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A fruit and vegetable-rich diet has been associated with decreased risk of developing chronic diseases such as cardiovascular disease and cancer in humans. These protective effects have been attributed in part, to the presence of phytochemicals in fruit and vegetables, in particular flavonoids and phenolic compounds. Some plants have been used in traditional medicine for healing, ritual ceremonies and as health tonics or food supplements. Recent interest in the health-promoting properties of Malaysian traditional vegetables has been based on claims about their uses in health and medicine. However, scientific information to support these claims is largely unexplored. The overall objectives of the present study were to investigate, determine and quantify the phytochemicals, particularly phenolic compounds, in the seven samples from five species of selected Malaysian traditional vegetables (Anacardium occidentale, Centella asiatica, Colubrina asiatica, Pluchea indica and Premna cordifolia) and to evaluate their activities in vitro, including antioxidant and antibacterial activities of extracts of these plants and individual phytochemicals. In the first section of this project, discussed in Chapter 3, Malaysian traditional vegetable extracts were screened for phenolic compounds using several complimentary techniques, namely high performance liquid chromatography (HPLC) and HPLC-tandem mass spectrometry and the total phenolic content determined using the Folin-Ciocalteu assay. Flavonol glycosides were predominant in most of the species, particularly A. occidentale with levels ranging from 6434 to 12420 µg/g fresh weight. Chlorogenic acids were the main components identified and quantified in C. asiatica and P. indica. The total phenolic content of the vegetables were between 100 ± 7.8 and 415 ± 20 mg/ kg gallic acid equivalent (GAE) in batch 1 but lower in batch 2 ranging from 62 ± 2.5 to 386 ± 41 mg/ kg GAE. The total phenolic content of plant extracts was positively correlated with total antioxidant capacity, determined by 2, 2’-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and ferric reducing antioxidant potential (FRAP) assays. A. occidentale exhibited the highest total phenolic content and total antioxidant activity, whereas Colubrina asiatica, which had the lowest total phenolic content, also had low antioxidant activity in vitro. Phenolic content and antioxidant activity were significantly (p |
