Health Benefits of Bioactive Compounds
Numerous health benefits of bioactive compounds have been reported so far. Jang et al. (1997) reported anticancer potential of resveratrol from grape seeds. The interest in lignans and their synthetic derivatives is growing because of their potential applications in cancer chemotherapy and various other pharmacological effects (Saleem et al. 2005). Mantena et al. (2006) studied the effect of grape seed proanthocyanidins in inducing apoptosis and inhibition of metastasis in both cultured breast and colon cancer cells. Pomegranate peel extracts have been shown to retard proliferation of cells in several different human cancer cell lines (Kawaii and Lansky 2004). Pomegranate peel contains substantial amounts of polyphenols such as ellagic acid and gallic acid (Nasr et al. 1996). The presence of these polyphenols in the pomegranate peel may be responsible for antimutagenicity of peel extracts (Gil et al. 2000). Another study conducted by Jang et al. (1997) illustrated that resveratrol, a natural product derived from grapes, inhibited tumour initiation, promotion and progression. Several studies have shown that phenolic compounds reduce in vitro oxidation of low-density lipoprotein. Of them, phenolics with multiple hydroxyl groups are generally the most efficient for preventing lipid and low-density lipoproteins (LDL) oxidation and therefore reduce the risk of atherogenesis (Meyer et al. 1998). Apple pomace is the main by-product of apple juice processing plant and has been found to be a good source of polyphenols (Peschel et al. 2006). Grape seed extract has been found to decrease thiobarbituric acid reactive substances (TBARS) value and showed no effect on HDL-cholesterol while LDL-cholesterol, triglycerides and total cholesterol decreased significantly (Vigna et al. 2003). Grape seed extract has also been found to reduce chronic pancreatic problems, vomiting and pain (Banerjee and Bagchi 2001). Table 11.8 shows biological and therapeutic activities of various phenolic compounds that could be extracted from agricultural residues.
Therapeutic Activities of Bioactive Compounds
Different phenolic compounds act in different ways and follow different mechanisms in combating several disorders. One of the examples is the action of resveratrol, abundantly found in grape seeds in carcinogenesis. Resveratrol is able to prevent initiation phase by inhibition of carcinogen activation (R+) induction of carcinogen deactivation and subsequently blocking interaction between DNA and carcinogen (R+) [Fig. 11.4]. Resveratrol can block the action of tumour promoter and can act on tumour progression by inhibition of angiogenesis and metastatic process. Resveratrol could act on carcinogenesis by inhibiting the initiation phase which consists of the DNA alteration (mutation) of a normal cell, which is an irreversible and fast change. The initiated cell is capable to autonomous growth. The initiating event can consist of a single exposure to a carcinogenic agent, or in some cases, it may be an inherited genetic defect. The anti-initiation activity of resveratrol is linked to the suppression of the metabolic activation of carcinogens and/or the detoxifying increases via a modulation of the drug-metabolizing enzymes involved either in phase I reactions transforming a lipophilic compound into an electrophilic active carcinogen or in phase II conjugation enzyme systems converting the primary metabolite into a final hydrosoluble metabolite (Fig. 11.4).
Most of the research on bioactive molecules is still confined to screening of crude extracts. Elucidation of the structure of the active principles could be a priority area for further studies, if the extracts did show promising activity. A potential area for further studies is the use of “-omic” technologies to unravel the mechanism of action of bioactive compounds. The “-omic” technologies based on the technology platform of genomics, proteomics and metabolomics can be applied to relate
Table 11.8 Biological and therapeutic activities of bioactive phenolic compounds
the complex effects of the bioactives in the form of gene/protein expression profiles (Ulrich-Merzenich et al. 2007). Biotechnological approaches like microarray analysis are likely to give insights into the differential gene expression when the cells are exposed to the bioactive molecules. With the advent of bioinformatics, in silico modelling in the research on bioactive molecules could also be exploited. Such an approach is being currently applied in drug discovery wherein the bioactivity of natural products is manipulated through computer simulation.
Fig. 11.4 Effect of resveratrol in carcinogenesis
In addition to the natural bioactive molecules, several studies are focusing on the production recombinant molecules. For instance, production of monoclonal antibodies and recombinant allergens, development of immunoassays, recombinant proteins with the aim of contributing to the development of diagnostic kits, have great potential for commercialization (Chu and Radhakrishnan 2008).