Identification and quantification of health-promoting phytochemicals in fruits, vegetables and other plant foods

Plants contain many bioactive substances, called phytochemicals that provide protection against chronic and degenerative diseases. Carotenoids, phenolics, phytosterols and glucosinolates are groups of phytochemicals which have been shown to have significant health potentials. Thus, the occurrences and levels of these phytochemicals n Philippine fruits, vegetables and other food plants were determined. Carotenoids were separated by open column chromatography and identified and quantified by visible spectrophotometry. Watermelon (sugar baby) was found to contain a very high amount of lycopene, while rock melon was high in beta-carotene. Malunggay leaves were shown to contain very high levels of beta-carotene and lutein. Among the yellow flowers studied, wild sunflower had the highest lutein content, followed by wedelia, marigold, squash and patola. Phenolic compounds were extracted from various fruits and vegetables (sibuyas Tagalog, malunggay leaves, siling labuyo fruits, gabi leaves, sweet potato tops, spring onions, siling labuyo leaves, Satsuma orange and calamansi) by methanol-acetone-water (MAW). Additionally, the MAW extracts were subjected to acid- and base-catalyzed hydrolysis in order to release phenolics bound as glycosides and esters. The phenolic profiles of the extracts were determined by descending two-dimensional paper chromatography. Various phenolics with health-promoting properties were identified from the extracts such as quercetin, luteolin, apigenin, caffeic and ferulic acids. The total phenolic contents of the extracts were determined using the Folin-Ciocalteu reagent, all had high phenolic contents, with malunggay leaves having the highest. The total sterol contents (gsterol/100 g oil) as determined by using the Liebermann-Burchard reagent were found to be: rice bran oil 3.044, sesame oil, 0.733 and corn kernel oil 0.903. Employing reversed-phase HPLC, stigmasterol, beta-sitosterol and campesterol, wre identified and quantified in the unsaponitiable fractions of the three oils. The occurrence of indole glucosinolates in cabbage, petchay and mustard was determined by paper chromatography (mobility and color reaction) and UV spectrophotometry. The appropriate concentrations of indole glucosinolates (mg/100 g sample) were found to be cabbage 9.92 plus or minus 1.22, pechay 8.84 plus or minus 0.59 and mustard 6.94 plus or minus 1.23, as estimated by quantifying the thiocyanate ion released on enzymic hydrolysis of the glucosinolates. Based on TLC and HPLC analyses and comparison with literature data, the breakdown products of cabbage indole glucosinolates were found to be indole-3-carbinol, indole-3-carbaldehyde, 3,3'-diindolyl-methane and skatole. Several assays were employed to evaluate antioxidant activity: 1) measurement of peroxide value and thiobarbituric assay (TBA) on corn oil autooxidation, 2) free-radical scavenging (DPPH) assay, 3) TBA assay on metal-catalyzed lipid (lecithin liposome) peroxidation, and 4) TBA assay on Fenton-induced oxidation of calf thymus DNA. The anti-oxidant activity of phenolic extracts from malunggay leaves and sibuyas tagalog were determined by measurement of peroxide value and TBA assay of corn oil autooxidation. The phenolic extracts from malunggay leaves and sibuyas tagalog were found to have an antioxidant activity comparable to BHT, quercetin and caffeic acid. To gain insight into the mechanism of action of antioxidants, the DPPH assay was conducted. The malunggay, gabi and siling labuyo extracts have comparatively higher percentage free radical scavenging activity. The glucosinolate extracts exhibited lower activities than most of the phenolics. The antioxidant assay on lecithin liposome metal-catalyzed oxidation and Fenton-induced DNA oxidation gave greater insight into the mechanism of action of the antioxidants. The anti-oxidant assay on lecithin liposome metal-catalyzed oxidation and Fenton-induced DNA oxidation gave greater insight into the mechanism of action of the antioxidants. The antioxidants capacity has been demonstrated to be a combined action of metal chelating and free radical scavenging properties of the antioxidant. The citrus fruit extracts effected the highest percent TBARS inhibition in lecithin liposome metal-catalyzed oxidation. All the phenolic extracts at a very low concentration of 8 ppm effected greater than 30.0 percent TBARS inhibition in Fenton-induced DNA oxidation. At the same concentration, the glucosinolate extracts exhibited lower activities (15 to 26 percent). The phenolic extracts, lutein, phytosterols and glucosinolate extracts (whole and autolyzed), at all concentrations tested, effectively reduced the formation of blood vessels in the duck embryo, only beta-carotene was found to be pro-angiogenic. The hamster assay showed that RBO sterols caused 18.78 percent serum-cholesterol lowering, while the unsaponifiable fractions of corn oil and sesame oil caused 18.99 percent and 18.20 percent lowering, respectively. Lipigem, a commercial statin drug, caused 22.34 percent lowering. It has been shown by this research that fruits and vegetable contain a variety of phytochemicals (including phenolics, carotenoids, phytosterols and glucosinolates) that are beneficial to health. Lower incidence and mortality rates of cancer, cardiovascular diseases, cataracts and brain and immune dysfunction are associated with the consumption of fruits and vegetables. Thus, at least five servings of fruits and vegetables are recommended daily. Filipinos should be aware of this.