Pectin in Health and Disease

Many higher plants produce economically important organic compounds. such as oil, resins, tannins, natural rubber gums. waxes, dyes, flavors, fragrances, pharmaceuticals, and pesticides. The major groups of secondary metabolites of sugars include cellu lose, pectins, starch. gums, and mucilages. These make up dietary fibers, which are basically the skeletal remains of plant cells that are resistant to digestion by enzymes. The particular dietary fiber of interest in my laboratory has been grapefruit pectin. We reported at the First International Symposium or Horticulture and Human Health in 1987 our initial studies. which involved the development of in vitro techniques to systematicall y study dietary grapefruit pectin (Cerda. 19888). We were initially interested in assessing the effectiveness of grapefruit pectin and lowering plasma cholesterol in miniature swine. In this study the effect of grapefruit pectin (Cirrus paradisi) on plasma cholesterol, triglycerides, and low- and high-density lipoprotein cholesterol was investigated. Miniature pigs were randomized to either 1) controlled diet (hog finisher), 2) a high-cholesterol diet with 3% cellulose, or 3) a high-cholester ol diet with 3% grapefruit pectin. Animals were bled on a monthly basis for the duration of the experiment (326 days). Plasma was assayed for cholesterol and triglycerides and lipoprotein was assayed on the ultracentrifuged fractions. It was concluded that grapefiuit pectin significantly lowered plasma cholesterol by nearly 30%. improved the LDLC : HDLC by 31% (compared to a non-pectin high-choles terol-fed pigs), with no effect on serum triglycerides for the duration of the study. At the end of the feeding experiments, the animals were sacrificed and the effect on grapefruit pectin under development of atheroscleros is was examined. Thoracic and abdomi nal aorta and the main branches of the coronary arteries were removed. The arteries were prepared and stained for histopathologic evaluation of the severity of atheromatous plaque formation. Although there was some variability, the affected pigs on the pectin-supplemented diet showed an 85% decrease in plaque formation on the surface area of the aortas and an 88% decrease was observed in the narrowing of the coronary arteries. We concluded from these studies, that not only does grapefruit pectin lower plas ma cholesterol, but there is a significant reduction of formation of atheromatous plaque in the aorta and coronary vesseis. Furthermore, the aforementioned 30% reduction in total plasma cholesterol, with grapefruit pectin-supplemented diet in these miniature swine, was primarily due to a drop in the LDL cholesterol. In this model, grapefruit pectin seemed to be a potent hypercholesterolemia agent. In addition, it appeared that the severity of the atherosclerosis that developed depended on the level of hyperc holesterolemia that could be induced, particularly with the most-affected animals on the high-fat cellulose diet. A strong relationship (R = 0.836) between percent of surface area with plaque vs. total cholesterol (milligrams/deciliter) for aortas and 0.735 for coronary arteries [percent cross sectional narrowing vs. total cholesterol (milligrams/deciliters)] was observed (Baekey et al., 1988). We then studied the effect of grapefruit pectin on plasma choles