John T. Landrum, Associate Dean
University Graduate School
and Professor
Department of Chemistry and Biochemistry
Florida International University
Miami, Florida  33199

phone: (305)-348-2455
FAX: (305)-348-3772
Email: landrumj@fiu.edu
 
 

Research Interests:

Macular pigment:  Identification of the components of the macular pigment, their absorption, transport, uptake, function, and metabolism are the major activities of our research group.  We have in demonstrated that lutein, zeaxanthin, meso-zeaxanthin are all major components of the macular pigment present in the human macula.  Meso-zeaxanthin is not a dietary component and is most probably produced by metabolic processes within the central macular region of the retina.  We have been able to demonstrate that dietary lutein and zeaxanthin supplementation will produce increases in the level of macular pigmentation.  The probable functions of the macular pigment involve the absorption of blue light by the highly concentrated  pigment found in the inner layers of the retina and possible direct action as an antioxidant within the photoreceptors themselves.  Our recent comparison of the amounts of macular pigment found in the retinas of control eyes and those diagnosed with age-related macular degeneration (AMD) show that individuals having the highest levels of macular pigment (as measured in the peripheral retina) have a ~75% lower risk of AMD than individuals in having the lowest levels.

Macular pigment of the macaque retina and the cross-section of the retina showing the macular pigment concentrated in the inner neural layers.

Carotenoids: Carotenoids are brightly colored natural products that are synthesized by plants, algae and bacteria. More than 600 naturally occurring carotenoids have been extracted and identified from a wide variety of biological sources. The majority of carotenoids are tetraterpenes and contain eight isoprene units. These tetraterpene carotenoids have a C40 carbon skeleton and are typified by a conjugated polyene chain containing 9 or 10 double bonds. It is this linear conjugated polyene that is responsible for the characteristic intense colors of carotenoids. Carotenoids are natural dietary components of higher animals which are unable to synthesize these compounds. They serve a variety of functional roles in higher animals which absorb these lipophylic components from the diet and deposit them in many different tissues. In virtually all higher animals the provitamin A carotenoids are a source of vitamin A (retinol) which is essential for normal growth and health in addition to its function as a visual pigment. In birds yellow, orange, and red plumage are due to a variety of carotenoid compounds.

Eschscholzia mexicana (eschscholtzxanthin), golden finch (lutein), Lobelia cardineli (lycopene?), Calthus palustrus (epilutein)

beta-carotene has been identified as an anti-oxidant and its accumulation in many tissues is believed to protect against free radical processes which degrade and damage cellular structures leading to carcinogenisis, apoptosis, mutations, and structural damage associated with aging. Similarly, other carotenoids are found in a variety of tissues and may serve an anti-oxidant role. The possibility that metabolism of non-provitamin A carotenoids occurs producing essential or non-essential compounds that are biologically active cannot be neglected.

Our research which has largely been devoted to an elucidation of the composition and function of the macular pigment now includes the broader goal to understand the nature of the metabolism of the non-provitamin A dihydroxy-carotenoids, particularly lutein and zeaxanthin. The presence of meso-zeaxanthin (3R,3'S-beta,beta-carotene-3,3'-diol) in the human retina requires a complex transformation which is thought to be enzyme mediated. We are working toward a basic understanding of the oxidation and degradation reactions of lutein and zeaxanthin. Understanding the role of non-provitamin A carotenoids in human health will necessitate a complete clarification of the metabolism of these compounds, their metabolic products, and their fate.

Vita

Recent Publications
 

Courses:

Freshman Exp, SLS 1501 -  Rope Course a Go For Fri. Oct 21 , Ropes Photos

General Chemistry I,     CHM1045 - syllabus, assignments
General Chemistry II,    CHM1046 - syllabus, assignments
Organic Chemistry I,     CHM2210 - syllabus, assignments
Organic Chemistry II,    CHM 2211 - syllabus, assignments

Survey of Organic Chemistry,  CHM 2200 - syllabus, assignments

Advanced Inorganic Chemistry, CHM 4610 - syllabus, assignments