Structure-antioxidant activity relationships of flavonoids and phenolic acids

http://amborella.net/2010PlantSystematics/DATA/3-24-APG%202003%20Bot%20J%20Linn%20Soc%20APGII.pdf

An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II

Flavonoids are nearly ubiquitous in plants and are recognized as the pigments responsible for the colors of leaves, especially in autumn. They are rich in seeds, citrus fruits, olive oil, tea, and red wine. They are low molecular weight compounds composed of a three-ring structure with various substitutions. This basic structure is shared by tocopherols (vitamin E). Flavonoids can be subdivided according to the presence of an oxy group at position 4, a double bond between carbon atoms 2 and 3, or a hydroxyl group in position 3 of the C (middle) ring. These characteristics appear to also be required for best activity, especially antioxidant and antiproliferative, in the systems studied. The particular hydroxylation pattern of the B ring of the flavonoles increases their activities, especially in inhibition of mast cell secretion. Certain plants and spices containing flavonoids have been used for thousands of years in traditional Eastern medicine. In spite of the voluminous literature available, however, Western medicine has not yet used flavonoids therapeutically, even though their safety record is exceptional. Suggestions are made where such possibilities may be worth pursuing.

The Effects of Plant Flavonoids on Mammalian Cells:Implications for Inflammation, Heart Disease, and Cancer

Estimation of total flavonoid content in propolis by two complementary colorimetric methods

Antimicrobial activity of flavonoids

The conformations of the two conformational isomers of isabelin (1), a germacranolide dilactone isolated from Ambrosia psilostachya DC. (Compositae), have been determined in chloroform solution by use of the intramolecular nuclear Overhauser effect; and further, the configuration of the endocyclic double-bond in its ten-membered ring has been confirmed. It has been concluded that the major and minor isomers of isabelin mainly adopt the conformations (A) and (B), respectively, which have a trans-orientation of the endocyclic double-bond. Since isabelin has been correlated with artemisiifolin (3), salonitenolide (4), and cnicin (5), the results obtained here have also established a trans configuration for these three germacranolide monolactones. In addition, isoisabelin (2), a geometrical isomer of isabelin, has been examined to determine the configuration of its C(9)–C(10) double-bond and its conformation.

Configuration of the endocyclic double-bond and conformation of the germacranolide dilactones, isabelin, isoisabelin, and related germacranolide monolactones, as studied by nuclear Overhauser effect

SUMMARY

We previously established that xylulose inhibits the growth of the green alga Chlorococcum echinozygotum. Utilizing experiments involving exposure of the alga to NaHC14O3, it was possible to show by counting the C14 activity of methanolic extracts of the algal cells that xylulose inhibited CO2 uptake. Subsequently it was shown that xylulose does not inhibit or otherwise influence the Hill reaction in this alga.



Several enzymes related to xylulose metabolism were investigated. It was found that xylulokinase was active in C. echinozygotum while phosphoketolase activity was absent. Transketolase was present but its activity was not notably affected by xylulose. Crude carboxydismutase preparations were found to be inhibited by xylulose and xylulose 5-phosphate. However, as carboxydismutase was purified further, this inhibition was relatively less. When xylulose 1,5-diphosphate was prepared synthetically, this compound was found to be the most effective inhibitor of purified algal carboxydismutase. We conclude that d-xylulose enters the cells of C. echinozygotum where it is converted to d-xylulose 1,5-diphosphate which acts as a competitive inhibitor of carboxydismutase.

On the mechanism of the inhibition of growth by xylulose in chlorococcum echinozygotum1,2

2-(3,4-Dimethoxyphenyl)-5,7-dihydroxy-6,8-dimethoxy-4H-chromen-4-o ne, C19H18O8, Mr = 374.38, monoclinic, P2(1)/n, a = 9.026(4), b = 15.054(6), c = 12.829(6) A, beta = 100.98(4) degrees, V = 1711(1) A3, Z = 4, Dx = 1.450 g cm-3, lambda (Mo K alpha) = 0.71073 A, mu = 1.07 cm-1, F(000) = 784, T = 295 K, R = 0.0778 for 2280 independent reflections. The nearly planar AB ring system (0.04 A r.m.s.d.), O(1) to C(10), and the planar C ring (0.001 A r.m.s.d.) are almost coplanar with an interplanar angle of only 4.4(4) degrees. The methyl groups at C(6) and C(8) are rotated out of the molecular plane on opposite sides with torsion angles C(5)C(6)O(6)C(11) = -94.5(4) and C(7)C(8)O(8)C(12) = 109.0(4) degrees. The methyl groups of ring C are coplanar with the ring, C(3')C(4')O(4')"(13) = 0.2(5) and C(6')C(5')O(5')C(14) = 1.3(5) degrees. The carbonyl group forms an intramolecular hydrogen bond with O(5), O(5)...O(4) = 2.612(5), H(5O)...O(4) = 1.85(4) A, O(5)-H(5O)...O(4) = 151.9(8) degrees, and an intermolecular hydrogen bond with O(7) of an adjacent molecule, O(7)...O(4) (-0.5 + x, -0.5 - y, 0.5 + z) = 2.689(5), H(7O)...O(4) = 1.92(4) A, and O(7)-H(7O)...O(4) = 163.2(8) degrees.

Structure of the flavone hymenoxin.

Flavonoids and other phenolics of Haematoxylon campechianum

Hasakol, an inhibitor against Ba++-induced contraction of smooth muscles, has been synthesized in six steps starting from 7-O-geranylumbelliferone via an improved Claisen rearrangement.

Tom J. Mabry

Papers

Configuration of the endocyclic double-bond and conformation of the germacranolide dilactones, isabelin, isoisabelin, and related germacranolide monolactones, as studied by nuclear Overhauser effect

On the mechanism of the inhibition of growth by xylulose in chlorococcum echinozygotum1,2

Structure of the flavone hymenoxin.

Flavonoids and other phenolics of Haematoxylon campechianum

Synthesis of Hasakol, an Antispasmodic Coumarin from the fruits of Citrus hassaku