Progress 10/01/02 to 09/30/04
Outputs
Our analytical methods were first validated by comparing results obtained for the analysis of flaxseed with results from the literature, since flaxseed lignan have been widely studied. For flaxseed, the data reported by Charlet (et al 2002), using acid hydrolysis, was 5.9 mg/g SDG; our results after acid hydrolysis of flaxseed were 5.6 mg/g to 6.8 mg/g SDG, depending by the cultivars tested. For base hydrolysis, the range of data obtained by Johnsson et al. (2000) was 13.1 mg/g to 20.7 mg/g SDG. For the base hydrolysis of flaxseed, our data ranged from 13.8 mg/g to 14.9 mg/g SDG, again depending on the cultivars tested. Liggins et al. (2000) found that the hydrolysis time needed for maximum analyte recovery (using acid) was significantly affected by the type of plant material being tested. Due to the highly acidic nature of cranberries, the amount of NaOH used for hydrolysis required modification from the methods published for flaxseed. Cranberry extracts were titrated
with NaOH to pH 7.0 and then excess NaOH was added to obtain 0.05M for base hydrolysis. Cranberries were analyzed for lignan contents using either base or acid hydrolysis before HPLC analysis to determine how lignans were associated to the tissue matrix or the effect of analysis on lignan recovery. Overall, more SDG was recovered from base hydrolysis than acid hydrolysis for flaxseed. Acid hydrolysis of several cranberry cultivars (including Chatsworth, Aberdeen and Stevens) resulted in lignan contents that ranged from 0.16mg/g to 0.33mg/g (dwb). For base hydrolysis, the values ranged from 2.2 to 3.0mg/g (dwb). Overall, more SDG was recovered using base hydrolysis than acid hydrolysis suggesting that either lignans are associated with the cranberry tissue as esters or that the base hydrolysis resulted in better recovery of extracted lignans. The lignan content of cranberries found in this study indicates that cranberries may supply significant levels of these potentially
health-beneficial compounds to cranberry consumers. While flaxseed is still the major known source of SDG lignans (containing 4 -20 mg/g, dwb, depending on the method and sample), the levels found in cranberry may be greater than many other foods that have been tested for lignans and comparable to high tannin beverages such as tea and coffee (Mazur, 1998). Cranberry seeds, pulp, and skin were compared for lignan contents. Using either acid or base hydrolysis prior to extraction and quantitation, the pulp was found to contain approximately 3 to 3.5 times higher levels of lignans compared to the skin or seeds. When tissue yields were taken into account, however, our results indicated that when whole cranberries are consumed, both the pulp and skin provide similar amounts of lignans.
Impacts
Identification and characterization of health-beneficial compounds in cranberries will enable farmers and processors to gain more value from their products and provide consumers with more information, regarding a GRAS food, and potentially assist them to make better choices regarding diet.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Secoisolariciresinol lignan analysis methods, previously published for the testing of flaxseed, were evaluated for the analysis of lignans in cranberry samples. The two methods tested included 1) base hydrolysis followed by HPLC analysis of released lignan glycosides or 2) acid hydrolysis and dehydration followed by HPLC analysis of the anhydro-aglycones. HPLC-PDA (at 280 nm) allowed detection of lignan standards down to 0.01 mM. A linear detection range was obtained between 0.01 and 7 mM secoisolariciresinol diglycoside. For cranberries, preliminary results showed that results obtained following published methods gave higher lignan yields using base hydrolysis vs. acid hydrolysis methods, indicating that cranberry lignans are associated with extractable polysaccharides. Base hydrolysis methods were found to be inadequate for cranberries, however, due to the high titratable acidity of these samples. Hydrolysis conditions are currently being optimized for analysis of
lignans in cranberry samples. Preliminary results revealed that cranberries contain at least 1.5 mg/g lignans, with the greatest concentrations found in the pulp and skin. The values found for cranberry lignan contents are expected to increase with more efficient extraction/hydrolysis methods.
Impacts
Identification and characterization of health-beneficial compounds in cranberries will enable farmers and processors to gain more value from their products and provide consumers with more information, regarding a GRAS food, and potentially assist them to make better choices regarding diet.
Publications
- No publications reported this period
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