing membrane that covers the human skin.
18.1.2 Natural antioxidants: phenolic compounds
Antioxidants are of interest to the food industry because they prevent rancidity. However, they are also of interest to biologists, biochemists and clinicians, because they may help to protect the human body against damage by reactive oxygen species. A broad definition of an antioxidant is 'any substance that, when present at low concentrations compared with those of an oxidisable substrate, significantly delays or prevents oxidation of that substrate'. The term 'oxidisable substrate' includes almost everything found in foods and in living tissues including proteins, lipids, carbohydrates and DNA (Halliwell et al., 1995).
Phenolic compounds are the largest group of plant antioxidants and, according to Harborne (1990), one of the most important classes of plant chemicals. In terms of pharmacological activity, it is well known that phe-nolics act against the oxidation of high-density lipoproteins (HDLs). Hence, they help the body retain important HDLs while helping it get rid of problematic low-density lipoproteins (LDLs) (Hagerman et al., 1998). In addition, plant phenolics have also been found to have anti-ulcer, anti-carcinogenic and anti-mutagenic activities. The reason behind these activities is the strong antioxidant power of phenolic compounds, since they are able to scavenge free radicals (Shi et al., 2005).
All plants contain oils or fats, and mainly in their seeds. In most plants storage lipids are in the form of triglycerides (Murphy, 1990). There are a very few examples of alternative forms of storage lipid in higher plants. The most well known of these is the desert shrub, jojoba, which stores its seed lipid as a liquid wax.
Triglycerides from vegetable oils can be considered as important raw and renewable materials for the preparation of products useful for foods, pharmaceuticals and cosmetics (Barrault et al., 2002). Currently, products claiming to be rich in polyunsaturated fatty acids (PUFAs) are marketed in many countries of the world. Interestingly, the development of these products started around 1960, when the lipid hypothesis (dietary fat composition influences blood cholesterol levels and a change from saturated to more unsaturated fats, which lowers cholesterol, is beneficial for heart health) emerged. Medical groups approached the margarine industry to see whether they could provide products that could help consumers to achieve this change. These products were developed based on linoleic acid, the fatty acid with the strongest cholesterol-lowering effect. The initial pharmacological product (sold in pharmacies) was developed into a product for the total population over the ensuing years (Korver, 1997).
The use of many plant-based oils in cosmetics is generalised. The protection of the skin hydration, and the production of skin and hair preparations with softening effects is achieved using seed oils rich in fatty acids and triglycerides that reduce transepidermal water loss.
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