Science Adoption2011 Citrus County Schools Citrus County Schools.
[PPT]Brief Introduction to Citrus Limonoids · Web viewDifferent Limonoid groups and the...
-
Upload
truongxuyen -
Category
Documents
-
view
224 -
download
1
Transcript of [PPT]Brief Introduction to Citrus Limonoids · Web viewDifferent Limonoid groups and the...
Brief Introduction to Citrus Limonoids
Jiaxing LiTAMU-College StationTAMUK-Citrus Center
Bitterness problem in citrus industry
• Cause 1. The flavonoids e.g. naringin-- species related to pumello
• Cause 2. The limonoids e.g. limonin
Biochemistry of Limonoids in Citrus
• A group of highly oxygenated tetracyclic triterpenoids -- Citrus & related genera
• Tow forms in citrus: 1. Limonoid aglycones (LA) -- >50 isolated
from the Rutaceae (36 from Citrus&related genera)
2. Limonoid glucosides (LG) -- 17 isolated
Biochemistry Cont.
• Relation between LA and LG 1. LA: bitter, insoluble in water 2. LG: non-bitter, water-soluble 3. LA glucosidated to LG--fruit maturation --- Natural Debittering process --- Occurs only in fruit tissues and seeds
Delayed bitterness
• PH<6.5• Limonoid D-ring
lactone hydrolase• Closed D-ring is
the key structure
An example of natural debittering and delayed bitterness
• Navel oranges and Valencia oranges in California
• Early to mid-season Navel juice has delayed bitterness, Valencia dose not
• Reason: Short maturation period of the Navel (2 months); 6 months for the Valencia allow:
LA LG
Structures of some of the major Limonoids in citrus
Structures Cont.
Biosynthesis of Citrus Limonoids
• Four groups of LA 1. Limonin group 2. Calamin group 3. Ichangensin group 4. 7α-acetate limonoid• Biosynthetic pathways of each group of
these limonoids have been elucidated
Example of Biosynthetic pathways: limonin group
Analytical Methods of Citrus Limonoids
• Thin-layer chromatography (TLC) -- for limonoid detection• Nuclear Magnetic Resonance (NMR) -- determination of limonoid structure• HPLC -- detection & quantification• Radioimmunoassay --detection&quantif.• HPLC-MS -- detection& quantification
Distribution of limonin in Citrus fruit and vegetative tissues -- by Radioimmunoassay
• Limonin levels in fruit and vegetative tissue (White Marsh)
High: Seeds Pith Lamella Albedo FlavedoLow: Juice vesicles
Limonin distribution within grapefruit leaves
• More concentrated in areas adjacent to the conductive tissues
• flushing leaves > mature leaves
Biological activities of citrus limonoids
• Inducers of GST, a detoxifying enzyme in mice and rats:
-- to inhibit formation of chemically-induced neoplasia in forestomach, small intestine, colon, lung, skin and oral of lab animals;
-- to inhibit the proliferation of breast cancer cells in culture
Biological activities contd.
• Antifeedant activity• insect repellents• growth disrupters• reproduction inhibitors
Limonoids and the Taxonomic Studies of Citrus
• Theoretical bases1. Plants have incorporated many secondary
metabolites into specialized physiological functions such as reproduction and intracelluar signaling
2. secondary metabolites are often functionally unique at the species level.
3. Different compounds are responsible for identical functions in different species.
Different Limonoid groups and the Chemotaxonomy of the true-citrus tree
species and hybrids
Future research
• Nutritional research: determination of the roles phytochemicals play in the long term health of humans.
-- Food additives for cancer prevention
The End
• Thank You• References Mark A. Berhow, Shin Hasegwa, and Gary
D. Manners.Citrus Limonoids -- Functional Chemicals in Agriculture and Food/ 2000, American Chemical Society.