Antioxidant Activity in Dry Beans
March 07, 2008
Jay Cao, Ph.D., Principal Investigator (PI)
Objectives of the study:
To determine whether antioxidant factors in dry pinto beans slow age-related bone loss in an animal model.
We hypothesized that antioxidant factors in pinto beans can slow age-related bone loss in mice by inhibiting osteoclast activity and, thus, can be useful in preventing osteoporosis.
We proposed to determine the long-term (up to 6 mos.) effects of the consumption of pinto bean hull extracts on bone structure and bone cell activities in older mice (12-mo-old). To accomplish the goal, 12-mo-old male C57BL/6J mice were fed either a control diet or a diet containing bean hull extracts for up to six months. Animals from each group will be euthanized at 3 and 6 month for tissue collection. Antioxidant capacity of the diets, pinto beans, and pinto bean extract will be determined. Bone structure will be evaluated with micro-computed tomography (µCT) and quantitative histomorphometry of distal end of femur and lumbar vertebrae 2 and 3 (cancellous bone volume, osteoblast and osteoclast surface, mineral apposition rate, bone formation). Primary osteoblasts from bone marrow will be cultured to access in vitro bone formation (alkaline phosphatase, colony formation, mineralization nodules). Gene expression of RANKL, OPG, cbfa-1, c-fos, collagen ?1 (I), osteopontin, osteocalcin, alkaline phosphatase, and M-CSF (quantitative real-time PCR) will be measured by real-time PCR. Cell proliferation and apoptosis will be measured. Liver will be analyzed for total glutathione (reduced glutathione + oxidized glutathione). Thioredoxin and thioredoxin reductase will also be determined.
Work conducted and results obtained in 2007:
Since 12-mo-old mice are not available from any commercial vendors and the aged mice from the National Institute of Aging (NIA) are only available to those researchers who have grants with the agency, we purchased the oldest mice wherever possible and raised them in house. These mice are now 12-mo-old and feeding trial was started January 16, 2008.
We have performed bean hull extraction from commercially available pinto beans. We separated bean hulls from beans manually. About 1.5 kg of dry bean hulls was obtained from 18 kg of pinto beans (the yield is about 8%). Then, based on a published paper (J Nutr Sci Vitaminol, 50: 380-383, 2004), we prepared water extracts from pinto bean hulls. About 75 g of extract were prepared (the yield is about 5%. We performed the oxygen radical absorbance capacity (ORAC) assay to assess antioxidant capacity of whole bean extracts (WBE) and pinto bean hull extracts (BHE). We found that ORAC values were much higher in BHE than in WBE (77 vs 17 µmol/g as expressed as Trolox equivalent). These ORAC values are comparable to those in published reports.
In an effort to mimic a human diet, the experimental design was slightly modified. We now have three groups: Control, 0.04% bean hull extract supplemented group, and 0.08% bean hull extract supplemented group. According to extraction results, 0.08% bean hull extract would be equivalent to about 20% pinto bean in the diet. Using extracts we prepared, all experimental diets (20 kg/group) have been made in house.
Benefit of Research to Bean Growers:
With osteoporosis being a major health concern affecting nearly 50 million Americans, the findings from this study will provide new information about the usefulness of pinto bean hull extract in maintaining bone health and preventing age-related bone loss. A positive effect could mean good news for many Americans, but for bean producers in particular.